[urq] suddenly lean again

Buchholz, Steven Steven.Buchholz at kla-tencor.com
Tue Jan 9 15:48:13 EST 2007

... I've had similar plans, but I was actually thinking about switching over to the MC's airflow sensor plate so I'd have the potentiometer on the airflow sensor plate to provide extra input in situations such as this.  Scott Mockry even had a data acquisition setup for the MAC-11, so you could get similar data to what the newer ECUs provide.  With that you'd know most of the variables ... ignition timing, boost as measured by the ECU, OXS Freq Valve duty cycle and airflow sensor position.  

You know, one thing that just came to mind ... the mixture is most closely tied to the control pressure ... and the control pressure regulator (on the WX) is plumbed to the manifold pressure through some flow restrictors and such ... perhaps there is something that happens with the big backpressure pulse you get with the lift on throttle which screws up the control pressure?  As I've mentioned here before, one of the things I'd like to be able to read from the cockpit while driving is the control pressure ... precisely for this purpose.  It can be *so* difficult to track down these dynamic gremlins ...

Steve B
San José, CA (USA)
> Unrelated, I have changed from the original ECU to a complete MAC11 system
> (harness, ECU and all related bits), wihile retaining the stock urq fuel
> metering unit.  Throttle switches tested operational to the ECU connector.
> No change!  So makes me think the problem may be something about the fuel
> metering unit.

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