Boost Pressure
06-13-2001, 03:53 AM
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Boost Pressure
I recently rebuilt my 993 tt engine with 3.8 P&Cs, RS cams, and a RS clutch. The car still uses the standard ecu and turbos. The engine runs well and is powerful. The problem is that the digital boost gauge will show only a maximum of 0.5 bar boost whereas before it easily shows 0.8 bar. The engine engine was hooked up to a computer to check for fault codes but shows no none. I ran the car with another completely stock 993 tt and my cars easily keeps up. My car feels more powerful. BTW my friend's car easily showed 0.8 bar boost. Please help! Anyone!
06-13-2001, 04:44 AM
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See if Rick could help. I saw a paragraph in his website describing your problem. His website is www.993tt.com
Good Luck!
Good Luck!
06-13-2001, 04:27 PM
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The 993TT's Motronics unit doesn't control the boost pressure very well. It actually doesn't know anything about boost, and the control algorithm in the ecu is based solely on throttle position and rpm to generate a specific pwm frequency for the boost control solenoids.
what this means, is if you do any modifications to the car, the boost will change as the car is not really controlling the boost, but just generating a specific output frequency for any given throttle postion and rpm.
If you put on big turbo's, the boost goes down, if you reduce the backpressure, the boost goes up.
You probably are running .5 bar vs. the stock .7-.8 due to the larger displacement and larger turbo's.
The easy solution is to put on an evc to externally/properly control the boost pressure.
You could also reset the base pressure at the w/g's by tightening up the rods. But mostly, the ecu should be reprogrammed, otherwise, once you get the boost up, you'll probably run into the mass flow error charts and start generating faults.
We can supply whatever you're after
what this means, is if you do any modifications to the car, the boost will change as the car is not really controlling the boost, but just generating a specific output frequency for any given throttle postion and rpm.
If you put on big turbo's, the boost goes down, if you reduce the backpressure, the boost goes up.
You probably are running .5 bar vs. the stock .7-.8 due to the larger displacement and larger turbo's.
The easy solution is to put on an evc to externally/properly control the boost pressure.
You could also reset the base pressure at the w/g's by tightening up the rods. But mostly, the ecu should be reprogrammed, otherwise, once you get the boost up, you'll probably run into the mass flow error charts and start generating faults.
We can supply whatever you're after
06-13-2001, 08:10 PM
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D.V.
The first things I would check are the hoses from turbos to intercooler. Porsche has upgrated the hoses three times because of tearing and burning. Also make sure the connections for the wastegate boost sensing lines are hooked up correctly to the boost solenoid.
Good luck,
Pete.
The first things I would check are the hoses from turbos to intercooler. Porsche has upgrated the hoses three times because of tearing and burning. Also make sure the connections for the wastegate boost sensing lines are hooked up correctly to the boost solenoid.
Good luck,
Pete.
