2.5" muffler on 3" straight pipe. performance loss?

[ed1380]

on a big 16g with supporting mods, Just wondering if there will be performance loss running a 3" straightpipe and the muffler is only 2.5" input

 

[Absit]

Sure, but you won't notice it. Generally speaking, a 2.5" exhaust is plenty for the sub 400 WHP crowd.
That said, I don't know a ton about flow science, so I can't say for sure if the opening and then restricting of the system will do anything worse than just running a straight 2.5".

 

[Joseph503]

From everything i've read its best to go from small - big. So once you hit 2.5" (or 3") you'll want to stay that size or larger from that point back, otherwise it causes turbulence in the flow and cause a restriction at the end of your exhaust.
Correct me if i'm wrong, but thats what i've gathered from reading other threads, etc.

 

[ampsyco]

you wont notice the difference. on a dyno you might see a tiny difference. but maybe not.

 

[2GbTalonGuy]

It will create a bottle neck at the end of your exhaust system. There really isn't a point in going from 3" back down to 2.5. You might as well save your money and stick with your stocker at that rate.

 

[ed1380]

well actually the cheapest downpipe is 3" out. Thats why I was wondering if i would be losing performance.

 

[Absit]

The cheapest route is almost never the best one..

 

[BigNugg99]

i am only going from what i have read about in forums and exhaust therory write ups but i would say that using a 3" downpipe and to into a 2.5" exhaust would be more benificial than going with a 2.5" downpipe and the you will still see a gain with the new bigger turbo. i just read from an exhaust theory write up that mentioned this delima and it suggested to run the 3" as far as possible and atleast 12-16" before tappering down to a smaller diameter. they also suggest to tapper up from a smaller diameter to a larger diameter as well as tapper down from larger to smaller because the suddeness of size will cause the exhaust to "stall" and screw up the exhaust pulse. basically go 3" as far as possibleand tapper it down to 2.5" if possible. hope this helps. look up exhaust theory for turbos on google to learn more. general rule is 300+whp 3" and it goes up from there but if you go too big than there is too much space and allows the exhaust to cool which slows the molecules=heavier&slower

basically i say that there is a performance loss going down in size but it is still worth adding the bigger turbo bacause the loss of power with the smaller exhaust will be much less than the gain from more flow to a properly supported and tuned engine. when you get the funds to upgrade to 3" exhaust i think it would be wise to get it because there will be a performance gain.

 

[phunny]

on a big 16g with supporting mods, Just wondering if there will be performance loss running a 3" straightpipe and the muffler is only 2.5" input

No you won't lose any performance. It's not the best setup but you will not lose anything.

 

[ed1380]

Thanks

Does anyone know if a 1g awd downpipe will fit a 2g awd since the they both use the same tranny

 

[gofer]

I don't know what the transmission has to do with downpipe fitment or where you read the 1g and 2g AWD transmissions were the same?

A 1g AWD downpipe/exhaust will NOT bolt into place on a 2g AWD DSM. You could probably modify a few of the exhaust hangers to make it work, but to say the least it won't be hassle free.

 

[STLskater92]

Any upgrade to a downpope will yeild power gains and quicker spool. Now as for dropping back to a 2.5" exhaust, you don't seem to be runnin enough power for it to make a noticeable difference but on a turbo'd car, 3" is deffinently better. I'd plan on going full 3" if you have bigger plans in the future. But for now, with what your running, you should be good to go

 

[GsxEcutioner]

I don't know what the transmission has to do with downpipe fitment or where you read the 1g and 2g AWD transmissions were the same?

A 1g AWD downpipe/exhaust will NOT bolt into place on a 2g AWD DSM. You could probably modify a few of the exhaust hangers to make it work, but to say the least it won't be hassle free.

1g dp is also shorter in length than a 2g.... Both go the same path just the distance is different.