Overrun cutoff Issues

[KSeries4Life]

KManager 4.3.5.0
KPro4 PRB ECU
K24/K20 swapped 2004 S2000
Magnus Sheet Metal K-Series Intake Manifold
90mm KTuned TB
Injector Dynamics 725
Overrun cutoff manifold pressure set to 12 KPa on low/high cam

My first issue is that "Disable fuel over-run cutoff delay" doesn't seem to work. I've got the box checked, and the ECU has been flashed several times with it checked before these logs were taken. This can be seen in "2018-06-18_4(Overrun Cutoff Issue).kdl"

Second issue I'm having is that it takes almost 1.5 seconds (starting from when I press on the gas pedal) for the injectors to turn back on after an overrun. I'm not seeing anything popping out at me in KManager that would allow me to tweak the conditions to restart the injectors. Can be seen in both logs I attached.

[Spunkster]

1) it is not reaching 12 kpa to shut them off.

2) This is probably because it is decelerating and not with the larger throttle body there is not much of a change in vacuum when this is occurring. That would be my best guess.

[KSeries4Life]

Hello, Thanks for the response.

1) I reflashed my ECU yesterday with an Overrun Cutoff of 18 kpa. There still looks to be an exact time of .5 seconds delay before it goes into overrun, even when going below 18 kpa. This can be seen in the log I attached.

2) Is there anyway you could let me know the exact conditions required to come out of overrun on kpro? I'm trying to smooth out the huge jerk in power I get after getting back on the accelerator after overrun. Is this based on the TPS or MAP sensors? In my logs, I tried several different ways of getting back on the accelerator to see if I can isolate the conditions. For sure, I have ruled out there being any kind of delay like there is when going into overrun (this is regarding the 1.5 seconds in my initial post). I did this by slamming on the accelerator and it basically instantly came out of overrun (seen @ 1:06). The times where I slowly got back on it, I can't definitively say if it was going past a set MAP/TPS value or if it had to do with the rate of change. But, if I were to take a guess, it almost looks like there is a hard coded value of 25 kpa where it comes out of overrun. This can be seen @ 0:49, 1:12, 1:17 and 1:23. Any way to tweak this value if that's the case?

[Spunkster]

There is no access to these values in the software and I cannot see what these values are.

[KSeries4Life]

What about my overrun cutoff delay issue?

Is your response confirming that it is the MAP value that brings it out of overrun?

Do you know if the IACV lets air in during overrun? If so, this might explain some of my issues. I tried using one with the KTuned 80mm setup w/IACV, but it let way too much air in to idle properly.

[KSeries4Life]

So last night I decided to make some tweeks to my knock sensitivity (I've got some loud cams) and while I was in there, I figured I would uncheck "Disable fuel over-run cutoff delay" since it didn't seem to be working any way. Looking at the logs I took this morning, I noticed there is no longer a .5 second delay before entering the overrun conditions I have set...

I'm happy I can now toggle this setting, but is this the way this check box is supposed to work? The way it's worded, I'm getting the opposite effect.

[Grise]

That's very peculiar, KSeries4Life. But if it's working, that's awesome. It was a stroke of genius to uncheck that box and see what happens. haha

[futureal33]

So last night I decided to make some tweeks to my knock sensitivity (I've got some loud cams) and while I was in there, I figured I would uncheck "Disable fuel over-run cutoff delay" since it didn't seem to be working any way. Looking at the logs I took this morning, I noticed there is no longer a .5 second delay before entering the overrun conditions I have set...

I'm happy I can now toggle this setting, but is this the way this check box is supposed to work? The way it's worded, I'm getting the opposite effect.

This is really interesting, I wonder if Hondata fixed / changed the way the software works since this post was made?

On mine, I have thix box checked (disable over run fuel cut) - so I beleive that means the fuel cut delay is DISABLED (therefore, no delay)
However, on my logs, I am getting a huge rich dip when lifting off, and my SFTF goes to -27% (the maximum allowable STFT) every gear shift. I am considering un-checking this box to see if this will change this?

[Tehdango]

That is uncanny. I was just about to post a log and kal because I am having this exact issue. At first I was thinking "wow this is an old thread why reply" lol. I put a check in that box yesterday and thats when this issue started. It was unchecked before and I was noticing a bit of roughness between shifts that I thought it would clear up since thats what the help file says it does with large injectors. I am going to remove this check mark and reply back later tonight.

