i have a supercharged 91z28 and i'm in the process of switching from my 730ecm to a 749ecm to help with tuning and drivability issues. anybody here in so-cal running the 749ecm w/the $58/$60 patch? i have some questions for you.

thanks,
-dan

 

No, but I am curious why are you switching?

 

8T8IROC,

i'm switching to the 749 and a 2-bar map sensor because these ecm's can handle the timing/spark/fueling better than the 730ecm's. the 730's don't handle boost all that well. plus i will be able to eliminate the fmu for fueling needs and will be able to stop using the msd-btm spark retard dial.

this set-up is a better option as opposed to spending big $$$$ for a dfi set-up. i was just hoping that someone around here (oc) has tried this set-up.

-dan

 

Cool, thanks for the info, hope you get some answers

 

I was reading about you post can you tell me were i can find this 749 ecm and out of what car does it come out of and were did you read this information email it back to me at gmartin1105@yahoo.com thank you

 

gmartin,

the 749ecm is from the 91-93 gmc syclone&typhoon trucks along with a couple of other gm vehicles using force induction, in this case a turbo. you can go to any major brand auto parts stores and purchase the ecm (you must exchange a core ecm to reduce the price). also you can order the 2 or 3 bar map sensors. the 2 bar works up to 14.8lbs. of boost, the 3 bar works up to 28+lbs. of boost

as far as the info for the ecm swap, look on this web site under the the diy prom & diy ecm boards. check under the stickies at the top of those boards and it will list how to convert from a 730 to 749ecm.

from there you must obtain a laptop, aldl cable, software of your choice, a memcal and a romulator for real time tuning.

-dan

 

I think it is also used in the early 3.8 front drivers with blowers.

 

Not yet, but I plan on it for the same reasons as you. Dont know if I can answer your questions, but what are they?

 

madmax,

i was just hoping that someone in the area has used this set-up so i could and find out what they used for tuning, how they got the car dialed in, etc. i will not be doing the tuning myself so i will need help and hopefully find someone in the area with experience in this field. i have talked to don lorentzen here in orange and he said his son kevin could tune it, but this would be a first for him with the 749ecm set-up.

-dan

 

It shouldnt be much different than the 730 as far as tuning goes, same principal. Where you will have a difference thats significant is controlling timing under boost.

Do you have a wideband? I'd recommend one if you dont.

 

You might want to "pony up" for some dyno time with Kevin if he thinks it's a good idea. That is probably the only way to get it dead on under boost without going way illegal for the street.

 

madmax,

no i don't have a wideband (at least not yet), i'm hoping that whatever shop i take it to will provide that. i know using a wideband is key to dialing in the proper tune i just don't want to spend the $$$$ at the moment. i've spent enough $$$$$ on this car as is....i don't know we'll see.


russ-so-cal,

yeah, i think using kevin to tune the car is going to be my best bet. i pretty sure that i will purchase tunercat rt for real time tuning, so this should work well while tuning on the chassis dyno and real world driving conditions. have you had any experience using kevin by any chance?

-dan

 

Yeah Don & Kevin did the chip in my TA. It has a 93 Vortec truck short block with the stock Vortec cam, 1.6:1 rockers, l98 heads, and speed density tpi. We just had one glitch to work out. Don had never done a tpi chip for such a mild cam, and my vaccuum was going so high under engine braking that it leaned out real bad. He and Kevin adjusted the chip. Don has been in the speed business so long that he knows about all sorts of high performance combinations. I'm sure they'll start a blower chip rich, and then lean it if needed under boost. The other thing is they can make your rev limiter an ignition limiter, instead of a fuel cut off limiter.

 

russ-so cal,

well one of the problems with the custom prom that i have now is the motor is spitting raw fuel out the exhaust at idle and when you whap the throttle. its bad enough for me not to drive the car or run the motor because i'll wash down the cylinder walls with fuel. in fact i just changed the plugs and they don't look good...way to much gas.
so i guess when its time to tune with them i can at least give them the prom i have in it now and hopefully they can use that info to start the tuning and just go from there.

thanks for the response russ.

-dan

 

If your current prom is already set up for the blower, it may be a good base line to start from. If your running rich n.a., and are looking to put on a blower, change ecm types, and then do a custom chip, your current one is probably of little use. Having seen a number of fourth gens with blowers and custom chips go "boom" when they either leaned out on boost, or in one case the engine hit the rev limiter, and the stock rev limiter was a fuel limiter instead of a spark limiter. I don't know much about chip burning, but I learned a little watching Don and Kevin burn mine, and then test. I have confidence that they will "sneak up" on the setting and not let it lean out and go "BOOM!"

 

Russ, I'm not sure what you mean by this. The only way I know of to get an ignition limiter is with an aftermarket ignition box such as MSD. The stock computer is only capable of a fuel cut off limiter.

I dont have a wide-band O2 sensor, but I know where to get one.

 

Sorry about that. I didn't realise that you couldn't make it an ignition cutoff. I guess you would want to install a MSD box on it and shut off the ecm rev limiter completely. You sure wouldn't want to allow it to lean out under boost.