Steve is basically teaching us how to make a billet big block lol He shows a crazy amount of information and stuff that other companies would keep behind a locked door 😂
More fuel and air = density. less distance between the molecules= flame travels easier. Heat and cylinder pressure increases detonation potential. Theoretically, timing required stays close to the same, but pressure and heat hasten the flame propagation, hence less timing needed or tolerated per fuel octane. Ultimately, you are trying to time the spark so maximum pressure expansion happens at 8-12 degrees ATDC. NA, boost or nitrous.
Same reason you need a heap more timing at low loads (50kpa etc) for MBT. Charge density / pressure directly affect flame propogation speed. A slower burn requires more timing to have complete combusion by x crank degrees, a faster burn needs less timing for MBT. If 'nothing has changed' then you'd see the exact same MBT at 50kpa as you would at 100kpa with the same timing. You don't.
@@SafetyUggs Thinking through this myself trying to understand, but if Steve is right and the flame front speed stays the same, the reason higher timing at low loads is needed is more to do with mixture at cruise/part throttle, correct? a leaner mixture burns slower so more advance is needed to keep the optimal combustion pressure point timing at the correct point in crankshaft rotation. I think AFR and density function differently here, since even with a higher KPA reading, either WOT or into boost would still have the same ratio of fuel to air, so it's gonna combust at the same rate just with a larget potential energy due to increased mass of mixture in the culinder. Just thinking aloud here to try and better understand this stuff myself.
My answer to your question, "why do we need to decrease timing when going from NA to boosted?" The mixture will be extremely tightly packed in the same size chamber as before. Oxygen molecules will be very close together and when the flame front starts, it will propagate VERY quickly when compared to a more sparsely distributed mixture. Peak cylinder pressure will then occur much earlier/sooner/faster - so you take away timing to keep that peak pressure occurring at the correct time. If this is untrue I might as well throw my engineering degree in the garbage.
You got to keep in mind he's using all these theories based off of running what I would consider molasses consistency fuels like c16 and methanol that's why he specified the fuel he would never run those fuels in the engine naturally aspirated so he's leaving out a critical factor in his equation he needs to consider the optimal fuel for a naturally aspirated engine and then just boost it he would be pulling timing
This is probably the number one reason I love Mr. Steve Morris, asks a question, gives an answer, then explains why the answer applies to real world applications. Anyone can give you an answer but most don’t explain why. I learn so much watching this man and don’t understand why he isn’t over 500k yet. Like and share people, let’s get him up there.
Good point on "what has changed". Its like putting an intake and cam on a v8, yet only the carb is tuned for more fuel or changed for a biggrr carb for more fuel and air. Reading plugs is key, Vanderhoof said that the plug is the witness and the 02 sensor is the guy around the corner who didnt see the murder.
An easy way to explain what's changing you now have to compress more air in fuel Therefore your Dynamic compression ratio has increased you wouldn't run the same ignition timing in an 18:1 motor as you would 10:1 well if you run the math just basing this off of a generic 540 big block running 20 lb of boost would be the equivalent of an 18 to 1
The one other thing that changes with “boost” is pressure Air/Fuel burns faster when compressed in the cylinder then when you just light it on the ground….so timing should compensate for that. I know you said ignore the temperature, but temperature and pressure are “tied together” by….science. That’s why air coming out of a turbo is hot (under boost) So here’s the deal: the pressure at tdc is compound by the compression ratio: 14.7psi(N/A) x 10:1CR= 147psi at tdc Now add 20psi: 34.7psi x 10:1CR =347psi at tdc So 20 psi of boost increases cylinder pressure by 200psi at tdc Since the pressure at tdc is much higher when we add 20psi, the temperature will be higher as well (starting with same charge air temperature). I tried really hard to explain this without science and with examples people can relate to; it’s an over simplification so don’t burn me too hard for it :) Love the videos! Keep them coming!
This one definitely qualifies to get added to the Steve Tech playlist which by the way I listen to Everyday while I'm working as a truck driver over and over LOL I keep listening because every time I do I learn something that I didn't pick up the last time super good information from an honest trustworthy Builder.
As someone who loves to spell, but knows a little bit about engines, I love your honesty that some of the written words were a challenge! Thanks for the tutorials!! 👍
Bro you sounded like you were aggravated that you were even having to stand there and explain any of that so ppl I'm guessing will stop asking you about timing. Just know us little ppl do appreciate you taking time to teach all of us. Be safe and God Bless
I'm an engine machinist and teacher. I observed a very direct and thorough class for all of us, at any and all levels of knowledge and capabilities, to grasp a basic understanding and most importantly for us to do it ourselves. It saves us money(by not having to pay somebody) - it allows us to get our stuff performing better- it helps us not screw up our timing and potentially destroying our engine.
20:20 Not strictly true. Research shows that max power is always found with TRACE detonation. This is because it is the only way the crevice volume mixture can burn at least a little bit. Otherwise it does not burn or burns far too late.
Cylinder pressures. Timing is specific to prime cylinder pressure. On all engines, and fuel. The spark starts the ignition process. Light it too soon, and cylinder pressure spikes before efficiency. Late, and the ignition is slowed down. Change mechanical or static compression (boost). And your prime timing will change. Notice i say prime...the most efficient point of ignition to build cylinder pressure. Go ahead Steve...test it yourself. Measure cylinder pressure and change your Timing back and forth. Both N/A and with boost. The higher the cylinder pressures, the later ignition will provide the most power. Advanced ignition at low rpm has time to expand. Burn rate is the ability for the flame to transfer between fuel and oxygen molecules. More air and fuel, compressed the same. Will not need as much ignition. Because the molecules are closer together.
3:28 I would assume, because of _pressure._ Adding boost pressure, especially high boost pressure, should be similar (timing wise) to running a much higher compression ratio on an NA engine. Mybunderstanding is that more pressure, via boost or higher compression ratio, means the flame front travels faster during combustion, which would require less timing so the combustion event doesn't cause too much of a pressure spike before the piston has reached TDC. That's my theory/understanding anyway.
Great stuff. Describing what makes the knock. Knock is when the flame fronts from the spark plug and pre ignition source clap together as each of the pressure waves collide in the combustion chamber.
Some very good explanations. Maybe I suggest having drawings/diagrams on flip cards or exchanging better drawings instead of drawing them. Not to mention writing the terms You are talk about total advance timing? How come Chrysler BB always gets neglected? What’s the advantage of higher initial advance? You did talk about reading the spark plug to identify timing adjustments. Thanks for sharing
I hope people didn't stop watching at the LS part without the clarification a few min later that you're talking about a good RACE FUEL hahah. Thanks for the quick lesson!
Thanks Steve this was a really good class, Thanks You! again I'm gonna say I'm old, ran F/mp through the late 70's , never even saw a dyno, rarely could afford H&H super blue. Had all the compression a custom dome could give and all that went with it, cast block and cast trans am heads. when it ended, i was 22 year old privateer the old guys would coach from a distance none would go. I' now think being older and listening to what you pros run for timing now, I think we were running way too much. I can tell you that the little 287 after 4/5h would tell me in kind of a weird click in very cold or sea level conditions to lift. You know young and dumb just that red haze in front of me! LOL really miss those days!
