1996 850R Hitting boost cut at 7-10PSI

bwe95 · Post by **bwe95** » 13 May 2018, 00:56

Been trying to figure this out for a while now, I have a modified 850R w/ 5 Speed manual. PO has put forged pistons in along with a "tuned" ECU which I have been lead to believe is just a basemap tune. CBV has been bypassed with an IPD plate.

At around 7-10 PSI the car bucks hard like its about to throw you into the dash. It's not a mild shudder, its sudden as if you turned the key off and back on.

AFR stays around 14.7 idle and WOT@7PSI is around 13.0-13.5.

I have replaced Spark plugs, TCV, Intercooler, Vacuum lines, all hard intake lines and couplers, and Fuel Pump.

Any advice on what to look into next would be much appreciated as I'm at a loss at this point.

Post by **abscate** » 13 May 2018, 01:54

How about the CBV,the diaphragm on the turbo that limits boost to stock?

bwe95 · Post by **bwe95** » 13 May 2018, 08:31

abscate wrote: 13 May 2018, 01:54 How about the CBV,the diaphragm on the turbo that limits boost to stock?

The CBV was bypassed with an IPD blockoff plate by PO

Post by **abscate** » 13 May 2018, 10:07

CBV has been bypassed with an IPD plate.

Post by **wizechatmgr** » 13 May 2018, 16:18

I'd toss the CBV back in. It is likely unhappy about an engine parameter and cutting fuel.

Post by **tryingbe** » 13 May 2018, 17:05

What's the ECU exactly? Turbo 850 never came with manual transmission in the US.
Bypass CBV and using what to replace it? BOV?