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Re: Adjusting Boost Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Wed, 30 Mar 2005 12:55:35
In Reply to: ajustable boost !!!, samsaab, Wed, 30 Mar 2005 11:26:39 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Boost is controlled by the APC solenoid and the wastegate actuator automatically. If the APC doesn't detect knock, it will allow full boost. If it detects knock, it reduces boost.
Full boost is set at the factory. Yes, it is possible to go to higher than stock boost, but you have to make changes. There are no stock adjustments. There are two ways to do this -
(1) install an aftermarket boost control, or modify the existing boost controller. This still provides you with some protection.
(2) over-ride the boost control loop. Boost is controlled by pressure in the hose going from the APC solenoid (W port) to the Wastegate actuator. If you can reduce the pressure in that line, you will get more boost. This can be done by putting a controlled leak in that line. I have heard of folks putting little adjustable valves in that line to increase boost. You lose a LOT of the protections with this. If the engine is in good shape, you're running high octane fuel, and a bunch of other things, the engine can run higher boost levels without damage. But if the engine starts to knock, it may not be able to reduce boost enough. And damage will ensue.
Lastly, there is an overboost cutoff switch in the driver's footwell. It gets the same boost pressure that the turbo gauge sees. It is a simple switch - too much pressure, and it opens the wire to the fuel pump. A very abrupt fuel cut off. That switch is adjustable. However, the fuel cutoff switch is a safety device - it should never come into play unless something fails in the normal control system. For example, if the wastegate actuator failed, or the hose to it fell off, the cut-off would protect the engine. You have to bury the boost gauge well into the red to hit the cutoff.
posted by 192.249....
, Wed, 30 Mar 2005 12:55:35 <-- Viewing This Message, Wed, 30 Mar 2005 12:40:19
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