Steve, from one (less successful) engine builder to another, I really appreciate all your vids. I will ramble my answers in a minute, but a serious question. With the investments you've made in time and effort, as well as machines and parts, why don't you have something like a TFX data system for cylinder pressure? The ultimate race tunes and ultimate trouble shooting will come from something like that. In fact, I can't believe you don't have the sensor port hole for that in your CNC design... ;-) My short answer on timing question... You are adding cylinder pressure with boost. A 10:1 motor starting with 1 atmosphere (NA) at BDC as a starting point will be less efficient of a flame front than the same motor starting with 2 atmospheres at BDC... so you will need less timing on the boost to achieve the end goal. HOWEVER you are so right about either situation, the end goal is the same, MECHANICALLY.... Peak cylinder pressure sweet spots relates to bore and stroke and V angles and crank design, but most v8s desire about the same starting point in a narrow range of like 8-10 degrees ATDC to create maximum usable force on the crank. So at high rpm more crank degrees happen while the flame front is taking time to travel and burn, IE ignite it sooner. But even at either idle or peak torque of the motor, you want whatever timing for that RPM and load that is needed to create maximum cylinder pressure at the sweet spot for your geometry. The amazing thing is that once you are tuning for peak pressure, the individual needs of individual cylinders vary wildly thru the load and rpm range and the gains there can be amazing. As you say on your beasties, you don't have to chase peak hp but rather chase reliability. Now if you are racing with engine rules, that's different, but that is another topic.... BTW I suspect you have been exposed to all this already from your team drag racing days... but I thought it might be useful comments to start discussion... Thanks Steve, love the vids.
The Old man Garage and uncle Bob did carb vs injectors and the carberator needed more timing. Same head, pistons and everything, they only changed the intake and fueling method
Because air compresses, just like when you increase compression ratio the same amount of charge in a smaller area the timing needs to decrease since molecules are closer together, same thing happens under boost just inverted, more charge in the same space, the molecules are still closer together thus requiring less timing, physics baby physics.. Still thanks for the think and your time. Totally agree though every engine chamber shape and efficiency changes the timing requirment.
This. Compressing air and fuel causes the chemical reaction to speed up. The more compression, the faster the chemical reaction. This is why compression ratio increases engine efficiency.
That’s not Steve’s point. Fuel willing, heavily boosted engines make more power the closer you can keep timing to what it would have been naturally aspirated. They all do, period.
We were taught that initial timing was selected to achieve peak cylinder pressure at 5 degrees ATDC and flame propagation to be finished at 15 degrees ATDC.
A real important part about all these timing numbers also is to make sure the numbers in the ucu are the same as what your engine is actually seeing, the whole way through the rev range, not just at idle! Great info as usual Steve
All of it! I think of detonation as the mixture stops burning too soon (for whatever reason, the are several). Preignition occurs independent of the spark event.
I kid you not! I am right now in my car with my Engine Management open on the laptop and the Audio Knock detection program running after a few data logging runs, and I get this video in my feed!
Reducing timing with a boosted engine, if ignoring temperature and AFR, my initial thought is we reduce it due to air fuel density in the cylinder. Of course, correct me if I'm wrong. I believe if you're running an engine at double atmospheric pressure in a boosted application, the flame propagation and chemical reaction speed will increase theoretically 50 to 100% over the na version. From other research and insight from a few other people, The flame propagation speed is actually considerably faster in small areas of the Piston because pressure actually goes up exponentially when the density increases. Now, if the flame front moves faster, we can retard the timing slightly to optimize cylinder pressure. Again, this is somewhat theoretical without having data in front of me. The other thought is, if you leave the timing where it was, and ignition begins, this could actually lead to knock or detonation somewhere else in the cylinder as the spark ignition will cause a sudden increase in cylinder pressure, which might tip other areas over their threshold.
The way I see it is that if you loosely pour gun powder onto a table and light it, it will barely fizzle and spark. If you pack it tightly into a cartridge, it will explode over 2,500fps. I'm not saying I'm right. Cylinder pressure and density was just my first thought
Not disagreeing with you... You da man! I asked my friend, JV Brotherton why I couldn't use more than 26* total advance on my, low boost, small cam, 10:1, blown pump gas, 383 SBC, and his answer was, "What does it like?" I reiterated "26*" He said, "The combustion chamber is pretty efficient there, I'd run it!" Thanks JV, I think I figured it out. He smiled and said... In perfect world we would need ZERO timing advance. The more timing needed is a sign of inefficient combustion in the chamber... No squish band, lots of space for the flame front to propagate, causing the mixture to burn uninterrupted and out of control. However, higher static cylinder pressures are more efficient, and usually require high octane fuel, turbulence, squish bands, flame grooves, increased ignition intensity (more amperage), to get the spark to jump the gap and fire the plug. Then the flame front burns evenly, like a grass fire, without auto-ignition, pre-ignition or detonation. Also, electrons are like herding sheep in that you have to throw the first one over the fence and the rest of them will follow, that's why we use small plug gaps and high energy ignitions. On the other hand, your design is rather mild at low rpm and pressures, and make it up on the top with extremely high cylinder pressures, RPM, turbulence and AFR, when there is less time to make the combustion happen, therefore requiring more advance to get the job done. Keep up the good work!
Normally Knock in a tuned engine happens due to the air fuel mixture being unable to hold off compression ignition during the further compression caused by the nearby expanding flame front expanding and further compressing the air fuel mixture just before its enveloped by the propergating flame. Im not sure about what steve is saying about timing staying the same. If thats correct it would mean the propergation speed of the flame front would be the same regardless of density of the molecules (average distance between reactants) My thought would be mbt would require less and less timing as cylinder pressure went up as the flame front speed would increase meaning you need to delay the spark to ensure the most effective expansion/push at the correct crank angle.
One thing Steve forgot to mention is a blow thru turbo with a carb or supercharged blow thru with a carb application can run a few degrees more timing. Because the fuel charge right below the carb cools the intake charge. Fuel injection at the very end of the intake runners does not have this cooling effect on the intake charge.
I’ve always wondered why people back the timing down so much on a boosted motor it never made sense. Ive always wondered why you didn’t have to bump the timing up but thanks for the great video.
Hey Steve, it's pretty straightforward that the timing would remain the same as far as what makes the most power. And that with boost this is true if the fuel is tolerant. The thing is most of the time the fuel isnt tolerant. So personally and i feel for others watching. We still dont know what the right timing is. Because we dont know what to remove given the stability of the fuel. Even though the concept of what makes the most power remaining consistent across NA vs. Boosted.
Hi Steve. I just watched that guy from EFI U try and debunk your timing vid. He's a classic 'all the gear and no idea' person. Claiming locking the bov's open on a bbc with the turbo's on the motor is the same as N.A. holy hell. I had to comment on his you tube vid. Keep up the good work.
I'm at 4:25, There is one thing that changes greatly. The piston top skirt area to combustion heat ratio. Or BMSF to skirt area ratio. Why is this important? Because once you have a good chamber, a flat top piston or a dish with pads. You then have your 20-30thou squish area, the next thing you do is try and move the top ring up as far as you can to get rid of that area. So FI actually makes that less of an issue, so predicted timing might be down a little for that reason. Also you have to add area to the skirt to try and get gas pressure to the ring. When you boost, you actually see this area increased to deal with the chamber hammer around the skirt of the bore.
Favourite channel right now Steve! Can you do a vid on chamber softening? Eg: machining a taper into the chamber to help flame front and help make the chamber less sensitive. Cheers!
I always thought that adding boost effectively increased the compression, therefore needing less timing to avoid knock. I guess the caveat "if the fuel is tolerant" takes care of the knock problem without backing off the timing.
