Busting the exhaust backpressure myth | Banks Entry Level
Вставка
- Опубліковано 2 тра 2024
- "A little backpressure is good, right?" In this latest episode of Banks Entry Level, we explore why exhaust backpressure is always bad and where the "some backpressure is good" myth originated. This one is sure to cause barstool banter.
Protected by @AMSOILinc the leader in synthetics
Featured products:
1991-1999 Jeep Wrangler Headers
bnks.pw/3QyPzUk
2019-2024 RAM 5" Monster Exhaust
bnks.pw/4aewNbG
____________________________
Check out all our full line of exhaust products | www.bankspower.com - Авто та транспорт
That scavenging demo with the header and sticky notes was simple and beautiful. Thanks for continuing to battle misinformation!
That particular header is the Revolver. For 4.0L Jeeps.
Yeah that was really neat to see
Backpressure is bad, but exhaust velocity is good for an N/A engine. An exhaust that is "too large" will reduce exhaust gas velocity AND back pressure. The loss of back pressure isn't the issue, but the loss in exhaust gas velocity IS a problem, because it reduces scavenging. This is only applicable to non-turbo engines.
This is very true. So many times you hear of people who put a high flow exhaust on their car, then complain of loss of low rpm torque.
It also very much applies to turbo engines. It's harder to target an appropriate runner length and diameter and the effect isn't as dramatic but you can definitely modify your VE at various RPMs both on and off boost with a properly designed turbo header. The improved VE off boost can actually help low rpm spool time as well as provide a bit more part throttle response without hindering higher flow performance (within reason).
Agreed 100 %. Just change your small cam 283 exhaust from 2 to 2-1/2, you will notice right away lost low rpm torque. Big pipe only benefits high rpm power.
I could be wrong, but if you reduce the exhaust gas velocity and there's no scavenging there should be technically more back pressure than an exhaust that has higher flow exhaust and scavenging. Since you need a pressure differential to cause the scavenging effect.
Yes and no, scavenging is caused by a negative pressure differential in the combustion chamber, backpressure goes against this as it creates a positive pressure differential. It's better to have absolutely no backpressure in any engine, even in N/A engines due to modern engines taking advantage of the benifit of scavenging, turbocharged/supercharged engines are already forced induction engines, so scavenging is a really, *really* bad idea, as the extra boost will leak out the exaust port if u tune it that way. All scavenging does is pull more air in near TDC between the exaust and intake stroke, by leaving both the exaust and intake valves open slightly at the same time. High cam profiles on drag cars take advantage of this affect all the time, but have shitty low-end rpm power due to the side-effect of the exaust gasses being pulled back in near TDC during the intake stroke. What manufacturers did to mitigate this side-effect is introduce tech like VVT (GM's variable valve timing solution) and VTEC (Honda's variable valve hight solution), which allow for smooth low-end torqe and punchier high-end power utilizing only all the benifits of scavenging. So backpressure is really only an limiting factor of your vehicle no matter if its N/A or not. And if u say "what about Nitrous Oxide emmissions, isnt that more dangerous to the environment than loose hydrocarbons?", ill just say there's already a device that mitigates that issue, it's called the EGR valve, get a bigger EGR valve if u dont want backpressure from it.
Erik is getting really good at this, almost like he as taken an acting class or two. It is awesome to see him teaching like this, and following in grandpa's footsteps.
Is Gale Erik's grandpa?
you can’t tell?
Yes
So he's not a DEI hire?
@@JohnSmith-xu7ev shit man... that had me laugh good.
Backpressure is one of those things where its presence is a negative factor but since improving other factors (exhaust velocity and pulse tuning) tend to increase it, people think its presence is what is making the improvements. The reality is backpressure needs to be minimized while maximizing the other factors. Everything is a compromise.
I like to put it this way, "backpressure is a necessary evil that should be minimized".
