WHAT IS THE BEST COMPRESSION FOR BOOST? (8.5:1 VS 10:1 540 BBC STROKER TEST)
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- Опубліковано 10 сер 2021
- HOW MUCH POWER DO WE GAIN WITH HIGHER COMPRESSION? WE HAVE ALL BEEN TOLD THAT WE NEED LOW COMPRESSION WHEN BUILDING POWER ADDER (SUPERCHARGED, NITROUS AND TURBOCHARGED) MOTORS, BUT IS THAT STILL TRUE? IF YOU LOOK AT THE VARIOUS PRODUCTION TURBO AND SUPERCHARGED MOTORS, ALL OF THEM HAVE LOW COMPRESSION, BUT WHAT HAPPENS IF WE RUN HIGH COMPRESSION WITH BOOST? CHECK OUT THIS VIDEO COMPARING A PAIR OF 540 BBC STROKERS (8.5:1 AND 10.0:1) TO SEE HOW THEY DIFFER IN POWER. GOOD STUFF!
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I thought we were going see what the blower on the 10 to 1 motor did.
Yeah wtf lol
lol i was thinking the same thing! i rewound and watched back to see if i missed the numbers somewhere lol
Ditto. I was expecting to see what power it made in the 4-6# boost range... maybe one more pull at 8-9.
Rich prob didn't do it bc he knew what was prob going to happen! ;)
@@nabilguffey3201 No way he could have run the same blower speed on the higher compression motor with the same fuel. Less boost, less power.
I don't think this comparison is terribly helpful. The question I think we're all wanting answered is: if you're OCTANE LIMITED, say building a pump gas motor, which is a better approach, low-compression/high-boost, or higher-compression/low-boost.
Even if your octane limited you can always pull timing out to keep.it happy with the higher compression.
@@chadcollyer4957 yeah, but will you pull so much, you would have made more power from the low compression engine?
@@chadcollyer4957 to a point.
all of you are wanting?
get a 9:5.1 compression, high compression will develop knock eventually if a mistake is made, then you need a rebuild, plus you'll always need high octane gas, no exceptions.. High compression is like having a gf who is only happy when you kiss her ass, the day you don't, she dumps you n you're stuck with pink eye..lol
Richard I think you're videos are fantastic my only issue is you rarely use pump fuel i understand the limitations and possible engine damage when testing but I think its what a large percentage of viewers run. I would love to see more of it. The power you get on hi octane would be unobtainable for a lot of us.
The issue we had back in the day with high static CR's was timing, the quality of the head gaskets and the carb technology. Today, you can pull timing out of the motor exactly where you want it, tunable closed loop MPI with knock sensors and MLS head gaskets, so yes, I feel you can run higher static ratio's and pick up torque down in the lower RPM band, especially with turbo's.
Ethanol baby!
and aluminum heads help reduce the tendency to detonate as well as offer better shaped combustion chambers.
@@albertgaspar627 Yeah, I'm doing a Saturn 1.9 LDOHC build on mine with 10 to1 comp with low boost 8-10 PSI and an E85 blend. Building the most velocity instead of volume, JE forged pistons, ARP main and head studs, knife edged 3rd gen crank and lower tie plate, port and polished head, mild intake deshrouding, mild bowl blending, dual intake cams, ported polished intake manifold, bigger TBI and low boost E85 like I mentioned.I figure it'll be better if the machine shop builds it well. The car is light with the polymer panels, carbon fiber hood from Seibon, and the 15X7 Einkei RPF1's that are 9.8LBS each, and Mfactory limited slip differential. Should be a fun ride to surprise some people as well with my little baby car, ha ha...lol My engine is light too at 220 LBS, half the weight almost of a normal 4 banger from the lost foam casting..lol
@@junechris sounds like a nice design, check out David Vizard's channel too. he does dyno work with headers, you might find some tech there to help the velocity you want by clearing out the combustion chamber as fast as you want to fill it in. As you know, the joy of DOHC is you can play around with overlap and lobe separation by moving the individual cams around instead of having to buy a new re-grind.
