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Old 06-09-2013, 08:53 PM   #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?
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Old 06-10-2013, 08:12 AM   #42
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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.
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Old 06-10-2013, 11:36 AM   #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.
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Old 06-10-2013, 07:55 PM   #44
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Ive locked my 20kpa row. Like brain I manually adjusted it to be similar to rows above. Autotune liked to remove copious amounts of fuel that affected drivability.

Last edited by miatauser884; 06-11-2013 at 03:09 PM.
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Old 06-11-2013, 11:48 AM   #45
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Quote:
Originally Posted by Braineack View Post
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.
This is why I was so baffled with the issues I was just having. I used the advice of matching the bottom row to the one just above it, and it has always run well. I also use 95-97% decel enrichment for the stop and go in the lower gears to prevent large rich/lean swings on and off throttle. It worked great until the TPS failed. Until I get a new TPS, I putz around town with accel enrichments off.

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.
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Old 06-11-2013, 11:52 AM   #46
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use mapDOT while you wait for a new tps.
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Old 06-11-2013, 11:54 AM   #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

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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Old 06-11-2013, 12:49 PM   #48
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Quote:
Originally Posted by Braineack View Post
use mapDOT while you wait for a new tps.
One of those,"Why didn't I think of that?" moments. Great advice and good time to learn a new tool.
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