whats wrong when your car doesnt hold boost

 

Seized turbo, split intercooler, engine worn, take your pick.
How about some more details? Like what car, how much boost do you get, etc.

 

its an escort cosworth it hits 30psi and holds 25psi

 

So, it does hold boost, just at a lower level than you think it should be?
And how much boost do you expect it to hold?
Did you check anything and if yes, what?

 

that sounds about right, especially if its a slightly old actuator going weak.

 

Weak actuator is my gess to

 

What turbo?

What chipset?

What actuator?

Did it used to hold more boost?

 

its got a t34 turbo ahmed bayjoo chip and a collins 31 actuator it used to hit 35psi and hold 30psi at 430bhp

 

Possibly just a weak actuator then mate but thats MONSTER power for a T34 though (more than I would of thought possibly TBH!), so it could well be showing some signs of not wanting to do it anymore.

 

its running rs 500 setup with eight injecters light blues it had just under 400 lb of tourque

 

Running that kind of boost needs an inconnel arm on the wastegate. What has happened is that the turbo has got hot and the arm has twisted so now it is bleeding off a bit of boost. You can adjust the actuator, but you will find that now that has twisted it has weakened it, so it will keep doing so until you run out of adjustment on the actuator.

An inconnel arm is made out of the same material they use in jet engines, so is more than able to take the temps the turbo generates without twisting.

However, I personally think that is WAY too much boost for a T34, and it SHOULD be tailing to 26psi by 7000rpm anyway, or it WILL die (the turbine will shit a blade) .