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Discussion Starter · #1 ·
Okay, so first a little background on my car. It's a 1997 900 2.0T, automatic, stage 3 BCB @ 21PSI, 3" DP, intercooled, intake, and straight pipe.

So here's my question. When I put my car into sport mode I and give her the beans my boost spikes to 20PSI and then falls down to around 16PSI. BUT when I manually put it in third gear (remember my car is auto) and I EASE into WOT (without trigger kickdown) I can hold 21PSI all the way up to 5500rpms where it tapers off to about 19PSI. What would cause my car to do this? I have a helper spring on my wastegate, so that can't be the problem. I'm 99% sure the BPC valve works correctly. The only thing that would really make sense is the BOV, which mine is just the stock Bosch one? Could some one give me a little insight on this? Or at least point me in the right direction? That would be great! Thanks guys! ;ol;
 

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The wastegate spring isn't really a solution, wastegate controls can be modified within the tune, itself. So not a good basis to rule the wastegate out.

However in this case, I don't think the wastegate is a problem. Turbochargers can only maintain a certain efficiency within a given range and the stock turbo is well outside of that as rpm approaches your rev limit.

So in short it's normal to see some loss of boost but if you want, it wouldn't hurt to pick up a Forge BOV to replace the stock one. It may help to some small degree. Just keep in mind that the efficient range of your turbo is early to mid rpm's, where torque is still abundant.

Also, you say 'intercooled' but the cars have intercoolers from the factory :D do you mean you've upgraded it from stock? That's always a big improvement to maintaining boost levels, with the cooler charge air.
 

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Discussion Starter · #3 ·
However in this case, I don't think the wastegate is a problem. Turbochargers can only maintain a certain efficiency within a given range and the stock turbo is well outside of that as rpm approaches your rev limit.
So in short it's normal to see some loss of boost but if you want, it wouldn't hurt to pick up a Forge BOV to replace the stock one. It may help to some small degree. Just keep in mind that the efficient range of your turbo is early to mid rpm's, where torque is still abundant.
Yeah I think that's my problem, that when it's in sport mode and I put it to the floor I'm already so high up in the revs that it runs out of breath. Thanks for solving my problem for me!
 
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