[Tehdango]

So i can confirm that enabling the Disable Fuel Overrun Cutoff checkbox caused my STFT to hit -20% plus and run extremely rich, like 10:1 after every pull. It would clear up after about 5-10 seconds and AF would stabilize. When I unchecked the box the issue stopped happening and runs as expected after consecutive pulls.

I am in no way qualified to say what is happening here but it almost seems like its causing the injectors to stay open and flood the engine for some reason. I can upload a log of it happening if it helps anyone.

[futureal33]

So i can confirm that enabling the Disable Fuel Overrun Cutoff checkbox caused my STFT to hit -20% plus and run extremely rich, like 10:1 after every pull. It would clear up after about 5-10 seconds and AF would stabilize. When I unchecked the box the issue stopped happening and runs as expected after consecutive pulls.

I am in no way qualified to say what is happening here but it almost seems like its causing the injectors to stay open and flood the engine for some reason. I can upload a log of it happening if it helps anyone.

Brilliant timing and I'm glad someone else is experiencing the same thing! What car are you on?

I also tried unchecking the box last night and can confirm that my results were exactly the same as yours....

With it UNchecked, when changing gear my AFR did not drop into the 10/11s and my STFT stayed at 0%.

With it checked, when changing gear my AFR is dropping to like 10/11 and STFT goes very negative to try and correct it. This causes some turbulence on the AFR for around 1-2 seconds when going into the next gear and reapplying throttle.

I too believe this box seems to be acting the wrong way round?

[Tehdango]

Yeah it seems this feature isnt working as intended, or described at the least. I wonder if Hondata can chime in and tell us if maybe we are understanding what it does incorrectly.

[Arno]

The wording is quite ambiguous on the option...

The docs here: https://hondata.com/help/kmanager/index ... meters.htm

Tell us that:

Disable fuel over-run cutoff delay - this disables the 0.5 second delay between closing the throttle and the fuel injectors being shut down under over-run conditions. Disable this if you experience a hesitating while shifting with large injectors or see the short term fuel trim go sharply negative while shifting.

The latter (explanation) part seems to imply that if the checkmark at this option is SET the (factory) 0.5 second delay is actually ENABLED and CLEARING the checkmark turns OFF the delay.

Which does seem to correspond to what people see when using this.

Seems like the actual option text is worded in a misleading way. Perhaps hondata can change the 'Disable fuel over-run cutoff delay' to something like 'Fuel over-run cutoff delay enabled', which would be clearer for this option.

Bye, Arno.

[futureal33]

The wording is quite ambiguous on the option...

The docs here: https://hondata.com/help/kmanager/index ... meters.htm

Tell us that:

Disable fuel over-run cutoff delay - this disables the 0.5 second delay between closing the throttle and the fuel injectors being shut down under over-run conditions. Disable this if you experience a hesitating while shifting with large injectors or see the short term fuel trim go sharply negative while shifting.

The latter (explanation) part seems to imply that if the checkmark at this option is SET the (factory) 0.5 second delay is actually ENABLED and CLEARING the checkmark turns OFF the delay.

Which does seem to correspond to what people see when using this.

Seems like the actual option text is worded in a misleading way. Perhaps hondata can change the 'Disable fuel over-run cutoff delay' to something like 'Fuel over-run cutoff delay enabled', which would be clearer for this option.

Bye, Arno.

Completely agree - the wording is a little complicated... I am not used to ticking a box to disable something, it would make more sense to have it the other way round...

Checked = enabled (fuel cut delay of 0.5s)
UnChecked = disabled (instant fuel cut)

In my head that makes more sense.... but I think it currently works the opposite way round (by having it checked the fuel cut is supposed to be disabled...however in my testing that isnt the case)

Would like a bit more clarity on this from Hondata

I've attached a screenshot from a recent log showing what I am experiencing when lifting off...
On the top row, the dark blue line is TPS and you can see when this drops to 0% the AFR instantly goes very rich (11.94 here) and the STFT goes to -8 to try and correct this (I've set my max STFT +/- 8% in Closed Loop, otherwise this would go to -27% max limit)

Unfortunately in my testing, having the fuel cut delay box checked OR unchecked isn't making much difference