Jumpy start, but smooth accel on SDU in VW T2

[Kitlacey]

Hi all,

We have an SDU in a VW T2. We've used several of these with success using Zero EV's inverter settings. We're now using an Open inverter board so I'm copying a lot of settings from my previous Zero EV boards to this one. Everything is working great except setting off from 0RPM. At present, I slowly press the throttle until it reaches 30% travel (my regen limit) and then the SDU jumps us forwards into motion. Once it's moving, it drives great, but setting off is scary and a little uncomfortable. The inverter temp doesn't love me for it, and slow manoeuvers in reverse are nearly impossible.

Any suggestion what figures to adjust? I can supply full parameters if necessary, I just wondered if someone knows the magic bullet!

Kit

[johu]

AAP - Always attach parameters

Sounds like ampmin too high

[catphish]

Almost definitely ampmin or boost are too high. Post parameters and we can comment more accurately.

[Kitlacey]

here you go!

AAP - Always attach parameters

Sounds like ampmin too high

[Kitlacey]

AMPMIN was 5 so I lowered it to 4
BOOST was 2900 so I oput that back to the 2200 default.

The Jump is a little better after that, but the acceleration now feels very sluggish

[johu]

At least for me the parameters don't look suspicious. Anyone?
Is your throttle signal all nice and linear?

[Kitlacey]

Yes, it's a new 0-5v variable pedal so it's all very smooth

At least for me the parameters don't look suspicious. Anyone?
Is your throttle signal all nice and linear?

[catphish]

For what it's worth, I believe everyone suffers with "jumpy" start on the SDU. It's one of the primary reasons I created my fork, and I believe a major reason why ZeroEV stopped using this drive unit. I spend weeks tuning the SDU so you might want to try these parameters to see how it compares:

boost: 3200
fweak: 230
ampmin: 0
fslipmin: 1.50

It's also worth noting that the throttle dead zone makes this "feel" worse, because your foot isn't used to finding the zero point. I don't use regen so my throttle doesn't have the 30% deadzone, and I found that made the experience quite a bit better.

[uhi22]

Is it possible to create a plot which shows the throttle and the torque for some seconds while the "jumpy start"?

[muehlpower]

It's also worth noting that the throttle dead zone makes this "feel" worse, because your foot isn't used to finding the zero point. I don't use regen so my throttle doesn't have the 30% deadzone, and I found that made the experience quite a bit better.

uhi22, tom91, I and others have discussed the "dead zone" problem here.

viewtopic.php?p=60101#p60101

Maybe it's time to implement something like this in the firmware.