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The mkiv Supra Owners Club

Getting C02 gasses down for the MOT


Brian Jackett
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Do you think it would be possible to add an electronic device to the Supra that  changed the fuel mapping to be very very lean for the MOT. Something that the car would not run very well but fine for tick over at the MOT.

 

This device could be temp fitted for MOT or installed all the time and you simply switch it on.

 

Perhapes Pete could build something. Or does the FCD have the ability to be twiddled with to give the same result.

 

Pete are you out there

 

 

 

 

regards

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I suppose you could modify the O2 sensor output to fool the ECU into running leaner than it should do at a particular RPM.

 

It wouldn't be the FCD as this is used only on boost and during normal opertaion it is the O2 sensor that controls fueling.

 

In OPEN LOOP control the ECU uses the MAP sensor (or MAF) to calc fueling etc etc, and this is when accelerating.

 

In CLOSED LOOP control the ECU uses the O2 sensor to calc fueling. It tries to maintain the stochiometric air fuel ratio of 14.7. It does this by richening and leaning the fuel periodically to maintain an average of 14.7.

This is obsereved by viewing an air fuel ratio device and watch the LED's (or what ever display it has) go up and down about every second. This is when at a constant RPM (cruising etc) and would thus be the area to tackle for the MOT.

 

I've already considered this but I'd have to be careful not to lean it too much.

 

Pete

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