Overboost issue above 4k... Help? Ideas?

[Red-KAT]

So ever sense I took out my cat I have been having boost issues! I got it mostly under control. All the way up to 4300rpm my boost hold a good 10psi. But at about 4200-4300 it jumps up to 12-13psi... I have held it a bit after it jumps to see whats up and it kinda hangs at 12-12.5 psi for a bit...

I don't know what the fix would be for this besides putting a cat back on my car.

I have tried to make the wastegate rod longer to reduce boost, And i'm not adding any with my E-01. I just have it set to start at 10psi... Even with my E-01 off it still jumps up.. just takes longer.

I'm tempted to take off the wastegate arm and see what it boosts up to... But this is kinda annoying I been fighting this stupid issue forever and cant race it without the risk of smokin my engine.

Help? Ideas? Can the wastegate just not handle the flow and needs back-pressure to keep the turbo speeds down?

If I just had a built engine and bigger injectors I would care less about this issue!

[IvanAtSPRacing]

By elimnating the cat, you have sped up the flow of exhaust out of the engine. Your WG can not bypass enough exhaust to keep the boost down at the higher rpms. The only cure for this is to port the WG orfice to allow more exhaust to get thru.... or put the cat back on.

[IvanAtSPRacing]

Oh.. one more thing. Your not overboosting, your boost creeping.

You can send me your turbine housing and I can port it for you if you like.

[Red-KAT]

Ehh wrong term...

Thanks for the info!...

Now I have to find a car to drive while I get this ported. :/

[virus77]

if you want your SET boost to be 10 psi and you have inputed your START boost at 10 psi on the boost controller it will cause overboosting, you should set it 3 psi less then what you want your boost to be at. I noticed you said with the eo-1 off it still does it but that will make it even worse.

[GEO]

RED, this si teh greddy kit? Correct?

[Red-KAT]

Yes this is the Greddy Kit.

Once I get this ported I'll let ya know if thats the issue... Corse Ivan is never wrong

Ivan I'ma shoot you an E-Mail about the porting.

[GEO]

god damn it. I wanted the greddy kit too, but all these issues..

[Nismo_Freak]

if you want your SET boost to be 10 psi and you have inputed your START boost at 10 psi on the boost controller it will cause overboosting, you should set it 3 psi less then what you want your boost to be at. I noticed you said with the eo-1 off it still does it but that will make it even worse.

He's just seeing boost creep as Ivan said. A boost controller issue would have irregular control all over the boost threashold and is often time the result of too much duty and too less gain, or visa versa. Automatic modes on boost controllers also are hardly ever worth a damn.

As far as his problem... notice the VE of the KA, it gains very sharply at 4k which will lead to more mass flow. This causes an overpressure situation in the manifold that the W/G can not flow, so the air is passed over the turbine blade and you have boost creep.