ok im wounding if there is a way to do this, can i hook up a diffrent harness and ecm with MAF, but the car will be runnig off the TBI SD, but all use the MAF just so i can log the air flow going into the motor, to help me tune? how can i go about this, this seems like it might work, how would you get the ecm to think the engines running? basically like runnig 2 ecms but only one will be runnig the car and the other just the MAF,

 

I’m not real sure how you plan on using the MAF signal. You could piggy back a whole MAF ecm and just log it, but that would be the hard way in my opinion. The new EBL board has some extra inputs you might be able to plumb the MAF signal in there. There may even be an unused input on your ECM you could use, maybe you could input it through the IAT pin since the IAT sensor doesn’t do a whole lot in the code, just zero out the IAT tables.

The MAF might give you something to look at, but I don’t think you really need it. You can either look at what’s going into the motor or what’s coming out of it to decide on how much fuel you need. Since you already have a SD system figuring out how much air is going into the engine, why not just monitor what’s coming out in order to tune the SD system. A good WB will tell you all kinds of things about your tune, and really you don’t need to know how much air is going in as long as you have the proper AFR coming out.

You need to look up Dimented247 (check spelling) he converted a TB setup to MAF and has done a lot of work on the code side of these ECMs. You’ll have to double check this, but I think he said that the MAF system did work well, and required less overall tuning than the SD system, but the actual out put of the MAF sensor wasn’t really what ended up in the combustion chamber. He had to do the same test and check method to tune the MAF output to get the desired AFR as you would with a SD system. He also noticed a delay in what the MAF read and what was going on inside the combustion chamber.

You may be thinking way over my head, and if so please disregard my ramblings and let us know what the goal of this project is.

 

You, can.....
Just power, ground, ref pulse, MAF input into the second ecm, and disable most all the diagnostics. Then you have to mess with the defaults, so that it actually reads the MAF, not the default MAF readings.

And you have to have a MAF, and the matching ecm/ calibration data.

 

A stock bosch MAF, or any other voltage based MAF that you have flow vs. voltage tables for, would be a good canidate for this. You could feed it into the LM-1 stand-alone wideband unit and datalog it with other things like MAP, RPM, TPS, etc. You could also use a frequency based unit, and feed it into the VATS input (needs minor mods), but the resolution wont be very good at high frequencies. There will be something like 30% error at high flows. If your going to use a frequency based input, it should be able to generate interrupts in the ecm so you can read it in at a very high freqency with only 1% to 2% error. This didnt appear until the early to mid 90's. Im planning on using this, but it would be way too much work for just datalogging. For a little more then the price of the MAF, you could get an LC-1, and EBL, and have the WB in your datalogs, along with other features.