I have a naturally aspired GM EcoTec 2.2 litre in the "pile" of project cars, would love to play with its potential since GM already went ahead and had a supercharged version (like the Saturn Ion). As you know, in a light car it can be a sweet piece when done right.
@@albertgaspar627 Yeah, I've heard about the cam options you mentioned about. Right before u messaged me, I was happy to find Ross makes forged pistons right in their catalog for the Saturns. And one of the other guys I spoke to on here was a 30+ year machinist that seems quite fond of the Ross ones in regard to the ring gap recommendations being more or less right on the money so i'm gonna relay that to my friend doing the build for me tomorrow.
The only reason to run lower compression in my mind is if you don't have access to quality high octane fuels. Otherwise, more compression, the better, assuming you can time it/tune it correctly
Even in that situation you can always pull timing out to keep it happy with high compression.
This is exactly my issue
@@chadcollyer4957 until you run out of timing Dx what I'm dealing with.
Higher SC and TC MAP.
Even then that's what AEM's meth kits are for. $700 for their biggest kit and $2 a bottle for winter washer fluid.
If you have race gas, high compression and high boost is best. Lol
Even on pump gas I think the higher compression would be better. Off boost performance would be better and if you are tuning for maximum power for a given fuel the maximum output should be the same because the cylinder pressure where knock occurs would be the same.
@@christianmeeks4430 pump gas and high compression means your ignition system and timing needs to be dead on lol
@@rcairforceone the difference is that "dead on" is much more attainable today than it was in 1990, let alone 1980.
High compression vs low compression. High compression runs better out of boost.. but runs the same in boost but with a smaller tuning window.
Also, having Richard Holdener making motor sounds when your motor is under load is worth a few more octane points
Man, this is a timely video. I am looking at these exact motors and wondering the same things discussed here. Thanks Richard for the comparisons.
Before even watching it I know the high compression one will make more power with boost because boost just enhances the NA curve of that engine. The better NA the better with boost.
The noise you made for each engine at the beginning made my day! Well done sir! 👏
You said it, the roots application is probably best off with the 8.5:1 long block. By my rough calculation, the 11 psi boost would have given you well over 1100 hp if not for the power needed to spin the blower, about 195 hp if the formula held true. That’s basically lots of heat added to the intake charge. If I had a couple GT-45s making that same 11 psi, I’d want the 10:1 or even more, EFI, and E85, too! That 540 would be a beast either way, I think.
I like stock compression + ring gap + boost because well, pistons are expensive and junkyard engines are cheap!
Imo for street usage lower CR sounds nice to run regular pump gas. Go on the track and pump up the boost with better gas.
Finally some quality content coming across my notifications…
For running on pump gas, I think it makes a difference how much boost you can run without running into detonation. The dynamic compression ratio based on cam specs is a big factor, too. Even though the static compression may be 10:1, the dynamic compression may be a lot lower with a big cam, so lots of variables there, tough to do a true apples to apples. Good stuff to talk about, though!
If one wants to run high rpm and 30-40 psi boost, then 9:1 would be as low as I would ever go... Tuning becomes critical with higher compression, but will always make more power, and efficiency on daily drivers... The way the compression is made is also important, like having a dome piston with it down in the hole 60 thou would be asking for detonation and/or pre-ignition. Proper design combustion chamber is imperative for the proper platform.
Great Information Rich
To answer the CR question just look at diesel tractor pulling. They use lower CR pistons so that more boost can be put into the engine. So yes, depending on the extra air to be added, lower static compression can be a benefit.
For anyone with little to no experience with tuning any boosted applications I would always lean towards the lower compression but anyone with experience that can ballpark a base tune pretty close to where it needs to be for the engine to be happy then the only question would be do you have a trans or rear end that can handle it with out grenading one or the other if not both
Higher compression with boost increases the likelihood of detonation. Lower compression gives more wiggle room to withstand that issue. If the tuning is spot on and the fuel has really high octane (91+), then the higher compression will not cause an issue. Lower compression is often recommended for boosted engines because it just allows for more error.
I think this is an excellent question. Most people are going to be limited by the fuel octane availability, and I also dont see anyone else providing any data on this subject.