Yes but the fuel you would run in a boosted engine is not the same as you would run in a naturally aspirated engine however a lot of us builders are limited to running say pump 93 octane therefore we have to pull timing he's basing his assumption off of switching your 93 octane engine to c16 which is basically like trying to ignite molasses the flame front propagates slower than my grandma getting out of bed in the morning therefore you can pour all the timing to it I've got engines running 30 lb of boost with 34° of timing in them because they're on c16 but that same engine on 93 octane I would have 10° of overall timing in it
The noise and the reason for detonation killing power is because of 2 or more flame fronts colliding. So instead of all of the pressure being somewhat equal across the face of the piston it has small pinpoint pressure spots. Steve Thank you very much for all the information you give
Could we have a follow up please on: Compression chamber na and boosted. Atmosferic air becomes 10x that pressure. Boosted starts at (example) 2x atmosferic and becomes 20x? That pressure. How do you prevend self igniting here? You mentioned the glow plug in a diesel. Thats a starting aid. Diesel timing p pump?. I mean the old mecanical one! The camslope, the hp line and burning itself determine the advance. This pump will always start at the same point(° wise). It starts at boost (fueltank/boostpump) pressure and builts up to atomizer pressure taking a miliseconds. Then the hp line will expand so it takes b miliseconds before were on pressure. Then the fuelhaze in the combustion chamber must ignite taking c miliseconds. So a+b+c is a fixed miliseconds delay. Now engine revs, they determine how many ° the engine turned. So we know the timing. Then the compression ratio gives the combustion pressure and this gives an accomodated temp as well (see boyle gay lussac common gaslaws) so the fuel selfignites. Thats why we use ,,dieselen,, as expression for selfignating gas engines. The glowplug is only heated up on initial starting and depends on the system. Some have their own key position the heat up, some also work during crancking. But they are not used in an gasoline engine. Also please on fuel injection. Portinjected acts as carburated but how about direct in the combustion chamber? Or doesnt that exxist?
the 1 thing that does change is the area filled with non compressible liquid (fuel)... I don't know how much compression ratio changes when fuel is doubled, but I bet Steve knows.... thanks SM for all that you explain
Thanks mate these videos are the top shelf and best available to watch for any engine guy! And in this vid lol you've discredited 90 percent of those who've argued how i tune. This video is simply great info! As per norm! There's decades of experience summarised in one short vid.The chamber and timing info is on point! And the fact you can still put the level of information in these videos is a lot of effort and time! Thanks again you are a Legend!
My first N20 car I ate a hole in a valve from that perpetual lean burn, smh lol. It was actually pretty impressive that the car still got me home for the win! 😂
Thanks Steve! I run a Buick 3.8 out of a Grand national in my Vega with about 20lbs of boost my timing numbers seem to be close to what you had for an LS motor this was very educational like always!
Timing required is all based on flame speed. The only reason we need timing advance is due to the delay from ignition to full charge combustion. There was a 50cc race bike engine that was set at '0' degrees TDC because the chamber was so small and getting the charge burning by the time the rod has enough angle relative to the crank to create torque it didn't need any lead. Remember that all the pressure in the world on the piston does nothing until the crank goes past TDC and creates a thrust angle to be pushed forward. Timing also depends on rpm as the time window for combustion obviously decreases as the revs come up.....higher revs with a constant flame speed needs more and more advance to get the charge burned by the same crank position. But a well tuned engine will have increasing flame speed as the revs come up and it starts to breathe so beyond a certain point around the 3000 rpm area the increasing flow and resulting charge density makes the fuel charge burn quicker and no more timing lead is needed if the increasing flow can keep up with the rpm. Back in the '60's when Honda was running F1 engines they wanted to see if they could 'outrun' this flame speed increase and made a test engine that ran up to 24,000 rpm...and the flame speed was still increasing so it needed no more timing. Some engines need the timing retarded when they 'get up on the pipe' as the power surge you feel is the intake and exhaust tuning starting to cram air into the chamber more efficiently. So it's all down to the mechanical relationship of rod/stroke and charge density unless you are artificially limited by detonation.
Now, no matter how he may have sounded, to some people.. or seem very happy to some....NOW, come one man, you have just received, years and years of experience from ONE OF THE BEST, TRUE ENGINE BUILIDERS IN THE WORLD !!! SO I'd suggest rather than trying to find something to be a a-hole about... To give the man the respect that he deserves, and from what I've seen, He is a man with great self control, by being so respectful to most of the people that want to say mean things about him or what he is teaching people, and talk all that $hit about him.. very soul crushing after you put your hart and soul into making something so ground breaking in the engine world, and building so many engine's over the years. YOU NEED TO SHUT YOUR MOUTH, AND LISTEN VERY CLOSELY TO WHAT HE HAS TO SAY!!! And if he is taking time out of his day to make a video. just to help people understand one more over looked things often forgot about until its to late, And now of day's some people just don't understand the . And why is that?? Because 😂 like myself are done trying to give good advice to people online anymore. I've been at the top of what i do for a living for many years, and still learn something new everyday or at least every week!! We never have all the correct information. And there's getting less and less, of the best hi-tech guy's out there willing to share their information and experiences over the years.. and we know so many different tricks of the trade that you won't find in a book.. or find a different UA-cam or any other good high performance engine builder like Steve!!! Willing to give all that information out there to the world... 99.9 percent chance of finding another Steve Morris, willing to help with good correct information that you can trust with your 50 to 150 thousand dollar engine, and then work like he does... NOT GOING TO HAPPEN,!!!!!!!! RESPECT THAT IS THE ONLY THING THAT SHOULD EVER BE GIVEN TO A MAN LIKE STEVE HELPING PEOPLE OUT, AND TRYING TO TEACH THEM THINGS THAT ARE GOING TO SAVE THEM MONEY, BUT STEVE IS THE TYPE OF PERSON THAT WILL LOOK AT A PART YOU THINK IS BAD. AND ARE READY TO SPEND 2500.00 DOLLARS,!!!! AND then STEVE TELLS YOU NO THAT PART IS PERFECT. ITS THE 2.00 DOLLAR PART THAT IS BAD , SO SINCE YOU ALREADY HAD GIVEN ME THE OK TO GET THE 2500.00 PART, IT'S ALL DONE SINCE IT CAME IN A BIT UNDER YOUR THOUGHT PRE-APPROVED 2500.00 HUNDRED DOLLARS!!! THATS HOW COME YOU SHOULD LISTEN TO PEOPLE LIKE STEVE AND OTHERS IN THERE FILD OF WORK . ESPECIALLY IF THEY HAVE BEEN IN BUSINESS IN THE SAME LOCATION FOR OVER 40 YEAR'S.. THAT'S NOT VERY EASY NOW OF DAYS, SO THANKS STEVE FOR EVERYTHING YOU SHOW,ESPLANADE, AND TEACH, US IN EVERY VIDEO. .. TAKE CARE BOB FROM HOUGHTON LAKE MICHIGAN,,
Some caveats, boost adds turbulence. Flame propagation speed in a stagnant compressed volume is not equivalent to flame propagation in an engine with swirl, tumble, squish. By the logic I’m understanding in this video, and engine would want the same timing at any load value, given unlimited octane, which is clearly not the case even if the engine would tolerate it.
Absolutely agree..... assuming you're using multi spark type ignition and a very healthy dwell time. Flame travel across the piston can kill or cure an engine. Too short flame travel will side load a piston and do some ugly things to a cylinder. Ask any shovel head Harley engine builder.
Steve, the one thing that has changed is dynamic compression ratio, and that could be why u have to take away timing… more air and more fuel mean more combustion pressures and or dynamic compression ratios between na and boosted
Steve, I'd love to see you get your hands on the mid 2000's LNF Ecotec engine. It's the weirdest (conventional combustion) engine I've ever seen and delt with. I feel that even you would struggle to play with it. The LNF variant is a mystery to the Family II Ecotec platform, considering how much power they make, stock or modified. Examples: If you port the head, looses power everywhere, if you bore it bigger, massive power losses, they run SUPER SUPER LEAN, (my current build is in the 13.0 afr range), The head flow makes no sense for the power they put down, and I don't believe they like to have a whole lot of timing either, which is what drew me to this video today. I'm constantly trying to improve on the build, but all the "conventional" tips and tricks in the racing industry, just don't seem to work, for this particular engine. The current answer always seems to be "Just throw more boost at it and prey"
I 100% agree. The plug will need to have a very high amp spark to compete in that high pressurised chamber. You can get spark out under too much pressure. ( Ions under pressure. )
Love it!!! Thank you. I use a vacuum gauge to determine initial ignition timing . Race engine and race gas is a different animal altogether however a vacuum gauge is a great way to determine best initial ignition timing then you read your spark plugs. Advance timing to max vacuum and back off 1 " of vacuum per thousand feet above sea level for a base . Steve says 28 ° 10:1 compression BBC. With what fuel octane rating?
