MPFI N/A Horizon

[1986GLH]

My brother and I started rebuilding an engine for my 87 Horizon this spring. The car has never run the greatest and always sounded horrible in the higher RPM's. It has always leaked oil too. So the Friday before Labor day the car started running even worse and was leaking oil more than normal. I lost a half quart driving 30 miles. Turns out that one of the bolts holding the fuel pump on backed out and was missing. My brother and I have talked about doing MPFI with Turbo I electronics and decided to give it a try. It now has an 84 block with 88 SMEC electronics in it.

The old engine.


The rebuilt engine on the stand.




Engine in the car.


How it is sitting right now.

[86Shelby]

Interesting. What are you doing for a calibration?

[1986GLH]

Interesting. What are you doing for a calibration?

Just going to use the stock 88 T1 calibration for now.

[shackwrrr]

Just going to use the stock 88 T1 calibration for now.

1 bar map? If so its going to be rich. If you go to the 2 bar it might be lean. Call up rob or use a AFPR.

Something I wanted to do for a MPG monster.

[135sohc]

I'm very interested to see how this turns out and runs. Will be doing something very similar to my dd Shadow someday when the stars and bank account align to let me do everything I want to do to really make a strong n/a engine.

I believe the potential of a really dialed in and built mpfi n/a 2.2/2.5 is alot more than most people are willing to think it is.

[turbovanman²]

Run the stock turbo 2 bar and don't go to WOT, it will run just fine or get it recalibrated or find a flex fuel computer.

[Vigo]

Get a narrowband afr gauge (close enough for N/A work) or tap it with a voltmeter temporarily for tuning purposes and see if it goes super rich at WOT. If it does, i think the easiest thing to do might be a 'Map Clamp' i.e. limiting the voltage coming out of the map sensor so that the computer never 'sees' 0 vacuum. That can be done with zener diode just like people used to do to get around the overboost shutdown. Although, i dont know how that affects the computer's BARO reading.. If you use an AFPR it will lower the pressure EVERYWHERE, i.e. at idle and midrange so it might cause the car to idle or drive bad before it goes into closed loop. I biult my own AFPR out of a log-motor FPR though, so it can be done almost free if you have the tools.

So is this a low compression turbo motor? I hope not.. because they barely move without boost. The tbi motor is MUCH stronger than an off-boost turbo motor.

Also, unaclocker built an NA mpfi rampage at one point and got it to do 42mpg highway (5spd of course) but he was running it on megasquirt and i dont know how much of that MPG was based off the tuning he did with megasquirt vs what it would do on a stock cal.

[turbovanman²]

It goes super rich, when I lost my turbo, I drove around, it was fine except when I hit wot, it would go pig rich and bog badly,

Agreed on tricking the computer so it never see's WOT.

[1986GLH]

It is a 2 bar map. Won't it only get rich if the Map is seeing boost? When my GLH wasn't boosting right it ran fine at WOT. It was only getting boost at 4k rpms and under that there was no boost and it ran fine.

[turbovanman²]

It is a 2 bar map. Won't it only get rich if the Map is seeing boost? When my GLH wasn't boosting right it ran fine at WOT. It was only getting boost at 4k rpms and under that there was no boost and it ran fine.

WOT is preprogrammed so it doesn't care if boost is present, it dumps a preset amount of fuel. 4000 rpm isn't the factor, its your right foot.

[contraption22]

How about a zeiner diode for the TPS? Think that might help?

[Vigo]

Doing it on the TPS would get around any BARO read problems (which i might have made up..) but i dont know if the computer only uses MAP or TPS or a combination of both to determine when to go open-loop. If limiting the TPS signal keeps it from going to open loop when you floor it that should do the trick.

[contraption22]

Thinking about it some more, this may not be a good solutuion, depending on what fuel and ignition the engine needs at WOT.

Ideally, the best solution would be a custom cal.

Not knowing much about building calibrations, is it possible to simply take the Mexican or Flex fuel SBEC tables and put them into a SMEC chip?

Also, is it possible to get a TBI computer to fire 4 injectors?

[1986GLH]

Doesn't the computer determine how much fuel to inject based on what the map sensor is reading? Yes at WOT there is a predetermined amount of fuel but it is based on what the map sensor is reading. When you adjust the boost the amount of fuel is also adjusted. So when it isn't seeing boost it shouldn't be adding a lot more fuel. Yes it may run a little rich at WOT these cars always do.

[turbovanman²]

Thinking about it some more, this may not be a good solutuion, depending on what fuel and ignition the engine needs at WOT.

Ideally, the best solution would be a custom cal.

Not knowing much about building calibrations, is it possible to simply take the Mexican or Flex fuel SBEC tables and put them into a SMEC chip?

Also, is it possible to get a TBI computer to fire 4 injectors?

Its easy to take out the fuel.

Doesn't the computer determine how much fuel to inject based on what the map sensor is reading? Yes at WOT there is a predetermined amount of fuel but it is based on what the map sensor is reading. When you adjust the boost the amount of fuel is also adjusted. So when it isn't seeing boost it shouldn't be adding a lot more fuel. Yes it may run a little rich at WOT these cars always do.

Not really, WOT is preset, that's it, good night. When it see's it, it starts dumping fuel, it probably does use a bit of the MAP but it will go pig rich at WOT without boost. Tweaking the cal is easy to fix that.

[contraption22]

The transition from vacuum to boost, in my understanding, is the hardest area of the MAP to tune for. Weird things happen there.

[contraption22]

Not really, WOT is preset, that's it, good night. When it see's it, it starts dumping fuel, it probably does use a bit of the MAP but it will go pig rich at WOT without boost. Tweaking the cal is easy to fix that.

Huh? The computer needs SOME input to calculate fueling. It uses MAP sensor input primarily for this at WOT.

[turbovanman²]

Huh? The computer needs SOME input to calculate fueling. It uses MAP sensor input primarily for this at WOT.

Ok, probably alot more but still, it see's WOT and goes into a fixed fuel mode, Rob can add more info.

As for fixing it, its not that hard, you simply rescale the fuel maps, sure it might not BE bang on, but should be pretty close.

[1986GLH]

Huh? The computer needs SOME input to calculate fueling. It uses MAP sensor input primarily for this at WOT.

My point exactly! So whether it reads no boost or 13 lbs of boost the computer will adjust it based on what the MAP sensor is seeing.

[84omni]

Not really, WOT is preset, that's it, good night. When it see's it, it starts dumping fuel, it probably does use a bit of the MAP but it will go pig rich at WOT without boost. Tweaking the cal is easy to fix that.

We will all find out hopefully after this weekend what the cal does as we should have it all together. We will hook up a dvom and check if if gets rich at wot. If that is a problem then we either need a custum cal of just stay off wot as this is a dd not a race car.