A/F Dyno test -- get a custom chip!

[911st]

Don't blow up your car! ........(Got your attention?)

Dyno your car and if necessary get a custom chip that matches your specific needs.

I now think that if you are pushing or tracking your car, stock or modified, one should check their Air/Fuel ratios above 5000rpm.

Further, running a modified exaust with a stock chip, may have the potental to put one at risk under high rpm / load conditions.

My WOT run indicated I have a great A/F ratio till about 5000rpm, then I start to go to a lean quite fast. (From arond 12.75 to 14/1)

I am not an expert but this is the point where the Air Flow Meter flaper valve is thought to max out.

At this point fuel delivery must be mostly determined by RPM's-- not air flow.

Thus, any unexpected mod like custom exaust, flowing the intake, playing with cam timing or anything else that can get more air in and out of the motor may make for a lean (and power robbing) condition.

I am now a big beliver in the 911Chips or any other good providers "custom tuning program".

Further, a mass flow conversion seems promissing not only from a reduced air flow restriction but more so for it's ability to mesure changes in air flow at higher rpms where the stock system seems to have a weekness.

For the record, I pulled 210rwhp from 6000-6200rpm with a peak of 217hp at 6100 with an A/F of 14/1.

My car is all stock except for a Cat Bypass tube (not pre-muffler), stock 85 muffler, and a chip tuned for a Bypass & sport muffler.

If we use the normal 15% drive line loss, that would be 247 to 255 flywheel hp, which seems high (about 20% over stock) for just a SW chip and a cat bypass with a stock muffler.

I used a SuperFlow WinDyn V2.2 dyno at 72 deg air temp. My pull was in fourth gear. My print out notes it is "STP Corrected Wheel Power vs RPM" ????

I am not an expert by any means and discussion in the search of truth is highly wellcomed.

Thx.

[911st]

Don not know if it maters but we unpluged the O2 sensor as advised and put the dyno's wide band in it's place. I had to ask for this and show them how to do it.