Two points While degrees of crankshaft rotation is easy to measure, piston distance to TDC is what we really care about. This would mean that a change from 30 to 31 has more effect due to longer piston travel than from 20 to 21 correct? How about timing on dual spark plug engines? Fire both at same time / stagger? Mercedes V6 / V8 , Gen 3 Hemi ( plugs about 2 inches apart ) Porsche air cooled ( and purpose built light aircraft ) one plug at top , one at bottom Ford Ranger 2.5 4 cylinder ( like the 2.3 overhead car Pinto ) with one plugs on each side of the head.
on my old dirt track engines the most we could run was 355 ci and 194 /150 valves. and a 488 lift cam and i ran about 36 deg timing with the 041 chevy heads. and my car ran great then i cracked a head and went to the old 882 chevy head and my timing dropped to 24 deg. to make it run good. but also everything i refreshed my engine the head gasket was ready to blow. i was never so glad to find some 993 chevy heads i don't know anything about chevy heads other than 882 sucked and 041 had the 13/16th plugs and you couldn't find them. and the 993 heads put me back on top.
WOW! You learn something new every day. I remember years ago reading a performance book 32 total is all you need. In the old manuals you would see it as high as 38 total. I never knew that some engines like lower like 22 total. In coming air temps is major, even with carbs. Many guys don't even think about it.
Talk about a trigger Mr. Morris-I flashback to my teen years were my teacher would pose a question and waiting for me to answer😯😂The theory with a soft chamber is to slow down the mixture motion in the chamber prior to combustion, vs a tight quench (ignoring any pre ignition issues) high turbulence/swirl motion? Thank you for sharing!!!!
I usually just set it at a range that it will run at then go with ear and operation. Fuels are always different in my area so I go with how the vehicle performs for what I want it to do.
Good video, my experience with n/a small block Chevy engines generally want 32 to 36 degrees. Of course there a many deviations that can change what the engine wants.
My answer is most of us are running 91 or 93 Octane gas, which has limited detonation tolerance. If you run 14.6 PSI of boost you are adding 1 atmosphere to the cylinder and you are doubling your compression ratio. So on a 9.5:1 NA engine, you are now running 19:1 compression. This is why timing has to be taken out of the engine.
Detonation is usually from poor in cylinder mixture, i.e lack of homogeneity in the chamber. Boosting increases turbulent motion in the chamber, and is a major contributor to improving mixing. You spark less for 2 reasons. 1) with more air and fuel in the cylinder, temperature at peak pressure (ideal gas law) and higher temps increase burn rate. 2) more timing is not necessarily better, it's an indicator of slower flame speed. A better more uniform mixture improves burn rate. A better indicator of combustion performance is CA50. This is a common metric in normal boosted (production) engines, but may not be as useful in super duper high cylinder pressure race engines.
All about achieving that leverage point/cylinder pressure peak of about 15 degrees ATDC. Too much before towards TDC=bent broken parts, too much after=inefficient power transfer to the leverage of the pump. As you said here, Nitrous is a different animal with the Oxygen availability being almost instant and very abundant in it's liquid state.
He’s right about timing initial timing until you hit a really high cylinder pressure or beyond the fuel capacity. I use the same Timing from 15 psi up to a 30 psi on many engines. You can argue all you want but if the fuel is good you’ve good until you hit ridiculous airspeeds from too small port causing mixing issues and or excessive cylinders pressures.
Thank you, Steve, for this video. Its great to have you talk about this subject. I have a basic understanding of ignition timing, and this made a lot of sense. I know you focused on getting to MBT, but I'd love a more in depth video on ignition curves through the rpm range at some point. Since you build drag and drive engines, I'd be interested to learn more. Thanks for all the great information!
the one thing that does change is density(more air, more fuel, same space = higher density). I don't know the physics of how much/little that changes the speed of the flame front/combustion at all, but if anything would cause a difference, that would be it.
First question answer: charge density. The molecules are closer in proximity so they will actually burn fast. You have to change timing to keep pre-ignition or detonation from happening (multiple flames fronts interfering). Also can cause combustion to become more like an explosion. So if you are not mechanically or knock limited you "could increase timing" but I don't know of many cases of this even the best of fuels and most optimized engines this is uncommon unless we are talking f1 tech here. So this is why it's more or less considered theory. There are lots if limiting variables like having a perfect homogeneous mixture of are and fuel is next to impossible and so on.
Thanks for sharing your view and experience on timing. I also like hearing Brent @PFI talk about his way with timing in Hondas. He uses timing to limit lower rpm torque on stock Honda crankshafts. I guess it’s more exact and easier than playing with boost down at lower rpms. I could be wrong. I might get roasted in comments.
6:55 Not "nothing". If you put double the amount of mixture in in the same time frame You should have more turbulence than before leaving aside everything else. An increase in turbulence should require less timing.
The fact that Steve takes the time out of his day to make this content and educate us is just awesome! Thank you so much, Steve.
You know he makes around 5000$ in ad money per video right? He not doing it cause he’s a cool mother trucker
@@gregorholmes1837. It can be both.
@@gregorholmes1837
He was doing these sorta videos WAYYYYYY before he had ad money or giant viewership
Steve is basically teaching us how to make a billet big block lol
He shows a crazy amount of information and stuff that other companies would keep behind a locked door 😂
@austincassell4741 newsflash... that's how all youtube channels start.
Instructions unclear
Rods in oil pan.
Send help
😂
Rinse repeat. Literally. 😂😂😂😂😂
Props to your oil pan for being strong enough to contain the flying rods
New firing cycle, piston goes down, never comes back up.
@gothicpagan.666 that's that new 5th stroke they been talking about
More fuel and air = density. less distance between the molecules= flame travels easier. Heat and cylinder pressure increases detonation potential. Theoretically, timing required stays close to the same, but pressure and heat hasten the flame propagation, hence less timing needed or tolerated per fuel octane. Ultimately, you are trying to time the spark so maximum pressure expansion happens at 8-12 degrees ATDC. NA, boost or nitrous.
I support this comment
Same reason you need a heap more timing at low loads (50kpa etc) for MBT. Charge density / pressure directly affect flame propogation speed. A slower burn requires more timing to have complete combusion by x crank degrees, a faster burn needs less timing for MBT. If 'nothing has changed' then you'd see the exact same MBT at 50kpa as you would at 100kpa with the same timing. You don't.
this 👆
Then why when the air is SUPER cold (think -100F), can you run lots of boost with full NA timing
@@SafetyUggs Thinking through this myself trying to understand, but if Steve is right and the flame front speed stays the same, the reason higher timing at low loads is needed is more to do with mixture at cruise/part throttle, correct? a leaner mixture burns slower so more advance is needed to keep the optimal combustion pressure point timing at the correct point in crankshaft rotation.
I think AFR and density function differently here, since even with a higher KPA reading, either WOT or into boost would still have the same ratio of fuel to air, so it's gonna combust at the same rate just with a larget potential energy due to increased mass of mixture in the culinder.
Just thinking aloud here to try and better understand this stuff myself.
My favorite line ever, "IDC.Ask Brett Lassala" 😂😂
My answer to your question, "why do we need to decrease timing when going from NA to boosted?" The mixture will be extremely tightly packed in the same size chamber as before. Oxygen molecules will be very close together and when the flame front starts, it will propagate VERY quickly when compared to a more sparsely distributed mixture. Peak cylinder pressure will then occur much earlier/sooner/faster - so you take away timing to keep that peak pressure occurring at the correct time. If this is untrue I might as well throw my engineering degree in the garbage.
