I do have a question concerning where I should be taking my
AFR readings on my 13b powered RX7. I have one sensor installed on
the header about 8" from the engine and as I accelerate I see
readings going from 14:1 at 3K RPM and going to 10:1 at 75K RPM as I am on
track.

Two weeks ago I ran the car on a dyno after my second
session of the day and that showed that in fact, the AFR reading at
the top end is actually just going lean at 75K RPM. So, is it better to
install the sensor back at the rear of the exhaust, just down
stream of the collector and before the muffler?  Thanks for your
input. Love reading the emails.

Regards,  Ray Hellstrom

Check the fuel pump volume Ray. Sounds like the fuel pump is running
out of grunt.

Paul Lamar

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