This is correct
I was thinking about this, I don't think there's increased back pressure on an exhaust that has great velocity compared to one that has a larger diameter and no scavenging. I think it's just the idea that people got in their head was bigger exhaust automatically equals less back pressure and smaller means more. So in their head they think there's a happy medium because too big made less. But the reason why a properly designed exhaust with great scavenging and high exhaust velocity works better than an oversized exhaust is because it reduces back pressure. Higher velocity air exhibits reduced pressure, not more, that's how scavenging works it creates a greater pressure differential. It's part of Bernoulli's equation. It's the same issue when sizing irrigation pipe. You go too small you start increasing the speed of the fluid, if the fluid starts speeding up too quickly what will happen is that it'll start causing turbulence along the sides of the wall effectively making the diameter of the pipe too small. It's the same issue when old gear heads think a high flow water pump doesn't allow coolant to "cool off" in the radiator because it's moving too fast. In reality what is happening is the volume trying to be moved at a certain speed has to deal with the fluid friction on the walls at a certain speed it create eddies along the walls, which reduces overall flow because it's effectively decreasing the size of the interior diameter of the pipe. Same thing when tuning an exhaust.
YES! Thank you! And scavenging efficiency can be optimized to fit the demands put on the engine by using a tuned header. ANNND if you want your N/A 6.2 to pull a house up hill in overdrive &&& sound good doing it, you will have more back pressure than a racing header will create. THE END
@@jasonreynolds9097 You mean you'll have less back pressure at low RPMs. It's all a game of reducing back pressure at different loads. Since there's not perfect way to reduce back pressure completely at all RPMs builders have to tune for how they want it to best perform per it's intended purpose. If the goal is to improve TQ at at 1500rpms then you'd tune the exhaust so that it flows the best at that RPM, so tubing sizing, runner lengths, etc are best matched to the power output and load characteristics of the engine, resulting at that RPM lower back pressure. But since it's a give and take system at high RPM you might not get as much power because the back pressure will increase. Unless someone has a really ingenious way of controlling exhaust gas pulses in a way that isn't a give and take you'll choose where to reduce back pressure to provide the best power and efficiency anywhere else on the power band will encounter more back pressure and reduce efficiency.
In the end it's all about how to reduce back pressure for your intended purpose, it's just we currently have no way of eliminating it from every part of the TQ curve. That's why it's silly to say "we need back pressure".
I love how concise and accurate this video is about the back pressure argument when it comes to exhaust scavenging for an NA engine.
Hands down the best video I’ve seen so far explaining this engineering concept.
you are Close the word Scavenging is the problem here still missing the point of air to fuel intermixing to attain the most possible work to power from the fuel that is consumed
there is a point where back presser is needed and at a point where it becomes too great
Completely agree devyn! Was really well done
Clay backpressure isn't needed. If you have freah fuel/air going out the exhaust then it's now about optimizing valve timing for the setup
@mattmorrison6958 if you have fresh fuel and air coming out of the exhaust you have a major issue. The fuel should be converted to carbon. Nox indicates an improper burn.
@@claycoates5056 yeah what you said here completely contradicts everything they showed in this video. back pressure of any kind is bad. scavenging is different and good but only works with a proper set of headers as shown.
That demonstration of scavenging with post it notes was the best thing way to show it ever. Love it
It was a great party trick but it wasn’t a demonstration of exhaust scavenging specifically.
When one port is open and has positive pressure (the shop blower), the others are closed. That negative pressure at the other ports is lost.
On the exhaust side of the engine, there is both flow (from the piston moving the gases out) and continued expansion of hot gases from the combustion process (the continued expansion of these gases is primarily what a turbo uses to spin its turbine).
When the exhaust port shuts, that flow stops but the expansion continues. The flow created by the piston is only minor and hence why this demonstration is properly representative of how scavenging works. only good as a party trick.
The bulk of the required exhaust flow comes from the continued expansion (positive pressure) of hot gases after they leave the engine, and which continues well after the port is shut (and for several more combustion cycles for each cylinder).
That continued expansion presents a problem for other ports when they open and try to flow out their initial gases, they are stuck trying to push against those previously burnt but still expanding gases.
Headers address this by separating the cylinders for longer, firstly avoiding the potential conflicts to other ports, and then by being “tuned” length, they can use the properties of the expanding gases (momentum etc) to help create a negative ‘pulse’, which if timed properly, can assist the piston extracting the next lot of gases.
