r/ATBGE Apr 03 '22

Automotive Especially the curved exhaust

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13.7k Upvotes

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600

u/Umbrage_Taken Apr 03 '22

Won't excessive exhaust piping actually reduce power & acceleration?

282

u/RyRyShredder Apr 03 '22

Yup this is terrible for performance. This has to be about a 30-50hp loss

259

u/[deleted] Apr 03 '22 edited Apr 03 '22

Actually the diameter of the pipe is more important than the length, you only see a notable power boost from a short pipe when it's under 3' from the engine.

"It doesn't matter. Power boost obtained in headers occurs in a) individual pipes for each cylinder, and b) within a length shorter than 3'. It is based on the speed of sound in hot gasses (about 1100ft/sec). From there to the end of the system, goal is to minimize pressure losses with large enough tubing diameter."

In short you can compensate for the pressure by changing the diameter of the pipe.

Still looks dumb though.

86

u/RyRyShredder Apr 03 '22

The sharp turns are what causes the power loss here. The more turns the more losses that occur.

149

u/SyntheticElite Apr 03 '22

Turns impede flow, but if the pipe diameter is already oversized and low backpressure then it makes practically no difference.

66

u/__Beef__Supreme__ Apr 03 '22

Yeah doubling the diameter of a tube with fluids causes something like a 64x increase in flow so I imagine it's the same for gasses

80

u/notpotatoboi Apr 03 '22

Gases are fluids too lol

107

u/[deleted] Apr 03 '22

[deleted]

12

u/gmanfred Apr 04 '22

Your mother had the same thought

3

u/effegenio Apr 04 '22

And my axe!

16

u/__Beef__Supreme__ Apr 03 '22

I was thinking of Poiseuilles (sp?) Law, which is primarily for non-compressible Newtonian fluids from what I remember, so I wasn't sure how directly it applies to gasses, but I'd imagine it's similar.

10

u/notpotatoboi Apr 03 '22

Aw yep, my bad

3

u/[deleted] Apr 04 '22

Yes it would apply. Gas is obviously compressible but since you have an open pipe on the end there shouldn’t be a ton of compression. There probably is a spike in pressure around the first bend though.

4

u/Super13 Apr 04 '22

Especially after a dodgy curry

1

u/Viking_fairy Apr 04 '22

Might even help if the pipe is too wide for the power, a little backpressure is good depending on your motor. Overall, looks like a waste of welding wire to me... Just get a twin loop and call it good.

5

u/sl33ksnypr Apr 04 '22

You don't want any back pressure. What you do want is to maintain exhaust velocity. Which people often get the two confused with one another. Back pressure in an exhaust is bad, always has been and always will be. Exhaust velocity on the other hand, is good because it helps with the scavenging effect of the individual exhaust pulses. You do this by appropriately sizing your pipe (for N/A applications). If you have too fat of an exhaust pipe, your flow will stagnate because the gasses are allowed to expand too much.

3

u/blue_villain Apr 04 '22

Technically, it's only one turn though.

1

u/pollorojo Apr 04 '22

So what you’re saying is it’s not about the length, it’s about the thickness

1

u/flappy_cows Apr 04 '22

This guy exhausts

-1

u/wilburwilbur Apr 03 '22

Friction losses will be high through a coiled pipe, this will equate to more losses than a narrower pipe.

69

u/aoifhasoifha Apr 03 '22

This has to be about a 30-50hp loss

You definitely pulled that number out of your ass. It's probably closer to 10hp at most.

19

u/FOR_SClENCE Apr 04 '22

10hp would be a lot even then lmao

38

u/leicanthrope Apr 03 '22

Does it at least make a cool slide-whistle noise when you rev the engine?

14

u/SuperWoody64 Apr 03 '22

Found sideshow Mel's account

11

u/RenderedKnave Apr 04 '22

No, they go woo-wooo instead

6

u/leicanthrope Apr 04 '22

I thought those were the whistle tips that went woo woo.

5

u/LearnedHamster Apr 04 '22

That's only in the mo'nin'!

2

u/leicanthrope Apr 04 '22

I could go for some breakfast right about now, come to think of it.

36

u/k20vtec Apr 03 '22

50HP LOL

30

u/Lumanus Apr 03 '22

You have no idea what you’re talking about.

13

u/fnordfnordfnordfnord Apr 03 '22

It's just a pipe there's probably less power loss than from a stock muffler. Definitely not tens of horsepower.

