knfeparty

I was putting some thought into how to overcome the problem with turbocharged cars risking running too lean with increased boost.

The "solution" I was thinking of could actually be used as a tuning tool for any setup, however.

The idea: Adjustable fuel maps (motronic, maxtronic) that can be programmed in an automated fashion
Needed stuff:
laptop running maxtronic or some other similar custom fuel map software that is real-time adjustable

installed air/fuel mixture ratio sender (the accuracy and dependability of this guage, which I know NOTHING about, is paramount. This project idea is assuming that one of these things is a working, accurate tuning tool.)

A servo with some sort of bracket to operate the throttle cam. It would more than likely need to be a digital servo for precision, although an analog servo would probably be easier to operate. A small amp would need to be wired up, too, since MATLAB is not going to be able to put out much power on its own.

Numerical analysis program such as MATLAB and the special breadboards that interface with the program (I forget exactly what they're called. We have them at school.)

Here's the tricky part: some way for MATLAB to directly interface with the fuel map program.

It's a pretty simple idea, that I think with a good computer and servo could program a fuel map giving you the right air/fuel mixture across the rpm range in a couple of minutes.

The program would run as such:

servo would be zeroed at idle throttle position
lean, ideal, and rich output voltage ranges of air/fuel ratio sender would be programmed into MATLAB so that it would "know" which way to adjust

If the input voltage from the A/F guage is reading other than ideal, MATLAB sends the instruction to maxtronic to either lean/richen the mixture. Some time delay would have to be programmed in here for the engine to "catch up" with the programming. This repeats until ideal voltage is received by matlab.

MATLAB would advance the servo. A good digital servo will be very precise and have great holding power. An analog servo would be easier to run because MATLAB would only have to program an output voltage and not a more sophisticated digital signal. The increment of advancement should be the exact same as the precision of the fuel mapping program.

The last two steps would be repeated for the entire RPM range. Again, this could easily be made totally automated. This way, when boost or other changes are made, you could just run the program again.

I'm not exactly sure how many maps a 944 DME runs, exactly, but this process could be done on a cold engine for the cold map, adjusting to have the mixture a bit rich I imagine, and then for a couple of different temperatures, however many are necessary for smooth running. Tuning under load wouldn't even require a change in programming if it was done on a dyno. Trying to tune while driving under load on the road would be a challenge, though.

Possible problems:
A/F mixture sender is inaccurate / sends really noisy signal.
sol: If the instrument sucks, there is nothing I can do about that. If it is a little noisy, numerically integrate it to smooth it out! Again, MATLAB will have no problem with that.

Servo won't consistently hold position: there are strong and precise enough servos out there. Cost is the only limiting factor. I still don't know exactly how to program the movement of a digital servo.

Getting MATLAB to talk to MAXTRONIC/fuel mapper: It is easy enough to get MATLAB to send any sort of instruction out through a breadboard, but I don't know how to get "in" to maxtronic or any fuel mapping system. This would require the code for the fuel mapping program. At this point, things get a lot more complicated.

This system would be a lot easier to run on electronic-throttle cars, since the wires that lead to the servo in the aforementioned setup would be run directly to the car's already-existing servo that operates the throttle.

I think it can be done, and I have almost all of the tools here at school to do it. The MATLAB stuff is the most expensive, and for right now that is free for me! I've never used Maxtronic (although I was considering getting one. No fuel maps available for the SOHC 2.7 NA, though!) and I think "getting in" to that program will be the hard part.

I can also see how this would simply not work at all or has already been tried. I'm not aware of the latter, although it seems like it would have been. This method just seems to beat the pants off of tuning a fuel map "by hand," though, since to my knowledge all you are looking for is that ideal ratio.

Comments/suggestions/flames are all welcome.