This tuning or matching to application is also a reason why people think a little backpressure is needed. Put too big headers or exhaust onto a standard engine, you will lose the effects of headers and will not make more power. People’s minds tend to equate that to “you need less flow (backpressure)”, rather than “you should use the right exhaust for your application”.
Hi performance two stroke engines absolutely rely on a tuned exhaust to make power, they use specially designed exhaust systems, with different diameters and changes in diameters to make use of the expanding gases, and to create very strong negative ‘pulses’ back to the cylinder to not just evacuate exhaust but to also help draw in a fresh mixture (two stokes primarily draw in mixture when the piston is going up which is opposite to a conventional four stroke).
Also, residual exhaust gases in the combustion chamber can be good - Mazda are successfully using exhaust gases to reduce the effective cylinder volume in their new (and recently patented) supercharged two stroke to allow a much leaner fuel mixture without detonation, effectively achieving reliable diesel type lean burning.
Please do a video on the science of exhaust headers!
Seconded. I have much to argue/teach/scoff at on the subject!
The Eyes have it. Science them ex haust savaging skills them ther header jobers have. But please make a video showing us how to choose the proper exhaust tune to reach peak efficiency for both N/A and Turbo engines at different points of engine RPM. Then compare their size and backpressure so we can lay this to rest.
@@jasonreynolds9097it is engine specific... Nothing to lay to rest there. What works on ls not gonna work on k... I have tested that my self
Scavenging is the opposite of backpressure. It's sucking gases from the cylinder by creating a negative pressure wave. I hate when people say you "need" a bit of backpressure. Drives me crazy.
This^
Yes, we need an exhaust system, which is a bit of back pressure
Me too, i actually gave up trying to explain it to people. It’s just to much work getting thru the bullshit sometimes. I’ve had guys get red in the face and all bent outta shape arguing you GOTTA have back pressure 🤬. That back pressure myth is a strong one. Every once in a while someone will have enough knowledge and get it that you dont want/need any back press but most I encounter swear by it!
@@JohnSmith-xu7ev 🤦
@@JohnSmith-xu7ev any back pressure from an exhaust is due to some undesirable trait usually. Especially for modern cars.
I'm no expert, though I am a mechanic and an enthusiast, and I've been toying with exhaust for 20 years. The first time I put headers and pipes on a small V8 truck was 20 years ago and afterwards it could no longer do a burnout. I was young, confused, and devastated. Even put a smaller tire on it just to see what would happen, still no burnout. However, the truck did have a noticeable increase in acceleration after 3k RPM. A few years later I swapped the 2.5' pipes for 2' pipes and like night and day the truck could burnout forever, not even needing the break peddle. This was the beginning of my interest and research into exhaust. I promise this much, a stock non-turbo daily driver needs a smaller pipe to increase the velocity at the exhaust valve while in low RPMs to maintain cruising power and off idle torque. Also, my fuel milage increased with the smaller pipe. Scavenging and velocity is kind of my thing. lol I'd love to prove it.
These guys are talking about wide open throttle readings on a dyno. Has very little to do with real world driving.
@@19Borneo67 Mmhmm and if the dyno were reading idle to 3500 RPM, back pressure and velocity would win against open headers on any N/A engine any day. The "some people" he is referring to that say "you need a little back pressure to make power" are referring to both wide open throttle and part throttle on the street, where people push the skinny pedal.😂😂😂
@@19Borneo67 I really wish I had read your comment, cause I would have just liked it. I mean, the dyno in the video is built to recreate real driving. 🙉🙊
@@19Borneo67 Did you see the dyno in the video? No? Weird, must be because their real-world Dyno that they use for developing these parts isn't in this video. lol
break peddle? Ahhh... brake pedal.
I think the main reasons people used to think backpressure was needed was because headers do have a power drop if they're run open with no collector extension, and also because if you merely unrestricted a severely restricted exhaust (as was more common then) on an old carbureted engine, it could actually effect the fueling enough that it runs worse. On the topic of manifolds, as a gas guy I'm always shocked how even modern diesel engines are designed as if gases don't need to flow at all in a heavily turbocharged engine. All the same flow and reflected wave dynamics exist when a gas is under pressure. I'm curious how much free horsepower could be had on something like a duramax with a header style manifold over that horrific log.
