I heard everything from exhausts not doing anything to like 10-15% increase in hp output. does anyone have a dyno of a turbo car before and after an exhaust upgrade? any kind just so i can see what kind of gains i might see going to a 3 inch.

 

going to 3" up from what? also do you mean dual 3" or single?

anyhow, free flowing exhaust is one of the most critical components on a turbocharged car, especially up near the turbo where the exhaust gasses are at their hottest. you can never go too large on a turbocharged car, though there is of course the law of diminishing returns.

 

If you add an exhaust you will need to have some piggyback or parallel engine managment to tune the A/F ratio. 20-30 rwhp would not be unrealistic with a free flowing exhaust and a properly tuned A/F ratio.

JET

 

well single 3 inch.. but wanted to keep stock look.. so dual tips.. like the nismo or fujitsubo.

upgrading from stock..

i got the TN kit.. so engine management is not in the picture unfortunately. when i had my car dyno.. all stock + TN kit with cat vesion SAE corrected was around 320 and it went below A/F 10 after 4500 rpm.. so its running really rich.. i figure the exhuast might balance out the A/F a little more too and give me a little better gas milage.

 

yea, i'm taking my car to get an aps st installed tomorrow, however I don't have an exhaust at the moment....but I preorderd an aps st exhaust from GRD so hopefully it will be in before they are finished installing the turbo...I heard its supposed to make a big difference.....we'll see...

 

It all depends on what setup you have and what exhaust you choose.

I remember on 350zmotoring there was someone who pushed 500whp out of an APS TT with a full stock exhaust (cats, y-pipe, b-pipe and muffler)!

In there instance I am sure that they could have had a large amount of WHP gained via a new free flowing exhaust with no cats. However the main benefit would have been the reduction of lag!

AS you may know, there are a few main things which address lag:
-Turbo to manifold setup (volume to pressurize and areas of pressure drop such as intercooler and bends in piping).
-Exhaust routing to turbo.
-Exhaust leaving turbo.

In his case he had effective exhaust gas routing to the turbo but more than likely had a gas bunching up together after the housing. By freeing the flow he would reduce lag quite a bit.

In terms of WHP, you could more than likely gain 20-30 whp easily over some of the more restrictive system such as Nismo by switching to something like SVRTech true dual 3". Exhausts like the SVR one are nice becuase they also utilize a x-pipe to aid in scavenging and mufflers and resonators that are claimed to also aid in scavenging (don't ask me how but it has been claimed by Aeroturbine).