Q1: For those of you running turbo, did you have any problems with the stock exhaust system being too restrictive? I have a freshly turbo'd S with stock exhaust, and the car "falls on its face" when VTEC turns on. I had a very reputable AEM EMS tuner try to tune my setup with the stock exhaust, but he couldn't get rid of the drop in power after VTEC. As an experiment, he removed the exhaust entirely (open 2.5" downpipe), and gained almost 50 HP at 9000 RPM. It sounded a little ridiculous to me at first (how could such a high revving, high flow car have a restrictive exhaust?), but he showed me the dyno results, and it appears to be correct. Has anyone else encountered this?

Q2: Obviously I can't run open downpipe in California, so I need to find a less restrictive exhaust. Most of the exhaust systems on the market have 60mm (2.38") tubing, but that is that same size as stock... Other than "bling factor", what kind of improvement could that offer? Are there any 3.0" systems on the market, designed with turbo in mind? I want something that is quite, emissions legal, and less restrictive. Any ideas?

-Mike

 

inline pro and ultimate racing make 3" exhaust for our cars. check out their sites.

www.inlinepro.com
www.ultimate-racing.com


Kyle R

 

you can get a 3" high flow cat, buy an aftermarket muffler like apexi or hks 3" turbo muffler, have custom piping made with those things and you have yourself an exhuast system.

how much boost are you running?

stock exhuast is way too small because its creates too much back pressure. its good for n/a, but wont work for turbo

or make life simple and buy a premade one like he said

 

Is your wastegate blowing off into atmosphere, or back into the exhaust

 

Wastegate discharge returns to downpipe, as it should.

Running 7-8psi boost.

Anyone tried running a turbo with stock exhaust, and encounter the same loss of power after VTEC (indicative of a restricted exhaust)?

-Mike

 

unless you run an atmospheric wasetgate...
-Chris

 

I had the same problem with my turbo setup. I am only running 5pounds right now. When I had the AEM tuned by Jack @ P1auto.com he told me to look for another 50hp with retuning just because of the stock exhaust.

I bought two 3" four foot sections of pipe and 3 180 Ubends from summit racing and two 3" inlet HKS style Carbon fiber mufflers on ebay. I hope to get the exhaust fabricated by a friend in the next two weeks.

I should be going to 8-9 pounds of boost when I install the Gm boost solenoid and bring it back to P1 for more tunning. I will be purchasing a clutch and flywheel too and possibly lower gears for the rear end.

Right now I am getting 201.5hp to the wheel on a Mustang Dyno. I hope to get 250-270hp on it when I bring it back to the dyno.

I need to post some pics and dyno #'s when I am fully done.

 

For me at about 7000RPM the car just hits a brick wall and falls off.
I am using a hifi 60 series with a T3 flange . It spools really quick, full boost is achieved at 4500- 5000rpm.

To bad your in California. I am going to run 3" all the way back no cat. I have an open wastegate right now too.

 

I have a question to add to this, I'm using the Invidia exhaust at the moment but I'm going to be installing my turbo kit within the next few weeks, what on the exhaust will I need to change, or do I just need to buy a downpipe??

 

I'm willing to bet that you'll see quite a bit more than a 50 WHP gain by going to a 3"DP, venting the WG to atmosphere, and running a full 3" exhaust with testpipe.