Let's discuss VE Tables.
#41
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So, adding resolution to the bottom end of the VE table is only useful for auto-tuning?
In my car I only get below 20kPa during decel/overrun, and sometimes it will even come off of overrun fuel cutoff on it's own (I have it set at 20kPa threshold) before the RPM setpoint. I have noticed that both VEA and VEAL have a hard time tuning the lower end of the table (back when decel cutoff was disabled).
But I never saw any advantage to having it tuned with greater resolution as long as the car overruns smoothly and idles well? Why do it?
In my car I only get below 20kPa during decel/overrun, and sometimes it will even come off of overrun fuel cutoff on it's own (I have it set at 20kPa threshold) before the RPM setpoint. I have noticed that both VEA and VEAL have a hard time tuning the lower end of the table (back when decel cutoff was disabled).
But I never saw any advantage to having it tuned with greater resolution as long as the car overruns smoothly and idles well? Why do it?
#42
Boost Czar
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I dont let my ECU autotune that low, otherwise, no matter what I do it tries to pull too much fuel from that row and then it will run shitty on throttle off to throttle on transitions and be too lean. I just manually adjust them to be similar to the rows above albiet a little less fuel considering the load and deal with a slightly rich condition when I lift for a split second.
#43
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The drop in "VE" with MAP, that is consistent across RPMs, looks like an error in injector dead-time. Dead-time too small.
Also note that injector flow rates go nonlinear at very short injection pulse widths. The injector curve can be described by 2 numbers, at a given system voltage. So full characterization can be done with 2 sets of numbers at different voltages. The OEs go through a lot of trouble characterizing injector flow curves and coding for them, in order to get excellent light-load drivability.
The above correction can be "baked in" with a 3D VE table as Joe has done, resulting in funky VE tables at very low MAP, but this will only be truly accurate at a single system voltage.
Also note that injector flow rates go nonlinear at very short injection pulse widths. The injector curve can be described by 2 numbers, at a given system voltage. So full characterization can be done with 2 sets of numbers at different voltages. The OEs go through a lot of trouble characterizing injector flow curves and coding for them, in order to get excellent light-load drivability.
The above correction can be "baked in" with a 3D VE table as Joe has done, resulting in funky VE tables at very low MAP, but this will only be truly accurate at a single system voltage.
#45
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I dont let my ECU autotune that low, otherwise, no matter what I do it tries to pull too much fuel from that row and then it will run shitty on throttle off to throttle on transitions and be too lean. I just manually adjust them to be similar to the rows above albiet a little less fuel considering the load and deal with a slightly rich condition when I lift for a split second.
Joe, what are you using for injectors? Despite having the (now dinosaur) MSPNP gen1, I find that the speed and accuracy of the EV14 injectors compensate for the lack of resolution in the controller.
#47
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My TPS arrived today, I have been running mapDOT since forever and I'm pretty happy with the results (after massive headaches tuning the accel enrichment).
Not even sure it's worth the headache now![big grin](https://www.miataturbo.net/images/smilies/biggrin.gif)
Anyway, the last row on my map, I also tuned it to replicate the one above (if I remember correctly it's set at 28kPa) and made it just a bit leaner. Works great for me!
Not even sure it's worth the headache now
![big grin](https://www.miataturbo.net/images/smilies/biggrin.gif)
Anyway, the last row on my map, I also tuned it to replicate the one above (if I remember correctly it's set at 28kPa) and made it just a bit leaner. Works great for me!
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