Richard, you tease! Lil, thanks for the content
the test that needed to be done would be to boost the both motors to the same cylinder pressure at TDC, the lower compression motor motor is in theory larger then. All compression done in the motor creates heat in the charge, compression done outside the motor with boost and intercoolers, results in more mass flow rate.
Thats why I watched the video. I thought he tested both combinations. I am kind of pissed he didn't.
I totally agree with you, they both have their place. You just have to build what it is you are building for. In a W.A. Street Machine, I'd run low CR for the "just in case" factor.
W.A?
Pump 91/93= lower compression. No lower than 9 to 1 tho.
E85= all of it.
i'd take the 8.5 for longevity alone, but i'm not a competitor.
and considering the price per gallon of 93 octane, that 540's gonna gulp down the gallons. buy the cheaper gas, still have 600 + hp
The book I recall reading - mid-late seventies era; I think the title was something like “super power” - spoke of 20% *underdrive* and 8 to 1 compression when running a Roots blower. (For routine-level street use, I think.)
I'm REALLY GLAD to see this comparison. specifically the low compression comparison to hi compression. ive ben considering purchasing bbc pistons... sound i go for h581cp100@$390/set? (my compression limit with 10.3-1. ... OR save some $$ to select the h426cp100 set @$250. with lower comp at 8.9-1 ?? ill be useing pump gas...preferably 87. so i think you just helped me figure it out... thx for the video. i was wondering about this VERY THING
The shop that built the 4.3L for my Typhoon bumped up the compression to 8.7:1 but they also built it to handle 30psi.
All my best performing boosted 4 cylinders are 10.1 or more compression with good flowing cylinder heads ! E85 is key to keeping them alive
Good video
I was hoping to see the same blower put on the higher cr motor but driven slower to make the same power as the highly boosted low cr motor and than figure out witch way was better.
This is only theoretical, but I think more compression and less boost would heat the incoming air less, while creating equal cylinder pressure. Thus MAYBE the air would denser. Sure, there's intercoolers, but that's more expense.
What I want to see is a 13-1 compression with low boost
I'm just here for the awesome engine sounds
As always great content...
Haven’t seen you in a while, Hope all is well..
Really bummed you didn’t run the Higher compression motor with Boost?
I think everyone was expecting that.
Just Say’n
As always great videos.
Again, truly hope all is well with the family, etc...
the 10:1 wasn't mine-but we can guess what happens by now...right?
Not sure what Happens Now?
I do know quite a few mustangs running stock compression with Boost as well as LT1’s
My friend has a side mount whipple supercharger on his 03 v6 mustang it has a air to air intercooler hes making 605 / 645 at the wheels on a forged 4.3 v6
From my experiences with low compression motors, they do an excellent job in colder places. Ohio, Minnesota etc. Low compression motors are amazing for torque gains. Gives you a different feeling when you put your foot on the pedal.
I've seen the exact opposite. The high CR starts easier and makes more Tq overall.
Great video
I have recently taken a low boost paxton motor that was 8:5:1 to 11:1 in a corvette. I left 100hp on table for years by not running higher compression. Motor runs better, idles better, all drivability better. BUT it is compensated on boost by methanol injection … however it was at 8:5:1 also. So was winning combo foe me
Lower compression would be good in a drag week application to run pump gas on the street. I like E85 but no telling what availability would be on rou te. I would probably go 9:1-9.5:1. As you've proven Richie.....more efficient n/a the better the power will be boosted.
yeah i agree too, going too high in compression will eventually develop "knock" no matter what on a boosted application, n that's the reason many ppl end up selling their "builds"..lol i rather have a nice 9:5.1 compression as i have in my 2v n run pump gas or e85 n be good on boost..
When you factor in limited octane, it comes down to the detonation limit of the compressed charge. 8.5 to 1 at 14lb of boost will have 250psi compressed where 10 to 1 will have that same compression pressure at 10lb of boost. the difference is the lower compression engine will have a larger combustion chamber with a larger charge at the same pressure. obviously at the same boost the more efficient higher compression ratio will make more power. But that only works with fuel that will tolerate it. Run the same engine on pump gas boosted to the detonation limit and I think the lower compression combo will come out on top.
