Oval Exhaust Robs HorsePower - I Prove IT

[@Malibus_Most_Wanted]

Always feels good when you’ve been doing half assed math in your head actually turns out correct lol

[@samevans4525]

Vibrant is an amazing company. I have their pipe and muffler in my truck and love the quality and sound.

[@carlhansen9512]

Thanks for this video. Helped me figure out that my smashed exhaust pipe has the equivalent of a 1.85" round tube instead of 2.25.

[@THESLlCK]

they're also proven to carry the BEST sound, which as far as I'm concerned is a LOT more important

[@RedlineStands]

More important than power? Idk man. Depends on the driver I guess. I value both pretty strongly, but I think at the end of the day power is more important to me. To each his own.

[@static7415]

@@RedlineStands ah yes take advice from some KZbinr or nascar professionals

[@coreybrenner]

Thanks for this. Im looking to build a decent headpipe for my squarebody 3/4 ton 4x4 that is LS swapped. I hate headers, and Tru Ram exhaust manifolds from Speedway fit very nicely, even with the slave cylinder in its stock configuration. But, the exhaust builder and i made some bad choices, and now i need to build it a better, simpler, more easily serviced exhaust. One fat log down the drivers side it is. I will give props to the Black Widow mufflers, though. Mellow at idle, but a very lively loud pedal, and no drone on the highway.

[@michaelwurn6268]

Great explanation, thank you. This is what I was looking for. I would also like to know if there are restrictions to flow based on resonant frequencies due to the oval shape and / or varying pressure areas because of the oval. Logically a circle (a sphere is a perfect pressure vessel) has evenly distributed pressure, whereas an oval will have varying and different pressures throughout the cross section.

[@yucannthahvitt]

It's hydraulic equivalent, and it's the equivalent size for multiple pipes or a non-round pipe in order for it to flow with the same pressure drop as a round pipe of a given size and flow rate. I've had to explain this to people before, that just because 2x of a given size pipe has about the same area as 1x of another, does not mean it will flow as well. There's friction and shear in the fluid flow and drag is the result, seen as pressure drop/head loss or in car exhaust the opposite: pressure increase at the exhaust port or turbine exit. Car guys seem to struggle with seeing the bigger picture though, they think they see a weird pipe shape on their favorite race car because that shape must flow better, nope it's just because they had to use that shape to clear something.

[@krankywagon]

I tried the math the same as you but with 3.5" round to 3.5" oval, found a 15.6% decrease but when I measured the transition piece; there was only a 2mm (0.0787") difference between the oval and the round circumference.

[@chestrockwell8328]

Something to consider for sure, however this only matters if the upstream exhaust system is fully maximized, meaning there are not other upstream "bottlenecks" which would already have reduced flow to the point where none of the larger oval area even matters.

[@RedlineStands]

Hmmm. Idk. It's worth mentioning that increasing the size of the exhaust tubing so that you can smush it down and still retain the same, or larger, cross section, also results in a larger head loss, because the internal surface area of the tubing is now larger than necessary. Thus, this surely causes the engine to work harder than it has to.

[@michaelwurn6268]

Another point I would like to make is the myth that: for exhaust bigger is better. We should take into account the effect of exhaust scavenging, especially in multi cylinder engines. An exhaust sized accordingly to the displacement of the engine will get the best use of scavenging. You will have to look up where these calculations are.

[@rifleman7313]

Great analysis and explanation.

[@markwilliamson6905]

Good info..my supplier dimension for 3.5" oval are slightly larger than 3.5" round.(120mm x 60mm) best to check

[@Marty59143]

Awsome well explained vid, I did not think of that. Thank you.

[@hulkgqnissanpatrol6121]

How is it so many people are confused? flat square piping is what is going to give you power. Also exhaust gases dont push/blow through they tumble/roll. Hence Nascar.

[@rifleman7313]

What is the formula for estimating exhaust cfm airflow for a 2.5", 3",3.5",4", 4.5",etc. ? Thanks

[@bennyboyy7]

If the overall pipe volume is larger then it will be more free flowing and produce more power, I highly doubt the exhaust is going to be affected by such a small change. The sound will change for shure Instead of overthinking this (no offense math is important) I would try simply filling a 1 foot section of oval and round of the same size tubing. The oval being originally the same diameter as the round, then measuring how much fluid was inside each. You may be surprised, exhaust gasses are constantly being pushed out and trying to expand at all times. Expansion will allow for free'er flowing exhaust and free up power. Obviously if it's not any bigger nothing will change but math doesn't always provide the exact answers. The lift on a cam proves this since it hardly provides any power gains after a certain height

[@3rdGenGuy]

interesting, in my case the 3in round to 3in oval drop was about 10% I have heard round tubes flow more air even with equal square areas vs Oval.

[@yucannthahvitt]

Well yeah because for the same flow area there is still more surface for the flow to experience friction with.

[@PipewerksRacing]

Very well explained. Suppose you use the same 3” round to oval size, do you think it would result in a “faster flow rate” over the 3.5” oval? Do you think it would achieve a better efficiency rate?