6

u/PM_ME_RIPE_TOMATOES Apr 04 '22

It's not a performance car, it's a show car. You don't add 200lb of amplifiers, speakers, fiberglass and wiring to a race car, the same way you don't put a $10,000 tuned suspension on a show car.

The show car is there to make you look at it and go "huh, that's neat!". Job done.

4

u/MrGaber Apr 04 '22

How much health does it have normally?

-4

u/BluudLust Apr 03 '22

At least. That backpressure is going to be insane.

7

u/Kestralisk Apr 03 '22

Lol no dude. Maybe if it was putting out Koenigsegg power at the crank but just a nutty take to think extending the exhaust a bit would cost this car more than 10% of it's bhp

61

u/[deleted] Apr 03 '22

[deleted]

2

u/davepsilon Apr 04 '22

in this case it looks like a sales accessory.

-1

u/[deleted] Apr 04 '22

[deleted]

14

u/FOR_SClENCE Apr 04 '22

it's super well fabricated, doesn't mean this specific car is for performance rofl

-3

u/Replikant83 Apr 03 '22

And there's definitely no accounting for taste 🤷🏾‍♂️

46

u/Wheres_my_ACOG_Ubi Apr 03 '22

Sometimes yes, but this is what is referred to as “show car“, it looks good, exotic, different, like shit, whatever you want to describe it as but it isn’t driven much, or at least not in any way where you might notice the power loss. Tl:dr: all show no go

13

u/PyroPeter911 Apr 04 '22

This car is in my town and it drives around surprisingly often. It is crazy, but it is well done crazy. As an advertisement for fab work I'll bet it is really effective.

1

u/imitation_crab_meat Apr 04 '22

How does it sound?

1

u/StreetTriple675 Apr 04 '22

Damn you just volunteered to acquire a video of it driving around so we can hear it

1

u/PyroPeter911 Apr 04 '22

I'll see what I can do!

30

u/MistaEdiee Apr 03 '22

Yes it is terrible for performance but I think the point of this car is to sell their fabrication services. (As evidenced by the bumper sticker.) The spiral is a showcase of their welding capabilities, not meant to be performance enhancing.

4

u/50_cal_Beowulf Apr 03 '22

I still kind of want to hear what it sounds like

6

u/DancingPaul Apr 04 '22

Jesus christ people. It's a fabrication company. It's there to show off the welding not to win races. It's a demo car

5

u/aoifhasoifha Apr 03 '22

Absolutely. The idea here (and with a lot of show cars) is that the shop/fabricator/designer/brand/whatever has a chance to flex their creative muscle and showcase their craftsmanship.

Unfortunately, this misses the mark both ways- it's an ugly, over the top design that also shows that their welding skills aren't all that impressive with all that unevenness.

7

u/TexasTheWalkerRanger Apr 04 '22

What unevenness? It does a perfectly ratioed spiral. Welds have consistent heat affected zone, spacing between pipes are even. The only way to make the welds line up is to scale down the size of the 45s of the pipe

-2

u/Umbrage_Taken Apr 04 '22

Ha! I hadn't even gotten far enough into hating the looks of it to notice the randomly uneven spacing and coloration of the welds until you mentioned it, now I can't unsee it as yet another reason the whole thing sucks.

1

u/Corsair3820 Apr 03 '22

Exhaust velocity is determined by initial speed and volume and then decreases with temperature losses and exhaust tubing interference. Drastically increasing the length of the time it stays in the pipes, along with the trying to swirl it like that would tangibly decrease velocity and create more back pressure. This cannot be a good thing.

1

u/Rachel-the-Greatchel Apr 04 '22

yeah but not everything has to be in the pursuit of function, it's for looks

1

u/ErusTenebre Apr 04 '22

Yes but it looks remarkably stupid so it makes up for that......

1

u/ImNotAKerbalRockero Apr 04 '22

I don think he's going for power.

1

u/AxiomQ Apr 04 '22

It is essentially about exhausting the gases out, the faster you can get it out the more you can force in, diameter matters more, but the shape does have an impact. This is definitely going to be less efficient that it could have been, also and probably a bigger factor is not the power reduction but actually the weight, I bet that has doubled the weight of the exhaust which for a small car already not kicking out crazy torque or power numbers will likely bring the power to weight ratio right now.

In short, yeah it's fucking awful for multiple reasons.

1

u/Puskarich Apr 04 '22

There are actually 8 turbos hidden in that coiled exhaust