Boost wont hold a certain PSI.

[onebadtsi]

Well to make this easy to understand.
Im not having boost creep and I do not have any boost leaks, I did a test and no leaks at 20 psi.
When I give it full throttle boost will go to 20+ and stay there if I dont let off, I can hold it around 10-15 then near 5K and higher floor it and it sticks at 15. This will happen in any gear any speed. I have a 95 GSX, 3" turboback, greddy bov, t25. Its done this since ive had the car. I thought it was b/c i had boost leaks but it wasnt. What can it be?

 

[95blackGsTurbo]

You are spiking 20psi because your exhaust is too free flowing and the wastegate can't open fast enough. I used to have this problem with my Big T28.

 

[turbodsm18]

First of all, Boosting 20psi on a T25 is a bad idea and its not efficient enough to hold much past 14psi. Just my .02

-Kevin-

 

[95blackGsTurbo]

It's fine up to 16psi. And he isn't doing it on purpose.

 

[onebadtsi]

Thats what I thought, and yes I know 20 psi on t25 isnt good. I guess Ill look for a new 02 housing.

 

[turbodsm18]

You are spiking 20psi because your exhaust is too free flowing and the wastegate can't open fast enough. I used to have this problem with my Big T28.

Not 100% true. I ran no boost controller on my t25 for a long time with a 3in Turbo back exhuast and it never once boosted higher then 15psi. The T25 is not rated for more than 14psi, yes people run more boost than that but it doesnt mean its efficient enought to make a difference.

-Kevin-

 

[JayRolla]

Are you running a MBC. If so take it out and see if it fix's your problem. check the vaccuum line from the wastegate for leaks. Also the shorter the vaccuum line from wastegate to boost source the less chance of spiking.