boost question.

[TurboXT]

i had my grainger set at 13 psi. the turbo went out, so i put in another used stock T3. but the psi is around 8-9 and i havent touched the g valve yet. should the psi be the same or no becuase its a different turbo. LMK

thanks

[xtrempickup]

what kind of car, what yr and what motor, stock psi on T1 in 85 and 86 i think was between 8-9psi

[mpbiv]

Gabe, what wastegate actuator can do you have on it? You could possibly have a wastegate actuator with a weak spring, in which case the exhaust pressure is pushing the swingvalve open before the grainger allows the can to see any boost pressure.

[TurboXT]

i used the same waste gate from my other turbo.

BTW its a TII

[Frank]

It could be efficencies of the turbo, and how much energy it takes to spin the shaft etc. Used turbos dont nessecarily behave exactly the same.


Frank

[mpbiv]

Frank: isn't the wastegate operation still for the most part independent of the turbo efficiency, assuming the backpressure is not high enough either way to force the swingvalve open on its own? I mean would the efficiency difference really cause that much change in backpressure between same spec turbos?

But to be honest I am stumped. I don't understand why it would do what its doing when you are using the same grainger valve and wastegate. The grainger simply hasn't changed so it should still open at 13psi, and considering that you are getting 9psi, that indicates that the wastegate can is never seeing any boost to cause it to open. That just seems to indicate to me one of these possibilities:
-The grainger valve was inadvertantly changed, which you said was not the case.
-Weak wastegate actuator, again its the same you used at 13psi so it should be fine.
-More backpressure at 9psi of boost than with the old turbo, which in turn is forcing the swingvalve open.
-Swingvalve stuck open partially bleeding off exhaust.

Maurice

[TurboXT]

Quote:

Originally Posted by fkatzenb It could be efficencies of the turbo, and how much energy it takes to spin the shaft etc. Used turbos dont nessecarily behave exactly the same. Frank

thats what i was thinking

[TurboXT]

i just reset it to 13, so everything is ok now

thanks