First, I enjoy your videos and like your lowest common denominator style delivery free of arrogance, it's refeshing. I've subscribed. I'd like to make a suggestion. To truly understand the difference between the two combinations presented, you also should provide the basic tuning settings on each combo when optimized. This leaves me wondering if your NA test and boosted test on your low compression engine was at the same timing and fueling settings. Without that information, power could be anywhere in the range presented...I can easily tune down my 7.88:1 compression centrifugally blown BBF with nothing but spark and lose 100hp. What were the settings? Did you optimize each to the edge of detonation then back it off a few degrees? What is your process?
To respond to you about which I think is better, I need to also know what you mean by "better". If "better" means durable, the reason my 7.88:1 combo is what it is is because you CAN NOT detonate it at the limit of the supercharger, even if you have a brain fart and dial in 40deg total advance. It will just stop making power and nose over, it won't ping. I make all my power with flow and leave a ton on the table for safety margin. I don't need more than 1000hp, and I don't care about efficiency.
na and boosted timing values the same? no
Through my years I've found you will make more power on a higher compression engine. A lower compression engine really shines at very high boost 35psi + and large spark advance. You will detonate a higher compression engine allot easier. I would rather have low compression and high boost then higher compression and low boost.
I run 10:1 compression on my 429SBC with 26 pounds of boost from an F2 Procharger on E85. Runs great in my street car.
Very similar to combo I have right now working on an na tune with a terminator 4500 to break it in. Winter comes turbo, 10.3-1
E85 is hard to find. What would the minimum octane you would run on boosted applications that high of compression
With my 427 LS with an F1-A, I built it to 9.65:1 as there is not 1 E85 pump in my state. My combination with the blower maxed out makes 12lbs of boost, if I would have known this in advance I probably would have built it to 10.65:1.
I think lowering compression for boost is an old thing, fuel back in the day was trash, so they lower the compression to avoid nock or something like that, but now just getting a better fuel is probably enough that's what I think.
Still very relevant today, in a hot environment daily driving a boosted high compression engine is asking for a disaster despite high octane fuel
@@Airman.. that's why you don't rock an eBay intercooler, and in the video he is using carbs on top and that doesn't really help with knock.
@@donkeykiller69 ECS intercooler with 100% methanol injection 95 Octane, CR 10.6 @106F summer day engine under medium load rattles like a rattle snake
For DD bring the CR down, for track\NOS○race fuel take the CR to the moon it doesn't matters as boost/cr dynamic pressures will exceed static pressures
If your hard parts can handle the stress the higher compression version will always make more power.
Agreed with proper fuel
The advantage of high compression with boost is the reduced effects of boost lag. The advantage of lower compression is you can run higher boost levels before grenading the engine. I think a low compression engine with the same components will live longer with high boost pressures.
Build a grand national 3.8! I made 730rwhp with a 76mm precision and hogged out iron heads. Then with a set of champion aluminum heads and a bump up to 4.1L, I made 1,032 rwhp with a/c and went 8.89@164 back in 2000. But we Buick people need some love
What fuel were You running?
C16 on high boost, 38-41psi and sunoco 98 for street driving. I was also working for VP fuels at the time
38-41 psi sounds crazy. What psi for "street driving"?
That is a nice engine. I like it.
The 8 5 to 1 would last a lot longer due to the lower compression ratio,and you could run it a tad fat on E85 and drop the oil a 10K or 5K,be an easy one to love
No reason to run compression that low with e85. I’m using 10.6 to 1 static with 20 psi from a Procharger on e85. Been 4 years without issue.
Low CR is dinosaur inefficiency. Engine control systems and engine design in 2022 do not require low CR for boost.
The size of the booster can determine lower compression but cam crutching is the key.
This is a realy interesting test! I have never seen a similar one before, but always wanted to! Thanks for delivering 👍
I went with middle of the road 9.5 to 1 with my turbo coyote motor for longevity and forgiveness. I know the stock compression ratio is higher and guys boost them but they're not out there every weekend at 7500rpm either.