Peak cylinder pressure is the key.
That was my thought as well was hoping someone had asked and he’d answered
You got to keep in mind he's using all these theories based off of running what I would consider molasses consistency fuels like c16 and methanol that's why he specified the fuel he would never run those fuels in the engine naturally aspirated so he's leaving out a critical factor in his equation he needs to consider the optimal fuel for a naturally aspirated engine and then just boost it he would be pulling timing
Throw it .
@@liftedcj7on44syea yea
This is probably the number one reason I love Mr. Steve Morris, asks a question, gives an answer, then explains why the answer applies to real world applications. Anyone can give you an answer but most don’t explain why. I learn so much watching this man and don’t understand why he isn’t over 500k yet. Like and share people, let’s get him up there.
Good point on "what has changed". Its like putting an intake and cam on a v8, yet only the carb is tuned for more fuel or changed for a biggrr carb for more fuel and air.
Reading plugs is key, Vanderhoof said that the plug is the witness and the 02 sensor is the guy around the corner who didnt see the murder.
An easy way to explain what's changing you now have to compress more air in fuel Therefore your Dynamic compression ratio has increased you wouldn't run the same ignition timing in an 18:1 motor as you would 10:1 well if you run the math just basing this off of a generic 540 big block running 20 lb of boost would be the equivalent of an 18 to 1
Steve, I think it’s really cool. You still take time to do videos like this that help people understand everything better.
The one other thing that changes with “boost” is pressure
Air/Fuel burns faster when compressed in the cylinder then when you just light it on the ground….so timing should compensate for that.
I know you said ignore the temperature, but temperature and pressure are “tied together” by….science.
That’s why air coming out of a turbo is hot (under boost)
So here’s the deal: the pressure at tdc is compound by the compression ratio:
14.7psi(N/A) x 10:1CR= 147psi at tdc
Now add 20psi:
34.7psi x 10:1CR =347psi at tdc
So 20 psi of boost increases cylinder pressure by 200psi at tdc
Since the pressure at tdc is much higher when we add 20psi, the temperature will be higher as well (starting with same charge air temperature).
I tried really hard to explain this without science and with examples people can relate to; it’s an over simplification so don’t burn me too hard for it :)
Love the videos! Keep them coming!
You are that one guy that confuses everyone in the break room.
This one definitely qualifies to get added to the Steve Tech playlist which by the way I listen to Everyday while I'm working as a truck driver over and over LOL I keep listening because every time I do I learn something that I didn't pick up the last time super good information from an honest trustworthy Builder.
As someone who loves to spell, but knows a little bit about engines, I love your honesty that some of the written words were a challenge!
Thanks for the tutorials!! 👍
Bro you sounded like you were aggravated that you were even having to stand there and explain any of that so ppl I'm guessing will stop asking you about timing.
Just know us little ppl do appreciate you taking time to teach all of us.
Be safe and God Bless
Nope not at all
You sound like you were aggravated to listen to it.
Absolutely he wasn't! He was happy go lucky like always!
I'm an engine machinist and teacher. I observed a very direct and thorough class for all of us, at any and all levels of knowledge and capabilities, to grasp a basic understanding and most importantly for us to do it ourselves. It saves us money(by not having to pay somebody) - it allows us to get our stuff performing better- it helps us not screw up our timing and potentially destroying our engine.
He didn't have to do anything. He did it because he wanted to. Bro go find another channel. Your attitude is poor..
20:20 Not strictly true. Research shows that max power is always found with TRACE detonation. This is because it is the only way the crevice volume mixture can burn at least a little bit. Otherwise it does not burn or burns far too late.
Cylinder pressures. Timing is specific to prime cylinder pressure. On all engines, and fuel. The spark starts the ignition process. Light it too soon, and cylinder pressure spikes before efficiency. Late, and the ignition is slowed down. Change mechanical or static compression (boost). And your prime timing will change. Notice i say prime...the most efficient point of ignition to build cylinder pressure. Go ahead Steve...test it yourself. Measure cylinder pressure and change your Timing back and forth. Both N/A and with boost. The higher the cylinder pressures, the later ignition will provide the most power.
Advanced ignition at low rpm has time to expand.
Burn rate is the ability for the flame to transfer between fuel and oxygen molecules. More air and fuel, compressed the same. Will not need as much ignition. Because the molecules are closer together.
You nailed it.
It all works like he said I found out my old timing light was off by 9 degrees
Thank you Steve making these videos .....
Appreciate the information. Thankx for taking the time to help us little guys
Damnit! I learned stuff again. It's like listening to my dad.
3:28 I would assume, because of _pressure._ Adding boost pressure, especially high boost pressure, should be similar (timing wise) to running a much higher compression ratio on an NA engine. Mybunderstanding is that more pressure, via boost or higher compression ratio, means the flame front travels faster during combustion, which would require less timing so the combustion event doesn't cause too much of a pressure spike before the piston has reached TDC. That's my theory/understanding anyway.
@@bluegizmo1983 your understanding is a fine one
Great stuff. Describing what makes the knock. Knock is when the flame fronts from the spark plug and pre ignition source clap together as each of the pressure waves collide in the combustion chamber.
Some very good explanations. Maybe I suggest having drawings/diagrams on flip cards or exchanging better drawings instead of drawing them. Not to mention writing the terms
You are talk about total advance timing? How come Chrysler BB always gets neglected? What’s the advantage of higher initial advance?
You did talk about reading the spark plug to identify timing adjustments. Thanks for sharing
I hope people didn't stop watching at the LS part without the clarification a few min later that you're talking about a good RACE FUEL hahah. Thanks for the quick lesson!
Thanks Steve this was a really good class, Thanks You! again I'm gonna say I'm old, ran F/mp through the late 70's , never even saw a dyno, rarely could afford H&H super blue. Had all the compression a custom dome could give and all that went with it, cast block and cast trans am heads. when it ended, i was 22 year old privateer the old guys would coach from a distance none would go. I' now think being older and listening to what you pros run for timing now, I think we were running way too much. I can tell you that the little 287 after 4/5h would tell me in kind of a weird click in very cold or sea level conditions to lift. You know young and dumb just that red haze in front of me! LOL really miss those days!
I think back in the days of huge chambers, and sky scraper piston domes,, it took a lot more timing.
My 277 SBC w turbo heads and hand fit dome, needed 60degs of total timing. No dyno just MPH and ETs
Great Great video!! Steve. We Are all So lucky to have you!!! 👍🏼✅
Steve, from one (less successful) engine builder to another, I really appreciate all your vids. I will ramble my answers in a minute, but a serious question. With the investments you've made in time and effort, as well as machines and parts, why don't you have something like a TFX data system for cylinder pressure? The ultimate race tunes and ultimate trouble shooting will come from something like that. In fact, I can't believe you don't have the sensor port hole for that in your CNC design... ;-)
My short answer on timing question... You are adding cylinder pressure with boost. A 10:1 motor starting with 1 atmosphere (NA) at BDC as a starting point will be less efficient of a flame front than the same motor starting with 2 atmospheres at BDC... so you will need less timing on the boost to achieve the end goal.
HOWEVER you are so right about either situation, the end goal is the same, MECHANICALLY....
Peak cylinder pressure sweet spots relates to bore and stroke and V angles and crank design, but most v8s desire about the same starting point in a narrow range of like 8-10 degrees ATDC to create maximum usable force on the crank. So at high rpm more crank degrees happen while the flame front is taking time to travel and burn, IE ignite it sooner. But even at either idle or peak torque of the motor, you want whatever timing for that RPM and load that is needed to create maximum cylinder pressure at the sweet spot for your geometry. The amazing thing is that once you are tuning for peak pressure, the individual needs of individual cylinders vary wildly thru the load and rpm range and the gains there can be amazing. As you say on your beasties, you don't have to chase peak hp but rather chase reliability. Now if you are racing with engine rules, that's different, but that is another topic....
