I had a boost creep issue (BNR Stage IV w/ clipped P trim and 60mm external WG) that I could not solve. It would boost to 22psi w/ WG set below 14psi.

I removed my JIC Spec 90 3 1/2" turbo back and put on the Racing beat 3" turbo back and it now boosts wherever I set the WG.

The very low end boost is not as good, so it doesn't quite drive like a larger displacement engine now-it doesn't like to pull from below 1,500rpm. Also, it takes 500-1,000rpm longer to get to full boost.

But it is a GREAT feeling to see the boost rise up to desired level and STAY!

So, if anyone is wondering if Spec 90 3 1/2" turbo back or HKS 4" turbo back REALLY makes a difference over the usual 3" turbo back- absolutely.

 

So it was creeping because the exhaust was just that free flowing? That is interesting especially considering the 60mm wastegate.

 

Yes, basically Bryan believes the stock (modified) S5 exhaust housing was so restrictive it was overspinning the rotating assembly.

I had already doubled the width of the scrolls aperture in an attempt to lower pressure.

He offered to trim the exhaust wheel in order to slow the turbo w/ out me having to resort to adding restrictions, but the Spec 90 was way to much of a race exhaust for the street anyways- SOOO LOUD!

When the open vented WG opened up it was no louder w/ the Spec 90, the sound just moved from the rear of the car to the front and rear. Now w/ RB it is VERY quiet untill the WG opens up- then all hell brakes loose .

Anyways, Bryan was very good at working w/ me to correct any problems I had w/ the turbo. His customer service is THE BEST. I just have a very unusual set-up that did not respond to his turbo in the normal fashion.

Ian

 

So this solves one of the BNR hybrid creep problems. Good to know.