Running Speed Density w/ A9L?

Nathan Reible · Nov 25, 2012

Like the title says, can an A9L run a SD setup? I have an 89...just changed my car back from MAF to SD, and I know SD is a downgrade, but it just simplifies things for me. I started the car up and it ran fine, it surged a bit at idle but throttle response was great. I just want to know if I can continue running this computer with SD.

f8tlfiveo · Nov 25, 2012

How did you change it back if you are still running a a9l computer?

Nathan Reible · Nov 25, 2012

Well obviously the A9L is still in the car. When I switched it from SD to MAF, I hooked the MAF wiring up and switched a few pins. Tonight I unhooked the MAF harness and switched the pins back. My question is, do I need to revert back to a SD computer or will the A9L run with a SD setup?

Nathan Reible · Nov 25, 2012

The car seems to run fine, a little surging at idle but that's it. I just want to make sure an A9L will work, if not I'll post it for trade for an 8LF.

mikestang63 · Nov 25, 2012

If you repinned the TAD and TAB pins (11 and 51 for a speed density) and (pins 32 and 38 for Mass Air) I would think it should work. Never saw anyone convert back to SD....lol. My only thought is doesn't the SD computer have embedded VE tables in it that the MA computers don't for fuel and timing?

Is your car an auto? The 8LF is for an 88 auto because you have the A9L which is for a stick vs the A9P for the auto. Pretty sure you can run the auto computer for a stick but not the other way around.

All the following are mass air unless they say Speed Density
8LD - MANUAL 88 5.0L Mustang Speed Density
8LF - Auto 88 5.0L Mustang Speed Density
A9L - 89-93 5.0L Mustang 5-spd Mass Air stick
A3M - 93 5.0L Mustang 5-spd Mass Air
A3M1 - 93 5.0L Mustang 5-spd Mass Air
X3Z - 93 5.0L Cobra 5-spd Mass Air internally calibrated for 24 lb injector
A9P - 89-93 5.0L Mustang Auto Mass Air auto
A9S - 88-93 5.0L Mustang California Mass Air
C3W - 89-93 5.0L Mustang Auto
DA1 - 87 5.0L Mustang 5-spd Speed Density
J4J1 - 94-95 5.0L SVT Cobra 5-spd
T4M0 - 94-95 5.0L GT Vert 5-spd
U4P0 - 94-95 5.0L GT Auto
W4H0 - 94-95 5.0L GT
ZA0 - 95 Cobra R
D9S - Lincoln LSC
ZXA3
LLX3
CCA1
CCA0
AOL2
AOL3

88LX5.Oh · Nov 25, 2012

f8tlfiveo · Nov 26, 2012

This sounds like a bad idea.. You need to change to a sd computer if your going to do this. You can't just unplug the mass air and repin the computer.. Your gas mileage is most likely going to take a hit. A sd computer has tables in it that the Maf controls in a a9l..so your car is running but I guarantee its not running like it should. I have a sd computer if you want one, or I am sure if you post 1,000 other people have their old one from their maf swap also.

jrichker · Nov 26, 2012

Bad idea - the A9L depends on the MAF input to get the air/fuel mixture correct. No MAF or non functioning MAF means the computer runs in "Limp Mode" with reduced power and economy.

Fix whatever problems you have with the MAF & wiring and do it right.

Nathan Reible · Nov 26, 2012

Thanks for all your input everyone. While running a MAF is ideal, I would really rather go back to the original SD setup as the car is an 88 1/2 so it came from the factory with SD. This car has been through hell during it's life...I've already had to replace all the wiring, I'm in the process of putting the factory throttle and TV cable back in because they were ripped out and replaced during a previous carb swap...needless to say, this car is a TRUE project. At this point, I want to bring it back to it's original state and go from there.

It looks like f8tlfiveo is going to be sending me an 8LF so I can use the right ECU. I will probably endeavor with a MAF at some point in the future, but for now I just don't have the time or the money to get it done right.

Nathan Reible · Nov 26, 2012

mikestang63 said:
If you repinned the TAD and TAB pins (11 and 51 for a speed density) and (pins 32 and 38 for Mass Air) I would think it should work. Never saw anyone convert back to SD....lol. My only thought is doesn't the SD computer have embedded VE tables in it that the MA computers don't for fuel and timing?

