gt40 motor and mark VII ecu problems

[pantera77]

I was thinking about this thread earlier today. I find it odd that my wagon has a very similar setup and these exact same issues.

[gadget73]

I gave up trying to poke and prod at the SD setup and installed mass air. Car runs perfectly now. Take that for whatever its worth to you.

[jayh]

speed density is NOT the problem

[gadget73]

well, when I removed it the problems went away so for me it was the problem. It ran lean because the motor was moving more air than SD was tuned to deal with. I have maybe $100 in the mass air parts, and a tweecer was gonna be $350 or so. The wallet dictated a mass air swap and the results are favorable. I realize that its not the solution to all problems, but it was my solution to my problem. Take that for whatever its worth to you.

[jayh]

I've been mid-low 12's @ 110 on motor with SD @ 35000lbs. it was my DD and I delivered pizzas in the piece of shit; my only car at times, drove it EVERYWHERE.

Im not saying maf is a bad idea, but SD is alot more capable than people realize

[sly]

thing i like about SD is the throttle response... hammer the gas it goes. MAF - hammer the gas and a half second later after air flow gets going... it goes. SD is just a little more responsive (probably due to less calculations being done by the computer - look up tables and all).

[Pirate]

Gee, this sounds like the same problem i'm having, minus the running rich part!!

Yeah, no shit.

It ran lean because the motor was moving more air than SD was tuned to deal with.

I like speed-density setups....but I don't think the stock Ford SD ECM works all that well with mods, even mods that don't screw around with the cam/vacuum signal.

[jayh]

I was making right around 300rwhp with sd n/a :headbang:

[gadget73]

Mine made 202 at the rear wheels with an A/F ratio anywhere from 15:1 to 18:1, well into the "your motor is fuxxed lolz" range. I dont know why it was so awful. I've seen other cars with similar mods and in some cases many more mods run just fine with dyno sheets to verify the fuel mix, but mine just didn't want to play that game. I never use my car as an example because nothing ever reacts as expected with it. I've given up attempting to explain why things are the way they are. I ought to hire an exorcist, perhaps it will act more normally then.

[pantera77]

I just found it odd that these cars all have similar mods and components, and all have the same problems.

Personally, it's not really bad enough for me to care. I do wonder though if going mass air would fix it.

[cld783]

thing i like about SD is the throttle response... hammer the gas it goes. MAF - hammer the gas and a half second later after air flow gets going... it goes. SD is just a little more responsive (probably due to less calculations being done by the computer - look up tables and all).

I think its the other way around.. maf is on the fly and speed density has to do calculations.

[sly]

I think its the other way around.. maf is on the fly and speed density has to do calculations.

speed density uses look-up tables for manifold pressure versus speed (hence speed density) while Mass Air Flow uses the sensed flow of air based on a formula to calculate the fuel metering using an equation. The only calculation that a speed density does (IIRC - please correct me if I'm wrong) is with the oxygen sensors to tune the air-fuel mix. This is mainly due to the fact that older car computers were slower and could not calculate all the sensor inputs fast enough, so they limited it to a few simple calculations and used look-up tables for the answers to the other calculations that they did to make the tables. Newer car computers have the speed to calculate all the sensor data themselves. The lag I'm talking about comes not from the computer itself, but the difference in the air sensing. Speed density uses manifold pressure which will drop faster when you hammer it than the air will flow past a Mass Air Flow sensor initially so you get a fraction of a second better response time for that condition only. This condition is not a factor in drag racing if you're already revving the engine at your needed launch RPM. It really only happens on the from idle launch.

[Pirate]

I was making right around 300rwhp with sd n/a :headbang:

....I'm glad you got it to work. I have heard it mentioned that S/D will eventually teach itself to work with a lot of mods if you are willing to drive it that way for a while, but of course, not a lot of people are that patient. I've never had problems with S/D cars, even with performing a few mods.....but I've never owned a S/D mustang, and I've never had any customers who wanted to mod the hell out of one....it's usually just bolt-on goodies Being they they were only built from 87-88 for the most part ('86 doesn't count, the heads are garbage, lol), they were kind of a rare car to begin with. Given the 'you can't work with S/D!' mantra, nobody I know actually wanted a 87-88 5.0, they usually traded up to the 1989-1993 cars.

I have worked a lot with the lopo S/D engines, however, and the stock computers worked just fine with the HO swaps I've done to my own cars, or at least it seemed that way to me, anyway.

So far as my S/D comments go, it's directed towards the MK7 S/D setup, not the Mustang unit (if that is what you were referring to), of which I have seen some sterling exceptions to the 'you can't work with S/D!' mantra echoed earlier in this post (I'm vaguely recalling one early 1990's drag racer who got into the high 11's with S/D in a 1988 Coupe, and I think he was using a modded F150 302 intake). Concerning the MK7 ECM, I don't know of but maybe one or two here who have gotten the MK7 computer to work properly here....the rest all have problems.

[mcninetyone]

Ok, let me throw my problem into the mix.

1991 CV. now has a stock 96 Explorer engine installed using the CV electronics and running terrible. Surging at idle, very bad MPG and running rich. I've been told I have to convert to mass air or else. And I've heard the original speed density will work just fine, but how? Is there a computer that will work for this swap? The original 5.0 was running just fine when taken out of the CV, so I don't think it's a bad sensor somewhere.

Any advice?

Thanks,

[87gtVIC]

You do know that the explorers have a different cam, injectors and firing order that REQUIRE you to install a HO 5.o computer from a HO mustang or Mark VII.