the car is a 95 si (canada) with a greddy kit with drag intercooler. Boost is set at 5 psi right now but end of august iam going to be running the VAFC hack 8-10 psi. Which exhaust size should i be looking at? Will the Type R muffler be to small? Also what should i do about the cat? Gut it? Get a new one??

 

leave the cat on it will leave good back-pressure for the turbo....and i am using a Thermal Research and Development Exhuast. i like it anyways!

 

Test pipe (not gutted cat) with 2.5 piping should be ok.

If you go with Thermal's turbo exhaust system (3 inch), I'd go with a high flow cat.

 

thats something oyu dotn want for turbo " backpressure"

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by boostdB16a &raquo;</TD></TR><TR><TD CLASS="quote">leave the cat on it will leave good back-pressure for the turbo</TD></TR></TABLE>

That backpressure myth is BS. For up to 250whp get a 2.5" high-flow cat all the way back. No bottlenecks. For over 250whp get 3" like the thermal. Free flowing exhaust allows the turbo to spool up quicker!

(Within reason, don't go slap a 4" exhaust on a car only making 230whp or something)

 

Modified because I cant think with three hours of sleep.


Modified by Neptune at 6:22 PM 7/15/2003

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Neptune &raquo;</TD></TR><TR><TD CLASS="quote">

I would say 3" if you want to up the boost ever get a highflow 3" cat as well. I don't understand the back pressure myth. If the vacum created by the exhuast gases pulse pushes and pulls the next pulse out of the exhaust then to size the exhuast just right would make the exhaust delivery better right? Going to big is bad for the flow right? Isnt that what you just pointed out by telling him to get the 2.5 instead of a 3" for a car with 250 or less HP? What is your logic for the back pressure myth to be false, unless I am not understanding you correctly. </TD></TR></TABLE>
The turbo is going to create a litte backpressure anyway, you don't want any backpressure after the turbo that will affect spool-up and HP.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by boostdB16a &raquo;</TD></TR><TR><TD CLASS="quote">leave the cat on it will leave good back-pressure for the turbo....and i am using a Thermal Research and Development Exhuast. i like it anyways!</TD></TR></TABLE>

Backpressure on a turbo car is BS. You want the pipe to be as big, straight, and short as possible.

 

ok....great answers guys.....i will be going with 2.5 like I was before...is the type R muffler to resrictive?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Cee_mon &raquo;</TD></TR><TR><TD CLASS="quote">ok....great answers guys.....i will be going with 2.5 like I was before...is the type R muffler to resrictive? </TD></TR></TABLE>

Is that what is currently on the car?

 

The ITR muffler isn't straight thru, and the ITR catback is 2.25" anyway, so it isn't worth bottlenecking the whole system, IMHO. I'm pretty sure that it pinches it to 2" at the muffler too.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by quikB18B &raquo;</TD></TR><TR><TD CLASS="quote">

Is that what is currently on the car?</TD></TR></TABLE>
Nope ive got axle back Dynomax super turbo muffler.... But it is really resrictive.