10 PSI, then 6, then 10 again?

[dgreene]

OK, here's my problem(?). I go part throttle, get 10 PSI of boost then it drops to around 6 PSI, then it comes back to 10. Doesn't do this at WOT, just part throttle. It may be normal for my setup, but since it didn't do it stock, I thought I would ask and see. My combo is listed below, it's the one with the Astroroof that I'm working with. Don't see a problem on my DS, just can see it on my boost gauge.

Thanks!

 

[Scott231]

Donnie,

Does the boost drop occur at the shift point or in the middle of a gear?

If its the former, that can be expected as the rpms drop and thus the exhaust pressure going into the turbo decreases.

If its the latter, that can happen do to detonation detection, a goofy parameter in the chip, minor exhaust leak (remember the issue with the crack in the DS header!), etc., etc.

Please advise.

 

[dgreene]

Thanks for the quick reply......

It's not during a shift and there's no knock present. I just had my header welded up and it sealed good to the head. Every now and again I think I hear it leaking from the crossover where it meets up with the passenger side header........ I'll check that and see if I can find anything.

 

[jojo]

Originally posted by dgreene
OK, here's my problem(?). I go part throttle, get 10 PSI of boost then it drops to around 6 PSI, then it comes back to 10. Doesn't do this at WOT, just part throttle. It may be normal for my setup, but since it didn't do it stock, I thought I would ask and see. My combo is listed below, it's the one with the Astroroof that I'm working with. Don't see a problem on my DS, just can see it on my boost gauge.

Thanks!

Sounds a little what mine sometimes does. I think this may be normal. Does it have that fluttering sound from the K&N filter each time boost builds then drops then builds again?? I believe it is the symptom of what was said in your other reply. Pressure is trying to build, but cant get there quick enough at part throttle. But if you notice once you open her up, it wont do that, boost will stay rock solid. At least mine does. Once i put my foot down its all over baby, that needle shoots right to 21#

jojo

 

[dgreene]

sure does. Maybe it's normal for the larger turbo, intercooler, powerplate setup. I'm still going to check that crossover for leaks. You know, this board is such a wonderful place for answers on these cars. Before I found this place, I never could find any answers or suggestions. Thanks guys!!

 

[jastrckl]

Do a search on 'surging', but I've never heard of a turbo as small as a ta49 surging really....