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thanks, I enjoy running on about turbo stuff
Posted by dave n (more from dave n) on Sun, 27 May 2001 20:13:34
In Reply to: Turbo/APC/intercooler, Gordon
[Profile/Gallery]
, Sun, 27 May 2001 15:50:17
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Most turbo cars use only the mechanical wastegate to control max boost levels. When boost reaches a certain level, the pressurized air sent to wastegate canister to move the wastegate control rod. The canister has a calibrated spring that the air pressure has to compress in order to move the rod. The rod opens a valve in the exhaust (wastegate) that bypasses exhaust gas around turbo turbine. Since the turbine loses the diverted exhaust gas to keep the turbo shaft spinning, you get less boost.
Manual boost controllers are a bleed valve. The air line from turbo to wastegate canister is cut and the bleed valve is installed. The bleed valve is opened slightly to reduce the air pressure getting to the canister. Since the canister gets less pressure than the turbo actually has, the wastegate is not opened and you get more max boost. The more you open the bleed valve the higher the boost goes.
APC is pretty much an electronically controlled bleed valve. The apc box is independent of any other engine computer. It takes in electrical signals for boost pressure, brake lights, cruise control, and engine knocking. THe only output is to control the air bleed valve or "solenoid". The only difference is the solenoid is opened and closed very fast but functions just like a regular bleed valve. So the wastegate rod is set to give you max boost of around 6 psi. But the apc diverts air from wastegate until it reaches a preset limit. THen it chatters the valve just enough to maintain that level. If brakes, cruise, or engine knocking occurs it lowers boost.
Tired of reading yet?
dave n
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