Tuning limitations of the SFI 3.4 ironhead

[blownarrow]

What's the tuning limitations of the SFI 3.4 ironhead?
Running a obd "1.5" I think?
cams?
larger throttle bodys?
turbo?
Supercharger?

Can these ecm or brains be easly flashed, chipped, tuned?

[robertisaar]

with the stock ECU? No.

you would have to either run it as OBD1 or OBD2, or figure out how to reverse engineer GM's algorithms and then we can flash them the way the 94-95 LT1 cars can. we would essentially be OBD2 at that point, without the extra emissions check crap.

EDIT: you could get away with a light cam and a TB, but that's about it of the list you posted...

[blownarrow]

No emissions crap will be used, I'm thinking of going with BMCautos 3.4 harness.
I talked to Brian (nice guy) yesterday for a length of time about my set-up and what I was looking to do with it.
All I really want to do is run a lumpy cam... and If I can't do that then maybe a nice
6-7psi setup, turbo/SC....
I would like to have that option later if possable...

[IsaacHayes]

What is the 3.4 harness? What PCM does it run?? If it's the F body one then you can't tune at all...

[robertisaar]

the 94-95 manuals used the same PCM as us, the auto used a similar one with the same case/plugs, just slightly different internals. 93 used the same for auto and manual but still has the 1.5 plugs...

[blownarrow]

It will most likely be all F-body stuff, BMC harness, and a FWD brain "to get rid of the anti-theft stuff"....?
http://bmcautos.com/shop/index.php?m...574699ead5ba08

[IsaacHayes]

Well you'll need to re-wire for a different PCM if it's the F bod stuff as you can't tune that PCM. What trans are you going with?

[60dgrzbelow0]

Wow... Strange that the Brits would hone in the F-Body Stuff...and Very Pricey, too... I thought the "Freebie" about relocating the Knock Sensor was interesting, too. I wonder whether its necessary to do this for the Pacesetter Ceramic Coated Headers application.

Robert... Can anyone tell me what would be involved in de-engineering the PCM from a 4th Gen F-Body? I have an extra one... I just don't have any of the equipment, harness interfaces and the necessary programming engineering skills to do it... and burn a new EPROM Chip. I'm puzzled as to why the RWDs have not been "cracked" and understood by the folks who can do this kind of thing, to date. Has anybody ever made a simple external harness that would allow you to build a PCM controlled Engine Break-In Stand like the ones you see from time to time...?

[robertisaar]

reverse engineering: good luck, i've been studying it for about a year and JUST recently learned what the hell was going on. and that's with the P4 ECMs, not the P66 setups, P4 meaning the ECMs with 1 Motorola 68HC11 processor MEMCAL that includes the knock filter, PROM and NETRES all in one piece(found starting in 1986 and continuing to 1995 for certain applications), P66 meaning it has 2 P6 processors, a la the Northstar, 94-95 LT1, 94-95 3100, 93-95 3.4OHV and a few others.

cracking those is essentially cracking OBD2, since they are LARGELY similar.

they were never cracked due to the relatively small amount of vehicles that came with it compared to how tough it is and how long it takes to pour through it all. expect to spend a good year on a P4 ECM, P6 would be even longer, if you could pull the BIN off of it anyway. simple things like the VE and spark tables could be spotted pretty easily, but almost everything else important would REQUIRE hacking through it.

i'm not quite sure what you mean by PCM-controlled break in stand.... you mean like it automatically runs it at a certain RPM for a flat-tappet break in? something like that?

[60dgrzbelow0]

...I'm not quite sure what you mean by PCM-controlled break in stand.... You mean like it automatically runs it at a certain RPM for a flat-tappet break in? Something like that?

Precisely...

A basic, balanced and stable 4130 Chrome-Moly Tubular frame... with a modest Radiator up front... some Headers for easier breathing and a welded Y-Pipe out the rear... married to a small scale, dual exhaust to quiet things down and keep the neighbors from complaining about an engine that must run within the first, early moments of its new life for at least 25 minutes ...spinning at a steady, steady, steady two grand... work hardening the cam lobes and letting all the gaskets and seals become stressed enough to reveal any potential weaknesses. The area around this device is warmed from the heat...the light and the vibrations coming from a Brand New Engine breathing its first measured breaths of air...its first gulps of Gasoline... Safely off to one side and feeding the machine from an electric fuel pump... powered by a 12 Volt Car Battery to turn the engine over and get things started.

Nearby... on the outer frame area.. A simple pedestal... with some simple controls... A few "Idiot Lights"... A Key Switch to wake up the motor... and to tell it when to sleep... A few gauges ...A Tachometer for RPMS... An all important, analog Oil Pressure Gauge...A Water Temp Gauge...and some type of Throttle to raise, lower and control the New Engine's sense of excitement... And finally...a Mechanic to stand at the controls and watch over everything and smile at the wonder of his work...watching the new machine rumble and shake....and after the camshaft is safely broken in... Listening to the engine idling... grumbling and making the staccato sounds of it loping...like a newborn calf...staggering about while trying to find its footing.

Yes... Precisely ...and this is why we should not have to rely upon a Distributor and a Carburetor to do this part of the work ...outside of the prison of the engine bay.

Something like this... But perhaps on a slightly larger...if not less powerful scale...

http://www.youtube.com/watch?v=N8TXMUaC9Os

http://www.youtube.com/watch?v=CUfSIlIYy9o

http://www.youtube.com/watch?v=kPr_XbHY9u8

http://www.youtube.com/watch?v=LA77NziH0x4

[tkoforpresident]

i'm a living testamony to why a lumpy cam and ported TB etc. just wont work on the stock 3.4 tune. My car won't drive without stalling because i can' adjust the tune for my modifications. I'm currently in the process (thanks to the help of John, Robert, Isaac, and others) of switching over to obd 1 so i can tune like the older cars.

[robertisaar]

it wouldn't be too hard to make a tune that wants to idle at 2K RPM.... just have to watch the clock/stopwatch/the timer that gets displayed through the ALDL datasream...

if you can run fuel and coolant lines, then you've already done the toughest part of the operations...

[robertisaar]

Something like this... But perhaps on a slightly larger...if not less powerful scale...

http://www.youtube.com/watch?v=N8TXMUaC9Os

for only being about 5 1/2 cubic inches, that thing sounds wicked...

[ForcedFirebird]

Lol, there's a slew of those small motors on youtube.

You guys are forgetting that there are 2 variations of the OBD1.5 ECM's and one is in fact tunable. The lt1 ECM (or should I say PCM lol) has a removable PROM, whereas the v6 PCM has only a removable knock filter. The lt1 PCM has 4 plugs, the v6 has 3.

I just got done modifying a 1995 v6 PCM for use in fleenor's buggy, didn't do any research to see how much they are going to charge you for it, but you will make life much easier by just using a harness from a Lumina and '7727 ECM and extending any wires you need to to make it fit your application. It will just require a little more work on your end, since I haven't seen anyone that supplies the harness by itself, and you would have to pirate it from a junk yard.

EDIT: Holy crap!!! I just clicked that link and didn't realize they are charging that much!!! I can build you a custom harness for about $350-$400.

[robertisaar]

You guys are forgetting that there are 2 variations of the OBD1.5 ECM's and one is in fact tunable. The lt1 ECM (or should I say PCM lol) has a removable PROM, whereas the v6 PCM has only a removable knock filter. The lt1 PCM has 4 plugs, the v6 has 3.

you are refering to the 94-95 LT1 right? then how the hell can it be flashed through the ALDL port? does it have a flash programmer built into a daughterboard or what?

......i hate when i don't have anything to play with in person.......