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Discussion and questions related to the course Practical Reflash Tuning
Can you explain a little more what the vtec upper and lower bound tables mean? I saw in the worked example you only adjusted the upper.
Hey Christopher, of course. Basically the stock VTEC point uses a 'window' where the VTEC point is dependent on both rpm and load. What we find is that under light load/low throttle opening, there is a small advantage in the VTEC point being a little higher in the rpm range than what is optimal at WOT. Generally I'll set the Upper Boundary (confusingly the VTEC changeover rpm under light load) to be around 400 rpm higher. The upper boundary is not super critical in my opinion since we'll seldom be driving the car under that condition and instead it will more likely be accessed under transient conditions.
Would it be correct to assume that Honda set the Vtec changeover point at 5600rpm more for emissions and low down driveability rather than out right power? 4500rpm is quite a large change when you only have an aftermarket exhaust fitted. The dyno graph speaks for itself for why 4500 is optimal but just wondering what Honda had in mind when setting it from factory.