So I'm pretty positive that a turbo'd car needs little to no back pressure, and an NA car does, but what about SC? I don't want to go ahead and assume that boost is boost, because it's made differently

The reason I'm asking is that I plan on my next mod being an exhaust (ZZP or Hanh) I was going to go three inch, unless that would be a bad idea, I already have a 3inch DP


Also my DP has the 2.5 bolt in exit, assuming I bought the 3inch ZZP exhaust, would the place where it's connects being 2.5 produce any noticeable restriction? I could easily just buy it without the 2.5 thing on the exhaust and have the shop just cut my DP and connect them, If it would be worth the trouble

 

think about what you said, do you honestly think that a 1/2 difference in your muffler size is going ot overall affect your cars performance.

back pressure has to deal with your over all hp/torque curve.

but basically, yes back pressure is involved when you deal with s/c or any vehicle, rotory, boxer, v8 blah blah blah

for example, if you ran a 2.8 pulley on your cobalt, youd be at around 21psi, but with a header/downpipe you should be down to around 18psi. so yes.

 

Alright, I wasn't asking if it affected it, I was asking how it affected it but I think I gotcha


Just going to go three inch cause it'll be louder haha

 

it affects hp/torque curve, for every action is a reaction (more in you have to have more out)


the more back pressure the higher the torque, but as far as racing potential, do you hang out at 3000rpm or 7000rpm? you create more hp higher the rpm band.

so....200/200 stock.

example...header/downpipe/exhaust no cai or more boost... 220hp/180 torque (just example, not exact numbers)

 

3inch you loose a little low end power, but you have a better high rpm power. like fake evo said.
I have a 3" exhaust with a 2.8 pulley and from my experience:
aguer= a spiral device used to create back pressure in the exhaust.

I had an auger in and loved my low end, but when I got into the higher rpm range around 5k-6k you can really feel the restriction.

now I have no auger and wish I had it in, but I love the high end more!

 

If you ask me I think that the whole back pressure thing is b.s. Think about it what benefit would backpressure give you? From what I understand its more about the flow of the exhaust/velocity of gas exiting and getting the right exhaust that'll do the job best. There are a ton of write ups online busting the backpressure myth. I'm sure there will be plenty of people giving me **** but just throwing my 2 cents in there! Good luck with whatever you decide to do!

 

backpressure has ZERO to do with anything... its a side effect of velocity... n/a cars need to keep velocity up so that tha pressure waves help pull one another along, in boosted cars you pretty much just make that hole as big as possible because it has something pushing it harder...

 

right on

 

for any car you want as close to zero backpressure. think about it, all back pressure is is a restriction. engines are a big pump. the more air you get in and out the more power you should make. at least thats how i look at it

 

omg, you guys are dumb ^^^

yes it has to do with velocity and the flow of the exhaust.

 

I will tell you this, I ran a stock exhaust on my Ion with the M62, the M62 on the bottle, the M62 on E85, the Harrop, the Harrop on the bottle, and the Harrop on E85. When I opened the 3" cutout the top end screamed, but the car for sure did not pick up as well at 3000rpm. I never actually did back to back dyno pulls with the cutout open and closed, but I can tell you for sure in all honesty I preferred running the car on the street with the stock exhaust. I was just way more responsive and peppy to drive. It did make a difference in the 1320 though.

 

that's why i said it has more to do with flow/velocity over worrying "i need x amount of backpressure because cars need backpressure"

 

1.75" Primaries on your exhaust manifold of choice.
3" DP.. Catted or catless, which ever you prefer.
2.5" Cat-back.

YOU DO NOT NEED A 3" CAT-BACK! Bigger is not always better. You're going to be KILLING your low-end, and making a crap ton of noise for a whole lot of nothing.

If you laid down over 300WHP, sure I'd say go 3". My guess is you aren't.

 

going from 3" to 2.5" is going to do nothing but cause turbulence and slow down the exhaust gases... stick with one size and roll with it...

 

^agreed, this will mess up the whole pressure wave system that happens inside your exhaust and helps it. A turbo car has it's power adder after combustion, in the exhaust. The turbo thus helps push the exhaust out. However, on NA and s/c cars, this adder is before the combustion and has no affect on the exhaust. While bigger combustion does mean beefier exhaust push, you just don't have the help with a s/c you would from a turbo. Because your exhaust would be different sizes, the exhaust gas pressure waves would negatively affect one another whereas on a car with the same size exhaust, these assisting pressure waves would be consistent through the entire exhaust system and thus more beneficial.

 

I have a 3" cat back , but that's because I know I'm going to do a **** ton to the motor and would rather not keep swapping exhaust components.

 

long time ago i straight piped the redline for ***** and giggles and i felt that it was alot slower than my 2.5 catback