I am having serious problems with boost creep and its very annoying. I have an S5 6 port turbo running on the stock WG spring. The intercooler piping starts out at 1.5" from the compressor, to the front mounted stock TMIC, and exits with 2.5" piping to the TB. The exhaust is a 3" downpipe with 2.5" crush bent Y pipe to stock replacement RB mufflers. The car sounds stock. The wastegate is ported to 32mm (S4), the TID is 2.5" with one 45* bend. Stock block.

In 1st and 2nd gear the car will hold 5-6psi perfect, 3rd and 4th gear it creeps to 7. Is this normal? I don't like it because I can't run 7psi from the MBC because it'll creep to 8psi+ in higher gears (fuel cut). How can I stop this? maybe switch all the 2.5" piping to 2"? That would suck. How about switch the TID to 2"?

Thanks for the help, please don't tell me to search. 90% of the threads with "boost creep" in the titles have absolutely nothing to do with boost creep.

 

first thing i would do is check for leaks and make sure boost reference line to the waste gate is all good.

the next thing i would do is port the crap out of the waste gate.

tips here:
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/boost-creep-problems-718335/

 

What kind of filter on the intake? Maybe going back to the stock airbox will settle this thing down?

 

Reference line to the wastegate is good. The wastegate is ported to 32mm, I honestly can't even see how I could go bigger than that. I guess I could give it to my machinist and have him do it this time though. So a boost LEAK anywhere other than the wastegate line can actually cause creep? I thought it could only bleed boost pressure and cause slow boost response.

Filter is an HKS, same one that I ran when the car was NA.

 

Find an s5 turbo hotside and manifold = Larger ported wastegate

I run the 2.5" full RB setup and I run stock boost 5.5lbs


I think what trupain is saying is make sure your wastegate vac line is connected properly.

 

Did you back cut the ports in the wastegate?

 

Back cut? If you mean the plate then I ground the contact area down a little. Yeah I know the S5 setup is superior...I was really hoping not to take the turbo off..

 

You mean you don't want to fix the problem?

 

By backcut, I meant porting the passages as well.

You can get the hole where the flapper sits big, but that doesn't necessarily mean you will get improved flow.

 

The best way I have found to eliminate boost creep is by porting the hell out of the WG ports and by taking a grinder and removing material from the rear plate on the turbo, by doing this you allow the WG door to open fully and allow more air to flow out the ports, I have Dyno tested this, and I could NOT boost past ~7.5psi, we couldn't figure out why it wouldn't creep; then I remembered that I did this modification, so we hooked up the boost controller, and I was able to boost ~10-12psi.

Here is some info on it, NZconvertable is a smart man, but if you run more boost you are applying more pressure to the spring so it is going to compress more, and I have proved this on the dyno, and have knowledgable, and respected members that whitnessed it, and will back me up.

https://www.rx7club.com/showthread.p...ighlight=plate

 

The only issue with the S4 turbo is that the wastegate only leads to one runner. The higher compression engine and much larger ports easily overcome it. The only real solution is to swap to a S5 housing or go to an external wastegate.

 

I should say that the modification I did was on the S5 housing, not sure of the effects on the S4.

 

My old set up use to creep.
I had full exhaust,cone filter,s5 turbo on the stock s4TII motor, FCD,720ccx2.

Like he said. In third and higher gears my car would creep from 7 to 9 psi.