ECM questions.

[2.8-350TBI]

So, I have decided to keep my gm truck all (mostly) GM and have decided to ditch megasquirt for engine management and I will be using a gm computer.

I am wondering what my best bet for a computer will be though.
You guys are tuning masters and seem to know which ecm works best with each setup, which is why I ask for this advice.

The truck: '89 blazer 2.8/t-5

What will be in it though is a 3.4/3500 which will start off naturally aspirated, and recieve a turbo later in its life.

My computer is a macbook pro running snow leopard if it makes a difference with the tuning programs out there.

With the ecm, I wish to be able to run sfi, but as I know it, OBD-1 never ran SFI and doesnt have that capability.
And I dont wanna get into the big mess that comes into tuning OBD-2

As my truck is a manual, auto tranny control isnt necessary, so that leaves me with the question:
What ecm would be the best for my application, and what would be the best way for me to tune it?

[geoffinbc]

Every ECM before 95 was OBDI and millions of vehicles had SFI back then. A 93 to 94 Camaro would have the correct ECM to sun SFI for a 6 cylinder.

[2.8-350TBI]

Every ECM before 95 was OBDI and millions of vehicles had SFI back then. A 93 to 94 Camaro would have the correct ECM to sun SFI for a 6 cylinder.

But thats obd 1.5, which is basically as useless computer in terms of tuning.

[geoffinbc]

No that was 95 only when the government was beginning to standardize all ECM's and GM went through a change over period where they had an OBDI ECM with some OBDII capabilities and an OBDII connector. By 96 ALL vehicles had to have a basic set of parameters that had to be monitored and they all had to be compatible with a standardized reader/language and all the basic codes had to be the same. That standard is still in place today but manufacturers now monitor hundreds more parameters than what is required by the OBDII standard.

[2.8-350TBI]

I see...
Thanks for that info!

So that means that 93-94 camaros are straight OBD-1?
And that those ecm's are tunable?

I really hope so

[robertisaar]

i'll throw in some knowledge.

the 93-95 3.4RWD motors used flash PCMs that have yet to be cracked(and likely never will due to lack of demand).

if you want SFI on a 60V6, the simplest tuneable PCMs i can think of are the 94-95 3100 A-car and 94-95 3.4DOHC w-car PCMs. both are MAF systems and i put a lot of time into making the DOHC PCM VERY customizable.

[2.8-350TBI]

i'll throw in some knowledge.

the 93-95 3.4RWD motors used flash PCMs that have yet to be cracked(and likely never will due to lack of demand).

if you want SFI on a 60V6, the simplest tuneable PCMs i can think of are the 94-95 3100 A-car and 94-95 3.4DOHC w-car PCMs. both are MAF systems and i put a lot of time into making the DOHC PCM VERY customizable.

Thats what I was referring to it as being tunable or not. Thanks for clearing it up for me.
Now, as those A car and TDC ecms, are MAF systems, is there a way to convert those for MAP operation?
I would rather not have to deal with maf sensors.

My build isnt for the sake of SFI, but tunability more than anything.
SFI would be nice tho.

[RednBlack]

94-95s are left sucking hind teat. Unless something else has come down the pike. Mayhaps something has, I've been out of the mix for awhile. I'd like to know though.

[robertisaar]

not gonna happen on those. they have 2 basic fuel metering modes: MAF and alpha-N, MAF using the MAF sensor for damn near everything, and alpha-N basing fueling and spark off of throttle angle and RPM. alpha-N is more of a "oops, MAF failed, now i gotta limp it home" mode.

anyone feel free to correct me if i'm wrong, but i believe all OBD1 ECM/PCMs that were SFI used MAFs? otherwise, if SFI falls out of favor due to MAFs, then your next best bet would be to grab a 91-93 3.4DOHC PCM. not SFI, but it is a speed-density computer with enough complexity to work out any quirks you might come across. after that, there's the 1227730s that were in like everything 60V6 MPFI related from 1987-1993, or it's weatherproof brother, the 1227727, which was only in corvettes and w-bodies.

[robertisaar]

94-95s are left sucking hind teat. Unless something else has come down the pike. Mayhaps something has, I've been out of the mix for awhile. I'd like to know though.

feel free to send PMs unless you think it's relevant for the thread, i don't mind which.

[2.8-350TBI]

Thanks again for all your help guys.

IDK. I mean SFI is a blessing us GM guys got early but is MAF really a hindrance in any way to us?
Keep in mind I will be running boost eventually, so maf may cause problems then.

For mpfi:
What does a 91-93 TDC ecm have compared to a 7727/30 which I see a lot of guys here talking about?

[robertisaar]

actually, MAF's make boost SO much easier to deal with, since none of the other PCM/ECMs i listed deal with anything other than a 1BAR MAP sensor, unless you decide to run either TGP code(8F) or code59 on the 7730/27 or the 16149396(91-93 DOHC PCM).

MAF's really aren't much of a restriction, unless you're using one that's far too small for the application, then yeah, you'll drop power, but it's fairly easy to jump up to larger MAFs, just have to transfer the frequency response to grams/sec readings.

the 91-93 DOHC PCM's mask has quite a few more torque management settings in it compared to masks that were intended to run on the 7730 and 7727. it helps save a 4T60E for a little while. it can also be used in a way the factory didn't intend: limiting power at low MPH to prevent massive wheelspin in high power cars.

other than that, not much different.

[Superdave]

Just use a harness from a Cavalier, a '7730 ECM and run $A1. there are hundreds of cars running gen3 engines on $A1, most are daily driven stock setups but there are plenty that aren't stock as well.


SFI is only the idle mode and MPFI can idle just as nice. I can post a datalog from a 10.8:1 3500 with a P&P'd top end to prove it. Smooth as glass.



Now, if only i had time to finish my $SA1 project...

[2.8-350TBI]

I see...
Does SFI make that much of a difference to consider the extra steps needed to get it to work?

The thing that attracts me is the '91-93 DOHC ecm as it seems to have all the cool stuff I like, besides SFI.

What code is better to run on it though?
$59 or $8F?

[robertisaar]

SA1?

and i had the MC's 3100 running very nicely on $DF on it's first try, so it's definitely not something hard to achieve.

and don't suppose your scope can read at least two inputs at once dave? we can see just how high the PCMs attempt to stay in SFI mode....

i don't remember seeing any kind of RPM cutoff in the 2E hack...