Now that the engine is cranking, catching and idling using Alpha N tuning, it’s now time to build a VE table from scratch.
What is Alpha N tuning?
The first concept to know is Alpha N tuning relies solely on TPS to determine engine fuelilng. Alpha N does not measure air volume or flow consumed by the engine. This means that Alpha N tunes are normally specific to an individual engines characteristics and require some calibration.
My individual throttle body build is unique. My Whitleytune manifold for the Datsun/Nissan L6 is the first of its kind but I do not think it will be the last. While the manifold has been specifically designed, there is no real world information for the manifold on my motor. The volumetric efficiency (VE table) has to be determined.
Building the VE table from scratch
Without a base VE table to modify where do you start? First thing is the bins for TPS (MS1 is in ADC not %) and RPM. For RPM be sure to select hard columns that align with target areas for your motor. I used the following:
- idle RPM (900rpm)
- one below RPM (500rpm)
- one at expected peak torque (I have two 4800rpm determined from previous dyno data and 5500rpm for manifold design for the third harmonic)
- Cells above peak torque to rev limited
Respace the remaining columns around those aiming for as much resolution between idle and peak torque. I am using a MS1 with MSExtra code which allows for 12×12 tables.
From there I started by filling all cells with a blanket 50%. After my engine caught after cranking I hand modified the idle cells. Once the idle was established to promote maximum vacuum (60kPa for this ITB manifold) and an AFR around 13.5:1. I then moved onto free revving the engine and populated the cells. The engine needs to be to operating temperature and all enrichments and corrections disabled.
You need a wideband O2 to tune. I had my Innovate LM2 (highly recommended unit) running next to me which I simply read the screen while I was building the table. From here a bit of trail and error as well as intuition is required. Do not rely on Autotune software at this stage. I could quickly tell if my engine was running out of fuel even without the WBO2 knowing that my idle fuelling was around 41% and my table was flat 50%.
After an hour or two of work (and annoying the neighbours) I had a VE table that the engine would rev freely throughout. It is not possible to hit every cell free revving, some engine resistance is required, so I projected the known cells and added a bit of fat because It is better to be rich than lean. The result looked like this. You can see the VE tends past 100 toward the very top left. This is an estimation and it is likely these cells will never actually be touched.
The next step is for some road tuning! Stay tuned! (pun intended…)
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