I would never consider 8.5:1 with that cam size and a limit of 11 psi. Flat torque curves are what win races and generate efficiency on the streets, not peak numbers. I once watched a video of BMW m7, 770hp 4.4 v8 outrun a late model Dodge Challenger at 1100 hp w/ blower from a 60 mph drag. 1100 hp is nothing to cough at, but the Bimmer just ate his lunch.
Personally, I am about efficiency, and it is more about building what works than cool dyno digits. That's how I got an 11,000lb dually 5.9 Cummins to outrun an Audi A6, on a 62mm turbo, w/o melting down...
And with 300k mi on the clock...
The man to singlehandedly end all forums arguments
Only to the 90%' ers. Most of these test are rather superficial. The main points of lower compression is to run higher boost pressures without exceding about 930C exhaust temperatur and without excessive peak cylinderpressure.
Pr. lb/ft and pr. hp lower compression ratio engines has lower peak cylinderpressure but higher BMEP.
An honest test would be to put twin turbos on these engines, use pump fuel and boost and tune them to the 930C limit.
That would be an eye opner to lots of folks. Nitrous is fine with high compression ratio.
@@finnroen2334 Sorry I'm too free to speak metric.
@@chipcurrey653 No problem. 930 degrees C is 1706 F witch is depressingly easily exceded when boosting on pump fuel. We struggle with this all the time and had to develop someting we call "The theoretical NA hp" to keep an eye on things. This engine produces 649 hp Na, 1.20 hp / CID. When boosted to 11 psi it produces 939 hp and that is only 534 hp from "the theoretical NA engine", not even 1.0 hp/CID = junk.
If the engine is not in a race only (or boat) application where a certain amount of practicality goes out the window, higher compression is the way to go, you'll make more power for a given amount of fuel, so the fuel system can be smaller and you don't have to stop at the pump as often. You will also make more power off boost which will make the thing easier/nicer to drive in a few different ways; it can compensate (a bit) for a wilder cam at low engine speeds making any low speed driving much nicer, it also means you might be able to shave a few 100 rpm off your stall on your torque converter.
Modern ECUs can do closed loop boost control, knock retard, IAT retard, exhaust backpressure retard and table blending based on ethanol content; people are talking about driving on pump gas and lower comp being better, but really all you would need to do is either change map with slightly lower boost and less timing, or do nothing and let the ecu pull timing if your ECU is tuned correctly.
Not exactly. Knock sensors are not exactly scientific level sensors and some setups can suffer catastrophic damage almost instantly if they encounter detonation. It takes a dyno and good tuner to find that line in the sand. You add tiny amounts of timing until the motor no longer produces increased output. Then you back it off, to each tuners opinion, on what they feel is adequate safety margin...
Compression is great for power and if you have detonation issues add a camshaft with overlap to help I like compression with less boost then lower compression high boost
For the street I would rather run 10:1 with less timing and boost than 8 5:1 with more timing/boost.
I'm just gonna run NITRO dude... you're statement means nothing. It has no qualifiers.
A missing element in your test: the cylinders exchange the same vol of air NA. Not so on boost. As a result, can you run more boost on the PA motor while achieving the SAME dynamic compression or peak cylinder pressures? It stands to reason you can. The net effect of using boost may be the larger compression volume of the PA motor would effectively act like a larger displacement and has the potential to make more power at the same peak cylinder pressures.
Higher static compression just requires less boost for the same power. This is why my LSA motor is 11:1 static. I don't have to spin the blower above its max efficiency to make the number I need...
To me I like higher compression and lower boost levels. 10:1 with about 4 to 8 lbs of boost. With an intercooler. I think a street engine would do fine with 93 octane at this combo. Of course if needed timing can be pulled out or octane booster can be used or e85 for sure would make it very streetable. I like twin turbo best then the procharger is good but I wouldn't run a roots blower for the street unless it's for a street rod to look cool and then I would cut back the boost of it lower the compression and it would be more show than go.
The higher the compression the lower the Boost. I want to try 12.5:1 at 4-8lb of boost in a LS3 or K24/20 head. Twin Garrett 3776's or single Garrett 3776 for the K, electronic wastegate. Start at 1lb. and work up to the max. I'd stop at 8lb. even if it took it like a champ. 4 boost settings, 2lb. 4lb. 6lb and 8lb.
