I was having some issues with the Boost creeping on my TC as you guys might remember. I also had a boost leak somewhere which I fixed, now the boost goes even higher and is sometimes erratic. I am going to change the back housing of the turbo to a larger 5.8 it currently has a 5.0 housing. This will also give me some more overall whp with a little more lag. The good thing is that my barely has any lag at all the car starts to boost at about 3500rpm with a T4 ball bearing turbo. Do you guys think this will fix the problem? I really don’t think it is the waste gate.

 

Give us some details on your wastegate? Have you done a leak-down test on your vaccum lines? Do you recirculate the waste gate?

 

It is a TIAL 38mm and yes it is recirculated but so is anoter guy I know with a GT35r turbo running 12psi which is what I am trying to do. I changed the wastegate awhile ago I used to have a Tubonetics evolution here is a pic. It has a 60 trim compessor with a 3" exhaust all the way back.

 

Port it! lol

 

bigger wastegate??

 

I doubt it man but that will be the next time I am going try after the housing change

 

It might be related to the 3" exhaust. I had my boost dialed in 9.5 with a manual boost controler when I decided to cut out my cat. For fun I drove it for 2 days with no exhaust comming off a 2 1/2" down pipe, but I had MAJOR boost creep. Up to 13 psi and would of went higher if I kept pushing it. When I buttoned the exhaust back up it ran a solid 9.5 psi.

I've been told that 3" exhaust are to big for the low boost applications 99% of us are running. One of the major issues being boost creep do to the lack of back pressure.

 

ya 2.5 exhaust is what ya need

 

yea may want to do 2.5" all the way. ive herd 3" doesnt have enough back pressure for the tC.

 

[quote="peteyd"]yea may want to do 2.5" all the way. ive herd 3" doesnt have enough back pressure for the tC.[/quote

That is a myth...Forced induction does not need back pressure like a N/A car.

 

Then what made me have boost creep when I went no exhaust? Then it was gone as soon as I hooked it back up. The only thing that changed was the back pressure.

 

I dont know why, but logically boost creep is caused by exhaust backing up in the engine not by it coming out faster. What kind of turbo, wastegate and manifold do you have?

 

Boost creep is caused by a turbo that is too efficient for your system. Your turbo is making more boost than your wasyegate can bleed off. Basically, adding a new exhaust side will make the turbo more efficient and cause even more creep.

What you need is an adequate wastegate or to run more boost. Only other option is to create backpressure which will slow down the turbo so your wastegate can keep up. Try adding a high flow cat!

 

Having said that I would think the bigger turbine housing on the back would slow down the turbo from spooling so fast thus eliminating the boost creep.

 

rasta how much boost are you running??

 

I am trying to run 12psi

 

But it will also move more air since it is more efficient. Why would you want a bigger turbine when your not using the one you have?????

Sounds like you do not want to change the wastegate since this is your second post about it. So, go have a cat welded into your exhaust. Problem fixed......

 

hmmm its possible it my be your WG then. but try the turbo housing first if its still doing it its your WG.

 

When you run a bigger turbo at low boost that is when a bigger waste gate is needed. You can run a 38mm waste gate on the biggest of turbos at really high pressure's (or should I say really high flow) but then you try and control a large turbo/efficient turbo at low boost it will tend to creep. This is why DSM's get boost creep with 3 in down pipes. The turbo becomes more efficient. If you had a properly sized turbo for the power you are trying to make then you could live with a properly placed small waste gate.

 

Well I guess we will see what happens what I might do is just buy a bigger wastegate I already have the housing to put on, so I will do both at the same time.