I'm needing some help with an overboost issue that I can't seem to resolve. I've searched multiple threads and sites but haven't read anything that helped with my issue. My 2008 Evo X Gsr is hitting peak boost over 29.5psi according to the AEM TruBoost (which is the max reading of the guage) and EvoScan is showing 30.2psi. It hits at WOT generally in a 3rd or 4th gear pull, then drops to 20-25psi and holds steady. My custom tune is set for 25psi on 93octane pump gas. I've tried multiple fixes but cannot figure out why it keeps overboosting and won't let me control the boost.

At first I thought it was the Forge WGA. I swapped to a weaker "Blue" spring, but it still hit 29.5 on the AEM gauge. Thanks to Forge, I got a brand new WGA with a standard "Red" spring to swap thinking it was possibly a faulty WGA altogether. The new one seems to hold the boost better after the spike but it is still hitting 29.5psi. I adjusted the preload from 3 full turns down to only 1 turn and no change. I believe I ruled out a faulty WGA.

Today, I did a boost leak test. I did find a few leaks and fixed them all, but after a test run there was no change. The car still spiked to 29.5psi then dropped and held at 23psi to redline.

I have tried controlling the boost with the AEM Truboost gauge settings with no luck. Since, I have been running straight wastegate. Both options are hitting 29.5psi. The wastegate flapper arm on the outside turns 45 degrees with no issues, so I've ruled out a gasket issue that stops the flapper from opening all the way.

I've also read that some people have a bad tune causing an overboost issue. The custom tune I have is excellent and guy who tuned it has tuned multiple other Evo X's with no issues. I have no doubts that it's not the tune.

So, now I'm pretty much stumped. I'm thinking of upgrading to a Synapse DV since I've read that the stock diverter doesn't perform well at +25psi. I'm also considering going back to the stock wastegate or using a Hallman mbc to see if I can control the boost.

Any ideas/suggestions??

Current Mods:
AMS UICP
AEM Intake
AEM TruBoost
AEM UEGO
ETS Divorced DP
ETS HFC
ETS V2 Quiet CBE
282 Cams
Forge WGA
ACT Streetlite Flywheel
ACT HD Clutch
AMS CMC Kit
Stock Turbo w/Custom Tune on 93oct

 

Have you tried bypassing the boost solenoid and just running it on wastegate? If so- how does it behave?

 

Yes. I bypassed the AEM solenoid and ran straight wastegate with no changes at all. Both options spike to 29.5psi which is why I'm considering going to a stock wastegate.

 

Well you have eliminated your tune and electronic boost control as being the offender. The only thing left is a possible crack in the vacuum hose going to the wg or the wastegate itself. Only one way to find out and thats put the stocker back on and see how she behaves.

 

I checked all the hoses during the boost leak test today. No vacuum leaks now.

I've read alot about people having overboost issues with the Forge WGA, so there's a chance that the stock one could resolve the issue. And my tuner said the Evo X's that he has tuned with no overboost issues ran the stock wastegate; One with an AEM TruBoost and the other with the Hallman mbc.

 

Still having issues. I got EvoScan installed and have been logging a lot lately. It's spiking to 31 and 32 based on the logs from both 3rd and 4th gear pulls and on straight wastegate. I have no clue whats going on. I'm looking at going with a Hallman Pro MBC or a Grimmspeed 3 port BCS. Will either of these be able to dial down the boost when the WGA is hitting so hard??

I also recently swapped my HFC for an ETS TP, added an AMS FMIC, and I have 900cc injectors, a DW65C fuel pump, and Synapse DV ready to go in next. I'm just trying to get this boost issue resolved.

 

I installed the Hallman Pro MBC and it had no effect at all. Still hitting 31.5lbs, tripping the ASC warning, and hitting the cut.

Any ideas/help? I'm getting no feedback here.

 

Did you ever switch back to the stock wga? Did you still have the same issue?

 

Not yet. I put a BLUE spring in the original Forge WGA and there was no change in the boost. I thought maybe it was a faulty wastegate, so I called Forge and they sent me a brand new one. The new one also didnt fix anything. I've tried adjusting the pre-load and theres no effect.

Next Tuesday I'm putting it on the lift to check and see if theres any DP gasket issues causing the wastegate flapper from not opening/closing all the way.

I'd hate to spend more money on a stock wga and that not be the issue. I've already wasted more than enough $$$ on a TruBoost controller and Hallman MBC. It's hard to believe that noone in the Evo community has had a similar problem.

 

did you double check your vacuum line arrangement? more so with the AEM setup since there isn't much to check if you are only running straight wastegate now.

it really sounds like the WGA isnt opening and the only reason the pressure is dropping back down is because of the stock diverter valve leaking air after the initial boost spike.

if you put an upgraded DV on you might hold a lot more boost than intended so becareful.

maybe try pulling the spring and see if you can actuate the wastegate by hand.
not sure what else to say, i dont know why you bought the wga, the stock one is perfect for the stock turbo.

 

I dont think a dp gasket could cause boost spikes. Not the wga, bcs the only thing else i could think might cause it would be a vaccum line hooked up wrong or maybe the boost pills in the vaccum lines.

 

I've double/triple checked all the vacuum lines. I've tried using the stock solenoid setup, TruBoost config, straight wastegate, and Hallman Pro mbc and they all had the same 31.5lbs result. I'm running the Synapse DV now, so no issues with the leaky stock one. As for the Forge WGA, it came on the car when I bought it back in February. I figured if it was a WGA issue then there would have been some kind of change swapping to the Blue spring and trying a brand new WGA, but they each had the same result. Weird.

Some of the early ETS DP's had a problem with the gasket on the outside preventing the flapper from opening all the way. However, mine is the divorced one and there isn't any clearance issues externally. My flapper does turn 45 degrees but hits metal inside once it reaches the 45 degree mark (not sure if this is normal). All vacuum lines are good, but I will double check for boost pills next week. I'm certain they were all removed when I ditched the stock solenoid setup and tried the AEM TruBoost solenoids. Wouldnt hurt to check again just to be sure.

 

If you're spiking on straight wastegate pressure then the actuator is set too high...what's it supposed to be set for?

Swap to a stock actuator and I bet you get control over it.

 

I've tried adjusting the preload on the actuator and swapped the spring out. There was no difference. That's what makes me think that it's not the WGA.

The Forge WGA currently has the Red spring (30+). I've also tried the weaker Blue spring (23-30). I tried various preload settings with both springs and it still overboosted.

I'm tuned for 25lbs.

 

Is your flapper in the wga even opening?