For the street on pump gas low compression for the win. Easier to control detonation.
Why though would you recommend low compression for boat motors at wide open throttle say on E85? Is it the extra heat from the higher compression motor that causes problems????
I'm running 11.3:1 compression
E85 and 5 lbs of boost
With the cam I'm using
My effected compression is 15.47:1
I've done a few things to help
Heat coated tops and dry lube on skirts Total seal gappless second ring gapped at .028 4.31 bore 4.25 stroke 496ci AFR heads with mirror polished combustion chambers.
I don't have any problems
This was so interesting to me. The whole compression thing vs boost has always been the issue going back (obviously) decades to the gale banks twin turbo days. Overall, I think you've proved to me to build a stout na engine then boost it. However, you pointed out that the tuning window is "larger" w lower compression. Hhmmmm
THEY ALL WORK
@@richardholdener1727 I made a comment above regarding my blower engine . Hp estimate please sir..Thanks in advance buddy 👍😉
Hey Richard, didn’t Freiburger and Brule do a swap of solid roller lifters onto a hydraulic roller cam and had a power increase therefore the 540 solid cam likely had the edge?
you have you conclusion backward
I think the question is what the goal is. Absolute max power? Low CR and lots of boost wins. More return on boost than CR. Driveability with a flatter curve without spikey boost curves? Higher CR and slightly less PSI from the whistle bits.
Back in the day it was 3 things, 1 fuel. Didn't have e85 at the pump, 2 didnt have computer software that could control things properly. 3 we didn't have you Richard.
well, 2 out of 3
I like the lower compression because it is more forgiving. More power is always better, until you break something because it's temperamental.
I believe we have reached the next plateau in internal combustion engines. Now the parts are stronger can we get the cooling and lubrication systems to meet these higher demands???
I’ve ran 9.25 :1 on 6 to 8 psi in a marine application , the problem is the load that exist in a boat to put that into perspective have you seen a brake pedal in a boat ? But we also have the biggest radiator there is that being lake water , so cool engine temps say 140 to 160 combined with aluminum heads , coated pistons , allows us to get away with a lil higher compression, but 10:1 in a marine app I mean I’d doit but wouldn’t recommend it to a customer
In a boat with crappy gas docs - no, in boat with severe load all the time - no, with out fresh water cooling - would help things , another aluminum head justification - IE 1 point of compression as a gift - I went with a roots from mooneyham for the sound and nostalgia and 8.8 - 1 with ICON pistons
You CAN run a high boost on a high compression engine, IF!!! you have an inter-cooler. The problem with a super charger on a high compression engine, is temperature rise during compression. Too much compression could mean reaching temperatures high enough, for fuel to "auto-ignite", much like a diesel engine. The fuel may not wait for the spark. That pre ignition will destroy the engine. If you're going to boost, without inter-cooling, lower compression is a MUST! No matter what, I do recommend a high octane fuel on a boosted engine, because of its higher ignition temperature.
You can but, what's going to produce more power?
I originally built my 540 now 555 with (8.5) but when measured after it was really 8.2 so that I could run 13-14 lbs boost on 93 octane with a carb and water/meth injection non intercooled , but now I have a dedicated second tank with 114 for the track and pound 20 lbs down its throat with a intercooler into it so I say if you have to run pump gas then low compression but in my case I would do 9.5 . Also Steve Morris still builds some boosted BBC’s with 8.5 so what does that tell you ?
It tells you that Power Tour setups need to be compatible with pump gas...LMFAO
Good tune good gas good to go
I thought they were going to put the blower on the 10:1 motor lol
What fuel will it be running is the biggest factor in my opinion.
If your concerned about drivability low compression higher boost on premium gas or e85. if drivability isn't a concerned and you're more all-out drag racing or weekend warrior you want higher compression racing fuel like e85 c16 C32 or methanol to control predetonation with high boost. You either have low compression 14 lb of boost premium fuel for E85 and get 1000 horsepower or high compression racing fuel or methanol had 7 pounds of boost and get 1000 horsepower. my opinion. P.s boost and hp numbers is just an example
An actual true comparison is to have two Motors that are built the same with every part the same the only difference would be is ring Gap and compression ratio. but video has good information.