Is that why drag cars that are chasing every last HP run like that? Makes no sense
Headers dont "drop power", they "move" it. The same as any other exhaust setup. This is why Honda uses a Single outlet "header" on their J series v6's that make 250 hp from the factory... They use it to put the power down low for take off and drivability rather than your "wide open free flowing" headers that make all their power at the high end (where you want it for drag racing).
@@D.L.PDevelopments see my comment about honda J series single port "headers". You can also look up actual dyno results with back to back testing to prove this claim. Banks power is WAY late... Decades.
@@D.L.PDevelopments Like what? Open headers? I think you'll find most NA drag cars now have either collector extensions or a full exhaust.
@@crisnmaryfam7344 They use it because it's cheap and easy, period end of story. Long tube headers pickup torque hugely over an otherwise well flowing manifold with no scavenging
When a hairdryer outlet is blocked the load decreases because it is no longer moving air. That is why the rpm of the electric motor increases. By blocking the outlet you have moved all the way to the left of the pump curve 🤯
A better analogy would be throttling the outlet 😁
I was about to make a long and technical post about how the hair dryer has no load. You beat me to it lol
Would that only be accurate if you are blocking the inlet side causing a vacuum? I thought this at first to, but then i realized that he was covering the compressed air side, and that side being blocked would make it hard to spin.
@@levimayes8488 No. It applies even if you completely block the OUTLET side as well. This is because if no air can go out, then no air can go in. And if it isn't moving any air, then it isn't under any load. Which is why you can hear the motor speed up. It's important to remember that devices like hair dryers also use the air moving through them to cool the motor, so blocking the airflow, whilst reducing the load on the motor, will still cause it to overheat.
Came here to say this as well.
That's true of centrifugal blowers and pumps. The opposite is true of positive displacement blowers and pumps. Purposely throttling the exhaust on a diesel engine is one method of increasing engine braking on a diesel engine.
I learned this 40 years ago while studying engineering. I've had so many 'discussions" about back pressure it is NOT funny. A great video that fully describes the matter in ways that would make any engineer proud. Cheers.
Gale, you are one slick ol’ dude I swear.
While making everyone think “wow cool I just got a killer education on back pressure” you smoothly slid those advertisement in for your products, 😂😂….small, quick, but they were there, …nicely done sir 👏
And btw, well done on the exhaust and header, they look top notch! I try to tell my buddies if you ain’t buying Banks your getting second best.
Great video and I'm glad you touched on even, though very briefly, that belt driven boost is the only parasitic loss boost. The shop air in the 4.0 header was amazing. Best demonstration of exhaust scavenging I've ever seen.
Common misconception about hair dryers and vacuums when you hear the motor spin up faster it is because the load on the fan (impeller) is actually decreased allowing the motor to spin more freely. You can feel the pressure build but opposite of a piston pump which gains resistance as pressure is built.
Came here to say this.
Yep. I used to design pumps for liquids and it's the same thing where if you close a downstream valve the torque required goes down. Counterintuitive but it's true.
Interesting i wouldnt have thought about that with a liquid pump.
@@MrPdiggity Centrifugal pump yes, piston pump no.
When a vacuum cleaner gets clogged and spins faster and someone remarks that "it's straining" my head nearly explodes.
There is so much I cant stand about this subject. Especially when people try to "debunk" backpressure. The term was an oversimplified misconception that was likely made up by a sales person. In my opinion the common understanding of "backpressure" in an exhaust system can really only start after the last meaningful point of harmonic tuning in the system its self. These points generally being dictated by the changes in pipe diameter and the distances between them. Examples being, exhaust runner to header/manifold primary, primary to collector, collector to emissions or turbo, and so on. Everything after that "can" only create back pressure if that part of the exhaust is able to present a meaningful impedance to the engine's exhaust flow at or beyond some point in its operating exhaust cfm range. In this circumstance I do agree backpressure can only be a bad thing, but it also generally only becomes significant in max engine mass flow situations that most trucks rarely experience. I'm attempting to speak as accurately as I can, so apologies for the wordiness.
