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testingq Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Tue, 26 Aug 2003 13:13:47
In Reply to: Re: Hold on ! --> wrong info (w/full respects to Ari)..., Dan Y, Tue, 26 Aug 2003 12:44:43 Members do not see ads below this line. - Help Keep This Site Online - Signup |
As to which line is which - I never worry about where they're located (top, middle, etc), because I can never remember. However, C, W, etc are correct.
If you pull the hose off the wastegate actuator and don't get full boost, it isn't necessarily a turbo problem. The turbo has a wastegate that regulates boost. The hose being pulled off goes to the wastegate actuator.
When the turbo boosts, it pressurizes the intake manifold. That pressure goes to the C port on the APC solenoid, where it also connects to the W port, which goes to the wastegate actuator. The actuator is just a piston held in place by a spring. As the pressure builds up, the piston moves against the spring, and the rod moves out from the actuator. When it moves out, it opens the wastegate on the turbo, reducing boost.
When the APC solenoid is DE-ENERGIZED, the line goes directly from C to W. All the pressure goes to the wastegate actuator. This is base boost. When the APC wants full boost, it ENERGIZES the solenoid. This bleeds some of the air off back to the input side of the turbo. What does this do? With some pressure bled off the wastegate actuator, it takes MORE pressure in the intake to cause the actuator to extend and open the wastegate. More Boost.
If the wastegate actuator is stuck open, or there is a problem with the linkage, the wastegate can be stuck open, limiting boost. So you could remove the hose and still get low boost.
Quite frankly, I've rarely seen a low boost situation to be a bad turbo or clogged exhaust. Boost is pretty easy to come by. Most turbo failures aren't low boost - it's absolutely no boost. Even a really noisy turbo will still boost. And if the exhaust is clogged, low boost will be the least of your symptoms - the car won't idle or run very well.
If the boost needle gets anywhere into the yellow, the turbo is boosting. In fact, if the needle gets into the upper parts of the white at part throttle, the turbo is working. A non-turbo car always has vacuum in the intake (otherwise, why would air go in?), and at partial throttle (say, going up a hill with a part throttle), there will be significant vacuum in the intake. If the needle is in the upper part of the white (not much vacuum), the turbo is working.
posted by 192.249....
, Tue, 26 Aug 2003 10:45:28, Tue, 26 Aug 2003 13:13:47 <-- Viewing This Message
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