Zootx8

Alright, we all know there is a fair amount of variability from car to car on the MAF readings, and some like Polak get great mileage and power because his car runs a little leaner. My thought is this, could we place a variable resistor in-line with the voltage out on MAF and then adjust the resistor to achieve a more desireable MAF output voltage. The only problem I see is if I have this conceptually backwards - but it should work if voltage goes up with airflow. Then after the variable resistor is properly adjusted you could effectively alter the MAF readings and lower the A/F ratio across the rpm spectrum. What do you guys think on this? By the way I'm a ChemE not an EE, so if I'm a way off on my electronics don't be too harsh.

alnielsen

iTrader: (4)

You are working with a closed loop system. You change one setting and the ecu will work to return the system to its nominal condition. If you change the signal going to the MAF, sensors else were on the car will identify the rich/lean condition and make adjustments. As I understand it, these are the two O2 sensors. This is the more likely place to make the mod, but I think if you change the reading of one sensor too much, in relation to the other one, the ecu would identify an error error condition and throw a fit.
I was looking at doing this on my 85 RX7 (13B w/EFI). I wanted to create a rich condition to create more horsepower. On the 8, the engine management system is more advanced and I wouldn't think about doing it. I am waiting for a good ecu replacement to do this.

Xyntax

Interesting. I have used my CZ unit to do a similar job. I have basically modified my maps so that the Airflow signals going to the ECU would be less than what it actually is. The way I understand it is that I am fooling my ECU into thinking less air is coming through and so the ECU will pump less fuel to the appropriate amount in order to get a stoich AFR. Less fuel with same amount of air means leaner mixture right?

I have subtracted 1%, 2% and 3% over the past month now and I have found 2% to be the optimal reduction. At 3% reduction, I suspect the ECU to compensate for overleaning mixtures and thus pump more fuel than needed. This is just a theory because I did not have my CANscan (got it repaired) when I did this. I actually wasted more gas during the 3% than stock form. I gained a bit at 1% and a lot at 2% even when I kept blipping to 9K rpms.

I'm sticking with 2% right now until I get my CANscan back. And then I will repeat the whole experiment once more, but this time logging my AFR.

ps. no ignition adjustments in the closed-loop range because the ECU doesn't seem to like it. It bogs down throttle response as if it's not getting enough air. Canzoomer did this with the stock CZ1.1 and it was causing that low rpm lugging or bogging that people were experiencing.

Zootx8

yeah, the canzoomer was what got me thinking, i was just thinking about it and it came to me that a variable resistor may do something similar, but just a thought.

Nemesis8

iTrader: (3)

What's up with this new version of the A’PEXi SuperAFC?

http://www.rx7.com/store/rx8/rx8ecu.html

Zootx8

Not really sure... looks like it does sorta the same thing as a CZ minus the timing advance, and seems to have less control over the throttle position.

Nemesis8

iTrader: (3)

I'm waiting on a response to see if the A’PEXi has been updated to use on the SE3P. The old one was for the FD3S and FC3S years '85 thru '95.