As a retired Master Plumber, I can say with confidence, that any bend in a pipe of any kind reduces flow. Any time gasses or liquids have to merge into itself will create cavitation to some degree. How much does a 90 degree bend reduce air flow?
A long radius 90-degree bend (a bend radius of 4.5 inches, or 11.4cm) has a flow restriction equal to about 5 feet (about 1.5 metres) of straight pipe.
Doesn't happen that way on exhaus gasses.
Where i come from the issue of backpressure was with 2-stroke engines. It should be tuned to the motor, if too low you waste fuel by letting the the air-fuel mixture going unburnt into the exaust or if too high you loose power.
One of the better videos you guys have done. Animation and production values getting even better. I always tell people you don't want backpressure, but on non-turbo engines it is important to maintain exhaust velocity for scavenging with a proper header.
Can’t love this enough, thank you for putting this together!! ❤❤
Great vid in lots of ways. It’s worthy to note, however, that the physics at play in boosted apps are differently influential than those in N/A apps. Apples and oranges.
To be strictly technical, the best exhaust system in boosted apps is basically as close as possible to no exhaust at all, which is obviously illegal on the road.
In N/A, the fluid dynamics in the exhaust influence torque curve and effective rpm range, among other factors.
This is why I appreciate you folks. Actual research and testing. Perfect example being the 4.0L Jeep "Revolver" header. It WORKS! I love mine. Definitely worth the money. Thank you for great products that actually improve efficiency.
I think the whole back pressure argument came from the race cam in a street car crowd believing they fond a way to regain some of the cylinder pressure they were losing through their wide open cam timing. The fact is thinking you can gain power by leaving unburnable gas in the combustion chamber is ridiculous.
Strange - I missed the part where he explained the principles of valve overlap... Good ad for exhaust systems that use turbos.
I've never heard that backpressure is a good thing for 4-stroke engines, but have heard it can benefit 2-stroke engines.
Engines are basically air pumps, so basically any back pressure or restriction slows down the flow of air.
You guys are awesome!!!! Thank you so much for informing us on this matter!
Amazing video! Please do that header explanation one too!!
My wife said this morning, "i need back pressure,for my gas control",as i waffed the duvet, i'm writing this from the comfort of the sofa.
Beautiful video! Marvelous! Thanks for sharing!
Thank God you're doing this video, I've been arguing with people forever about this. At best your reducing overlap any way your doing it your reducing the atmospheres ability to move air into the motor. If you need to shrink primary tubes to the collector then do that but after the collector there should be zero pressure as fast as possible.
Nice work Eric. Thank you. 😊
Been more of a fan each video I see but now I like it so much I'm going to ask for motorcycle products. Ya boy wants a top tier exhaust from the geniuses you are. Unbelievably brilliant and extremely easy to understand content. Never stop. But also please start motorcycles. Thank you for the education time and time again.
Outstanding job Erik!!!
I had open pipes exhaust with my 2002 Harley 88tc, I put the original pipe tips back on that greatly reduces noise, and I added 10 hp easily by using restrictive factory pipe tips.
Hi Erik, I happened across your channel and found it to be extremely informative and interesting. I found myself binge watching a lot of them. It is extremely apparent that Gale is a genius to say the least. However, I have one small problem, and that is I have absolutely no idea what language you and Gale speak (that’s code for a lot of the technicalities go over my head). Hello from Australia. Keep the informative information coming.
the scavenge demo with the sticky notes and air was excellent! awesome video!
Thank you for sharing this, I learned a lot! I have a 2000 jeep xj and will for sure be looking into a bank full exhaust system for it after watching this video!
Back pressure is bad according to banks, run no exhaust
Excellent presentation!
Depends - in theory it's bad because the piston has to push against the pressure to expel it and in a perfect world there would always be a vacuum in the exhaust.
In practice it can't be achieved, although Detroit diesels, and some other large 2-stroke diesel engines, used exhaust scavenging pumps - that were re-purposed by "hot rodders" to became the foundations of the x-71 series superchargers!
Best one can do is try and control the pressures to best achieve exhaust scavenging and initial intake flow - this is done with tailoring the pipe diameters for velocity, and lengths so place the low(er) pressure waves in the exhaust pipe to be low at the best time for cylinder filling and net torque.
