Is this overrun cutoff?

sinistrs2k · Post by **sinistrs2k** » Tue Apr 28, 2009 1:38 pm

Hi,

So I've got some jerkiness at low throttle deceleration. I read as much as I could find on the subject and it seems like a pretty common occurrence. I've calibrated the TPS and it seems good to me.
Datalog will show it sitting very steady at 4% while the injectors bounce on-off-on-off for as long as I hold the throttle there. Only way to stop it is to change the throttle position up or down. I tried to hold it steady for a while to really show the issue, so I got a lot of bounces in a row.
It begins around 3500 rpms, so the overun cutoff should not be happening right? Or can it hit cutoff at any RPM?

Anything else I should look at?
Thanks,

Post by **Spunkster** » Tue Apr 28, 2009 4:30 pm

Have you tried recalibrating the TPS sensor, because it seem strange you get this at 4% throttle and your TPS is adjusted to -3.9%.

sinistrs2k · Post by **sinistrs2k** » Tue Apr 28, 2009 6:34 pm

I've never physically changed the TPS sensor at all. I have done the TPS calibration under the parameters section, which is where the -3.9% came from. You may recall another post I made where the negative adjustments would gradually fade out every time I made a save to the file.

The -3.9% seemed to be the lowest value it would accept. When I perform the setting procedure, that is where it ends up. I once tried setting it to something greater, like -5% and it still came back at -3.9%. I assumed this was some sort of hard limit. But often it would gradually get phased out and end up back at zero after a few saves. I usually couldn't tell much difference in driveability regardless of which setting was active. Initially I thought the surging was due to the TPS not being calibrated properly, which led me to those settings.

I do agree that there could definitely be something related with the -3.9% and the fact that this seems to hit right at 4%.

J

Post by **Hondata** » Wed Apr 29, 2009 9:55 am

Normal throttle cut off is around 4% (it varies). Go to advanced, then overrun cutoff and change the pressure values to 15 kPa. Test again with those changes.

If you still find the same issue then I'll make the TPS cutoff value adjustable.

sinistrs2k · Post by **sinistrs2k** » Wed Apr 29, 2009 10:35 am

Cool, I'll test it on the way home today.

On the way in to work this morning I set the TPS calibration back to 0% and was going to try to datalog the issue again. It didn't bounce like it did before, instead it just jerked hard once. Wasn't able to get a good capture of it so I'll try it again as well as your recommendations.

Thanks,
J