I see what you are saying with the S-AFC, and the idea you have in combo with the S-AFC may work, But have you looked at A/F ratios on the dyno with the stock ECU ??? It really isnt that rich until WOT...before that its pretty close to stoich....

Think the p5 runs rich ??/ My MX-6 runs 9:1 at WOT stock !! Granted it's turbo but that's still horribly rich

 

IMO....
Regarding the TPS idea, there has to be a way that an out of range output (modified by a resistor or otherwise) would be recognized by OBD. This is a critical sensor for engine management, and can affect emissions if it is out of range. My guess is that the ECU probably looks at sensor resistance in the closed throttle position, and sets a code if it is out of range. Isn't it also possible to reconcile the signal coming from the MAF with the TPS? After all, you wouldn't expect a great deal of air to be rushing through the intake if the throttle is just slightly open.

 

I'm not exactly sure how/when the ecu goes into closed loop mode but I'm assuming there is a switch over at 5V exactly...anything shy of 5V would not trigger the change over. So if there was a way to lower the TPs signal by say .1V then you wouldn't affect idle or part-throttle cruising by any noticable amount and you'd still be able to use th AFC....this is all just theory and I suck at electrical so don't go by what I say.

Stock AFR's I haven't seen at anything other than WOT. I'll try to get someone with a personal wideband here for me to play with.

 

So there are just a few questions that have to be answered for me to really make up a good solution to this problem.

I have come up with a good circuit that will allow the user to set a 0-2V cutout limit (so you can cut the TPS voltage to anywhere between 3 and 5 volts. The question is, will the ECU catch onto this? When it sees a peak level, will it assume this must be WOT?

Also, in order to create this circuit, I had to put a diode in line with the TPS signal, meaning there will be a constant .3V drop on the TPS signal. Will this cause a problem? I really wish there was someone around here with a Protege I could do some tests with....anyone in the Central, VA/DC area wanna let me tamper with your TPS sensor?

BTW, does anyone know if there any indication that the car has gone into open loop mode?

 

BRian, might wanna go back and edit that post....I've started a S-AFCII feeler thread and you don't wanna go and give out all of our little secrets!