I hope that this isn't the wrong forum, but I thought that you ECM gurus would know something about this. The EFI tech at edelbrock said that all I would need to complete the swap successfully would be an ECM from an 87-95 truck. IS this true? Why? What would be the difference between it and the one in my RS now? What else would I need to do? Any input appreciated.

Don't know the exact reason....I know that Edelbrock designed their TBI/MPFI retro kit around a trucks ECM and harness. If you do have to get an ECM from a truck, remember that in 1993 GM started putting the 4L60E's in trucks. Make sure you get the one for your specific tranny.

Of course Edelbrock is right. Get a 1227747 ECU from a 1988-1992 or so truck. VERY cheap ($25-$75) and easy to find. You don't need the OEM PROM as Edelbrock supplies it for you but you do need the CALPACS.

You'll be pretty happy with that system once you are done. Nice.

EDIT: I suppose you could use your ECU, but you would probably have to make PIN changes and PROM changes, too, as the two ECU's have different internal languages... Ie, you would have to convert the Edelbrock PROM into your ECU's BIN language with the appropriate TDF file on TunerCat (ex).

It sould be MUCH EASIER and I am sure CHEAPER to just buy the ECU, unless you need a new harness to match the 7747 ECU? Not sure about that one but I think PIN changes in your ECU will allow you to run the 7747 truck ECU.


[This message has been edited by FastBroker (edited April 11, 2001).]

Forgive my ignorance, what is a CALPAC? Will my stock harness work? Thank you both very much for the info. I've tried getting information on other boards, but you guys have been the first to help out! Thanks again. I hate to clutter up this board with this topic. Is there anyone I can e-mail that knows more about this? Of course, if you guys don't mind me being here, I'm happy to stay. Thanks again.

James

As I stated, I DO NOT know if you can use your existing harness with the 7747 ECU. You may be able to outright, you may have to change some of the "pins" in the ECU connectors, too. I AM NOT SURE and someone else has to help you with that. Also, if you change harnesses, you may need new sensor connectors and/or new sensors themselves to match the conenctors/ECU???

I am not a GM mechanic and have little experience w/GM TBI, too. I'll let someone else with value-added jump in. I am pretty sure someone here knows what to do.


Good luck!

From what I've read, the CALPACK is a simple resistor network that sets the appropriate time constants for delivering the right amount of fuel in "limp home" mode. They're engine-specific just like the EPROM is. I guess you could think of it as analogous to the EPROM, but for the analog limp-home circuitry.

I'll try asking about the harnesses on another board, too. Does anyone here know if I can use my RS wiring harness with a truck ECM of the same year?

the 7747 should plug right in. I originally had a 746 but swapped to a 7747, at the time I was told i needed to swap some pins but looking back I believe it was unneccessary since they were grounds

if i were you I wouldnt waste my cash on that system though

That system is GREAT! you can make one yourself, but you gotta be a good wrench, burn a PROM, put the thing together without leaks and you have no warranty/customer support.

The single plane manifold on the system is matched quite well to the TB unit and injector sizes. Hey, they make 270+hp on that system w/Al heads and I only made 245hp with the SAME TBI and SAME EXACT CAM (mellow 194/214, .398"/.442") before I gave up...

Man, I'm not sure what to do here... I have been trying this TPI swap for the past few months and it just isn't working. I've been thinking of going carb, but now I see this Edelbrock system. What should I do? Pablo, why don't you think I should spend the money? I know that you are the TBI man, but it sounds like a great way to easily upgrade an injection system.

IMO, if you already have TBI, stay with it. I just made more than 300hp with 55pph truck injectors at 20psi, XE250 Comp Cam, Vortec heads, RPM AIr Gap manifold, BIG prom fuel/spark/EGR changes and 9.0:1 CR. I have no problem with 300hp/400lb-ft on such a driveable combo. Putting the engine back in the Wrangler tomorrow/Sat cause dyno work is done. Mileage testing and burnout testing with 31x12.50x15 BFG AT's and 4.11's begins Easter Sunday.

If you need a cool/easy MPFI system and are ok with 300hp or less, the Edelbrock is a good system and will work out of the box pretty much because of the dyno work Eelbrock did for you to make their PROM.

If you have the time/money/PROM savvy, do your own MPFI conversion or do the TPI conversion IF YOU NEED MORE THAN 350hp...

ditto on what pablo said on the 747 swap.

When I did my swap, Howell-EFI told me that 2 pins needed to be swapped and two cut. I did the mods but in retrospect, I dont think the harness mods were needed.