Im sorry if this has been posted on over and over again, my internet is horribly slow and i can't search that well.

I have a '87 TII that is 100% stock.
What I want to do is replace the entire exhaust system with hopefully just a solid piece of 3" ID steel. The car will only see the autocross track and is running very strong(I believe the seller said engine and tranny have around 15,000kms). What I am worried about is boost creep and overboost. I have read Aaron's website about porting the wastegate. This is my big question, If I get the wastegate ported to the recommended 35mm am I still going to need any amount of backpressure? I'm wondering if I should bother with a catalytic converter at all, or a smaller tubing diameter. Any info would help.

Also I'd like to note that I am NOT trying to increase my boost level. My main reason for this is the get rid of the 20+ year old exhaust system and do so without spending $1000 on a nice racing beat system.

Thank you

 

You will have boost creep and a higher overall PSI level than it was stock. You will run around 12 psi, as soon as you remove the cats.

You should have a precat and the main converter.

Keep the stock intake piping and filter box, this will keep the boost levels down alot. expect a rise of about 3 psi from changing the intake.


You will need to get the FCD... so you don't push more PSI that you can support with fuel.

Porting the wastegate will only stop some of the boost creeping past a set level. It will still spike.

Put a cat back on the car, that will help keep stock levels of boost

 

well said!

 

I'm not sure if your Auto-X has restrictions on sound level, but with just a straight pipe, you will probably exceed them. By a large amount.

 

I don't think you realize how loud this well be. When under load it should be about as loud as an open wastegate, which is ear-splitting. And I think with that open of an exhaust you will still run higher boost even with the wastegate maxed out. I couldn't keep boost under control at 10psi with an HKS 40mm wastegate and a 3" exhaust (no cat).

 

It is not that bad... I have a full 3in. turbo back and my bros evo with full 3in. is just as loud as mine
I only have a resonator and my bros evo has straight pipe.

 

I have an 87 TII with the 2.5" Racing Beat exhaust & ported s5 turbo. Really had to port the wastegate as big as it could go and now I have no boost creep.

First thing you will need is a boost gauge cause the factory one lies to you if you change the exhaust!

 

^^ I guess it is quieter on an internally wastegated turbo.

 

So if I keep the main cat, and port the wastegate I should stay within reasonable boost levels? I don't want to play with the fuel system at all. Im trying to keep this on a budget. And if I put in a better intake system its going to increase boost again by 3 psi no matter what? is there no way around that.

 

My car used to have a cone filter and full exhaust with a resonator ,non ported turbo and it would hit 7 psi 1st and second gear and on 3rd and 4th it would creep to 9 psi somewhere around 6,000 rpms then fall to 6-7 psi at redline.

U will need a FCD.(fuel cut defender) SInce stock ecu cuts fuel at 8.5 psi

 

You can get cheap single exit stainless turbo-backs on ebay for about $300 and then just weld in a borla XR-1 muffler or high flow cat.

 

What is going to increase boost is a free flowing exhaust. But if you port the wastegate an intake will not increase boost. I have a TID w/ cone filter and I still hit 5.5lbs all day long.

So what you should do is...

1 port wastegate
2Hollow out 2 precats(NOT MAIN CAT) and buy a Catback exhaust or buy a downpipe that will hook up to the cat and run the stock mufflers.

 

IS the FCD the same thing as the Racing Beat fuel cut controller? I'm just a little skeptical about allowing the increase in boost pressure, even if the fuel system isn't getting cut down by the ecu. Will a stock system keep up with upto 10psi?

 

What the FCD does is trick the computer into thinking it isn't boosting past 8lbs. If it does hit 8lbs without the FCD it will cut fuel which is bad while boosting. I did it once in my car and almost kissed the steering wheel. I forgot to add---GET AN FCD CAUSE YOU MAY NEED IT.

So now your list could read

Boost gauge
FCD
Ported wastegate
exhaust of some kind.

 

Yup yup.

I have a full SSAC single exit exhaUst. It was like 300 shipped. Bolts in to stock mounting points and sits tight under the body.

Im happy with it even though its a bobo exhaust. I mean what can go wrong.. Its just piping hehe.. Not mechanical.(no moving parts)