Last Lemming

The PO has the Vitesse chip and I have installed a Lindsey racing 3" exhaust. Can someone tell me what bar I should be hitting. I'm trying to determine if I have a boost issue or not.

I have an otherwise stock 86 turbo.

BReif61

1.) Are you reading boost pressure off the OEM gauge or an installed aftermarket gauge?
2.) Do you have any data points from before the exhaust?

Disclaimer: I do not have a 944 Turbo, but have dealt with turbo cars in the past.

The exhaust should not increase your boost pressure, which should be controlled by the wastegate. The increased flow from the exhaust should reduce spool time, and could cause a boost spike before the wastegate can react.

What kind of boost pressures are you seeing now?

Last Lemming

Well before I installed the exhaust (but with the Vitesse chip) I seemed to be hitting 1.75 as read from the cars gauge. After the exhaust it went to 2 on the gauge. Then a few days later it went back down to maxing out just a hair above 1.75.

The owner told me he had the WG shimmed for 15 psi.

400hp944

The Lindsey Exhaust has nothing to do with your question (unless you changed out your entire system including the cross over). Get rid of the stock wastegate and install either a Lindsey dual port or Tial with boost control. You will be much happier. Install an aftermarket boost gauge as well. The stock one is useless and not accurate.

Last Lemming

I don't mind getting an aftermarket WG but I'm not sure what boost I'm suppose to be going to.

400hp944

I wouldn't go over 15 PSI. You should also consider getting a wide band AFR gauge so you know what's going on. Try sending John at Vitesse an email and give him the serial number off your chip. He will be able to provide you with particulars.
info@vitesseracing.com

fast951

It sounds that you are experiencing a boost control issue. I would examine the boost controller (KLR/CV or external boost controller), WG... Once you get the boost control functioning properly, then you can proceed to adjust it. Don't rely much on the factory boost gauge, a mechanical gauge is a must if you intend to alter boost.

How much boost you run depends on many factors. Octane, Turbo, Intake temps.. to name a few.

Not knowing which exact chip you have, as a general rule and to play it safe, stick to 15-16psi with 93oct. Yes many run more boost and get away with it. On the street, not a huge deal as you are not on boost for long (well not in most places). On the track it's a different story.

The higher boost you run on pump gas, the less of a safety margin you have. Your choice!

Last Lemming

Thank you for your reply. I have since found that my WG was tired. I've replaced it and I'm hitting 15 psi now.

bumflick

Last - how did you determine the WG was fried? Did you have to remove it and apply shop pressure?

Last Lemming

Basically I tested everything else and the only variable left was the WG.

Some of the things I did:

Pressure test system for leaks
Borescoped crossover pipe foe collapsed inner pipe
Borescoped my inter cooler to see if oil filled
Pinched of hose to WG
Rebuilt throttle body
Replaced vacuum hoses
Replaced TPS

I did pressure test the WG on the car but the test was inconclusive.
My WG worked but the spring must have been going out, so it didn't hold the pressure well