I thought I would share some things I have learned when it comes to understanding how to manipulate the VVE table more successfully.
First:
I have found the secret starts with understanding that within each zone, the X-axis values can have a convex, concave, or flat shape. And the same thing for the Y-axis. In other words, no S shapes are allowed.
The key take away:
The important thing then to understand is that you need to break up your zones to dance around these shapes, creating zones to prevent S shapes from forming in a single zone.
Bad: S-curves are never acceptable (and will get lost if you click the Calculate Coefficients button) S curves.jpg
Second:
The ECM does NOT interpolate the cells in the VVE table like any other table you are used to. Instead, it plugs the RPM and MAP values into an equation (along with the coefficients) to generate the value. Here is the equation in all it's glory:
Constant Coeff = defined in table [ECM] 13400
MAP Coeff = [ECM] 13407
RPM Coeff =[ECM] 13412
MAP2 Coeff = [ECM] 13410
RPM2 Coeff = [ECM] 13414
MAPRPM Coeff = [ECM] 13409
MAP = the current manifold pressure as reported by the MAP sensor
RPM = the current engine RPM
The key take away:
Having large gaps in the RPM values (in the VVE column editor) can create terrible intersections where zones meet up, but you WILL NOT see those. So you need to be tactical in how you setup the RPM column breakpoint labels. You can test the intersection smoothness by subtracting 1 RPM from each zone.
Here is a large gap in RPM's (2600 - 3000) and that flat spot looks like a decent transition. Not perfect, but nothing to throw any red flags. zone intersection 1.jpg
However, here is how the ECM will calculate the transition. You can see the zone starts at 2800 RPM, so I added a new row for the value for 2799 RPM which reveals quite a harsh transition. The image I generated here for a quick example, and is just a 2D shape, but when you get into a real VVE table with 3D concave and convex shapes intersecting, you will see lots of crazy valleys, mountains, and spikes.
Not sure I would suggest creating a new RPM column with -1 RPM for each zone permanently, it is worth testing out when you are setting this up, especially as you are re-zoning everything. From my experience, having to do this with the MAP row labels is not needed (YMMV). zone intersection 4.jpg
Third:
The VCM editor does NOT preserve your custom RPM/MAP breakpoint labels. This is fine if you are tuning one car and only dealing with one tune file. But as you start emailing tune files to different people, they are seeing their RPM/MAP breakpoints and not yours. This is why when you look at someone else's tune file and look at their VVE, you can see some terrible transitions (this is going back to my second point). I logged a ticket to HPT support and they did not seem interested in the enhancement I asked for to include these breakpoints in the .HPT file so we are all dealing apples to apples across the board when looking at the tune.
Last edited by Cringer; 10-13-2023 at 10:29 PM.
A standard approach will give you standard results.
Thanks Cringer. Along the topic of this post, I would like to add something that I had issues with in my first Gen4 VVE experience. As I tweaked my vve, it would end up making it harder to start at times. I had not even changed any components of the long block from stock. It wasn’t until I expanded the visible RPM columns down to 100 rpm, instead of the default 400 rpm, that I saw the coefficient calculator was skewing the numbers at 100 rpm, even when the visible 400 rpm column was not changed much at all. After that, I would monitor the 100+ rpm columns, from 100kpa down, to ensure they were not being skewed during coefficient calcs.
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