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Discussion and questions related to the course Road Tuning
When reviewing a data log after some WOT runs I’ll look for centered cells on the fuel table and adjust accordingly vs lambda/target delta. This works very well! I am curious what strategies you guys might use when you see fat or lean spots on your ramp run that isn’t centered on a cell but is landing between cells.
Bonus question. When tuning for transient tps fueling, is it a goal to see the lambda always staying on target even when you’re hitting accel enrichment or overrun? Cause my car drives very smoothly but during transient states it’s going lean and rich all the time on the log.
2nd bonus question. Anyone have much experience with the wall wetting % setting in link g4+ vs using accel enrichment? The help file is quite vague for the wall wetting parameter.
thanks as always! Y’all rock
It depends on the spacing between the columns/rows in the map, as well as the trend being shown. If it looks like there is a trend that there is a correction needed and the cell spacing is 1000rpm for example, then I will put another column in between. It may be that at that load point there is a resonance in the engine that is increasing (or decreasing) mass flow through the engine that needs to be compensated for.
The ideal conditions for transient behavior is for the lambda to follow the lambda aim without rich or lean shifts, this is not always the best for driveability and response of the engine, so sometimes you will have the lambda trace going lean or rich. I always tune the transient to give the engine what it wants to provide a smooth transient response, if this means that the trace isn't following aim, so be it.
1) It depends on the number of samples, whether it was a transient, how far off cell center it is. Based on those factors, the closer to trustworthy data it is, the more I'm inclined to apply changes to correct the logged AFR error.
2) Steady state first, then transients later. This is extremely critical, otherwise you'll end up trying to cover up VE table error with transient fuel. Then adjust transient fuel to keep it relatively on target. Depending on the system you ma or may not have independent control of tps, MAP and wall wetting based transients, so keep in mind you may not be able to account for all factors at play.
3) I disable decel fuel cut so the walls remain wet, tune transients, then enable decel cut and tune wall wetting.