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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
As to timing:

Could add MSD with boost retard.

We can also use the fuel quality switch on the ECU.

There is also the brown wire jumper at the ECU.

One could also move the timing sensor at the flywheel.

Suck v blow throught.

Turbos do not like restriction in the intake to the turbo which makes a blow through a positive.

However, there is temp sensing at the AFM. With heat it pulls back timing and fuel. This may or may not be a concern if we get enough fuel w pressure or injectors.

On the 944T Porsche did a suck through. I think that was up to about 270-300hp.

I think the early BMW M5's used the same size AFM and the euro was good to about 310hp.

I suspect the AFM on the intake is more restrictive.

Also turbo's pass oil. As such with a blow through there will be some coating of the AFM with a blow through.

One of the issues with the 3.2 system is after about 170hp the AFM bottoms out. After that it is a referance system. Not sure what would happen of we bottom it out at 3500rpm with a turbo.

This is part of the reason I was thinking we would probably have to tighten the spring on the AFM.

As Jim noted, loosening the AFR spring lets the motor go fatter earlier so that is something to think about.

Over on the 944T board there is a pretty cool product they are using. It converts the system to a Mass Air Pressure system using an interface computer in place of the AFM.

Seems pretty tunable and gets rid of the AFM restriction. I believe is also allows playing with the timing via the temp signal.

Having said all that Protomotive's Vacuum Sensing (now offered through dealers like S Car Go) is something to consider. Especially of big HP is a goal. He adds a TPS to the throttle body and a MAP connection so the AFM is eliminated (somewhat like the RUF Yellow Bird) It was about $2k and he gives you a program so you can burn your own chips.
Old 01-26-2010, 07:44 PM
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