Some basic VVE & VT Theory Questions

[BDPhoto519]

Hey guys,

I am looking for a better understanding on some things and have a few basic VVE & VT questions I haven't seen clear answers on in my searches and past year or two learning this new Gen V stuff on here. These questions are based on my setup specifically for clarity. (2018 Camaro SS A8 w/flex and all the usual FBO goodies)

1) In the VVE section the "VE Mode" drop down has the standard 4 options (Manifold Switch Closed, Manifold Switch Closed DoD, Manifold Switch Open DoD, Manifold Switch Open). I know the standard solution is to just match the 2 non DoD tables when making changes for good housekeeping even though one is only used I believe. But which one is THE actual table that is referenced on this platform, and what platform uses the other option and how does it work?

2)In the VT section the "Table Group" drop down has the standard 8 options (Airmass, MAP, E85 Airmass, E85 MAP, + the 4 DoD versions). At what alcohol% do switch from using the regular to E85 tables? Especially considering even typical pump gas seems to be 5% to 15% range at all times around here? Also the same question applies to all the other tables that have a similar Gas/E85 versions I suppose.

3)In the VT section I don't fully understand the difference and when to use the different tables individually "not linked" (eg. Spark = -10, Spark = 0, Spark = 10, Spark = 20, Spark = 30).

I know these are pretty basic theory questions and I am starting to have a decent understanding of dialing in my own car on this new Gen V platform short of major VT changes. But these are still a few things that have been sitting in the back of my head I don't have a 100% clear answer on and I like learning the whys as well and the how's.

I appreciate anyone who has a solid understanding of these and can answer them for me!

[M3T1]

1) Not sure. I just follow the 'good housekeeping' rule haha. Make sure if you're speed density tuning via the VVE tables that you fail the MAF sensor so that your data isn't poisoned by MAF input.

2) It doesn't 'switch' between these per se. If anything, it interpolates between them automatically based on alcohol content. That said, my pump gas and E85 VT tables are identical. The power difference is so minuscule that it doesn't cause torque management to do anything weird if you copy/paste your gas Airmass VT and MAP VT tables into the corresponding E85 Airmass VT and MAP VT tables.

3) These are approximations from what I understand. Basically, you're telling the system that "if you run X degrees of timing, here's the power output you can expect at different RPM/Airmass (or MAP) values." So, for the -10 table, you're laying out the torque output that you'd expect when running -10 degrees of timing. Same for 0 degrees, 10, 20, and so on. Notice that after you change all these, you need to "extrapolate" them before "calculating" new coefficients. Basically, once you populate enough of these tables, the software can extrapolate based on what you modified, and then you can use those new vales to calculate new torque coefficients. Realize that this "virtual" tuning is just that....virtual. It calculates new torque coefficients based on a virtual model that you're setting up. Those coefficients are what the torque management ends up actually using to approximate and control output. It's also worth noting that unless the delivered output is more than a certain amount off (what that threshold is exactly, I'm not sure), it won't kick torque management in. You can actually log how much timing the torque management system is adding or pulling in VCM Scanner. In my experience, if you're within 50 lb/ft of the expected output, it won't do anything. It's just when you're way off in either direction that it begins to try and correct by messing with spark advance.

As a general rule, you shouldn't be doing anything super drastic in the VT tables if your car is basically a bolt on car. It's only when you throw a cam in there that you'll have to make some more significant changes to the VT tables. Even so, the changes aren't as crazy as you'd think. It's mostly changing stuff in the lower RPM range because you have much less output around idle with an aftermarket cam with a lot more overlap than stock. If your car is basically bolt-ons (intake, exhaust, pullies for LT4 cars, etc), you mainly should just be messing with driver demand. The whole virtual torque range should basically be good with the stock cam. If you're making more boost, you'll just progress further into Airmass/MAP. Those values are still extrapolated by the factory tune, so it should work fine. What will happen if you don't mess with driver demand up top is that you'll be commanding a certain amount (let's say around 400hp for a stock LT1 motor) in your driver demand table, but your torque management will pull timing and close throttle on you if you have a bunch of work done because your output will be way higher than the commanded output at 100% accelerator pedal. So, i'd focus more on that. Inch that up until you no longer see throttle closure or torque management advance (torque management pulling timing on you) in your logs.

It is worth noting that many of the E85 tables in the factory ECU for Camaros and Corvettes are not set up properly. So, the one change I would make for a bolt on car is I would copy/paste the Airmass and MAP VT tables into the E85 Airmass and E85 MAP VT tables. Do not assume that anything E85-related is correct, since the car didn't come with a flex fuel sensor from the factory.

Hope this helps. It took me a long time to figure out what the hell was going on in those VT tables.

[eficalibrator]

1) In the VVE section the "VE Mode" drop down has the standard 4 options (Manifold Switch Closed, Manifold Switch Closed DoD, Manifold Switch Open DoD, Manifold Switch Open). I know the standard solution is to just match the 2 non DoD tables when making changes for good housekeeping even though one is only used I believe. But which one is THE actual table that is referenced on this platform, and what platform uses the other option and how does it work?

Manifold switch open is the default. As you said, it's "good housekeeping" to just make them all alike though in your case.

2)In the VT section the "Table Group" drop down has the standard 8 options (Airmass, MAP, E85 Airmass, E85 MAP, + the 4 DoD versions). At what alcohol% do switch from using the regular to E85 tables? Especially considering even typical pump gas seems to be 5% to 15% range at all times around here? Also the same question applies to all the other tables that have a similar Gas/E85 versions I suppose.

It interpolates between gas/ethanol for these the same way it does for the spark tables. It should follow the same weighting as defined in the "Mult. vs Composition" table. (By default, this is usually bounded by zero at 10% and full at 80% ethanol.)

3)In the VT section I don't fully understand the difference and when to use the different tables individually "not linked" (eg. Spark = -10, Spark = 0, Spark = 10, Spark = 20, Spark = 30).

Properly displaying the relationship between spark retard and torque reduction has long been on my wish list for the VT model. Slicing it into tables of absolute spark value can be misleading for those who don't have years of experience with torque based control systems. There are multiple forces at work here in theory, but you are probably best off leaving them linked unless you know more about the relationship between your engine's raw spark changes and torque output than the team of engineers at the GM dyno lab who had three years to develop the model on it.

I know these are pretty basic theory questions and I am starting to have a decent understanding of dialing in my own car on this new Gen V platform short of major VT changes. But these are still a few things that have been sitting in the back of my head I don't have a 100% clear answer on and I like learning the whys as well and the how's.

I appreciate anyone who has a solid understanding of these and can answer them for me!

They're actually GOOD questions. Many "trainers" out there honestly don't know the correct answer either. If you want more, check out our streaming site for some GEN-V specific stuff that covers this and more.