I do wonder if some work on the turbine housings, to improve the transition from the turbine outlet's inlet through the housing to the outlet's outlet, and the pipe's transition from that flange to the full diameter, wouldn't show some significant improvements?
Outstanding presentation in every respect. I developed technician training courses and instructional materials for most of the Asian car and motorcycle companies based in So Cal for 20 years. This was top level stuff.
Love this series! Teach me everything!
Great stuff guys!!
Got into this video with questionmarks. But as you stated. Backpressure is often mistaken for exhaust scavaging. And yes.
Good video, nicely made, good sequence. And hella informative
Well done Eric! So true.
Please do the headers video. These tech and explanation videos you guys do are the best 👌 keep em coming !
I love it, right out the gate!
Negative back pressure, that's what's up!
Please make the header video!
Yes, please. An exhaust header video would be great! I eagerly await it's release.
Its funny for me to hear Erik referring to his grandfather as Gale. Love your products and the vids keep it up!
i would absolutely love watching Gale do a video explaining how tube size/length/style effects backpressure and how that translates out to power band
This is some good info, a video on exhaust manifold/Header design and applications would be useful too!
You explained that so well breaking down each step. It seems so obvious but you can see how people got sucked into believing it.
Awesome, thanks for sharing!
Absolutely 100% spot on. I've been building older carbureted V8's, carbureted Inline 4's (motorcycles) and of course the almost indestructible Jeep fuel injected 4.0 HO's for decades. This whole "back pressure is good" myth started in my experience back in the 70's and 80's when guys would bolt on a respectable brand of headers, decent mufflers and loose power on a stock machine... WEll, YEAH! They never jetted the carb up to take advantage of scavenging and the Helmholtz effect of resonant tuning on, of course, carb'd vehicles/bikes. Once tuned in, a genuine (oh damn man!) response was typical. On FI vehicles, the stock computer fuel trim can easily compensate for reduced back pressure especially if you live at high altitude. Case in point.... On my 4.0 I had a Magnaflow cat, generic SS header (AFM which I believe is out of business and had to weld up the the cracks twice) and generic cat back system that always passed emissions until my state changed to California emissions standards. I band clamped in a Cali spec cat, passed with flying colors but lost 2+ mpg and it lost a huge amount of power while merging into traffic (above 3k rpm), it was sad. Just for grins, I got a Banks after cat system and popped my old cat back in and gained 3+ mpg and my 3000+ rpm power was back! On top of that, the Banks sounds so much better at idle and no more drone than the summit cat back turbo muffler. I'd love to try your headers but is there any guarantee in regards to cracking?
My favorite type of Banks videos
Nice trick. On the headers you have the air gun down inside the header manifold. On the log manifold you had the tip outside the manifold.
Backpressure is essential for two-stroke engines though.
Maybe that is where the 'myth' comes from.
Well done Erik 👏👏👌nice presentation
Yes please do a header video. I also learned that glass packs have back pressure? I never would have thought that.
Interesting video, nice demo on the scavenging affect and lack off.
Ties in with stuff I’d been taught in the 00s about turbo exhaust system
“ the best post turbo exhaust is no exhaust “
Not always practical lol 👍🏻
Awesome video thank you
Very interesting. Thanks.
This comes up so often, people absolutely adamant that ‘you always need back pressure, it gives you more torque’ then they get really upset when they can’t explain it 😅
Being a truck mechanic, I remember Gardner diesels having issues meeting minimum horsepower requirements as truck weights increased. Their quick fix was a tuned exhaust, Gardner called it ‘negative pressure’ for a loaded 32 ton truck , it used about a five inch diameter pipe that with matching stack.
It used a flapper to stop rain getting in, but the pressure pulses were so strong that at three quarters throttle it still sucked shut, made a proper din 😂 drove the driver mad
Hi there, first of all thx for the very interesting video about back pressure. I enjoyed watching it and also learned a bit at the same time. But, my understanding of back pressure is that it is needed as to not burn up your exhaust valves or in other words to reduce the exhaust gases flow a little but not too much! But it seems I was wrong!
This is really awesome. I would love to see a more technical video with fluid flow principles.
Solid video friends, well done.
