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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Motronic's turbo conversion thoughts?

We are lucky to have 911chips.com and Protomotove to support converting 3.2 Carrera's and C2's to turbo. Such conversions seem to work well and can make a huge amount of HP

However, I am wondering if the following ideas make any sense or have potential.

On the fuel side:

For something like running .4 bar (6psi) with a stock 3.2, we could get more fuel by increasing the fuel delivery with a stock style higher pressure fuel pressure reg (stock 3.2 is 2.5bar) or change to larger injectors with the goal of increasing fuel delivery about about 40-50%.

Then to balance, tune and adjust for this by tightening the spring in the AFM so it progresses about 30-40% slower.

On top of this we can also play with the fuel quality switch to add 3.1 or 6.3% more fuel or subtract 3.9% of the fuel delivery.

On the ignition side the stock chip is pretty conservative. Also, with a blow through AFM, temp sensing is at the AFM and I believe can retard timing up to about 3 deg with heat. One could also use the Fuel Quality Switch on the ECU to retard timing 2 deg.

There is also the Calif/Japan brown jumper at the ECU that leans part throttle fueling and retards timing 3 deg. This might be a good fit with such a strategy.

A 3.2 running about 1.4 boost should make about 340fwhp.


As to a 3.6 (89-95 w AFM's) one would probably need to cut the dome's off the pistons or run J&E's. I believe that cutting the stock pistons down can get us to about 8.5/1 cr.

With this one might be able to run up to 1.7 bar for about 440fwhp.

With the 3.6 we would probably have to add injectors that flow some 70-80% more. Not sure if we can slow down the AFM flapper valve that much.

Increasing fuel deliver at the same duty cycle and slowing the AFM meters rate to a percentage of this is key to this concept.

On the ignition side, the 3.6 is timed for 11.2/1 compression already. If we stay at .7 bar and set the compression to 8.5/1 we will have about the same effective compression rate on boost as the stock N/A motor.

On top of that the 3.6 has knock sensing ability. If we do not get to carried away we may not need to worry much about the spark side on a 3.6. If they have a fuel quality switch, we could pull timing back a bit just to be safe.


Of course the best approach is to convert to a fully programmable system or go the with a Raising Rate fuel pressure reg and or Protomotive chip.


Dose anyone else think this might work or see any big holes in such an approach.

Last edited by 911st; 01-26-2010 at 08:34 AM..
Old 01-26-2010, 08:22 AM
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