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Tecra

ideas to lower engine compression

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hello to all, finally had my car on the dyno and the mechanic was very informative. my supercharged 996 3.6 is pumping out a little less than 300 to the rear wheels in hp and torque. not too happy about that as i was hoping to have upwards of 400. understanding more and more of producing power, how would one go about lowering the compression to the motor? where can i buy better 996 pistons? anyone know of a shop in CA to do a complete engine rebuild?

best,

tecra

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Assuming you have a high efficiency intercooler downstream of the SC using two head gaskets each side might lower the CR enough to have a more positive effect. Otherwise an intake camshaft regrind to get an Atkinson cycle effect might help.

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hello to all, finally had my car on the dyno and the mechanic was very informative. my supercharged 996 3.6 is pumping out a little less than 300 to the rear wheels in hp and torque. not too happy about that as i was hoping to have upwards of 400. understanding more and more of producing power, how would one go about lowering the compression to the motor? where can i buy better 996 pistons? anyone know of a shop in CA to do a complete engine rebuild?

best,

tecra

There is obviously something wrong with your SC setup or with the dyno/operator. You should be conservatively getting 350+ rwhp. Currently, my high boost 99 C2 is delivering in excess of 450 rwhp with stock compression. Check your boost behind the throttlebody, plugs and timing. A vacuum gauge may show a large vacuum leak. Many of these units were installed by people who did not know what there were doing.

It's relatively simple to produce 400 rwhp once your current system is running as designed.

Edited by 1999Porsche911

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Assuming you have a high efficiency intercooler downstream of the SC using two head gaskets each side might lower the CR enough to have a more positive effect. Otherwise an intake camshaft regrind to get an Atkinson cycle effect might help.

wwest, ive heard of doing to two head gaskets but hear more about changing out pistons. look at response for 1999Porsche991 below.

hello to all, finally had my car on the dyno and the mechanic was very informative. my supercharged 996 3.6 is pumping out a little less than 300 to the rear wheels in hp and torque. not too happy about that as i was hoping to have upwards of 400. understanding more and more of producing power, how would one go about lowering the compression to the motor? where can i buy better 996 pistons? anyone know of a shop in CA to do a complete engine rebuild?

best,

tecra

There is obviously something wrong with your SC setup or with the dyno/operator. You should be conservatively getting 350+ rwhp. Currently, my high boost 99 C2 is delivering in excess of 450 rwhp with stock compression. Check your boost behind the throttlebody, plugs and timing. A vacuum gauge may show a large vacuum leak. Many of these units were installed by people who did not know what there were doing.

It's relatively simple to produce 400 rwhp once your current system is running as designed.

1999Porsche911, the SC is installed correctly. what is wrong is the ECU is not mapped correctly. i should have the data soon to support that. my dyno guy explained where in the low-end there was not enough gas then also in the high-end it would drop off too. he mentioned that fuel pump maybe be bad or not pushing enough fuel but further testing he came to the conclusion that the ECU is not mapped correctly and not sending enough fuel out. who did your SC install 1999?

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Assuming you have a high efficiency intercooler downstream of the SC using two head gaskets each side might lower the CR enough to have a more positive effect. Otherwise an intake camshaft regrind to get an Atkinson cycle effect might help.

wwest, ive heard of doing to two head gaskets but hear more about changing out pistons. look at response for 1999Porsche991 below.

hello to all, finally had my car on the dyno and the mechanic was very informative. my supercharged 996 3.6 is pumping out a little less than 300 to the rear wheels in hp and torque. not too happy about that as i was hoping to have upwards of 400. understanding more and more of producing power, how would one go about lowering the compression to the motor? where can i buy better 996 pistons? anyone know of a shop in CA to do a complete engine rebuild?

best,

tecra

There is obviously something wrong with your SC setup or with the dyno/operator. You should be conservatively getting 350+ rwhp. Currently, my high boost 99 C2 is delivering in excess of 450 rwhp with stock compression. Check your boost behind the throttlebody, plugs and timing. A vacuum gauge may show a large vacuum leak. Many of these units were installed by people who did not know what there were doing.

It's relatively simple to produce 400 rwhp once your current system is running as designed.

1999Porsche911, the SC is installed correctly. what is wrong is the ECU is not mapped correctly. i should have the data soon to support that. my dyno guy explained where in the low-end there was not enough gas then also in the high-end it would drop off too. he mentioned that fuel pump maybe be bad or not pushing enough fuel but further testing he came to the conclusion that the ECU is not mapped correctly and not sending enough fuel out. who did your SC install 1999?

Who did your install? The ECU update is a standard part of the system, so your computer has either been updated or not. Lack of fuel would not allow you to even get close to redline so a proper dyno run would not be possible.

Basic readings should be known, such as fuel trim, MAF signal, timing and level of boost; at idle and near redline. Further tuning is not possible without these readings.

Edited by 1999Porsche911

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Assuming you have a high efficiency intercooler downstream of the SC using two head gaskets each side might lower the CR enough to have a more positive effect. Otherwise an intake camshaft regrind to get an Atkinson cycle effect might help.

wwest, ive heard of doing to two head gaskets but hear more about changing out pistons. look at response for 1999Porsche991 below.

hello to all, finally had my car on the dyno and the mechanic was very informative. my supercharged 996 3.6 is pumping out a little less than 300 to the rear wheels in hp and torque. not too happy about that as i was hoping to have upwards of 400. understanding more and more of producing power, how would one go about lowering the compression to the motor? where can i buy better 996 pistons? anyone know of a shop in CA to do a complete engine rebuild?

best,

tecra

There is obviously something wrong with your SC setup or with the dyno/operator. You should be conservatively getting 350+ rwhp. Currently, my high boost 99 C2 is delivering in excess of 450 rwhp with stock compression. Check your boost behind the throttlebody, plugs and timing. A vacuum gauge may show a large vacuum leak. Many of these units were installed by people who did not know what there were doing.

It's relatively simple to produce 400 rwhp once your current system is running as designed.

1999Porsche911, the SC is installed correctly. what is wrong is the ECU is not mapped correctly. i should have the data soon to support that. my dyno guy explained where in the low-end there was not enough gas then also in the high-end it would drop off too. he mentioned that fuel pump maybe be bad or not pushing enough fuel but further testing he came to the conclusion that the ECU is not mapped correctly and not sending enough fuel out. who did your SC install 1999?

Who did your install? The ECU update is a standard part of the system, so your computer has either been updated or not. Lack of fuel would not allow you to even get close to redline so a proper dyno run would not be possible.

Basic readings should be known, such as fuel trim, MAF signal, timing and level of boost; at idle and near redline. Further tuning is not possible without these readings.

I had install done with a race shop in San Carlos, CA. They had sent the ECU out to TPC in MD, and re-installed here. The dyno was never pushed to redline as I was afraid of blowing the motor. Dyno was setup not to reach further than 6500 RPM. It was more diagnostic then anything. I will obtain the results later today or tomorrow and forward them on to you guys here as well as TPC. Im pretty sure that the ECU is not flashed correctly.

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