2300cc

1988 Turbo S, bone stock. Car runs full boost 1st and 2nd through the rev range. In 3rd-5th it runs full boost up to about 5k than drops down to 1.2-1.3. I checked for vacuum leaks and all seems fine. Would a knock sensor cause this?

Thanks!

t3rra

Stock boost as well? Turbo won't hold 1.3 bar to red line dropping off after 1 bar that's 2 bar on dash.

Maybe your waste gate is sticking open. And letting anoth exhaust flow to the turbo. Or possible cv issue?

2300cc

The boost is stock as well. Cycling valve appears to have been replaced at some point according to service records. Anyway to check if the wastegate is sticking open?

2300cc

And yes I mean 1.3 bar on stock gauge so .3 actual boost.

t3rra

There was a long topic on this only last week. I believe if you can pinch the vacuum line from ic pipe between turbo and intercooler it should cause the turbo to over boost not sure how well u can monitor that inside the car.

The idea is it tells the waste gate there's less boost then there is sort off like mbc so the waste gate will close more then open, forcing more exhaust gasses to spin the turbo

Be careful as you could make crazy boost, however the krl will then fuel cut if working correctly

2300cc

I don't need to tell if the car can make full boost because it is doing so in the first 2 gears along with the others up to 5k rpms. I don't think pinching the wastegate line will tell me anything.

Rogue_Ant

Reducing boost pressure is the KLRs tertiary protection level. After this happens, I suggest checking the KLR for trouble-codes (don't turn the car off beforehand). The protection could very well be triggered from excessive knock.

Incorrect, any fuel cut would be at the command of the DME.

Techno Duck

If its making full boost in the lower gears i am inclined to think the wastegate is not stuck open. As Josh mentioned i would look into what the KLR is doing. If your only getting 1.2-1.3 bar in the higher gears this is about what you would see if the KLR is running in safety mode.

LR has some good directions on making a blink code tester,

http://www.lindseyracing.com/LR/Parts/BLINKCODE.html

I would check all the connector at the TPS and make sure its working correctly. I would also look at all hoses and the connector for the cycling valve. If you want to pressure test your intake, i have an adapter that plugs into one of the intercooler couplers with a schrader valve on it that you can borrow if you want. I live probably 10 minutes away from you...also in Oyster Bay.