Cant get 100% Throttle -Tuning E78 ECM 2011 GMC 2500 6.0 HD Truck L96 VVT non AFM

[496Stingray]

Anyone have some pointers for me as to why I cannot hit 100% throttle? I hit 84% and that appears to be it. I have done a lot of reading, testing over the past 4 wks on this ECM and still havent solved that mystery.

[GMPX]

A couple of things, I thought the SAE throttle PID only showed 84% on GM vehicles (I can't remember exactly). The other thing is the torque based ECM's (E78, E92 etc), once they see 100kPa (or close enough) they won't open the blade any more than they need to.

[496Stingray]

Thanks GMPX thats what I wanted to know as it appeared to me that is what was happening.
Now if I could just get it to reach 1/2 the mileage of your Holden Cruze Diesel rofl..

[GMPX]

Yeah well mine runs in AFM all the time which helps :rotflmao:

[496Stingray]

Haha nice.
Well my 2011 L96 has AFM in the ECM as well as E85 with virtual sensing, however its all disabled and from what I am told the injectors arent the E85 ones and the AFM lifters and oil control hardware arent in the block.

[KLUG'S SS]

The other thing is the torque based ECM's (E78, E92 etc), once they see 100kPa (or close enough) they won't open the blade any more than they need to.

Glad I seen this thread, may have led me in the right direction. Been pulling my damn hair out tuning a 2015 Silverado and the turd doesn't want to keep the throttle at the 100% commanded on wide open throttle pulls. It's always wanting cut throttle back by sometimes 20%+. My question is with your statement is their a table known of to get rid of this limiting factor?

[GMPX]

If the engine is at 100kPa (or close enough) at WOT (even at 80% throttle) then the throttle will not open to 100%, it is the strategy in these ECM's.

[496Stingray]

Its exactly as GMPX stated above, once your at 100kPa there is no point in opening the blade any further as the engine physically cannot take in more air.
This is the point where we cross into force induction, blower, turbo, serious ram air setup at ultra high freeway speeds etc to eek out anything further. Mine hitting 97-98kPa tells me that the exhaust system, camshaft profile, intake etc are all becoming the limiting factors.

I did bump the theortical maximum up from 100 to 110 kPa to test a theory that the ECM might try to command more throttle. It did increase my kPa from 93 to 97 but only in peak areas of the RPM range where the engine could actually attempt to do something with the additional airflow. The table I tweaked was the Estimated MAP Maximum value.

[KLUG'S SS]

So basically what the deal is their is no "tuning" this out where I'm seeing throttle cut back on this truck? The thing is I have tuned other 2014-2015 trucks and I am not seeing this reduced throttle issue what so ever? So you can see where I am confused. Just tuned a 2014 Silverado with the 6.2 last weekend and after doing 4-5 wot pulls up to 90+ this truck never once deviated from the 100% throttle I was commanding!

[KLUG'S SS]

I understand the logic and strategy completely incorporated into these newer operating systems based on what's been said. Like I said the only confusing part for me is after tuning a good handful of these newer trucks now I've run across I think maybe just 2 that were pulling back throttle. The rest were good and solid 100% throttle for an entire WOT pull just like I have been used to seeing for the MANY gen 3 and gen 4 trucks I've tuned over the years.

If it is what it is that's cool, I took this 4wd V6 5500 lb truck (with driver) from a stock 1/4 mile time of 16.19 @ 84.27 mph to a 15.39 @ 88.81 mph. Yes this particular truck is one with just that little 4.3 in it.

[496Stingray]

Which operating system and ECM is the truck your tuning now that will not hold throttle @100% vs the ones that did?

Looking at my last log file it does make me wonder why commanded is still 84% throttle at 5000-6000 RPM when my manifold is showing 94kPa indicating it has not reached its peak flow. Checking the logs over again my 97 kPa was around 4200 RPM. The SAE TPS PID from what I can tell is also scaled so 84% is actually the maximum we will see on the scanners due to the 1-5v range and full open is not quite a full 5v. From what I can tell thus far it appears that if the blade is full open at say 4.2 volts then we will see 4.2v as a % of 5v. 5v being 100%

I am going out to test something I think the PID we want to use is GM.ETCTP which appears to be the actual indicated throttle position,.

