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

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

    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.

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    Forum tyhee Site Admin GMPX's Avatar
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    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.
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    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..

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    Forum tyhee Site Admin GMPX's Avatar
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    Yeah well mine runs in AFM all the time which helps
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    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.

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    Quote Originally Posted by GMPX View Post
    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?

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    Forum tyhee Site Admin GMPX's Avatar
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    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.
    Need official EFILive help, please go here.
    For tuning support please post your questions on this forum (or other auto forums).
    Sorry if I don't respond to your PM, don't take it personal.


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    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.

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    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!

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    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.
    Last edited by KLUG'S SS; May 30th, 2015 at 02:08 PM.

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