More E38 weirdness...

[gmtech16450yz]

Ok, this is interesting...

I just looked at an EFILive tuned '08 GMC Sierra 6.0 VMax ECM (E38) with both EFILive and HP Tuners programs and noticed a few weird things, A/C disable/enable was one of them and DFCO was another.

In EFILive the A/C disable rpm is set to 4000 rpm, the re-enable is showing 3800 rpm. If you look at the same tune in HP Tuners it shows the opposite- disable shows 3800 rpm and re-enable shows 4000.

In DFCO B2409 and B2410 in EFILive do not seem to make any difference in this OS (12617631), putting in any number does not change the vehicle at all. I noticed in EFILive the DFCO disable (B2409) shows 1000 rpm and enable (B2410) shows 1300 rpm. In HP Tuners disable shows 1050 rpm and enable shows 1700 rpm. Funny thing is the DFCO on the truck turns off when decelerating and it goes below exactly 1700 rpm, so I'm thinking the HP Tuners may be correct? (I haven't tried reflashing with different numbers in HP Tuners yet.)

Anybody know what's up?

[gmh308]

Ok, this is interesting...

I just looked at an EFILive tuned '08 GMC Sierra 6.0 VMax ECM (E38) with both EFILive and HP Tuners programs and noticed a few weird things, A/C disable/enable was one of them and DFCO was another.

In EFILive the A/C disable rpm is set to 4000 rpm, the re-enable is showing 3800 rpm. If you look at the same tune in HP Tuners it shows the opposite- disable shows 3800 rpm and re-enable shows 4000.

In DFCO B2409 and B2410 in EFILive do not seem to make any difference in this OS (12617631), putting in any number does not change the vehicle at all. I noticed in EFILive the DFCO disable (B2409) shows 1000 rpm and enable (B2410) shows 1300 rpm. In HP Tuners disable shows 1050 rpm and enable shows 1700 rpm. Funny thing is the DFCO on the truck turns off when decelerating and it goes below exactly 1700 rpm, so I'm thinking the HP Tuners may be correct? (I haven't tried reflashing with different numbers in HP Tuners yet.)

Anybody know what's up?

EFILive looks like it is correct for the A/C on/off.

And with DFCO, do you mean DFCO disables > goes from DFCO is enabled and fuel is cut, to fuel flow is = on/DFCO disabled and engine operating "normally", as the rpm passes through 1700rpm and is decreasing?

Reason for clarification: When DFCO is "on", "it" the fuel, is off, and DFCO should be "on" when decel anyway until it gets to disable rpm.

Have seen this with other parameters too, between EFI and HPT. Like speedo. The number in the ECM was the same, they both scaled it out differently. On one, the cal number was presented incorrectly......guess wHicH?

[gmtech16450yz]

And with DFCO, do you mean DFCO disables > goes from DFCO is enabled and fuel is cut, to fuel flow is = on/DFCO disabled and engine operating "normally", as the rpm passes through 1700rpm and is decreasing?

Yes, that's what I meant.

On the A/C, in the stock tune the disable and enable rpms are both 0, TPS is 100. Looks like all they're working off of is shutting it off at full throttle only.

Thanks for your reply.

[gmh308]

Yes, that's what I meant.

On the A/C, in the stock tune the disable and enable rpms are both 0, TPS is 100. Looks like all they're working off of is shutting it off at full throttle only.

Thanks for your reply.

You're welcome. Which trans in this truck?

[GMPX]

In EFILive the A/C disable rpm is set to 4000 rpm, the re-enable is showing 3800 rpm. If you look at the same tune in HP Tuners it shows the opposite- disable shows 3800 rpm and re-enable shows 4000.

To make sense of this you have to think about what the purpose of the function is and it is to protect the A/C compressor and give a little more power at High RPM.
So looking at EFILive's numbers, you want to shut the compressor off at 4,000 RPM and only allow it to come back on once the RPM falls below 3,800. That makes sense right?

In DFCO B2409 and B2410 in EFILive do not seem to make any difference in this OS (12617631), putting in any number does not change the vehicle at all. I noticed in EFILive the DFCO disable (B2409) shows 1000 rpm and enable (B2410) shows 1300 rpm. In HP Tuners disable shows 1050 rpm and enable shows 1700 rpm. Funny thing is the DFCO on the truck turns off when decelerating and it goes below exactly 1700 rpm, so I'm thinking the HP Tuners may be correct? (I haven't tried reflashing with different numbers in HP Tuners yet.)

Anybody know what's up?

This one can be a little more confusing, B2409 is used if DFCO is active then it will be disabled once it falls below that RPM value (1000RPM), to allow it to be re-activated it must rise above B2410 (1300RPM), I think you will find that the ECM is not using RPM as the main qualifier to have DFCO active, it will be an airflow thing, keep an eye on the airflow values and compare that to B2404.

Cheers,
Ross

[Redline Motorsports]

What I don't understand, and see there points, is that how can ANY software that is designed to read the same parameters be expressed in different values?

Why should IFR tables be differently scaled same year same OS? Just as an example. Is it avoid copy/paste issues????

Howard

[gmh308]

What I don't understand, and see there points, is that how can ANY software that is designed to read the same parameters be expressed in different values?

Why should IFR tables be differently scaled same year same OS? Just as an example. Is it avoid copy/paste issues????

Howard

Just not a perfect science mapping "black boxes" from the outside.

[GMPX]

Why should IFR tables be differently scaled same year same OS? Just as an example. Is it avoid copy/paste issues????

GM have changed the IFR table structure I think 3 times since the E38 hit the streets, in table size and scaling, that has nothing to do with EFILive, apart from annoying us

Cheers,
Ross

[gmtech16450yz]

Ok, first off this is NOT an EFI vs. HPT situation, I'm just trying to figure out some things that haven't made sense and I couldn't really care less which program gives me the answers. Truth is using BOTH programs has given me the answers.

I had a chance to play around with the A/C and DFCO, here's what I learned so far...

On the A/C, EFI reads the enable and disable correctly as far as which is which, but the rpm is only an enabler for the tps check. If you put the rpm at 0, the A/C will never cut out no matter what the tps is. It only cuts out at the tps setting if the rpm is BELOW the set numbers. If you set the rpm at 7000, it will then cut out at whatever tps you set, at whatever rpm.

On DFCO, EFI is not reading the numbers correctly. I can change the enable and disable in HPT and the truck definitely changes to exactly what I set the rpms at. If I read the HPT tune in EFI it still shows the same numbers it always does, they don't change even though they definitely have been changed by HPT. If you change the numbers in EFI, they have no effect on the truck. (I'm talking about B2409, B2410 and B2415.)

Yes I understand how and why the A/C cutout and DFCO work, that's not the problem. And yes, I've already figured out the airflow/DFCO correlation, stock settings would only allow DFCO if you chopped the throttle at about 80mph! There are a few parameters I've tried to work with and found that even going from one extreme to the other on numbers, they make no difference what so ever to the actual vehicle. Using HPT has shown me what I suspected, there are parameters that aren't working properly. At least in this particular OS on this particular vehicle. And yes, I understand reverse engineering this stuff is extremely difficult and I am SO happy you all have been able to figure how to get into GM's programming and be able to modify it.

[Redline Motorsports]

Nobody was making it a debate but the fact that both softwares should be reading the same info and don't was the point. I'm not a computer hacker so pardon my ignorance but the tables weather read buy either one should be the same. I have seen this myself on many occasions.