All my friends run 2.5 and your fine on their sc cavy's
They use pacesetter header's though.

 

I was going to use the lsj pacesetter but to be honest I hate the ball socket. Once you mod it with a v-band, add a flex pipe on the downpipe and get it re coated your looking at $500 for a sub par header.

I am liking the Bad mab because it seems to get good results for you lsj guys and is a bolt on to the stock downpipe. So I dont have to take it to a exhaust shop to do any welding.

I think I will be going the 2.5" route. If I get to the level that it cant support the power im making then so be it but I doubt itll be the hold back to my build.

Unless im off on this lol. Hard to tell from this thread. Seems to be a 50/50 split lol

 

We have a member on this site who makes 352 whp with a TVS setup....

His exhaust mods are as follows:

-Stock manifold
-2.5" catless downpipe
-2.25" GMPP catback

You should be fine.

 

Maybe this can be of some help...

tunes were the same for both.

I didn't post max values, instead here's temperature and humidity.
End result: 16whp gain

note: (2.5" was catless, 3" was with a high flow cat)



Don't see an issue with the noodle having an effect on the power band here... then again it's a mere 15.5 psi.

 

good post. subd

 

Wsfrazier's graph:



TVS, stock manifold, 2.5" catless downpipe, gmpp 2.25" catback

Smaller than stock piping seems to flow well enough for this kind of horsepower output, and airflow....

This is why the debate of "what size exhaust" will never really come to an end.

 

^gotcha...buy one and stick with it.

Now it comes down to sound I suppose. Is the 2.5" going to sound better?

Reason I ask is I already have a 3" superturbo I bought when I was going turbo but if its going to sound better being a 2.5 ill sell it and buy 2.5" parts.

*** and like you said. in two posts I get info supporting both sides lol.

 

Yeah, there is def info/results supporting both sides....

100% Meth posts good data for his particular setup. Not everyone will see those kinds of results though.

You can make a 3" sound decent with the proper muffler and resonator combo. A 2.5" will more times than none be quieter than a 3" setup.

 

I am going to open it back up.

I have no idea what his tune was, but if we had a more open exhaust he might not have gotten that KR up top.

 

Maybe so....

I don't know the full details of his tune either (timing, AFR, ect.), but he is still making impressive power with such a small diameter exhaust.

I am by no means promoting using a small exhaust, I just don't want some of the members to think bigger is always better.

There are a lot of factors that govern using a certain size exhaust for a particular application that many do not account for.

 

I agree with you that a 3" is not necessary for every car.

But using Wes's TVS results as an example has become even less credible now that I had seen that chart.

 

We do not know if that hint of knock in the upper rpms is indeed from the exhaust though. He has a pretty good powerband.

It could have been due to a number of things.

I do feel though that a car that is flowing the kind of air a TVS or MP90 can produce should run a larger exhaust.

I'm just trying to post some power examples to show what people have made with smaller than 3" exhaust setups.

Wes's was the only one I could really think of off the top of my head.

 

Stock exhaust yielded the best results for me.

 

corn is the great equalizer

 

That is an excellent hp/tq curve.

^^^This.

 

I'm sure fuel plays a big role here

Below is a comparisson of a TVS and MP90 on the same dyno. Over here our torque curves peak way sooner.
Note: I've substantially improved the advance table since my days on the dyno with the MP90.

TVS | 2.6 PULLEY | ZZP INTAKE | METH 21gph | PORTED HEAD | BADMAB HDR | 2.5" DP & CATBACK | 25-28* advance, knocked post 6500 rpm unfortunately. I'm pretty sure I've found the limits of water injection... If you throw a lot of timing at peak cyl pressure, the water injection can only do so much.

MP90 | 3" PULLEY | ZZP INTAKE | METH 19gph | STOCK HEAD | BADMAB HDR | 3" DP & CATBACK | 18-25* advance



Maybe I'm going about this all wrong...

Figure with a aggressive head port, ATI Dampener, NB shafts or delete, supertechs springs, a set of stg2 zzp cams or similar, and a 8k redline.

I think thats a winning combination most should aim for, taking full advantage of our small displacement. Rather than throwing a million degrees of advance at it and 20+ PSI.

 

Well I know for myself somewhere north of 300 is the eventual goal. I plan on getting there with either a tvs or a mp90....whichever is available to me at the time.

But it maybe 2 years before I get there.

Unfortunately I don't have the luxury of e85........best I got is 94 octane and meth.

 

94 octane!!! man the things I could do if we had that...

 

We have that all over up here.....94 with no ethanol.

So with 94 and meth I should keep the knock at bay. Apparently our 2.2's arent as good at keeping knock down as your balts.

 

CAM2 is even better

 

start work again Monday...

the list I made above for a 8k powerband will be purchased soon... already have a spare short block and head.

 

The intake cam on the ZZP S1 cams and the exhaust cam on the ZZP S2 cams best match the GMPP cams just in case your wondering.


Have you been following this thread at all?

https://www.cobaltss.net/forums/2-0l...blocks-264562/

 

I ran the GMR cams on a very mild head port, with 10:1 pistons and it was a rev monster. Car pulled strong to any rpm honestly.

 

About the new 2012 Buick Regal GS Turbo with "only" 270 BHP at 20 PSI of boost:

"A three-inch-diameter exhaust system provides reduced back pressure, resulting in higher engine power"

 

You can't really compare turbocharged cars with supercharged cars when it comes to the exhaust system man. I agree that a 3" exhaust will produce more power than a 2.5" exhaust on some applications though.