Best video I have ever seen explaining the difference between backpressure and scavenging!
For those of us that are using non turbo engines There is calculators available online to find the proper size, however you gonna have to find the best design for your situation to minimize the losses from bends.
Excellent video.
Good video. Accurate info!
At 3:20 you spin the turbo and it spins quite freely for some time, thus a reduction in back pressure drag along with a decrease in spool up time would make a considerable gain in performance. I've worked with turbos that wouldn't spin at all brand new right out of the box!!
Some people are wrong.🤣🤣🤣
A "Tuned pipe" exhaust works, at the correct revs, by the having the high pressure pulses hit the exhaust port before the valve opens, bouncing away, creating a low pressure pulse as the valve opens, helping to "suck out the exhaust gasses", outside of that rev area, super high back pressure, which makes it hard to get to the correct revs.
Looking forward to the science behind the design and considerations for a tuned header 👌
I would be a bless to have gale make the video about how exhaust scavnging ties back to exhaust back pressure man, hope you guys at banks can make it one of these days. All the engineering about exhaust has it complexity y precision and it's so useful to learn it for any aplication! Hope to see that video soon💪
The very first time I heard of back pressure and the explanation it came with, I said to myself, "That doesn't make sense at all." Now, scavenging, that made sense. Backpressure always translated to resistance in my mind. Thanks to the Banks team and this video, it turns out I was right. I just couldn't put it into words. Thanks for proving I wasn't tripping about it all these years. 😅
This was a great video I used to believe the back pressure myth I know other people that still do! This is a great video to show why its always bad because they may not believe me when i tell them but they cannot argue with Banks!
One of the most shocking examples of back pressure on a turbo diesel I have even seen, was on the Cat C-12 diesel engines around year 2000. They were 410hp and fitted to Kenworths......and those engines had real problems.....exhaust manifolds were failing every 6 months, along with turbo's running crazy high EGT's. The engines were also under powered for their rating. After a few years, CAT eventually owned up to having the wrong turbo charger fitted to the engines......it was too small, and caused a lot of serious problems.
As a kid I was told headers were always better. Didn’t know exactly why but as grew older I found out. Great video! 👍🏼👍🏼
Love this video!
I bet the "engine needs back pressure" tale is a result of removing the exhaust restrictions causes the engine to be less powerful, but the less back pressure caused the intake side to become lean.
In my experience, when you remove the exhaust system, there is a small power increase: BUT, there is a 2 or 3 times more increase in exhaust noise. This makes you think that the engine is much more powerful, but when you drive the car you don't get the performance that the increase in noise suggests. (I spent 23 years in Ford R&E Engine Lab testing engines)
Yep. If top fuel dragster builders could get 5 more HP by using longer headers, they would certainly use them. They use just enough length to deflect the flames away from the car.
@@budgie98 my experience removing exhausts off standard engines is they run like a bag of shit and won't rev out!
@@Bob_Adkinstop fuel dragsters run at high rpm with a blower so there is no need for exhaust scavenging!
Now make some tuned manifolds for a ecoboost. Great video . Thank you
Want
They would cost as much or more than the FullRace manifolds I bet.
Lmao believe it or not the 2.0 after market headers is literally just a 90° elbow pipe because the head design although the 2.0 suffers from a small turbo
excellent Video!
Love this keep it coming
Thank you for informations, i want to make a custom exhaust for my 2008 Mitsubishi Lancer EX, and now I know for what to look in making it :)
I’ve been arguing against this bogus claim for so god damn long, it’s ridiculous.
So you dont run exhaust headers?
@@JohnSmith-xu7ev having scavenging from proper headers and mass flow is different to having back pressure
I remember trying to teach Honda owners this back in the early 2000's. Man that was hard work.
David Vizard proved that an Austin A Series (five port head) with cleaned ports and sports exhaust manifold will suck the cylinder to 50% vacuum the moment the exhaust valve cracks open. Much of this is caused by shock waves pulsing down the manifold. Higher gas pressure increases the speed of sound so you get a better suction effect.
Two strokes with expansion chamber exhaust actually run at a fairly high back pressure. This keeps the shock wave flinging along at a speed to suit piston speed. Two strokes literally suck new charge down the exhaust header. The pipes have a reverse cone that stuffs this new mixture back into the cylinder.
