Virtual Torque relationship to idle. Truck dies just in park now.

[H3Tex]

So I have the truck running mostly good getting through MAF and VVE so I decided to mess with my VTT. The truck was running on the factory VTT for the 09 5.3 that the truck came with; though it now has a GM hotcam LS3 crate motor. I updated the VTT using the beta app as the stable one was all grayed out. IMO the truck now drives a wee bit better (smoother and more natural feeling). Not a huge difference really. But something never seen before is that it now dies when I move it from drive to park. Especially if I pull into a spot, stop, and throw it in park all quickly. Never an issue until I messed with VTT.

My question is about the relationship of VTT and idle while shifting into park. Idle in park is fine if I wait a few seconds in drive, move it to neutral for a few seconds, then put it in park. It can idle in park all day without issue.

For adjusting the VTT I went to the MAP table and found the 355 which is exactly what my 5.3 was rated at from the factory. Took that row and bumped it up by 30% to get it to 460 which should be close to what the 6.2 is putting out. With the rows linked I then interpolated that bottom row all the way up to the 0 row leaving the negative numbers where they were. Then added 30% to the final airmass table doing the same thing. Is this a decent way to rough it in? Also, why are the values in the airmass table so much larger than those in the MAP table? Its like that for all the stock tunes that I have reviewed.

Thanks

[Alvin]

VTT would be the last place i'd look for this fix.

Post your file and I'll look for the likely culprit. It's likely a fueling issue. Or timing dipping when the idle dips.

[H3Tex]

Huh? So look at the only thing that was changed on a tune, which induced the problem, last? I guess I was not clear, sorry about that.

Truck was running fine where I never had any issues at all with my idle while going from Drive to Park.
I changed my VTT and my VTT only.
Now I have issues while going from drive to park.

Thanks either way. Ill try to get a fresh log of the event with some idle specific PID's.

[ns158sl]

VTT estimates the required airflow for idle on a gen4 (and gen5 but more involved). People for 20 years have been working around it, and that worked for 20 years too. But, and a big but, absolutely need VE/MAF/Timing calibrated. Also, for garage shifts there are multiple tables to adjust for that.

As far as adjusting VTT.. there is a lot more than meets the eye. Airmass values vs MAP values vs spark sensitivity. Blanket 30% is not the way to go about it.

[Tunercharged]

Easiest way is probably return tune back to before the problem. Then with smaller increments change only the areas on the tables that you want to or need to, avoiding any big changes that would affect your idle areas.

[H3Tex]

Easiest way is probably return tune back to before the problem. Then with smaller increments change only the areas on the tables that you want to or need to, avoiding any big changes that would affect your idle areas.

Not exactly what I did but it seems I got it back going. I found a GMPP 376/480 tune in the repository and used that VTT table. Thats the crate engine that I have in the truck. The problem is gone.

[Speedboosted]

Not exactly what I did but it seems I got it back going. I found a GMPP 376/480 tune in the repository and used that VTT table. Thats the crate engine that I have in the truck. The problem is gone.

I read something posted by Greg Huggins a bit ago where he suggested using the virtual torque tables from the various crate engines (480, 525, etc) as a good starting point for modded cars, especially if you're not familiar with everything that goes into them (which many aren't, myself included). Sounds like that worked well for you!

Does it "feel" better than before? Any maf/vve tweaks needed?

[Tfoggy]

How? Where? Did you find that gmpp tune ?? I looked in the repository, but can't seem to find one. I'm sure I missed a key search input.
TIA

[H3Tex]

How? Where? Did you find that gmpp tune ?? I looked in the repository, but can't seem to find one. I'm sure I missed a key search input.
TIA

I found it by luck. None of the keywords seem to work in searching for it. Just look at all the 2008 corvette's and its in there. Also linked below.

https://www.hptuners.com/my-account/...ownload&id=922

[edcmat-l1]

As Alvin said 2 weeks ago, VTT on this platform is the last thing you should be concerned about, using, tweaking, whatever. For years we didn't even have access to the VTT in these. And it doesn't really matter what it is. The rest of the calibration needs to be tooned correctly.

[Alvin]

His response baffled me.. He changed VTT, it messed up his idle so he wants to know how to change VVT.

It doesn't need to be changed in a GEN 4.

[kertisallen1]

Alvin is this still true in situations where you might be making more power than stock? For instance, my 5.3 bored to 5.7 with raised comp, ect ,ect? I have read (ghuggins I think) that not adding to Airmass in certain situations will cause Trans holding pressure to be lower then needed and cause issues?

His response baffled me.. He changed VTT, it messed up his idle so he wants to know how to change VVT.

It doesn't need to be changed in a GEN 4.

[Alvin]

Alvin is this still true in situations where you might be making more power than stock? For instance, my 5.3 bored to 5.7 with raised comp, ect ,ect? I have read (ghuggins I think) that not adding to Airmass in certain situations will cause Trans holding pressure to be lower then needed and cause issues?

Yeah he also claimed injector scaling effects VVT. I posted back to back logs showing it doesn't.

Calculated torque is primarily driven by air used.. with multipliers for EQ ratio. If the engine is moving more air, and that air is calibrated.. things fall in line.

Seems like that is the way the GEN 5 tuners are moving to also. Came up real recently. If VVE is accurate.. torque falls in line.

[H3Tex]

As Alvin said 2 weeks ago, VTT on this platform is the last thing you should be concerned about, using, tweaking, whatever. For years we didn't even have access to the VTT in these. And it doesn't really matter what it is. The rest of the calibration needs to be tooned correctly.

VTT was the only changed made and the effect was that the truck dies going from drive to park. Then changing the VTT and the VTT only to the GMPP crate engine tune made the problem go away. Yet yall are saying it should of been the last thing to look at. Seems like troubleshooting 101 to me.

[ns158sl]

Well a log would of helped to diagnose. Would need Integral and probably SS Airflow Channels to verify the VTT helped.

[gtstorey]

VTT was the only changed made and the effect was that the truck dies going from drive to park. Then changing the VTT and the VTT only to the GMPP crate engine tune made the problem go away. Yet yall are saying it should have been the last thing to look at. Seems like troubleshooting 101 to me.

They are saying it should not have been changed to start with.

[edcmat-l1]

They are saying it should not have been changed to start with.

Exactly. "I changed XXX and now it stalls". Well, logic would say put it back to the way it was before.

Why argue with 2 guys that have tuned literally thousands of these vehicles EACH?

[H3Tex]

Exactly. "I changed XXX and now it stalls". Well, logic would say put it back to the way it was before.

Why argue with 2 guys that have tuned literally thousands of these vehicles EACH?

Why use a stock 5.3 VTT on a GMPP 6.2 crate motor when there is a GMPP 6.2 crate motor VTT available to use? Using that VTT and the truck runs absolutely great. Not going to settle for something when there is a better alternative out there. Its hard to argue with results.

@ns158sl answered my question for the most part on day 1. It was a simple question of seeking understanding where I got a simple answer rather quickly. I have since read of others changing their VTT in the idle zone to make idle performance adjustments. It seems to line up. Either way the truck is running good after using a totally different VTT than prior so Im happy.

Thanks