wicks

Hi all - drove my old 73 up to Big Sur to escape the fires over the weekend...she did a gorgeous job, but she has a slight hesitation at part-throttle (full throttle no hesitation thankfully). The tailpipe is a bit sooty, but she does not blow smoke. My gut is that she's just a little rich, and maybe I should make a small adjustment to the MFI pump and see if she clears up. I have an AFR meter now (working on my turbo), so also could use that. What's a good AFR test for a 73 911s engine? I had the MFI pump rebuilt a couple thousand miles ago and it was set up to stock flow specs and the space cam "looked good".

At idle: __ AFR?
At 3k RPM __ AFR?
etc.

wicks

Tested at 12.7 AFR at idle and
11.7 AFR at 3k RPMs (but of course that's parked - no actual load)

r911

Glad you got out of the fire...

are you familiar with the Check/Measure/Adjust ?

wicks

Yes, very. All in spec per CMA but have not checked CO/AFR as I had no meter until recently. I guess this is meant to be done on a dyno, but I am looking for what I can do at home to get her closer to spec.

I guess what I don't know is can CO be directly converted to AFR?

Per a table I found, 2.4 motor spec at 2.0-2.5 (CO) would translate to 13.5 to 13.7 AFR at 2,400 RPM, and idle should be close to 2.5 CO translating to 13.5 AFR.

So she would be rich right now if I directly converted CO to AFR.

Steve Weiner-Rennsport Systems

Before you chase the MFI pump around, I'd suggest checking the distributor to make sure the advance weights are not sticking and that the timing is correct at idle as well as at 6K RPM.