Hey guys -

Been helping a buddy of mine try to find a weird overboost problem with his FD. Relevant mods -

- Downpipe, midpipe, 3" catback that's not TOO agressive
- HKS RS intake
- PowerFC with stock fuel map, more conservative timing
- Motor has stock ports
- Medium size stock mount IC
- Sequential twins, sequential system is basically working as advertised.

Wastegate hoses are run straight from the wastegate to the nipple, no boost controller hooked up and factory boost controller is not hooked up. We pulled the turbos (which are in good shape) and ported out the wastegate VERY nicely, it's good sized. Both wastegate and precontrol have been ported.

3/4 throttle in 2nd gear gets around 13psi. Should be quite a bit lower than that.

Really, the wastegate should be the only thing with any effect on boost at this point. There is no boost controller at all, it should be plain ole spring pressure. Also, this is in sunny Florida, temps are 60-70s right now, so it's not cold weather boost creep.

Any good ideas to look at here?

Dale

 

I had an issue where my time was off (retarded 20*) with a boost controller and ported turbos i was seeing 15psi no matter what i did. Once timing was set correctly boost controller worked just like it should.

 

Are the wastegate hoses open or do they have restriction pills?

I have never creeped here in FL except when it's freezing.


EDIT: Sticky wastegate actuator? What happens if you got WOT? I'm wondering if you let it rip, it will push the actuator hard enough to get it working.

 

I had the same issue. Full 3" exhaust with resonated mid pipe and ported waste gate. I was seeing 13-14 psi at 3/4 throttle, no pills and vacuum hooked up straight, same thing as you are describing. The only difference is that I'm running non-seq. I put a high flow cat and I'm now seeing 10 psi at full throttle.

 

check if the leading plugs are firing, my car was boosting really high when my leading coil died and was running on trailing only

 

Are you sure that the wastegate arm and flapper are opening all the way? Something could have gone wrong when you reassembled everything.

 

On a fully open exhaust and intake, I was never able to use the stock system to properly regulate boost either. I added a Greddy boost controller and that helped a bit but it would still creep at higher RPMs. Adding a high flow metal cat finally gave me the added bit of exhaust restriction I needed to control spike and creep.

 

Thanks for all the suggestions!

We're going to go over the map in the PFC tonight with my Datalogit, the timing suggestion is a good one.

The pills are gone, in the trash where they belong. The stock boost control solenoids are totally gone and out of the loop, he does have an aftermarket EBC but we're running it straight to the wastegate to troubleshoot.

I would also like to pressurize the wastegates and make sure they hold pressure and move properly. Both do hold vacuum so the diaphragms seem to be good.

Doubt the leading plugs are an issue, car starts, runs, and idles great, no leading plugs and it would run like ***. But, worth double checking as well.

I'll keep you posted, thanks guys!

Dale

 

OK, pulled out the Datalogit and checked out his maps. He's using the exact same timing maps as I am and I have no problems with creep.

In the near future I'm going to pull my high-flow cat off and swap it into his car and see if that makes a difference.

He has pressure tested the wastegate diaphragms but I'd like to test it again and verify full movement and everything.

Dale

 

I know you ported the wastegate but did you removed the metal behind the flapper door so it can open all the way?

 

Of course the moment that you put the cat on it's going to make normal boost. I wanna know why it's not normal with the ported w/g. The cat is just going to hide the issue. You should not be creeping... especially in 2nd gear... not even wot.

Even on my last FD, streetport motor, fully operational seq stock twins at 14psi w/non ported w/g, pettit i/c, intake, dp, resonated mp and cb all 3 inch... it only creeped high in RPM's in 4th gear when it was sub 40* out... which isn't very often in central fl.

At the same time, there isn't much that would be "wrong" to make it go screwy.

 

I hope you're right, when it happened to me the car started and idled fine, boosted too much but felt weak, slower. I couldn't figure out why. I only found out the problem after the metal cat core melted and I had to troubleshoot the ignition, finding a dead twinpower along with the leading coil.

New twinpower and coil, boost was back in check and power was back!

 

Hmm, interesting! That might be worth some further investigation then. His car has been down on power for a while too.

Unfortunately I've got a wedding to go to this weekend out of town so it will be a while before I can get my hands dirty on it again.

Thanks guys!

Dale

 

The pre control and wastegate sensors might be out out of whack.

Try swapping those out if nothing else works. Worked for me.

 

The wastegate control and turbo precontrol are GONE from the car, that's the factory boost control. The other parts of the turbo control system (charge control, turbo control door) can only lower boost by not working, not increase it or lead to creep.

BTW, he did test that he does have leading spark. He found that out in a let's say "shocking" way .

Dale

 

I went through all this suggestions with the exception of verifying the back of the wastegate door porting. The wastegate itself is ported but not sure on the rear to allow full opening which I bet isn't done. So I ended up putting a cat. Lowest boost I see is 10 psi all the way to 7k. I'm slowly going to 8k just to make sure the boost doesn't go to high.

 

If the cat fixed the problem, you can make a steel restrictor and place it after the midpipe and before the catback. I had the same problem on my first FD and made a steel restrictor, cut out exact dimensions as an exhaust gasket, just made the opening 2 1/2" instead of 3! Worked like a charm! Kept boost steady and didn't reduce my power output at all. Try that instead of a cat. takes 15 minutes to make and cost me about $20 for the sheet of steel.
Art