BTW I suspect you have been exposed to all this already from your team drag racing days... but I thought it might be useful comments to start discussion...
Thanks Steve, love the vids.
Your videos are getting better every time. Thank you for all the technical stuff! We all appreciate it.
The Old man Garage and uncle Bob did carb vs injectors and the carberator needed more timing. Same head, pistons and everything, they only changed the intake and fueling method
Cooler intake charge with a carb
Because air compresses, just like when you increase compression ratio the same amount of charge in a smaller area the timing needs to decrease since molecules are closer together, same thing happens under boost just inverted, more charge in the same space, the molecules are still closer together thus requiring less timing, physics baby physics.. Still thanks for the think and your time. Totally agree though every engine chamber shape and efficiency changes the timing requirment.
This. Compressing air and fuel causes the chemical reaction to speed up. The more compression, the faster the chemical reaction. This is why compression ratio increases engine efficiency.
That’s not Steve’s point.
Fuel willing, heavily boosted engines make more power the closer you can keep timing to what it would have been naturally aspirated. They all do, period.
We were taught that initial timing was selected to achieve peak cylinder pressure at 5 degrees ATDC and flame propagation to be finished at 15 degrees ATDC.
A real important part about all these timing numbers also is to make sure the numbers in the ucu are the same as what your engine is actually seeing, the whole way through the rev range, not just at idle! Great info as usual Steve
Very professional, and explained as a teacher with Hands on Experience. Thank you for your time. 😊
All of it! I think of detonation as the mixture stops burning too soon (for whatever reason, the are several).
Preignition occurs independent of the spark event.
I kid you not! I am right now in my car with my Engine Management open on the laptop and the Audio Knock detection program running after a few data logging runs, and I get this video in my feed!
Reducing timing with a boosted engine, if ignoring temperature and AFR, my initial thought is we reduce it due to air fuel density in the cylinder. Of course, correct me if I'm wrong. I believe if you're running an engine at double atmospheric pressure in a boosted application, the flame propagation and chemical reaction speed will increase theoretically 50 to 100% over the na version.
From other research and insight from a few other people, The flame propagation speed is actually considerably faster in small areas of the Piston because pressure actually goes up exponentially when the density increases.
Now, if the flame front moves faster, we can retard the timing slightly to optimize cylinder pressure. Again, this is somewhat theoretical without having data in front of me.
The other thought is, if you leave the timing where it was, and ignition begins, this could actually lead to knock or detonation somewhere else in the cylinder as the spark ignition will cause a sudden increase in cylinder pressure, which might tip other areas over their threshold.
The way I see it is that if you loosely pour gun powder onto a table and light it, it will barely fizzle and spark. If you pack it tightly into a cartridge, it will explode over 2,500fps. I'm not saying I'm right. Cylinder pressure and density was just my first thought
Not disagreeing with you... You da man!
I asked my friend, JV Brotherton why I couldn't use more than 26* total advance on my, low boost, small cam, 10:1, blown pump gas, 383 SBC, and his answer was, "What does it like?"
I reiterated "26*" He said, "The combustion chamber is pretty efficient there, I'd run it!" Thanks JV, I think I figured it out. He smiled and said... In perfect world we would need ZERO timing advance.
The more timing needed is a sign of inefficient combustion in the chamber... No squish band, lots of space for the flame front to propagate, causing the mixture to burn uninterrupted and out of control.
However, higher static cylinder pressures are more efficient, and usually require high octane fuel, turbulence, squish bands, flame grooves, increased ignition intensity (more amperage), to get the spark to jump the gap and fire the plug. Then the flame front burns evenly, like a grass fire, without auto-ignition, pre-ignition or detonation.
Also, electrons are like herding sheep in that you have to throw the first one over the fence and the rest of them will follow, that's why we use small plug gaps and high energy ignitions.
On the other hand, your design is rather mild at low rpm and pressures, and make it up on the top with extremely high cylinder pressures, RPM, turbulence and AFR, when there is less time to make the combustion happen, therefore requiring more advance to get the job done.
Keep up the good work!
This tool is a must watch, especially for the car builders and modifiers out there. I even learned something here as well.
Normally Knock in a tuned engine happens due to the air fuel mixture being unable to hold off compression ignition during the further compression caused by the nearby expanding flame front expanding and further compressing the air fuel mixture just before its enveloped by the propergating flame.
Im not sure about what steve is saying about timing staying the same.
If thats correct it would mean the propergation speed of the flame front would be the same regardless of density of the molecules (average distance between reactants)
My thought would be mbt would require less and less timing as cylinder pressure went up as the flame front speed would increase meaning you need to delay the spark to ensure the most effective expansion/push at the correct crank angle.
One thing Steve forgot to mention is a blow thru turbo with a carb or supercharged blow thru with a carb application can run a few degrees more timing. Because the fuel charge right below the carb cools the intake charge. Fuel injection at the very end of the intake runners does not have this cooling effect on the intake charge.
This is my favorite kind of videos. Thank you
Would love to see an updated start to finish on tuning for timing. Run it at X degrees, and step it up and show that on the plug. Would be nice to see
most unknown customer engine wanting a dyno tune uses this method
Get off your butt and do it yourself . Then you will be able to take pride in what YOU have achieved 👍
@@IANHANDS I have. My car makes 34psi, on my tune, on an engine I built. Would simply be a good video for him to make. Thanks for your useful input.
I’ve always wondered why people back the timing down so much on a boosted motor it never made sense. Ive always wondered why you didn’t have to bump the timing up but thanks for the great video.
Hey Steve, it's pretty straightforward that the timing would remain the same as far as what makes the most power. And that with boost this is true if the fuel is tolerant. The thing is most of the time the fuel isnt tolerant. So personally and i feel for others watching. We still dont know what the right timing is. Because we dont know what to remove given the stability of the fuel. Even though the concept of what makes the most power remaining consistent across NA vs. Boosted.
Hi Steve. I just watched that guy from EFI U try and debunk your timing vid. He's a classic 'all the gear and no idea' person. Claiming locking the bov's open on a bbc with the turbo's on the motor is the same as N.A. holy hell. I had to comment on his you tube vid. Keep up the good work.
Low budget small block Chevy open chamber 36 to 39. Closed chamber 34 to 37. Swirl port 32 to 34 or aluminum fast burn 34 to 36
I'm at 4:25, There is one thing that changes greatly. The piston top skirt area to combustion heat ratio. Or BMSF to skirt area ratio. Why is this important? Because once you have a good chamber, a flat top piston or a dish with pads. You then have your 20-30thou squish area, the next thing you do is try and move the top ring up as far as you can to get rid of that area.
So FI actually makes that less of an issue, so predicted timing might be down a little for that reason.
Also you have to add area to the skirt to try and get gas pressure to the ring.
When you boost, you actually see this area increased to deal with the chamber hammer around the skirt of the bore.
Favourite channel right now Steve! Can you do a vid on chamber softening? Eg: machining a taper into the chamber to help flame front and help make the chamber less sensitive. Cheers!
I always thought that adding boost effectively increased the compression, therefore needing less timing to avoid knock. I guess the caveat "if the fuel is tolerant" takes care of the knock problem without backing off the timing.
Yes but the fuel you would run in a boosted engine is not the same as you would run in a naturally aspirated engine however a lot of us builders are limited to running say pump 93 octane therefore we have to pull timing he's basing his assumption off of switching your 93 octane engine to c16 which is basically like trying to ignite molasses the flame front propagates slower than my grandma getting out of bed in the morning therefore you can pour all the timing to it I've got engines running 30 lb of boost with 34° of timing in them because they're on c16 but that same engine on 93 octane I would have 10° of overall timing in it
@@RingTuned Makes sense.
The noise and the reason for detonation killing power is because of 2 or more flame fronts colliding. So instead of all of the pressure being somewhat equal across the face of the piston it has small pinpoint pressure spots.
