Issues with Throttle Boost, 2014 Sierra

[ziknazoo]

I'm having an issue with the use of throttle boost on my 2014 5.3L Sierra. If throttle boost is used, the transmission shift points get screwed up. What I mean by that is the transmission shifts earlier than it should at part throttle. The best way I can explain this is that the more throttle boost I dial in, the lower the shift points become for a given amount of real throttle opening.

It's like the TCM doesn't know the throttle has been boosted and is still shifting at the un-boosted levels.

This causes less than smooth shifting, and bogging as the TCM is making shifts happen at a little over 2000 RPM under sprightly acceleration. As soon as the RPMs get over 2000 RPM the truck takes off - at least until it shifts again. This is really a problem in first gear. The truck takes off, then at 2000 RPM it kicks in and takes off - usually in a turn! This makes it more difficult to drive. Without throttle boost, this doesn't happen.

I'm guessing the TCM is trying to shift using pressures in line with the throttle opening it thinks I have, not knowing it's been boosted. This really sucks because the big selling point for the Diablo is the throttle boost function being able to fix the poor throttle GM stuck me with.

Is there a fix for this?

Thanks!
John

[mikel]

if you max out the throttle boost, the truck may shift sooner in relation to pedal input ad the throttle is opening more in relation to the pedal, try backing it down a little bit.

[ziknazoo]

That's exact what I see. Right now I'm at 10% (down from 15%). I really like 15% though... The throttle boost function is the single biggest important thing to me since what GM programmed as stock is simply a disgrace.

Why does this happen? Is there a fix forthcoming?

Thanks!
John

[John_chadra1]

Mikel or Vas... do you think the throttle boost could be some of my issue? I am going to try it and let you know.

https://www.diablosport.com/forum/viewt ... 2&start=15

[typhoon186]

can someone explain throttle boost a little more. How is 10% throttle boost different than pressing the gas pedal 10% more?

[mikel]

it increases the rate the throttle opens in relation to the pedal input

[typhoon186]

so not really a performance improvement, just less pedal movement for the same results?

[dmartell24]

I just posted about this EXACT SAME ISSUE!!
What is the latest on this? I noticed the last post wes several days ago?? I am dying to get this resolved. Hopefully someone will give the clear answer on how to fix this.

Is the custom tune simply the best way to go??

[ziknazoo]

Well here's what I found... The only sure cure for this is to turn throttle boost off. The good news is the throttle response with it off, is still MUCH better than GM stock.

I returned my 2014 Sierra to stock this morning having given up with the Diablo InTune. I drove it to the local home center and found within like 1/4 mile that I hated the truck as stock!!!

So, in the parking lot of the home center, I reprogrammed it: 87 Octane Tune, Speed Limiter Off, Stock TCM tune. And... throttle boost at 0%. That's it nothing fancy...

The truck still has noticeably better response than stock. But, without the clunky shifts of the firm tune and without the short shifting/bogging out I get with throttle boost.

So, all in all, the 87 octane tune is worth it, but as far as I'm concerned throttle boost is a broken feature - at least on these new 2014's.

Maybe Diablo Lew has some magic he can do to give us the best of both worlds, but I haven't found the time to shoot him an email to ask.

John

[mikel]

Well here's what I found... The only sure cure for this is to turn throttle boost off. The good news is the throttle response with it off, is still MUCH better than GM stock.

I returned my 2014 Sierra to stock this morning having given up with the Diablo InTune. I drove it to the local home center and found within like 1/4 mile that I hated the truck as stock!!!

So, in the parking lot of the home center, I reprogrammed it: 87 Octane Tune, Speed Limiter Off, Stock TCM tune. And... throttle boost at 0%. That's it nothing fancy...

The truck still has noticeably better response than stock. But, without the clunky shifts of the firm tune and without the short shifting/bogging out I get with throttle boost.

So, all in all, the 87 octane tune is worth it, but as far as I'm concerned throttle boost is a broken feature - at least on these new 2014's.

Maybe Diablo Lew has some magic he can do to give us the best of both worlds, but I haven't found the time to shoot him an email to ask.

John

good to hear.

fwiw, we add 15% throttle boost in the canned tune, so its just the extra you add on top that seems to be the issue

[ziknazoo]

I'm not sure. It seems any throttle boost (I tried 4% to 15%) makes the low shift points noticeable, although less so with reduces in throttle boost. It is not altogether absent when throttle boost is disabled though - just to the point where I consider it just acceptable with throttle boost set at zero. What is definitely unacceptable is the throttle response when stock.

I set it back to stock tonight and ran it around to see what the shift points for a given level of acceleration were before and after the 87 Tune and they were still reduced somewhat with the 87 octane tune. This bothers me a little but I have to accept it given the alternative - stock. Yech! It bothers me more and more as more boost is dialed in. Others may be more sensitive to this than I am and make them nuts even at 0% TB.

Nonetheless, IMHO the ultimate solution would be to bump up part throttle shift points as more and more throttle boost is dialed in to compensate. This would make this perfect I think.

With the throttle boost set at 15%, the truck's throttle feels like it should to me, but the shift points are noticeably very low. 2-3 is the worst because it seems those gears have the biggest gap. A 2000 RPM shift from 2-3 under light throttle and the truck bogs out after the shift (tach is something like 1200 RPM after the shift) and torque slowly builds back up again until you hit about 2000 RPM and the truck takes off again.

[selmahotrod]

This is the exact same problem I am having with my 2014 Silv., I hope an update will fix this throttle boost problem!

[Maverick1]

This is the exact same problem I am having with my 2014 Silv., I hope an update will fix this throttle boost problem!

Ditto!

[ziknazoo]

Bump...

Any word on a fix or a workaround (maybe adding a Lew tune) that will fix this? The more I play around with the Intune the more I find that throttle boost - even the built in throttle boost you get with the throttle boost set to 0% - lowers the shift points. This makes the truck bog on the 2-3 shift at light throttle. I got used to it when the weather was colder, but now with the A/C on it's rather annoying.

Like I postulated earlier, it's like the TCM doesn't know the throttle has been boosted...

John

[mikel]

Yes...we have been spending more time with our 14 sierra and have gotten things ironed out a bit when using the throttle boost.

New updates should be ready in the next week or two