Mine is an E78 ECM with the 6.0/6L90 in a 2500 HD 2whl drive.

-Rob

[KLUG'S SS]

Yes sir any truck gen 4 like the E38 ecm variety and newer the standard SAE tps % PID will only read a max of 84%. For any newer body style truck 07 and up I log ETC position and on the 2014-2015 trucks also been logging pedal position so I can compare the two.

Yes GM.ETCTP would be the correct PID to use!

[496Stingray]

So the 84% you are seeing with this particular truck is on that PID?

[KLUG'S SS]

Yes with the ETC PID throttle drops down to even 80% at times. But after reading what GMPX stated about how these goofy torque based operating systems work I went back over several logs and carefully thoroughly studied them and it looks like whether it was 100% throttle or 80% airflow did not drop off. Checked this through several logs I have of this truck at many different rpm points so it obviously isn't having a negative affect. MAP, g/cyl and dynamic airflow all stay the same comparing when the truck is seeing 100% throttle or even 20% less.

Looks like that's just the strategy that GM chose to use here. Which hey the truck runs very strong just for that 4.3 V6 in a 4wd double cab full size truck!

[GMPX]

I was once told the strategy is to only open the throttle (assuming the pedal is fully down) to the highest position to consider the engine to be at full load if that is what the driver wants. It benefits in a few ways (from GM perspective), less intake noise and if the throttle needs to be closed (eg traction control) it is not required to move back as far to limit power. There is probably a lot of other reasons for this idea, but those two make sense to me. On the boosted engines (eg, the turbo Cruze with the E78) you don't see this effect, the throttle will go to max opening as they are trying to achieve 100+ kPa readings.

From your logs...
84% throttle at 5000-6000 RPM when my manifold is showing 94kPa indicating it has not reached its peak flow.
Again that annoying scaling of the PID, think of 84% as fully open if using the SAE PID, you are seeing 94 kPa that is because the engine is not at its peak here, it is not a throttle restriction.

Checking the logs over again my 97 kPa was around 4200 RPM.
So as an example, if the engine was able to achieve 97 kPa with 70% throttle at 4,200 RPM, that is all you will see it get opened too, no more, the ECM won't open it any more than it needs to.

[KLUG'S SS]

Thanks a bunch for the explanation and info GMPX, appreciate it sir. Now I've got one other thought though..... Obviously guys are already boosting the new trucks and the handful that I've done to this point have all been naturally aspirated so what happens with this whole throttle business with the truck operating systems once of course they start going well over 100 kpa when throwing boost at them?

[GMPX]

I don't know, I would imagine there is issues with this.
It also comes back to the Torque Model tables, but as they are just coefficients it is hard to put numbers in there with any clue as to what effect it will have. I remember putting the Torque Model tables from a 2.0L Turbo in to a 3.0L N/A V6 I had years ago and although the car drove terrible any time I went full throttle it opened the blade and kept it open all the way unlike what it would do with the N/A tables.

[KLUG'S SS]

I do know and have somewhat of an understanding of the driver demand tables and the peak torque tables and how those work. These tables can definitely be limiting factors once the horsepower and torque goes well above factory levels. But their must be care taken when and how to adjust for example the driver demand tables. This isn't a table that can just be maxed out, basically just the very last row representing 100% only needs to be changed so that their is just a slight cushion. Needs to accurately represent the power the truck is expected to make. Same goes for the peak torque table.

Like I said I haven't tuned any 2014-2015 trucks with say a Magnacharger installed but I've heard in regards to the peak torque table maxing it out can actually prevent the motor from going into power enrichment. On the other hand if the torque exceeds what is in the table then it can limit throttle.

[496Stingray]

Ok so logging the correct PID solved my issue. Mine is commanding 100% whenever I want and will hold it. The SAE PID is the one reading 84%

[GMPX]

Does it feel faster now you know it is at 100% and not 84% :rotflmao:

[496Stingray]

Not until I added the stickers!

I knew it had to be hitting max throttle was just bugging me not to be able to log it accurately. Now if I bother to work on improving peak flow at least I can see if it makes a positive effect. Removing restrictions in the intake path etc.
Stickers are still the best mod. BLAHAHAHHAHAH :-)