Steve Thank you very much for all the information you give
It causes the pressure peak before top dead center so cylinder pressure to go sky high.
Read your spark plugs!
💯! I dialed in my timing that way reading the strap, then tuned my carb... Step springs, needles and main jet swapp... Runs incredibly strong now!!
Mine say NGK…. What’s that mean?
@@bob65656565656565 Nihon Gaishi Kaisha
Could we have a follow up please on:
Compression chamber na and boosted.
Atmosferic air becomes 10x that pressure.
Boosted starts at (example) 2x atmosferic and becomes 20x? That pressure. How do you prevend self igniting here?
You mentioned the glow plug in a diesel. Thats a starting aid.
Diesel timing p pump?.
I mean the old mecanical one! The camslope, the hp line and burning itself determine the advance. This pump will always start at the same point(° wise). It starts at boost (fueltank/boostpump) pressure and builts up to atomizer pressure taking a miliseconds. Then the hp line will expand so it takes b miliseconds before were on pressure. Then the fuelhaze in the combustion chamber must ignite taking c miliseconds. So a+b+c is a fixed miliseconds delay. Now engine revs, they determine how many ° the engine turned. So we know the timing. Then the compression ratio gives the combustion pressure and this gives an accomodated temp as well (see boyle gay lussac common gaslaws) so the fuel selfignites. Thats why we use ,,dieselen,, as expression for selfignating gas engines. The glowplug is only heated up on initial starting and depends on the system. Some have their own key position the heat up, some also work during crancking. But they are not used in an gasoline engine.
Also please on fuel injection. Portinjected acts as carburated but how about direct in the combustion chamber? Or doesnt that exxist?
the 1 thing that does change is the area filled with non compressible liquid (fuel)... I don't know how much compression ratio changes when fuel is doubled, but I bet Steve knows.... thanks SM for all that you explain
Thanks mate these videos are the top shelf and best available to watch for any engine guy! And in this vid lol you've discredited 90 percent of those who've argued how i tune. This video is simply great info! As per norm! There's decades of experience summarised in one short vid.The chamber and timing info is on point! And the fact you can still put the level of information in these videos is a lot of effort and time! Thanks again you are a Legend!
Read those plugs. The "timing" mark on the strap will tell you what it wants.
Hey Steve, Even though my dual carb, in-line 6, is nothing like your work, your informative instructions really helped. Thnx
Equivolent octane is a measure of resistance to autoignition. Detonation is two flame fronts hitting each other at hypersonic velocity.
There whole family is amazing. Can't wait to meet them. Moving to Muskegon really soon
Great info but what about Big Block Dodge 440 trick flow 240 heads
I thought this video wouldbe way too far over my head , it wasn’t. Fascinating stuff.
I am on my way to a doctorate in timing science ! great exsplainemenship. Thanks a million !
One thing has changed, density.
The compressed charge will burn faster due to that.
My first N20 car I ate a hole in a valve from that perpetual lean burn, smh lol. It was actually pretty impressive that the car still got me home for the win! 😂
Thanks Teachers! I will be on time tomorrow ❤
Thanks Steve! I run a Buick 3.8 out of a Grand national in my Vega with about 20lbs of boost my timing numbers seem to be close to what you had for an LS motor this was very educational like always!
Timing required is all based on flame speed. The only reason we need timing advance is due to the delay from ignition to full charge combustion. There was a 50cc race bike engine that was set at '0' degrees TDC because the chamber was so small and getting the charge burning by the time the rod has enough angle relative to the crank to create torque it didn't need any lead. Remember that all the pressure in the world on the piston does nothing until the crank goes past TDC and creates a thrust angle to be pushed forward.
Timing also depends on rpm as the time window for combustion obviously decreases as the revs come up.....higher revs with a constant flame speed needs more and more advance to get the charge burned by the same crank position. But a well tuned engine will have increasing flame speed as the revs come up and it starts to breathe so beyond a certain point around the 3000 rpm area the increasing flow and resulting charge density makes the fuel charge burn quicker and no more timing lead is needed if the increasing flow can keep up with the rpm.
Back in the '60's when Honda was running F1 engines they wanted to see if they could 'outrun' this flame speed increase and made a test engine that ran up to 24,000 rpm...and the flame speed was still increasing so it needed no more timing. Some engines need the timing retarded when they 'get up on the pipe' as the power surge you feel is the intake and exhaust tuning starting to cram air into the chamber more efficiently.
So it's all down to the mechanical relationship of rod/stroke and charge density unless you are artificially limited by detonation.
Now, no matter how he may have sounded, to some people.. or seem very happy to some....NOW, come one man, you have just received, years and years of experience from ONE OF THE BEST, TRUE ENGINE BUILIDERS IN THE WORLD !!! SO I'd suggest rather than trying to find something to be a a-hole about... To give the man the respect that he deserves, and from what I've seen, He is a man with great self control, by being so respectful to most of the people that want to say mean things about him or what he is teaching people, and talk all that $hit about him.. very soul crushing after you put your hart and soul into making something so ground breaking in the engine world, and building so many engine's over the years. YOU NEED TO SHUT YOUR MOUTH, AND LISTEN VERY CLOSELY TO WHAT HE HAS TO SAY!!! And if he is taking time out of his day to make a video. just to help people understand one more over looked things often forgot about until its to late, And now of day's some people just don't understand the .
And why is that?? Because 😂 like myself are done trying to give good advice to people online anymore. I've been at the top of what i do for a living for many years, and still learn something new everyday or at least every week!! We never have all the correct information. And there's getting less and less, of the best hi-tech guy's out there willing to share their information and experiences over the years.. and we know so many different tricks of the trade that you won't find in a book.. or find a different UA-cam or any other good high performance engine builder like Steve!!! Willing to give all that information out there to the world... 99.9 percent chance of finding another Steve Morris, willing to help with good correct information that you can trust with your 50 to 150 thousand dollar engine, and then work like he does...
NOT GOING TO HAPPEN,!!!!!!!!
RESPECT THAT IS THE ONLY THING THAT SHOULD EVER BE GIVEN TO A MAN LIKE STEVE HELPING PEOPLE OUT, AND TRYING TO TEACH THEM THINGS THAT ARE GOING TO SAVE THEM MONEY, BUT STEVE IS THE TYPE OF PERSON THAT WILL LOOK AT A PART YOU THINK IS BAD. AND ARE READY TO SPEND 2500.00 DOLLARS,!!!! AND then STEVE TELLS YOU NO THAT PART IS PERFECT. ITS THE 2.00 DOLLAR PART THAT IS BAD , SO SINCE YOU ALREADY HAD GIVEN ME THE OK TO GET THE 2500.00 PART, IT'S ALL DONE SINCE IT CAME IN A BIT UNDER YOUR THOUGHT PRE-APPROVED 2500.00 HUNDRED DOLLARS!!! THATS HOW COME YOU SHOULD LISTEN TO PEOPLE LIKE STEVE AND OTHERS IN THERE FILD OF WORK . ESPECIALLY IF THEY HAVE BEEN IN BUSINESS IN THE SAME LOCATION FOR OVER 40 YEAR'S.. THAT'S NOT VERY EASY NOW OF DAYS,
SO THANKS STEVE FOR EVERYTHING YOU SHOW,ESPLANADE, AND TEACH, US IN EVERY VIDEO. .. TAKE CARE BOB FROM HOUGHTON LAKE MICHIGAN,,
Sorry about my S÷ITTY message skills. My engine,and other fab work is all I care about being perfect ....lol.....Bob.
👍 thank you from one motor head to another!!! Bob..... have a great day
Some caveats, boost adds turbulence. Flame propagation speed in a stagnant compressed volume is not equivalent to flame propagation in an engine with swirl, tumble, squish. By the logic I’m understanding in this video, and engine would want the same timing at any load value, given unlimited octane, which is clearly not the case even if the engine would tolerate it.
