85 IROC TPI 1227730 conversion from 1226870

[zaut]

I converted my 85 to speed density from a MAF system. So far I feel I have made good progress. The car started, but is running badly. I have two codes set, code 41 Cylinder select and code 43 ESC errors. I am using a memcal from a 3.1l V6. I jumped pin 13 to pin 10 on the 16 pin chip. This is the HAC from Thirdgen to convert the chip to 8 cylindars. I assume there is something to do with that memcal as to why I am getting the cylinder select error. The 85 ECM 1226870 has a grounded input for selecting the ECM mode. Does the 1227730 ECM have a input like that, or is the HAC identified on Third Gen correct. I am a little worried about the ESC Code 43. I was under the impression the ECM/MEMCAL controlled the spark advance by direct input from the knock sensor. The 85 system had a separate ESC module that the knock sensor plugs into. The ESC module would signal the ECM to retard timing or not. By the wiring diagram for the 1227730 ECM, the ESC module is eliminated. So I have the knock sensor connecting directly to the EMC. Is this correct? I started my project (engine rebuild from a 305 to a 383) with an engine from the junk yard. It was a 1990 TBI 5.7L truck engine. That engine had a separate ESC module like my 85. This is why I wonder if I wired the knock sensor correctly or not.

[EagleMark]

I can only help with the ESC, yes it is removed and knock is wired to ECM where new knock module is on Memcal.

[Tunedperformance]

you cylinder select jumper should be on pin 56 cylinder select to pin 62 ground is the closest ground to set the fire rate. The knock sensor is wired in series to pin F9 of the 730 ecm. I would also reprogram out the knock error. The knock sensor will only do a retard but since the frequency does not match the sensor with the filter you will never have a knock retard. Not sure what you did about the vss signal but the 730 can except the 2kppm and control lockup just reprogram to optical vss from magnetic pin c6 of the 730, on the 870 it was A10.

[zaut]

Thanks Tunedperformance. I haven't been able to drive it yet so I wasn't sure if the VSS was correct. I guessed at connecting it to B10. All the documentation I have shows C6 unused. If you are certain about C6, I will give it a try.
Is the jumper you are referring to for cylindar select on the memcal or is it internal to the ECM? Is the filter for the knock sensor is on the memcal also? By saying I have the wrong filter, you are referring to me using a V6 memcal? I am looking for the correct one for my application. Do you know a part number?

[Tunedperformance]

I can send you a modified .bin to get the vss working if you like. I would start with a aujp gm acdelco 16151348. I have a few new ones that I will be selling. There are 2 ways to get the vss signal to work to help shut off the coolant fans at 35 and to control lockup. The above mentioned or wire in a wire in a 4k magnetic directly from the cable drive on your transmission tail housing and use pin b9 vss ground and pin b10 vss 4k input. the 730 has a built in buffer so if needed you have a output for cruise and newer style 87 up f-body speedometer non cable driven. The jumper I was referring to is on the memcal itself. The knock filter is on the memcal. A v6 memcal has a high resistance value on the knock filter and can be changed to a v8 but the resisters are very tiny to be replacing. I will be unable to reply to any response until this evening.


http://www.tpiparts.net/inc/sdetail/7587

[zaut]

Mark and Tunedperforamce,
I have to thank you for all your help today. The VSS works fine in C6. The programming was straight forward. Also, your help with the memcal jumper worked. The info I got from thirdgen said to cut the leg off the chip. That was at pin 56. I soldered that pin back to the connector and car runs like a champ. I owe you a few beers for the help.
I see in the programming that you can turn on EGR diagnostics. When I was changing over, I had nowhere to plug the EGR diagnostic switch. It was not on the diagram I had. Do you know what cavity that lead should plug to?
I eliminated the ESC error by shutting off code 43 and have know retard attack rate set to zero in temp vs attack rate table. I don't hear any knock, but would like to turn that feature back on. I am interested in buying a AUJP memcal. How much do you want for it?
All in all I am very happy with how the car runs and how much more you can tune with the 730 ECM. Mark, I remember you talked me into it. Thanks for the good advice. Now I get to learn how the VE tables affect engine performance. If someone has a $8d bin for a 383 TPI engine that would be great to see what they changed.