That particular header is the Revolver. For 4.0L Jeeps.

Yeah that was really neat to see

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.

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.

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".

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.

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.

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

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.

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 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.

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

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.

Doesn't happen that way on exhaus gasses.

Back pressure is bad according to banks, run no exhaust

So you dont run exhaust headers?

@@JohnSmith-xu7ev having scavenging from proper headers and mass flow is different to having back pressure

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

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.

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!

Its fine for toyota and honda

@@JohnSmith-xu7evDamn you’re stupid 😂

Humans exhaust and intake are the same orifice. Not a good analogy. Maybe more like farting a marathon through a straw. Which I think I can do, personally.

Try farting with hemorrhoids lol.

You described an intake restriction. Thanks for sharing though

This is exactly why chopping off factory exhausts especially ones with cast manifolds makes engines run like shit and not rev out anymore. My daily drive is a 92 Nissan Bluebird with stock spec rebuilt CA20e, headers running into standard 2" or 2.25'' tube, cat delete, original resonator halfway and rear muffler replaced with 3.5" resonator. The velocity is so good it makes big flames out the back like a race car when shifting over 3000 rpm!

The reason for low end tq to be lost an engine with an exhaust designed for higher RPMs is because they're designing it for the air flow amount. At low RPM you're moving less air, so an appropriately sized smaller exhaust will allow for better scavenging due to optimal exhaust velocity. That's why there's so many devices on an engine to help adjust the size the intake and exhaust systems among other aspects like runner lengths and duration. For a turbo charged engine there's going to be differing sizes of various components based on how the engine can pump out exhaust gases. Just like how if you over size the turbo for an engine and it takes forever for it to spool or vice versa, too small of a turbo and it spools up fast giving you instant power, but completely choked up top, same issues.

@@sigmaprojects Sounds accurate. Also sounds like it proves this entire video to be false on everything other than turbocharged vehicles. Sooooo you DO need some back pressure on most other vehicles.

@@boost331 I'm sorry if I didn't make it clear. You never want back pressure. I said the reason for loss of low end power with a larger diameter exhaust is because the exhaust velocity will be slower at those RPMs. Slow moving air equals higher pressure, but it's also about how much volume of air you need to move. So at low RPM not a whole lot of air is moving, so if you want to cause scavenging effect you need a little smaller exhaust to improve velocity which will reduce reducing back pressure. But if you're trying to make more power at higher RPMs when the engine is moving a lot more air you'll need an appropriately sized larger exhaust to improve exhaust velocity for the volume of air you're trying to move to keep up the scavenging. Reducing back pressure. In every situation for your desired results you always want to reduce back pressure. It's just about sizing the exhaust to be the most optimal. Tuning runner lengths and such to capitalize on the pressure waves is also reducing back pressure. It's just not easy to make a one size fits all exhaust for every single situation. Modern engines have some ways to do with it, like variable valve time and duration. Think like a big cam engine, where at low RPM it sounds like it's going to die. The valves are opening up super wide and because at low RPM it's not needing all that lift the opening being too large slows the velocity and doesn't help in reducing back pressure, but when you rev it up and you need to move a lot more air the size is appropriate for not being restrictive and the exhaust can move better. For an every day car auto manufacturers will design the engine to have the least back pressure at lower RPMs since they know for those commuters they're not revving them up, they're just getting them from point a, to point b. Basically in a perfect world engineers would design a sophisticated exhaust system that could change in size infinitely to maximize all the benefits of every size and shape to reduce back pressure at any RPM and load, but such a design doesn't exist so they try to just design for the least amount of back pressure at the point where they think the driver will use the car the most.

You are right, two strokes are a completely different design, and need the correct back pressure (pressure waves) to get the full potential of that engine Which is why you see expansion chambers on two stroke dirt bikes. It's a real science to make a two stroke exhaust, because it needs to resonate at the correct frequency to aid cylinder filling at a specific rpm range

@@Lorddxt back in the day when I had a scooter, I googled making exhausts for 2-strokes and I made one out of car exhaust, block of wood and hammer, grinder and a mig and I instantly got another 20km/h!

Watch real mechanic like scanner danner.

As an engineer and an auto tech, it is true. The guy contradicts himself in the video

​@@JohnSmith-xu7evany back pressure is bad.

I'm 51. My dad said the same thing. Bring a mechanic doesn't mean you understand fluid dynamics. People confuse a loss in velocity as a need for back pressure

@@randyschmidt19 Im both, and you do need back pressure. Tell me why you shouldn't put headers on a car

@@randyschmidt19 Then honda civic should have 6 inch exhaust like my diesel truck