LS1 383ci turbo overboosting

[BookMe]

Hi all.
In some real trouble only a few days out of powercruise.

Car was fine running on 98octane. Changing to E85 now and the turbo is overboosting to 15psi before the tuner backs off (still climbing).

Tuner has dropped the exhaust and checked the wastegate diaphragm (turbosmart progate 50mm). Diaphragm is fine.

Have disconnected the boost controller and run straight off the 7pound spring in the wastegate and still no difference.

Still not working. Can’t think of what else would cause this.

 

[delcowizzid]

need bigger gate to let out the extra volume of gases due to e85 or bigger turbine housing

 

[BookMe]

Would E85 really cause that much extra gases? Surely a 50mm gate would be big enough.

Turbine is 1.15A/R on a GT42.

 

[enroh]

50 mm gate is more than sufficient on a stock capacity ls1 on e85 with gt42 sized turbo an a rear housing that big. And even with the extra 37cubes you have the gate should be more than big enough. I would say either the actual valve in the gate is jammed/siezed, or the tuner has put in wayyyyyy too much fuel in the VE tables or taken out way too much timing. Whos your tuner if you dont mind me asking?

 

[delcowizzid]

yeah timing removes boost if its well retarded and you add heaps back in

 

[BookMe]

Tuner has done plenty of turbo lsx cars running e85. So shouldn't be a problem.
Have had two tunes previously and they were perfect.

I dropped off a 100% working wastegate on Saturday. So fingers crossed that's the fix.

 

[enroh]

Whats ya compression Ratio?

 

[BookMe]

9.0:1
.....

 

[enroh]

then just boost the b#tch to 20pound!

 

[BookMe]

Green line is 14psi on 98 octane
Yellow is 10psi on 98 octane
Red and blue is what it's doing now.