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Re: Red hot turbo Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Thu, 6 Feb 2003 14:41:27
In Reply to: Re: Red hot turbo, Jimluw, Thu, 6 Feb 2003 12:48:01 Members do not see ads below this line. - Help Keep This Site Online - Signup |
A bad BPC can produce both over and under-boost. But all the BPC does is port pressurized air in varying amounts to the wastegate actuator. It's the wastegate actuator that actually adjusts the turbo to control the boost. The BPC can do everything right, but if you have a sticky wastegate actuator, the turbo will be erratic.
Also, the BPC is controlled by the APC system, and the APC relies on its sensors. Incorrect inputs to the APC can cause it to make the BPC do the wrong thing at the wrong time.
If you take a look in the book "Two-stroke to Turbo" you'll see a really nice picture of a turbo engine on a stand. The turbo is running a lovely white-hot. Very impressive. Now, that was a non-water jacketed turbo, but the water jacket is there to protect the bearings, not the turbo housing.
Now, if you're running a very lean mixture, you can get some impressive exhaust gas temperatures. A lean mixture can also cause knock, so the APC will cut back boost. I don't know the history of your car - if it used to be OK, but recently has gotten bad, or you bought it this way and are trying to fix it. It's possible that there was a previous low boost problem that someone tried to fix by just jacking up the base boost pressure, a problem having to do with lean mixture induced knock.
What have you done to/for the rest of the system? How do the spark plugs look? Rich, lean? Any vacuum leaks? How's the ignition doing?
The boost pressure control loops have a lot of inputs, and it's easy to mess it up by trying to band-aid problems.
Yes, it could still be the BPC, but again, there are A LOT of parts to this system.
posted by 192.249....
, Thu, 6 Feb 2003 09:54:32, Thu, 6 Feb 2003 14:41:27 <-- Viewing This Message
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