Hi all, new to the forum, but I've lurked for some time. I've done one GM ECM conversion or a carb'ed car, starting my second... I'm initially *not* gonna control spark, just fuel for now, and it's a manual trans. I'll have to adapt/make my own VSS unit for this app (Nash six). I've used a '7747 before, but had a chance to grab a '7746 for $15, so I did... I was told that I can use a MAT sensor with the '7746 (PROM ID $41), which should be an incremental performance improvement over the '7747. I hope. The '7747 and '7730 are obviously more popular, but seem pretty close in functions. Is there any general criteria for picking one of these over the other? I'll shelve the '7746 if it was a bad buy. Any suggestions on picking a MAT sensor for a very low pumping motor? Every sensor will require custom install so none of that scares me.

The '7730 has many possible codes that can be used in it, from 4 cyl applications to 8 cylinder appliactions. Natrually aspriated and forced induction.

The '7730 has a higher baud rate (communications rate) than the '7747. The '7730 is 8192 baud, where as the '7747 (and other C3 ECMs) use a 160 baud. The '7747 also has limited number of items that can be displayed, where as most codes that run in the '7730 have many more items to display.
While items that are sent through the ALDL might not seem like a big deal on the surface, when it comes time to tune, the quicker refresh and and more items can help pinpoint any possible issues that come up.

The '7730 is also able to run electric fans, where as in stock for the '7747 is not able to do this. The '7730 also has a MAT sensor input in all codes I've seen it used with.

The other thing to consider would be the type of induction you will be using, TBI or MPFI. If you are going MPFI, I'd say '7730 hands down, since it's easier to run MPFI on the '7730 than '7747. If you will be using TBI, I'd suggest a different ECM, and that being the '7427, which comes in the '93 to '95 GM trucks.
The '7427 has the higher baud rate ALDL as well as other refinements to the code for use with TBI.

If I remember right the '7746 is pretty much a '7747.

Most popular codes used with the '7730 is AUJP, or S_AUJP. AUJP, was an MPFI V8 code used in the TPI F-bodies (maybe other applications as well), S_AUJP has some additions like wideband O2 datalogging through the ALDL datastream, extended tables, and some nice documentation. This is a naturally asprirated code. Mask is $8D.
Code59 is also popular, and is geared towards forced induction cars. It is based on $58, that was used in the Syclone/Typhoon and turbo Sunbird. $58 was a 2 BAR code (read up to 14.7 PSIG), code59 has expanded it to 3 BAR, up to 30 PSIG, expanded VE and spark tables, WBO2 closed fueling control (selectable), and a very information filled website dedicated to the code (www.code59.org). I have started on testing a 1 BAR version of code59, but have not yet got a car running that would use this code, so I haven't been able to test it that way yet.
$A1 is also a semi-popular code used with the 60 degree V6s from about 1990 to 1994.

Any information posted on your project? I have a '7749 (very similar to a '7730) using $59, running my Nissan L28, that is in my 1973 Datsun 240Z, also has DIS ignition on it.

Woah! What a breath of fresh air! Thanks for the informative overview!!

Oh yeah, no argument from me here. The 7747 was easy enough to work with, but...

Done! '7730 it is. The electric fan and MAT is a big deal for me.

I'll be running TBI. See below for why... but why is the 7727 better for TBI than the 7730?

The target for this project is a Rambler 195.6 OHV, in a 1963 Rambler American hardtop, with "Twin Stick" transmission (a craptacular T-96 3-speed manual with R10 overdrive unit, with two shift levers). It's my daily driver (12K miles a year). Very light car too.

I'm building another (same) motor based on a '58 block. Ultimately I wanna turbo it, VERY modest boost, 4 - 6 psi. I'd like to pick a 2 bar sensor now and stick with it.

Not many people are interested in this motor. My web page for it is at http://wps.com/AMC/1963-Rambler-Amer...5.6OHV-engine/ My general AMC crap is at http://wps.com/AMC

Not the '7727, the '7427, two very different ECMs.

The '7727 is basically an underhood version of the '7730.

The '7427 is a late model TBI PCM, that has the faster ALDL datastream, and more refined fueling and spark control.

Speaking of spark control, it's very easy to add that to most conversions. As long as you have a magetic reluctor (The proper name eludes me right now, Hall effect?), or convert a points dizzy to this, you can use a GM computer controlled ICM to both provide the needed RPM (AKA DRP) reference, but also provide timing control. I did this initially with my Datsun, just to get it going quickly and easily, the swapped to the DIS later. I mounted the ICM to the fender, and used a 280Z dizzy inplace of the orginal 240Z points dizzy.

I haven't personally tested TBI with a '7730, but it should be possible. a MEMCAL modification would be needed, to make the injectors fire correctly. This is something I want to test on my test bench, and have thought about using the resistance values found in the '7427 MEMCAL, but this is all speculation right now. Some of the codes I have looked at do seem to have a "TBI" setting for cylinder count/set-up.

The '7427 doesn't use a MAT or control an e-fan, so if those are a must than '7730 would be the ECM to take a look at, and see what it will take to make it fire correctly for TBI use. May take a bit of experimentation to work right for you.