I've always been told and it makes sense that the higher the boost the lower the compression to keep detonation in check with gasoline specifically. The comp eliminator guys with the blowers and gas I know run they very much on the edge for the most power, but I have no idea on what kinda compression they run. I know with alcohol based fuels with 110+ octane you can squeeze it a lot more, like start with 12.5 and feed em boost I know tad engines and high boost "street" cars on methanol can run some serious compression in them. As for what that actual number is.. I have no idea.. but I'd think you could get to pretty rediculas heights.
There are guys who are running 12:1 static, but when the boost is on it's effectively 20:1 thanks to the boost.
Hey Richard I got a L77 6.0ltr & I'll be doing a heads & cam package with a stage 3 ls3 intake "standard intake port" with an expected output of 500whp on ron98, it's staying N/A with future goal of going Boost. I've got the option of decking the heads to increase compression. How would this effect (torque, power & fuel consumption)?
I've did searches but can't find direct answers, just answers that beat around the bush.
compression adds power through the entire rev range-let me know if it makes 500 whp
I predict on turbo applications turbo lag down low will benefit from higher static compression. And high horsepower applications lower compression will do better.
How much power have you made on a big block 2 bolt main?
Yes on low compression for a blower motor on pump gas.
I don’t play with old v8 stuff. But on my 4g63 I run 10:1 and any e85 only car I build the motors 10:1. Motor has seen 47psi from a 67mm turbo and 788whp. E85 is amazing stuff. Performance is on par with c16.
What fuel octane are you using? It is my understanding that if you have enough octane, you can have high compression and high boost.
Would less ring gap be required if you used boosted the low compression option vs the high compression boosted version? Could you get away with not using forged components using the low vs high? Example, could you run 12-18 pounds of boost on a 5.3LS with 8.3:1 on stock internals and stock ring gap..... properly intercooled.
you can run high comp and boost on stock internals with ring gap with enough octane
Lower cr means more boost which is usually enough to cover the gap between a higher compression motor and then some plus your have the security of a little more wiggle room with tuning just seems like a better bet no matter how you slice it
I'm building an LS 403" stroker, 8.5 c/r. This will be a 66mm twin turbo. Why should this be a question anymore when it's been proven fact. You are better off low compression with high boots.
10.7:1 on my LS3 at 14 PSI, 20 degrees of timing on E85. It rips pretty good in a Corvette.
what will that do on pump fuel? I dont have access to e85, just water injection. My current LS3 runs 10psi was thinking of making a 10.0:1 CR and doing 15psi on pump fuel?
@Nathan Devine You can still run 15 PSI on pump fuel, I do as well, but you'll have to keep the ignition timing much lower. That isn't great for exhaust gas temps, though. So far, I've been alright. On 93 octane before torque peak (4400-4800 rpm or so), I'm around 15 degrees of timing. At torque peak (5200-ish), I have to drop all the way to 10.5 degrees of advance to keep out of knock. After 5200 rpm, I ramp up to 16 degrees little by little until 6500-6700 rpm. Probably need even colder spark plugs, too. On E85, I'm over 20 degrees, dropping to 20 at torque peak, then back up a little after. It makes a huge difference in power.
@@speedycpu Thanks for the reply i didnt expect one so soon. I have EGT sensors in all cylinders and water injection to keep cylinders cool hopefuly.
forget E85 for the moment i only have access to 99ron (UK) so thats probs your 93/94?. im at 10.6 maybe on my LS3 with 10psi and it does 650 at the hubs. I'm building a fully forged 6.0 steel block because i want to do more 20/30min races, it has a custom ECU so i can put in all the safety's i ever need.
i want to get about 800 at the hubs but i dont know whether to say stick with 10.5 CR or even 11 and go for say 12/13psi on pump or drop to 10.0 CR and go with 15psi on my maggie 2300 heartbeat thats in my E39 M5
my brain is telling me go with slightly higher CR and lower boost which means less belt issues also and in theory less air heat.