Four strokes almost never do this but they could if suitably designed.
Great video...
I always thought it was a funny one... one that in about 1983 I thought I had seen first hand.
Mates car ran 15.1 in the quarter... and we wanted to try and get below 15's... we dropped the exhaust at the Tri-Y's, and it ran a 15.4... we ran another and another and they were all thereabouts 15.4 .
We reconnected the exhaust... and it went back to almost flat 15's...
The engine had tri-y's so it was still getting the scavenging of the cylinders.
Now, no one ever said a Turbo doesn't cause parasitic loss... but it's a hell of a lot less than a supercharger.
You probably lost exhaust scavenging from dropping the exhaust.
The fallacy over exhaust back pressure probably comes from a poor understanding of 2 strokes with expansion boxes causing 'pulse tuning' to address over loss of incoming inlet charges into the exhaust? This is commonly known as back pressure - and the urban legend is born.
The science behind tuning is mind blowing - ppl don't realise the complex maths behind gas flow. Hats off to you guys for producing this vid and explaining some of it👍.
I assume you've looked into cooling the exhaust gases to reduce the size of the expanded gas and cause negative pressure? How about venturi effect to do the same?
The continued use of 'backpressure' had me gritting my teeth for the first half.
It's a reaction to the over-use of it over the years by those who couldn't tell chit from biscuits.
Motoring journalists, I'm looking at you.
Great info.
Volvo had an interesting Log style exhaust manifold for their 5 cylinder. It had 3 seperate holes for exhaust to exit at the turbo flange and it was set up in such a way that no 2 consecutive firings would use the same hole. That way, none of the pulses colided, although they did have an unequal distance to travel. I'm looking at a 90s t5 manifold right now and cylinder 1 has its own outlet, cylinder 2 and 5 share an outlet, and 3 and 4 share an outlet. With a firing order of 1-2-4-5-3, the manifold almost behaves like headers.
Did you know banks made the first Volvo turbo for production cars?
Having driven a '95 Volvo 850 turbo and later a '97 Volvo 850R for around 9 years I do remember the tri-divided exhaust ports on the exhaust manifold. I do think those disappear on the Volvo S60R manifold though and that manifold is more of a shared design...though it's considered and performance "upgrade" on the 850 turbo, R, and GLT. I miss the 850R, but I am liking the '04 Corvette I traded for. Both are fun cars for daily driving enjoyment.
@@mlc7boosted popup headlights FTW! Won't find a volvo with those unless you import a 480. The R manifold is still somewhat tri-divided but cylinders 3, 4, and 5 all share an outlet. It still flows better than the 850 T5 manifold because of its larger diameter but at higher RPMs, a "Japanifold" will flow slightly more than the R.
Banks constantly giving out facts for free. Thank you guys
Exactly. Race car exhausts are short and without mufflers, and the headers are blended not logs.
Love these!
Back in 1990s i had a motorcycle ( cx500 ) and i put a 2-1 exhaust on and it was very loud ( little back pressure) and flat out 55mph ....then i took out the baffle and welded a silencer on which increased exhaust lengh by 2 ft and was very quiet and very hot gas out the end ....now it had power everywhere and increased top speed by 5 mph from standard exhaust. The correct back pressure is important , for outright hp at just top less so but on the road you dont want a huge dip in power to gain a few hp in the last part of rpm
My MBRP exhaust rusted through, so I took it off 2’ after the turbo. According to this video my post turbo psi back pressure must be SUPER low, so I must be making crazy great low psi back pressure before the turbo. GREAT! 👍 😂
THIS IS GREAT!!! Make more of these! My kid is in the automotive program in highschool, when they take one semester, they become eligible to work on the diesel SFMTA busses. A sires of these videos would be perfect for them.
Just a LIIIIIITTLE less selling banks... just a little ;-)
Watch real mechanic like scanner danner.
Great video and great explanation about back pressure. I could do without that music in the background though. It's barely there but it's really annoying. Thanks for the video!
I’ve told people time and time again, an engine is a big air pump, getting air in and out as fast as possible is what makes power. (Including fuel)
And people still argue with me!