[@RedlineStands]

A faster flow rate? I don't see how it couldn't. Surely throttling the exhaust will cause it to move faster. Granted, you should expect the volumetric flow rate to decrease. It's the same thing that happens when you put your thumb over the end of the water hose. Speed and pressure go up, but the mass of moving fluid decreases. Better efficiency? I think that depends on what back pressure the engine requires, which will be different for every engine.

[@hulkgqnissanpatrol6121]

@@RedlineStands comparing water to gas is ridiculously funny 😂🤣 Thanks dude 👍 😂 Confident talking is great but most see through it. Lmfao air water comparison. 👍 😂 Thanks again....

[@TofumanFC3S]

@@hulkgqnissanpatrol6121 Not sure if trolling but uhm yes, fluid dynamics is indeed the study of both fluids and gases and fundamentally they behave the same

[@ryze_android17]

@@TofumanFC3S Yuppp

[@michaelwurn6268]

Very interesting question. In 2 cycle engine technology, the scavenging effect of the exhaust is almost like a supercharger. This is achieved by varying the size of the pipe to cause a low pressure area at the exhaust outlet, AT THE MOST ADVANTAGEOUS RPM. It's important to note this does not happen over the whole operating range of the engine.

[@aragrox]

Take two 3" tubing, turn one into oval, fill with water and measure. Thats the real test

[@dclipper8052]

Something else to consider is the shape of the transition from round to flat. For instance, the adapter piece you show will introduce a section of considerably increased cross sectional area as it changes from round to oval. This would occur even without your step up to a larger diameter circle so the effect will be especially exaggerated on yours. If you cut a section plane through the midpoint, for instance, you'll find that slice has an area greater than either end. The effect of this, I assume, is that the exhaust hits this low pressure pot at the end of the round tube before moving into the flat tube. What this does to overall flow, I don't know, but I suspect it's something worth consideration. I'm guessing it's not good... The way to avoid this would be to create specifically shaped transitions that attempt to retain constant cross section along their length, which would be fairly involved. If I were doing it, I'd probably develop the shape digitally, carve the top half into wood, and hammerform two pieces of steel and weld them together along the sides.

[@RedlineStands]

I couldn't disagree with this "if" this were a racecar, but being as it's a street car, I really just can't imagine being able to notice the difference. You make a good point, but it's probably not a concern on a street car.

[@JCnordic2983]

Why is there two circles and a rectangle? How is the half radius apply? The only aspect I see is the transition with welding causing turbulence, but from alot of testing is after secondaries its really moot point since the gases are cooled enough to not effect the flow. There's show even cats don't effect flow. But aft of exhaust system why not increase it!

[@Lexusturbo]

Very well explained!

[@RedlineStands]

Thanks! I try

[@SaulTamalezX8]

Doing the same with my exhaust, 3in to 3.5in oval then back to 3in to 3in straight thru magnaflow muffler

[@imoovabull6042]

i went 3" round into muffler with 2 x 2.25" round out. stopped the drone noise.

[@ed_1969]

Im trying to figure it out for the oval exhaust i just ordered Its 2.2inches x 3.5 inches....anyone?

[@ronaldpatton5906]

I think the nascar guys would dispute this . They have done a lot of testing.

[@hulkgqnissanpatrol6121]

Exhaust gases don't flow through as he says, Nascar says and has shown that the gases roll/tumble through. Hence flat square piping.

[@newfinishautospa]

Dispute what? It’s 8th grade geometry. Bmw has been using oval exhaust pipes for a long time, and they do in fact increase the diameter of the pipe where it is oval shaped.

[@yucannthahvitt]

False comparison, and using "feelings" instead of math. Race cars you run whatever size you need to flow what you need and budget is of little concern in comparison to rules, street car builds you are almost always limited in clearance with something you can't move somewhere and can't always spend multiple thousands on custom transitions and weird non-standard sizes of shaped pipe, there are no rules. A cup car is designed and built with massive budget and track only use in mind. There's no concern at all about routing or the cost of having someone fabricate that transition, the exhaust comes off the header, crosses under the car, and goes out the side. There is practically nothing to route it around, the car itself is designed to have big long tube headers and a crossover under the car. The ONLY reason they use a shape other than round at all is that they have to put the exhaust under the floor of the super-low race car and need to run those massive flattened pipes to get enough area to minimize pressure drop at the required flow. It's 100% indisputable that for a given AREA round flows better than oval, box, or whatever because round has the least surface area per unit area and FRICTION/DRAG is the primary contributor to pressure drop other than transition to turbulent flow. You can calculate Re for the pipe, it is trivial if you know the volume of the fluid flow and its characteristics, they 100% want to avoid transition to turbulent flow because head loss increases massively with turbulent flow. You will NEVER see any performance application use any shape other than round pipe unless it is necessary to clear something, because you can't increase the RATIO of surface area to flow area without also increasing losses...

[@radmon1898]

Yes. Because it’s not just about the total area, shape plays a part as well. Also the gases are much more dispersed the further from the engine. And if a tiny amount of power goes missing, who cares. It what point is it important that you need every bit of power? Is it real world that important? No. Much more important that my exhaust clears. This guy is just paying to his ego.

