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

[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.

[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.

[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.

[dave w]

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

Wow, posting that link moved mega bytes of memory from the Hard Drive to RAM Memory

[1project2many]

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.

Well, it's not quite that way. The ecm will still deliver injector pulses and spark pulses. The challenge is in how the ecm uses the information. If a V8 engine is spinning at 2000 RPM it's generating 4000 pulses per minute. A v6 engine at the same speed is generating 3000 pulses in a minute. So if the ecm is programmed for a v6 and it sees 4000 pulses in a minute, that's going to look like almost 3000 rpm to the ecm. Now you want to go in and add fuel or change spark advanced, what rpm is appropriate to make changes? If you're using the scantool data you'll see the same rpm as the ecm. But if you're using a tachometer then you're in the wrong place.

One good question, is the ecm actually using the code? Is the check engine light telling you that the chip is good?

[Dieselsj]

So, interesting update. I had written down that the memcal which came with my 7427 was for a 4.3 so I really thought I was onto something with switching to the 7.4 memcal. When I pulled the old memcal, I looked up the code and it was actually a 5.7/4l60. I don't know why I had noted that it was a V6. Not thinking anything would really be different between the 5.7 and 7.4 with the parts of the memcal that are still in use with the Moates adapter, I really didn't think anything would change. I went for a quick drive and it felt horrible, stumbling and just not running as good as it had been. So I hooked up the laptop and went for a drive and to do some datalogging and my VE values changed. Biggest changes were right in the area where I was having that spike in values, where now it brought those down slightly and several cells into more load and into higher RPM from where the spike was have now increased. So it smoothed out the big hump. I took about a 30 mile drive and got some good logs. I'm getting ready to burn a new chip right now. I'll get this chip in and go for another drive in the morning to see what happens. On the surface it would seem that there are differences between the 5.7 and 7.4 memcals that do affect the tune.

More later...