There is another option, that may actually be easier overall, and that is the EBL. basically it is a '7747 (I think a couple other ECMs will work as well), that gets an updated daughter board, with extra inputs and outputs, including E-fan use, not sure about MAT input. For more info go here: http://www.dynamicefi.com/

I'll take a look at your site.

d'oh, my bad! I read it wrong. To make sure I'm doin' it right -- you mean 16197427 vs. 1227727 etc I take it.

There's only the one Delco-Remy distributor available for this motor. I hacked it already for 32 degrees advance (instead of 19!) I figure spark control will be a good "revision 1" project; one change at a time. I was hoping I could coerce my Pertronix Ignitor to provide the timing signal, though I have the skills to make my own reluctor or hall effect distrib if I have to. Yeah, the GM HEI module is the way to go, it's very flexible and even works with a Ford Duraspark reluctor (my likely donor, I have 'em in the iron pile).

Well I'll let you go first :-) Too many variables for me at this time at least.

Eh, too bad, but overall project success is more important than fine points. MAT sounded good, but I gotta lot of low-hanging-fruit to collect with any decent EFI. Fan control would be nice, but I can do that externally.

Ahh... I saw the thread(s) here about the EBL but didn't find that page til you posted the URL. Yea that thing looks good, but I gotta do things on the ultra-cheap right now, so the $ outlay is too much. I already own a Moates AutoPROM and flash chip adapter etc.

Thanks a million, really, you gave me more info in this thread than I've been able to puzzle out in months of web-browsing. Detailed info is findable, but there's not a lot of strategic overview info.

It looks like 16197427 is the overall best choice for me.

I would agree with your last line.

Just read through the posts here about disabling the tranny control stuff. It doesn't sound too hard, and honestly I'll be finding out soon enough, since I'll be using that same ECM in a '71 Chev truck, with a Vortec engine, that I have adapted a Corvette crossfire intake to. We are retaining the mechanical tranny (TH350) for now, so I need to disable the electronic tranny controls.

I know there was also a manual bin posted once for that ECM as well, do a search on that ECM, also take a look at the threads that are discussing MPFI conversions with that ECM, since there is information in those threads that pertains to more than just the MPFI conversions.

If it needs to be ultra cheap, use what you have, you can use the '7747 or '7746 to get your engine running, and many sucessful swaps have been based around using the '7747, it's just that it's limited (in stock form), and the datalogging makes tuning a longer process than it should be, I noticed that when I was playing with the '7747 I would miss entire sections of information, or where I would have liked information. If I knew then what I know now after tuning the faster communications ECMs I could likely do a better job and be able to 'interpolate' between the points of informtaion I did have to see what I need to change. I just find the faster datalogging and more variables makes tuning much easier and more enjoyable.

Well thanks a ton for all the info. I have a lot to mull over, but now I feel a hell of a lot better informed!

The 7427 uses the $0D code for a 4L60E or the $0E for a 4L80E, either will work with a manual. Both $0D and $0E have provisions for a MAT sensor stock, though it wasn't used very often. E-fan control can be added easily if needed.

Cool. I saw a thread about a Manual/Auto bit, is that enough to turn off the auto-trans error checks and all that? I admit I haven't fully RTFM'ed this issue yet.

I assume the e-fan hack would be to use some unused EGR control or other output pin w/custom code?

Im using the E-Fan code on my EGR output but there are a few extra outputs on the 7427 so even if you still wanted to use EGR Im sure you can find an empty output to use. FWIW the 7427 also has WB02 datalogging and MPFI mode.

OK, I have a TMI headache! Read a lot in the last 24 hrs! (Every google search seems to come back to this forum or fullsizechevy :-)

The 16197427 sure seems like the best choice, and dimented24x7's MAF hack looks like a great thing, maybe even for a first pass. I remain a bit worried about non-late-model-GM vehicle applications, it's hard to figure out how much of the existing car guts the PCM depends on. Things like ESC sensors are a mystery to me (never owned nor had any interest in modern cars) and while it's certain I can read up and understand modern underhood stuff it sure adds to the learning curve and fatal-oversight-error possibility. The fundamentals of this stuff I got (knock sensors and algorithmic tactics to work with, etc) just never wrenched these late model donors!

The 1227747 is dumb as a bag of hammers but is a certainty to make it go in motors as old as the ones I hack, where every sensor install is a custom job (head drilling for the coolant sensor, for example) but the 16197427 sounds so superior in so many ways I'm still trying to figure out what it's assumed underhood environment is. The info is out there of course, just not in any one place!

There's a lot of info in these forums but not much overview/summary, but I do that for most of my projects and put it on the web so I'll be doing that here.

The most helpful threads so far are

"TBI MAF code and FAQ"
http://www.fullsizechevy.com/forums/.../t-274691.html

"PCM swap 16197427"
http://www.thirdgen.org/techboard/tb...6197427-a.html (PCM Swap (16197427))

Thanks tons for the info!

Hey, just an extra thanks, I realize I need to tread lightly -- this is THIRD GEN GM forum, not just a how-to-DIY-EFI forum. I truly appreciate the replies, as a non-GMer, and want to acknowledge the vast amount of knowledge and the free sharing of such outside of your favorite brand. Just wanted everyone to know I do appreciate it!