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trying to achieve stoich

compudude86

CEG'er
Joined
Apr 28, 2011
Messages
414
Location
Algonquin, IL
Alright, I had to do an engine swap after my original engine spun a bearing. I put another 2.5 in (would've done 3 if one was available in the yard but no luck), and threw on my 19-lb injectors, optimized and polished my TB, and put my CAI (short ram) back on and reattached my 2.5 inch exhaust and gutted precats.

I have a sniper special forces tuner, and used it to set my injectors to 19lb, turned off the lower o2 sensors, added in the catback exhaust, and the MAF with cold air intake option. It produced a base tune, which turned out too rich. I adjusted the low, mid, and high RPM fuel modifiers to pull out 0.2, to lean out my rich conditions. So far, no CELs, if I try to adjust the global fuel modifier for part throttle, dropping it to .9 (one point lean from middle) the car starts, but acts erratically in gear (car goes, when the pedal is let off, the idle jumps a bit, the transmission disengages, then reengages) so I put my global modifiers back to stock, and kept the -2 on all the rpm fuel modifiers.

I use FORscan and an elm adapter for watching my trims in oscilloscope mode. My LTFT is for the most part steady, going from -11(LTFT 1) -9 (LTFT2) or so in idle, to near zero in gear. It stays steady in-gear idle, fluctuating a bit with the gas pedal. The STFT however, goes all over the place, from -12 to somewhere around 30 (according to this program) to near middle on idle cruise, but from what I've read, STFTs don't really matter, its your LTFT that matters the most. So far, I haven't had a light trip, and my car seems smooth and doesn't reek like fuel with smoke puffs under acceleration, so I think I am ok.

As soon as I can afford it, I'm getting a wideband, but right now this project has me strapped for cash, so its trim tuning for me. I also think it is good to learn how the system works the hard way first, before going for the simple version, (N.A., no boost no juice of course). I am a certified as an engine builder, and I've learned more about engine and fuel management systems over the past week than I ever learned in a classroom.

The big question, is my car stable right now?
 
I see no reason why you should be running 19# injectors. Just put the stock injectors back in and drive the car.

Also I do believe that the STFTs should be more stable then you are discribing.
 
alright, well, I figured it out. apparently, I had a misunderstanding in MAF-injector calibration (this tuner is full of confusion, but it is what im stuck with now and the price for its end-user capabilities are worth it IMO) that I corrected, and then discovered that the setting for MAF with cold air intake must mean something else, because when I rewrote the tune with my MAF at stock settings, everything acts normal. I also had some fouled plugs that burned up from both the other engines issues, and from fouling/lean-rich back and forth from the previous tunes, so with new Motorcraft plugs and the proper tune it runs just fine.

as for the 19# injectors, I plan on writing another tune (I have a piggyback chip that lets me write 2 tunes, and attach a switch to be able to switch between them) for E-85, as I wish to run E-85 in the summertime (too cold here for reliability year round or I would, F OPEC) and read (calculated) that I need bigger injectors, and just happened to have some brand new green 19#'ers laying around that I previously bought by accident on ebay for something like $30 a set when I was looking to replace my old ones, and had a full set of USCAR connectors perfect to replace my disintegrating EV1 wires and connectors.
 
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