Odd pedal behavior in boost - VMP Gen 3R

[YukonRally]

I have a 17 GT with 15k miles, and about a month ago I installed the VMP Gen 3R kit and did OPG/TG at the same time. The initial tune was a little jerky, and have been datalogging with VMP on getting it smoothed out. That has for the most part been resolved after 4 new tunes, but there is one thing that has been consistent that they so far have come up with no resolution for:

If I get into boost, at all, even for a split second, the gas pedal goes sort of "dead" for the first 1/4 of its travel. I can press the gas down, and the car decelerates like the throttle body is completely closed. If I press more than that, it will accelerate still, but the throttle becomes very on/off and difficult to modulate. Shifting in boost is very jerky.

Doing some experimenting, the gas pedal returns to normal function as soon as I dip below 2250 RPMs. It is very consistent, regardless of gear.

If I don't get into boost, the car behaves like normal regardless of the RPM range. Has anyone experienced anything like this before or have any ideas what might cause this? Thanks.

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[Burkey]

What do the logs show?

 

[Kahboom]

What throttle body are you using?

 

[YukonRally]

To be honest, I'm not great at interpreting the logs. I've asked VMP in our correspondence about possible other ideas, and they ignore my questions and just send another tune to try.

I'm using the VMP dual 69mm throttle body.

 

[Avispa]

Interesting. I'm having a few pedal/throttle glitches with my VMP gen 2 and their tune being the cause. They haven't been very helpful getting the issue resolved, but there's no doubt the problem is in the tune. So is yours, although you might have a bad pedal position sensor or throttle position sensor, but that's unlikely given it seems to work OK when not in boost.

I ordered a tune from JDM Engineering. I'll follow up once its loaded and road tested, but I'm expecting all the gremlins to get booted.

Dammit we didn't have these problems when the throttle was connected to the pedal by a cable!

 

[YukonRally]

I've been trying really hard to not blame the tune anymore, thinking I messed something up in the install, but haven't been able to find a single reason. Plus the oddly specific 2250 change over in pedal behavior screams software issue to me. I've been mulling over getting a Lund tune to see if that resolves things. Let me know if yours starts working better with the JDM tune.

 

[Avispa]

Copy that!

 

[Avispa]

Just got the JDM tune today It was quite a wait. Test drive - throttle glitches are GONE! No more "hunting" in 6th gear at 1500 or so light part throttle. Revised shift points are awesome and the neck snapper 1-2 shift is much smoother. Check your tune.

 

[YukonRally]

Man your timing is uncanny. I'm downloading my first Lund tune as you posted that. I gave up on VMP, had a really bad experience with them overall. Started talking with Lund and those guys have been very helpful.

 

[Avispa]

Great! Post how the Lund tune does. It's hard to understand VMP. I was ready to drive over there to have the car retuned at their shop, and even offered to pay for it, but they just went radio silent on me. No biggie, been buying stuff from JDM for over 10 years and have been happy with their stuff.

That and too many tuners focus on HP and forget these cars get driven on the street. It's well worth giving up 20 or 30 HP to keep stock driveability.

 

[YukonRally]

Pretty much finished with tweaking the Lund tune, and it's fantastic. No throttle issues, better drivability, easy idling. This is how it is supposed to feel. Still hauls when I get on it, but the power comes on better and smoother, easier to control. The throttle acts as it should, no odd spots or gaps in control. Very, very happy with this. The Lund guys have been great to work with too, can't sing their praises high enough.

 

[Avispa]

That's what I like to hear!

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