Busting the exhaust backpressure myth | Banks Entry Level

That scavenging demo with the header and sticky notes was simple and beautiful. Thanks for continuing to battle misinformation!

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.

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".

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.

That demonstration of scavenging with post it notes was the best thing way to show it ever. Love it

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.

Please do a video on the science of exhaust headers!

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.

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.

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.

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.

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.

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 😁

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!! ❤❤

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.

Strange - I missed the part where he explained the principles of valve overlap... Good ad for exhaust systems that use turbos.

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.

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.