Is your car an auto? The 8LF is for an 88 auto because you have the A9L which is for a stick vs the A9P for the auto. Pretty sure you can run the auto computer for a stick but not the other way around.

All the following are mass air unless they say Speed Density
8LD - MANUAL 88 5.0L Mustang Speed Density
8LF - Auto 88 5.0L Mustang Speed Density
A9L - 89-93 5.0L Mustang 5-spd Mass Air stick
A3M - 93 5.0L Mustang 5-spd Mass Air
A3M1 - 93 5.0L Mustang 5-spd Mass Air
X3Z - 93 5.0L Cobra 5-spd Mass Air internally calibrated for 24 lb injector
A9P - 89-93 5.0L Mustang Auto Mass Air auto
A9S - 88-93 5.0L Mustang California Mass Air
C3W - 89-93 5.0L Mustang Auto
DA1 - 87 5.0L Mustang 5-spd Speed Density
J4J1 - 94-95 5.0L SVT Cobra 5-spd
T4M0 - 94-95 5.0L GT Vert 5-spd
U4P0 - 94-95 5.0L GT Auto
W4H0 - 94-95 5.0L GT
ZA0 - 95 Cobra R
D9S - Lincoln LSC
ZXA3
LLX3
CCA1
CCA0
AOL2
AOL3

Yes I have an auto, which does more to paint the picture for this car as it had an A9L in it when I bought it...lol

Mustang5L5 · Nov 26, 2012

Nothing wrong with SD.

My car still runs it

Nathan Reible · Nov 26, 2012

Mustang5L5 said:
Nothing wrong with SD.

My car still runs it

Yeah, that's what I thought too. I was doing some research this morning on the 8LF and SD setups in general, a lot more people run SD setups than what I originally thought. I will just have to get the SD computer tuned for my engine mods after I install everything. It seems pretty straight-forward to me.

ratio411 · Nov 26, 2012

I'll trade you my SD computer for the MAF computer.
It's an 87 T5 car.

I don't drive the car right now, and plan on getting a MAF computer for it.
It'll just be quicker this way.

ratio411 · Nov 26, 2012

In a perfect world, the SD system is better.
The MAF is best for user friendly operation.

Nathan Reible · Nov 26, 2012

ratio411 said:
I'll trade you my SD computer for the MAF computer.
It's an 87 T5 car.

I don't drive the car right now, and plan on getting a MAF computer for it.
It'll just be quicker this way.

I'm already trading with f8tlfiveo for his, he has a SD computer for a T5 car as well. I assume that it doesn't matter that the SD computer is for a T5 and I'm running an automatic since I'll eventually be getting it tuned. From what I'm told, a T5 SD computer will make an automatic car stumble a bit when put into gear...and since I'm running an AOD and not an AODE I shouldn't have any other issues.

If anyone knows of any other differences between and T5 and an AOD SD computer let me know.

Nathan Reible · Nov 26, 2012

Alright, so I've done a bit more investigating on the whole AOD/T5 ECU issue. I guess hooking a T5 ECU up with the AOD O2 harness will burn up the board on the ECU due to the jumpers being in different locations on the harness itself. Well, my car runs just fine with an AOD and an A9L installed with O2 sensors and all. With that said, I assume that when the A9L was installed in may car, the person who installed it also installed a T5 O2 sensor harness, or I would've already burnt up my ECU by now. Am I completely off here?

Bottome line, I don't want to fry any computer...but I should've already done that considering what my current combination is.

larrym1961 · Nov 26, 2012

An automatic computer will increase RPM to compensate for load put on the engine when put into gear, where a 5 speed computer will not.

Nathan Reible · Nov 26, 2012

larrym1961 said:
An automatic computer will increase RPM to compensate for load put on the engine when put into gear, where a 5 speed computer will not.

Ok, well that's not a huge issue for me right now...I'll get everything tuned properly after installing all the engine mods. Now that you mention that though, I remember my car getting pretty low on RPMs when I put it into gear with the A9L.

I think when the person I bought the car from put the A9L in the car, he installed an A9L harness with the T5 O2 sensor harness. I shouldn't have any issues running an 8LD since the O2 harness is for a T5.

Nathan Reible · Nov 26, 2012

Before I send off the A9L, does anyone have an 8LF sitting around that they're not using? I'm quite sure I can use the 8LD but want to see if anyone has an 8LF as that is technically the ECU I should use.

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