throttle jerking in low gears - worse with rev hang disable

Post Reply
bbrtuning
Posts: 5
Joined: Wed Feb 14, 2018 12:19 am

throttle jerking in low gears - worse with rev hang disable

Post by bbrtuning »

I've been experiencing jerking especially in lower gears at very light throttle, most noticeable in traffic, 1st gear, > 2500 RPM. It was just barely present on the stock flash, but is noticeably worse when rev-hang is disabled.

I took some datalogs and it's very clear to see the problem - between 0.1 and ~7% "TPS" (pedal position), the actual throttle angle ("TPS.CMD") doesn't change. From 0.0 to 0.1% pedal, the throttle suddenly goes from ~2% to ~8%. It doesn't seem possible to control the throttle angle between these two points. This can be felt exactly when driving the car - 1st gear, 2500-3000 RPM, it's impossible to hold a certain speed. The car is either accelerating or decelerating. Quite frustrating to drive in certain situations.

I attached a datalog showing this (EDIT: can't attach over 2mb - Google Drive link below) There are several examples in the log but a good one starts at ~9 seconds.

https://drive.google.com/file/d/1Mf4gmy ... sp=sharing

I'm sure this can be fixed with adjustments to the throttle curve tables (or maybe there's a minimum throttle % when not in decel-cut)? Is this something being worked on or something that will be available in the future? I don't have many complaints about how the car drives, but this is by far and away the most annoying quirk of the car to me.
KTuner
Site Admin
Posts: 3745
Joined: Mon Jul 22, 2013 8:13 pm

Re: throttle jerking in low gears - worse with rev hang disa

Post by KTuner »

When you are off throttle with rev hang disabled, the throttle closes. When you are on throttle at any level normal TP operation occurs, which includes the ECU opening up the throttle per command. There is a padding setting for the on off throttle transition in quick adjustments. You also have control over fuel cut delay for each gear, if you don't want fuel to kick in so quickly in lower gears.
bbrtuning
Posts: 5
Joined: Wed Feb 14, 2018 12:19 am

Re: throttle jerking in low gears - worse with rev hang disa

Post by bbrtuning »

Understood. The padding seems like a band-aid and helps very slightly but also increases rev hang a bit. Unfortunately this behaviour is felt even when fuel cut is disabled or not active. The real problem seems to be the low/bottom end of the "throttle command" table. It seems to not have a value below ~7 to 8% even at the lowest non-zero pedal position (besides absolute 0% which slams the throttle shut). Will this table be available for adjustment in the future? It would also allow manual adjustment of the throttle sensitivity. I think having this would really round out the CivicX features nicely. The rest of the currently available tables seem to cover what 98% of users will need to adjust.
KTuner
Site Admin
Posts: 3745
Joined: Mon Jul 22, 2013 8:13 pm

Re: throttle jerking in low gears - worse with rev hang disa

Post by KTuner »

It's not a band-aid, it's a setting. It does not affect rev hang because there is no rev hang with 0% throttle applied when rev hang is disabled. The throttle closes. The padding setting has no affect here.

Anything above 0% is subject to the ECUs standard control, where it will hold the throttle open for rev hang etc etc. The throttle padding setting affects the transition.

If you do not like the way no rev hang feels then I would advise you to re-enable rev hang.
bbrtuning
Posts: 5
Joined: Wed Feb 14, 2018 12:19 am

Re: throttle jerking in low gears - worse with rev hang disa

Post by bbrtuning »

Correct, the padding controls the transition between normal operation and closed throttle, which, by design, slows the throttle closing which also slightly affects the rev hang. Regardless, this isn't the main issue I'm trying to ask about so I'm not too concerned with it.

Anyway, you mentioned "subject to the ECU's standard control". When will this be available for adjustment? As I've stated twice, it appears that this is the table that's causing all the trouble. If we can have access to this table then we can fix this issue and also adjust the throttle sensitivity to suit preference. It's a pretty commonly adjusted and available table in most modern ECU reflash packages (speaking in general here, not specifically with Honda, Civic etc). Again, I'm talking about the pedal vs throttle % opening relationship, when pedal > 0%.
KTuner
Site Admin
Posts: 3745
Joined: Mon Jul 22, 2013 8:13 pm

Re: throttle jerking in low gears - worse with rev hang disa

Post by KTuner »

bbrtuning wrote:Correct, the padding controls the transition between normal operation and closed throttle, which, by design, slows the throttle closing which also slightly affects the rev hang. Regardless, this isn't the main issue I'm trying to ask about so I'm not too concerned with it.
No, it doesn't. It affects on throttle only, above 0% throttle. That affects the transition in itself because low throttle is above 0%. "Rev hang" is never affected by the padding setting, as it closes the throttle to 1-2% (rev hang removed) with 0% input at any time rev hang has been disabled and parameters are met to do so.

The logic for the throttle on this platform is more than just a "throttle table" I can give you access to in order to magically adjust this or it would already be there like other platforms we offer. We outlined early on that this setting is a pretty aggressive transition. I also noted above that you can adjust fuel cut delay to further sculpt the operation. In the end if the rev hang disable and accompanying settings aren't for you, don't use it.
amybydu
Posts: 4
Joined: Thu Apr 05, 2018 5:15 pm

Re: throttle jerking in low gears - worse with rev hang disa

Post by amybydu »

Disable rev hang , which should be selected for throttle padding to get the most comfortable driving experience ?
Post Reply

Return to “16-21 Civic 1.5T”