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I'm running a pair of Mikuni HSR42's on a stock B20F with Simons sport exhaust, MSD6 ignition, and Pertronix with Blaster coil.
Gasoline in Oregon is supposed to be E10 (ten percent ethanol blend year-round.
Temperatures are in the low 30's to 40's
Gauge is an Innovate Motorsports, with their LC1 lambda controller and a Bosch 5-wire wideband O2 sensor.
With the engine fully warmed-up, the (idle) air-fuel ratio (AFR) is around 13.8 to 14
E10 has an ideal ratio of 14.0 to 14.1, from what I can determine. The gauge needle wiggles around a little.
Partly open throttle while cruising shows an AFR around 11.8 to 12.5.
Quickly opening the throttle sends the AFR as high as 18, gently opening the throttle sends it to around 14-15 AFR.
Quickly closing the throttle sends the AFR as high as 18, gently closing the throttle sends it around 14-15 AFR.
I have had a suspicion that the mechanical advance on my distributor, may be a bit sticky at times (vacuum retard is disconnected from vacuum source),as occasionally after letting my foot of the gas after sustained high RPM, the idle will drop so low that the engine tries to stall, this does not happen instantly after throttle let off, there is a thirty second or more delay. The idle corrects itself after a couple of minutes. Perhaps the (excessive?)leaning out of the mixture could be causing this?
The engine hesitates a bit on wide open throttle. For normal, non aggressive driving it is very well behaved and reasonably responsive.
My dad suggested advancing the accelerator pump action or enlarging the accelerator pump nozzle to address the (excessive?) leaning out under acceleration. I will try advancing the accelerator pump tomorrow and see what happens.
Suggestion and comments are welcome.
Bill
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