[@mr.k.9019]

Hum.. Empirically speaking why the exhaust on the Ford escort rs cosworth wrc is flat then

[@yucannthahvitt]

There is only one reason you would ever flatten a pipe, clearance. Nobody is going to flatten a pipe if they don't have to. You can argue whatabout this car whatabout that car all you want, it'll always be clearance. Nobody uses anything but round pipe in any application ever unless they have to because round pipe flows the best for a given size.

[@newfinishautospa]

Oval tubes with the same flow rate as a slightly smaller round tube would naturally run cooler due to increased surface area therefore decreasing exhaust gas velocity. Pretty simple physics.

[@RedlineStands]

He's exactly correct. Engineers call this "head loss"

[@_.incredible_magnum._291]

My question is can you build headers from square tubing??

[@SaulTamalezX8]

You can but wouldnt

[@SuperTambo69]

good video

[@jeremymcclanahan2389]

The oval exhaust is an ellipse, not a circle

[@antimattergarage8147]

Ummm, only one flaw. Cross-sectional area does not equal horsepower.

[@edlingja1]

I was thinking the same thing. Pretty confident it’s all about the pipe diameter vs the bends and accounting for the way the gases make their way out in bursts or rolling flows determining back pressure information so you can circle back and size the equipment for the engine. An engineer’s job!

[@yucannthahvitt]

@@edlingja1 Back pressure is a myth/misnomer. It's what the uninformed call pressure drop/head loss. Yeah, it's the same when you want to maintain say 100psi at the end of an air line for a given rate, you see it become necessary that you have more pressure at the start of the line as you demand more of the line because the line causes pressure drop. With exhaust you want minimum pressure at the valve, as well as maximum velocity and of course wave effects like scavenging (tuned length is important here). Because you are juggling all of these effects with configuration that fits in the car there's no single answer but when you simplify! Take for example a turbo car's exhaust. You don't tune crap after the turbine, you only want the lowest pressure possible at the turbine exit because turbine efficiency depends on DELTA P, you maximize cross sectional area and minimize surface area (a circle!) to maximize flow. Pressure drop/head loss in pressurized flow is the same as pressure gain in an exhaust that is too small. The pressure at the tailpipe is atmospheric, and you don't want the pressure at the valve to be significantly more or you will lose power.

[@BUZDRIFT]

No one has lost HP going to oval tubing! FFS there'sd a channel on YT where they dented and squashed the runners of some headers and still made the same amount of HP, actually they made a few more hp! Plus the whole point to oval tubing is to tuck that shit! still a 3" to 3.5" will tuck better than a round tube!

[@SaulTamalezX8]

Smaller diameter tubing can increase power closer to headers thus making it lose some torque and vice versa. Thats why tuning is to balance hp and tq, but these days is about how much boost u can get outt of it. Plenty of guys out there with good tunes but can be better with proper exhaust builds and such

[@yucannthahvitt]

That's only because they weren't anywhere near a flow rate that the tubing would limit. If you were optimizing (this means maximizing the use of what you have) and you squashed the pipe, you would lose power, no question. If you have 1.75" primaries on an engine that would make no less power with 1.5" primaries, and you squish that 1.75" primary, you won't likely see any measurable power loss.

[@BUZDRIFT]

@@yucannthahvitt Not arguing the science, you're assuming engine and car builders wouldn't upsize the pipe to keep flow restrictions (Back pressure) down!? 4" Oval pipe can support over 3000hp, where are you ever going to see 3000hp using just one 4" pipe? Never as the builders know this! Now, Yes I do agree a 4" round has better flow (less restriction) than a 4" Oval, but that's not my initial argument Statement! P.S there's a video where they DYno a engine and compare Headers vs HP gains, they actually gained HP on a set of headers they dented and smashed and squished, vs headers with larger primaries! I'll actually try and find the YT link for ya!

[@DeadpanPear]

Good video, but that was a superscript not a subcript. Prepare to be banished to the math shadow realm.

[@crazytrain65]

You sir, deserve more views! Great info

[@eefmydee1slideways]

you saved my ass hahaha

[@k-dizz2520]

I’ve been scouring the internet and picking the brains of all the gearheads I know, hoping you could chime in on my predicament: I’m building a twin turbo LS in a narrow/cluttered engine bay. I’ve considered using oval pipe as downpipes straight off the turbos to allow for more clearance between turbo manifolds and frame rails. My thought process is if I ensure I get the cross sectional values right there should be little to no negative effect for using oval vs round pipe off the turbo. But I can’t find any real world data. Whatcha think?

[@RedlineStands]

This is "basically" true. I say "basically" because the losses associated with using the oval pipe will be negligible. You'll experience a tad more head loss, which is just a fancy way that engineers refer the drag associated with increased surface area of the inside of the tube. The more internal surface area, the more area to create drag on the flowing gas or liquid. Will this matter in your case? Not IMO enough to matter. I say, "Go for it!"

[@k-dizz2520]

@@RedlineStands exactly my thought process! It’s hard to get these old school gear heads to break away from “that’s how we’ve always don’t it” haha! I’m goin forward with the oval downpipes. Thank you for the reply!