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Bevan,
Hope all's well.
The APC will computer control boost pressures based on it's targeted destination. An OEM APC controI unit will typically target 11 psi, tailored potentiometer APC could target 15 psi, and an aftermarket APC could provide in excess of 20 psi. Base boost pressures will typically be 50% of maximum charge pressure thresholds. If your engine (not creating enough exhaust velocity into the turbine due to low compression, lean fuel deliveries, advanced ignition timing, improper camshaft timing, etc) and/or turbocharger are not up to this task, maximum charge pressures may be less than expected.
It may be a good idea to do an isolation test to see what charge pressures your vehicle are capable of achieving. We use a hose restrictor on the pressure hose from the APC solenoid to turbocharger wastegate actuator. This allows for a quick check of engine/turbocharger maximum boost pressure potential and provides information relative to problem areas. If we did this isolation test to your 900 and charge pressures where still not seeking more than 12-13 psi, we might suspect that the engine or turbocharger where not allowing for additional potential. We would then check engine compression, ignition timing, turbocharger condition, etc.
Check your ignition timing retard which should reduce timing to 10-11 DBTDC when the distributor diaphragm is under maximum boost pressure targets (in your case 12-13 psi). If not, adjust the distributor to allow for this correct retard.
Best of luck with your efforts and best regards!
George at SWEDISH DYNAMICS,INC
posted by 152.163.100...
http://swedishdynamics.saabnet.com
, Tue, 1 Mar 2005 09:25:33
, Tue, 1 Mar 2005 10:45:11, Tue, 1 Mar 2005 15:38:27, Wed, 2 Mar 2005 08:38:56
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