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RB26 with HKS Vcam VVT.
currently set up as TP vs RPM for the VVT table. VE table is TP/RPM.
I think the proper way to set up the VVT table is have it based on MAP vs RPM?
for instance, if i'm cruising at low RPM where there's no boost and I suddenly go higher up on throttle.
the intake cam advance more than it's needed at certain RPM.
which method is the best practice?
Why the intake cam would advance more than required if it is calibrated properly in the tune file?
Probably because the engine RB26 with the ITB, and on small loads it has certain problems with MAP
While typically the VVT load axis would be MAP< in your case with the RB26 and ITB you will need to match the load axis of the main fuel/VE table and use TPS. If you use TPS for the fuel table and MAP for the VVT table you can get some weird conditions where the VVT position is inconsistent for a given TPS and hence the VE table won't be correct.
I now always use TP/RPM for VVT and find it gives better control on every engine I have tried. I used to mostly use MAP, thinking with similar logic to what Andre mentions - that it would be best to reference the same load axis as the fuel table so any change in VE from the cam moving was easier to compensate.
But I have since noticed if you use MAP to control VVT what can happen at cruise where you have a relatively good vacuum, any movement in cam position causes a large change in MAP - and since you also have MAP controlling the cam position you end up with a self-perpetuating cam and MAP oscillation. You feel the car surging since VE, ign timing and cam position (therefore torque) are all oscillating due to the MAP. To get around that if you want to use MAP as one of the lookups you need to make the VVT table much flatter than ideal, especially at low/medium loads. OEM's generally use some other derived load type parameter for the VVT lookup to prevent this. But for me TP seems to work very well and I haven't yet had any issues with keeping the VE/fuel under control.
I was going to post similar last night but help off for someone with more experience. It's a feedback loop, with a more complex system it should probably be driven by a torque demand parameter, that way druve by wire throttle, cam & target AFR are working in unison for either fuel or air efficiency.
Thanks Andre and Adam
I'll keep the VVT load axis on TPS