7427 with G1 memcal mismatch

[Dieselsj]

With Moates being closed, I can't go ask over there. I'm hoping someone here knows or remembers. What functions are still used from the factory memcal when using the G1? In going back through everything from when I started with the 7427, the ECU that I purchased had a 4.3 Auto memcal in it. I just used that memcal when I installed the G1. I remember something about limp mode and spark retard coming from the memcal. However, since my 87 7.4 doesn't have an ESC box, I *thought* I read that it would not use the memcal spark retard and that it would just use spark from the tune.

Now I could be totally wrong with all of that. And I'm wondering if having a 4.3 factory memcal is what is causing some of my funky tune and driveability issues? I'd slap a 7.4 memcal in there, but vendors think those things are gold and they are going for $250-350 on Ebay just for the memcal. There is a full 7427 ECU with BHDC memcal (7.4/manual - this matches my truck and the base tune that I used) available. I'm wondering if it is worth the $200 they are asking just to get the memcal and have a spare ECU?

Or do I just need ANY V8 memcal? 5.7/auto memcals are $20-30 which would be a no-brainer to grab one if that is all I need.

[Tunedperformance]

Firing rate done by v8 netress, knock filter based on engine size and lhm.

https://www.ebay.com/itm/25636503529...mis&media=COPY

[Dieselsj]

Firing rate done by v8 netress, knock filter based on engine size and lhm.

https://www.ebay.com/itm/25636503529...mis&media=COPY

Thank you for that. I think I was too focused on 7427 in my search and forgot about the compatible ECUs.

[dave w]

The Memcal functions:
Limp Home Mode
Knock Sensor Filter
Cylinder Select

When possible, using an original Memcal for a specific engine / transmission configuration is a good plan. The computer is the same, only the Memcal is specific to engine / transmission configuration.

[Dieselsj]

So cylinder select... that could be my problem. If it thinks I have a 6 cyl then my injection pulses will be off. So fewer pulses would solve the riddle on why I'm needing to tweak my flow rate and engine size parameters so much. So I at least need a V8 memcal. Seems like a logical enough reason to swap memcals.

[stew86MCSS396]

So cylinder select... that could be my problem. If it thinks I have a 6 cyl then my injection pulses will be off. So fewer pulses would solve the riddle on why I'm needing to tweak my flow rate and engine size parameters so much. So I at least need a V8 memcal. Seems like a logical enough reason to swap memcals.

I dabbled with this issue a little so someone smarter on this topic please correct me if I'm wrong. I think it's more relevant if you have a CPI vs TBI memcal. CPI you get 1 injector pulse per crank revolution whereas TBI I believe it's still alternate injector per drp which shouldn't affect a V6 or V8.

[Dieselsj]

I dabbled with this issue a little so someone smarter on this topic please correct me if I'm wrong. I think it's more relevant if you have a CPI vs TBI memcal. CPI you get 1 injector pulse per crank revolution whereas TBI I believe it's still alternate injector per drp which shouldn't affect a V6 or V8.

Well then the question for the smarter people is how does it count? If it is counting 3 ignition events then firing vs 4 ignition events That would definitely mess up things. These don't have a way of knowing where TDC is so it would have to be based on ignition events .

I found a cheap ecu with a 7.4 memcal on ebay. I'll pretty much know immediately when I look at the live data.

[ralmo94]

This might help with the cylinder select knowledge.
http://www.gearhead-efi.com/Fuel-Inj...ull=1#post3374

Also, when you use the g1 adapter as far as I know it is only really used for limp home mode, and possibly knock, I have used mine with a chip only and no memcal, and I got no complaints from the ECU, but iirc, I had disabled the kr sensor, or at least the timing pull from it.