I know this subject is covered often. I have a free flowing intake and a racing beat turbo back exhaust with both mufflers in the rear. I have ported the gate opening out to about 32mm and the creep is still present in 3rd. Creeps to 13psi on nothing but the factor gate. Other then modifying creating a seperate outlet for the gate and tying it back into the exhaust any other possible ideas?

 

When I ported mine I also removed from the sides to enlarge the hole. About the size of a Honda exhaust valve. No creep.

 

I used a 1.8t exhaust valve which was larger then most of the honda valves ive come across. Thats why I am still scratching my head as to why it still creeps. Made sure it had plenty of clearance around the outside of the valve as well.

 

you can grind the back wall of the plate so the valve can open more.

something like this:


I have a super rare KSP down pipe that has a divorced pipe for the wastegate gases:





I have a separate one that's not as nice for sale... but it won't fit an S4 turbo.

 

Here is a picture of how large BNR ports the S4 gates:

 

I didn't quite go as far as the BNR port, didn't think I would need that much on the stock compressor still, though I guess I was wrong... I did work with the backing plate, but didn't take much out of it. Guess I can cut at that next. I have a spare plate I can experiment with.

Was thinking of working at creating something along the lines of a diverged/bellmouth setup similar to what the WRX/STI guys purchase as I readily see them in my line of work with working on Subarus and VWs. Was going to cut the backing plate and weld a pipe onto it and tie it back into the exhaust stream.

I will play with the backing plate first. Thanks for the input eage8. Trying to get this thing situated so I can make some track passes on roadcoarses and Autocross later this year.

 

You need back pressure. Otherwise youll over boost.

On my set up, I would still over boost. And that was free flow intake (no afm with lt10s) and 3 " exhaust to 2.5" duals. The waste gate was completely removed with the flappler and an external tial38mm in place. Still over boosted until I added some metal slits on the down pipe to add back pressure. Not so much free exhaist flow helped even tho its a "hack" I have a .9 bar spring and id stick 13 psi from 3k to 6k rpm. Then after 6k rpm boost pressure dropped to 6 psi.