Absolutely agree..... assuming you're using multi spark type ignition and a very healthy dwell time. Flame travel across the piston can kill or cure an engine. Too short flame travel will side load a piston and do some ugly things to a cylinder. Ask any shovel head Harley engine builder.
Steve, the one thing that has changed is dynamic compression ratio, and that could be why u have to take away timing… more air and more fuel mean more combustion pressures and or dynamic compression ratios between na and boosted
Steve, I'd love to see you get your hands on the mid 2000's LNF Ecotec engine. It's the weirdest (conventional combustion) engine I've ever seen and delt with. I feel that even you would struggle to play with it.
The LNF variant is a mystery to the Family II Ecotec platform, considering how much power they make, stock or modified.
Examples:
If you port the head, looses power everywhere,
if you bore it bigger, massive power losses,
they run SUPER SUPER LEAN, (my current build is in the 13.0 afr range),
The head flow makes no sense for the power they put down,
and I don't believe they like to have a whole lot of timing either, which is what drew me to this video today.
I'm constantly trying to improve on the build, but all the "conventional" tips and tricks in the racing industry, just don't seem to work, for this particular engine.
The current answer always seems to be "Just throw more boost at it and prey"
I 100% agree. The plug will need to have a very high amp spark to compete in that high pressurised chamber.
You can get spark out under too much pressure. ( Ions under pressure. )
Love it!!!
Thank you.
I use a vacuum gauge to determine initial ignition timing .
Race engine and race gas is a different animal altogether however a vacuum gauge is a great way to determine best initial ignition timing then you read your spark plugs.
Advance timing to max vacuum and back off 1 " of vacuum per thousand feet above sea level for a base .
Steve says 28 ° 10:1 compression BBC.
With what fuel octane rating?
Two points
While degrees of crankshaft rotation is easy to measure, piston distance to TDC is what we really care about. This would mean that a change from 30 to 31 has more effect due to longer piston travel than from 20 to 21 correct?
How about timing on dual spark plug engines? Fire both at same time / stagger?
Mercedes V6 / V8 , Gen 3 Hemi ( plugs about 2 inches apart )
Porsche air cooled ( and purpose built light aircraft ) one plug at top , one at bottom
Ford Ranger 2.5 4 cylinder ( like the 2.3 overhead car Pinto ) with one plugs on each side of the head.
on my old dirt track engines the most we could run was 355 ci and 194 /150 valves. and a 488 lift cam and i ran about 36 deg timing with the 041 chevy heads. and my car ran great then i cracked a head and went to the old 882 chevy head and my timing dropped to 24 deg. to make it run good. but also everything i refreshed my engine the head gasket was ready to blow. i was never so glad to find some 993 chevy heads i don't know anything about chevy heads other than 882 sucked and 041 had the 13/16th plugs and you couldn't find them. and the 993 heads put me back on top.
WOW! You learn something new every day. I remember years ago reading a performance book 32 total is all you need. In the old manuals you would see it as high as 38 total. I never knew that some engines like lower like 22 total. In coming air temps is major, even with carbs. Many guys don't even think about it.
Now you need to market a combustion chambers matter shirts
Talk about a trigger Mr. Morris-I flashback to my teen years were my teacher would pose a question and waiting for me to answer😯😂The theory with a soft chamber is to slow down the mixture motion in the chamber prior to combustion, vs a tight quench (ignoring any pre ignition issues) high turbulence/swirl motion? Thank you for sharing!!!!
I usually just set it at a range that it will run at then go with ear and operation. Fuels are always different in my area so I go with how the vehicle performs for what I want it to do.
Good video, my experience with n/a small block Chevy engines generally want 32 to 36 degrees. Of course there a many deviations that can change what the engine wants.
Man I love this channel! Thanks Professor Steve!
My answer is most of us are running 91 or 93 Octane gas, which has limited detonation tolerance. If you run 14.6 PSI of boost you are adding 1 atmosphere to the cylinder and you are doubling your compression ratio. So on a 9.5:1 NA engine, you are now running 19:1 compression. This is why timing has to be taken out of the engine.
bingo. 91 and 93 octane has inconsistent octane as well.
Detonation is usually from poor in cylinder mixture, i.e lack of homogeneity in the chamber. Boosting increases turbulent motion in the chamber, and is a major contributor to improving mixing. You spark less for 2 reasons. 1) with more air and fuel in the cylinder, temperature at peak pressure (ideal gas law) and higher temps increase burn rate.
2) more timing is not necessarily better, it's an indicator of slower flame speed. A better more uniform mixture improves burn rate. A better indicator of combustion performance is CA50. This is a common metric in normal boosted (production) engines, but may not be as useful in super duper high cylinder pressure race engines.
Boost affects the dynamic compression ratio. So, either the timing requirement would change or the combustion chamber volume would need to be resized.
Brother the knowledge you just gave makes others not doing it obsolete.
Cylinder pressure increases though correct which would be the same as compression
I can't help but keep thinking about a diesel with the piston dish to keep the combustion centralized.
I love this type of content. I have always wondered about timing. Thank you for taking the time to teach us
Thanks for teaching us again.
Thanks for the video, very informative. I’ve got a gen 3 hemi that I run 20 lbs of boost on so this was helpful
All about achieving that leverage point/cylinder pressure peak of about 15 degrees ATDC. Too much before towards TDC=bent broken parts, too much after=inefficient power transfer to the leverage of the pump. As you said here, Nitrous is a different animal with the Oxygen availability being almost instant and very abundant in it's liquid state.
He’s right about timing initial timing until you hit a really high cylinder pressure or beyond the fuel capacity. I use the same Timing from 15 psi up to a 30 psi on many engines. You can argue all you want but if the fuel is good you’ve good until you hit ridiculous airspeeds from too small port causing mixing issues and or excessive cylinders pressures.
Thank you, Steve, for this video. Its great to have you talk about this subject. I have a basic understanding of ignition timing, and this made a lot of sense. I know you focused on getting to MBT, but I'd love a more in depth video on ignition curves through the rpm range at some point. Since you build drag and drive engines, I'd be interested to learn more. Thanks for all the great information!
This is a fantastic and educational video. Thank you for taking the time to make this video.
Best part “detonation is that how you spell it? Sure” 😂😂
I agree with your timing numbers wholeheartedly as far as I'm concerned very accurate and probably pretty safe buy at least a few numbers
How about timing for mopar LA AND MAGNUM 5.2 and 5.9 ???
the one thing that does change is density(more air, more fuel, same space = higher density). I don't know the physics of how much/little that changes the speed of the flame front/combustion at all, but if anything would cause a difference, that would be it.
Why is cylinder pressure not a consideration ? More fuel and air = more pressure
I like the technical videos Steve! Knowledge is king
First question answer: charge density. The molecules are closer in proximity so they will actually burn fast. You have to change timing to keep pre-ignition or detonation from happening (multiple flames fronts interfering). Also can cause combustion to become more like an explosion. So if you are not mechanically or knock limited you "could increase timing" but I don't know of many cases of this even the best of fuels and most optimized engines this is uncommon unless we are talking f1 tech here. So this is why it's more or less considered theory. There are lots if limiting variables like having a perfect homogeneous mixture of are and fuel is next to impossible and so on.
Thanks for sharing your view and experience on timing. I also like hearing Brent @PFI talk about his way with timing in Hondas. He uses timing to limit lower rpm torque on stock Honda crankshafts. I guess it’s more exact and easier than playing with boost down at lower rpms. I could be wrong. I might get roasted in comments.
Steve, you would have an absolute field day with some proper combustion analysis system/crank angle based data acq! It is wild.
6:55 Not "nothing". If you put double the amount of mixture in in the same time frame You should have more turbulence than before leaving aside everything else. An increase in turbulence should require less timing.