EFIDynoTuning Forum

I have always been dialing in my MAF curve in 2nd gear; mainly because it goes 60mph and it's manageable in the mile of asphalt I use for a dyno. I logged a full 1/4 mile run today and it seems a little lean in 1st, and gets a little richer after each shift.

Has anyone come across this or is there anything multiplier that would affect it? Lambse is consistent 0.78 at WOT through the whole run. The only real variables I can think of for the ECU between gears are vehicle speed and intake temperature.

5 speed 4.6 with twin screw supercharger, 42lb green FRPP injectors, stock terminator airbox, MAF, intake tube, throttle body.

If anyone has livelink, I'll attach the datalog. just change the extension to CSV to open in livelink.

I put a bigger MAF in it, since I was close to pegging the 90mm Ford one. Made a new log, still seeing the same puzzling pattern. Lean in 1st and then richer in the higher gears. I don't quite have my head wrapped around the injector Pulse width, but it seems like it's shorter at the same RPM when the Wideband is reading leaner, so I don't really think it's an exhaust leak. It looks to my uneducated eye like it's reading less Mass Air in lower gears, and calculating less load and fuel required at the same RPM at WOT.

if anyone can see anything I'm missing in this log or the other one, I'd love to hear theories or suggestions.

Thanks,

Been thinking and reading...

Is there a modifier to the MAF transfer for IAT?

It would make sense to me that the MAF would read slightly less voltage for the same air mass as temperature increases. however with only one IAT input and the sensor located after the blower, it would be incorrectly inferring that correction during a pull as IAT goes up.

Am I on the right track? Is there a way to give the ECU IAT1 input from the MAF temperature sensor? Or to give the IAT less effect on air mass calculation?

Is it spinning the tires? There is less load on the engine in the lower gears. Are you sure you're not seeing that manifest as less cylinder fill? Plus it will sweep through the timing table faster and may give odd data.

if the inlet air temps are increasing that much through one pull to affect fueling you need a better intercooler or more water injection

but yea the VE correction table (maybe fn1037 OTTOMH) is what determines manifold volume through ect and acts. At ect of 200 and act of 100 it should be 1.00 and vary slightly from there. You can reduce it at higher acts for boost or hot air intakes (mostly incorrectly called cold air intakes),

Yeah it spins in 1st and slips in 2nd, it definitely runs through the rpm quickly. It still reads nearly the same air mass and load though so I was I little worried about being on the lean side of 0.80.

And temperature wise, on that pull it only went from 94 to 104. I just wasn't sure how much temperature affected it. It's a stock cobra intake sucking from the fender, and a fairly big heat exchanger. The only time it gets out of hand is when it's heat soaked I'll see 160s IAT

probably something else going on then usually its bad injectors that causes that.

Oh, that's actually good news, I have a fresh set of 60's to put in when I get a second.

Thanks for your help