whats the most youve run on pump fuel with say meth/water injection or even just pump
@Nathan Devine Personally, I'd go with the higher CR and try the highest boost possible, then ramp timing up until you either hit EGT or detonation limits. You can also run an octane booster, like Boostane, if it is available. The most I've pushed my Procharger and LS3 was to 14 psi, maybe 15 in perfect weather. If you are running a twin screw, you'll likely have a higher chance for detonation at lower rpms, but water/meth can definitely help a lot there. Are you tuning with HP Tuners at the moment? That's what I've been using, but a custom ECU would be awesome. I eventually want to go forged 454 from TexasSpeed and twin turbos, but that will be a while. I need to upgrade my 6L80E because the power it is making now is causing it to slip.
I'd say see how it goes with the higher compression. Just keep an eye on detonation and EGT. If that's all good, have fun. Later on, you can run higher octane and get even more out of it. I don't think under 11 CR is all that bad. Guys run a lot of boost with Gen 3 Coyote engines, and they're amazing.
@@speedycpu i have a maxxeccu pro with all the sensors
So you dont think that 10.5 with say 13psi on a heartbeat 2300 with fully forged internals is a bad idea? Iowering CR and making it up with more boost is just not my ideal scenario as more boost, more belt slip and less response down the RPM range essentially
i could go with 10 and 15psi but im concerned about controlling belt slip with a 2.85 inc pulley
Rich you're awesome
what do you think max comp ratio would be before you start getting self ignition?
Depends on the fuel and combustion chamber design
I think the right cam probably get you close to giving you The Best of Both Worlds a lot of things that factor into this!" I would have ran 10:1 in the street motor&sent the customer on his way boost is all about cramming as much air fuel mixture into into the cylinder for the biggest pop 8.5:1 on the same gas
I was told to go with lower compression, and I was told a supercharger raises static compression. Moroever, for a lot of boost. I was told to consider alcohol, but I rather run pump gas 91 octane, so I was told not to run too much boost for a supercharger roots style application. I am curious what you think.
supercharger has no effect on static compression. Pump gas and low compression are a good match with a roots blower
Higher CR always makes more power but you're limited by the Detonation resistance of Fuel used. Boost increases the need for higher detonation resistance.
High CR with boost is a very powerful combination, especially turbo as it spools much faster than a low CR motor
That's what meth is for.
Richard. Looking at their 408LS, is the 10.8 compression too high for boost?
NO
You can run high compression and power adders you just need to run a better fuel to stop pre detonation and I would think the engine isn’t gonna last as long running higher compression and power adders . But if you can tear it down at home and refresh the engine after a season of racing and run something like alcohol or e85 or something along those lines and just knowing what you’re doing helps alot
Did a comparison video with no comparison on boost!
I'd imagine blue print puts a high silicone alloy forged piston in them not a full race forged piston because of cost.
I would run high compression+boost unless it was gonna be ran with E85 or some other race gas. Especially if you live in a state that only offers 91 octane premium gas.
I been wrestling with the question of what cr to use on my 4v modular with an m122 eaton and an engine builder told me no more than 9:1 with 91 octane. (Best fuel I can get) I worry that it will be kind of a dog at part throttle but without high octane fuel i don’t think I have a choice.
9:1 is more than it has stock so it will be better than stock.
I'm here researching combinations for a 400 sbc build. Street & strip, going in a 62 chevy C10. Motor's out of a 1972 Cheyenne. I believe I'm going with Dart heads, with as big of valves that will fit, 206?. I love blowers, but think turbo will be my power adder, for the boost control. I'm having the bottom fully built. Stroker. I'd love to be 1100 HP, without lifting the heads, or hurting the block. Any guidance would be appreciated.
that is a lot of power for a stock 400 block
@@richardholdener1727 What hp number would you feel comfortable with. I've decided not to put it in the truck, because of the curb weight, and high drag coefficient. I'll save the truck for something bigger. I have a lightweight 1983Toyota Corolla wagon, I'm thinking of putting it in, so the power to weight ratio will be much better, and the drag coefficient is .34