I would like to keep the fuel injectors on all the time by adjusting the available tables. There is already a way to do this.
In addition I would like to retard the timing during overrun to generate a decel burble that results due to some of the combustion taking place on a slightly open exhaust valve.
Can Hondata please add ignition timing tables that are used in overrun mode?
Thanks...
Overrun - Ignition
Re: Overrun - Ignition
Why? This will wash the oil from the cylinder bores and wear out the rings very quickly.
Hondata
Re: Overrun - Ignition
No, it won't. Running overly rich does that. This would be the same as driving at low load with ignition retard since it will still be targeting a normal AFR.
Anyway, allowing the ability to tune the ignition timing at throttle lift will let me increase the delay before fuel cut and retard timing so as to not get rev hang. This makes the car more fun to drive. Right now, you have to shut the fuel off very quickly after lifting to prevent rev hang. Keeping the fuel on for longer lets you shift without having the AFR go lean during shifts. It also helps response in situations where you are oversteering and have to lift throttle quickly and then need to get back on it again.
This would be a great help for a track tune.
Ultimately, it is my car and I bought Hondata so I could tune it the way I want. Will you please allow me to tune this?
Anyway, allowing the ability to tune the ignition timing at throttle lift will let me increase the delay before fuel cut and retard timing so as to not get rev hang. This makes the car more fun to drive. Right now, you have to shut the fuel off very quickly after lifting to prevent rev hang. Keeping the fuel on for longer lets you shift without having the AFR go lean during shifts. It also helps response in situations where you are oversteering and have to lift throttle quickly and then need to get back on it again.
This would be a great help for a track tune.
Ultimately, it is my car and I bought Hondata so I could tune it the way I want. Will you please allow me to tune this?
Re: Overrun - Ignition
The fuel cut/resume event occurs between ignition cycles - there is not really a delay.
At some point the cylinder filling becomes low enough that the minimum fuel delivery will result in a mixture so rich that combustion does not occur. This is why the injectors are cut off. Otherwise the unburnt fuel will wash does the bores.
The AFR goes lean during shifts because the injectors are cut off. This is normal - the AFR is meaningless when combustion does not occur.
Added fuel and allowing combustion, even with ignition retard, will result in a higher MBEP, and the rev hang will be worse.
So the short answer is that it does not make sense to keep the injectors open upon overrun, for the reasons outlined above.
At some point the cylinder filling becomes low enough that the minimum fuel delivery will result in a mixture so rich that combustion does not occur. This is why the injectors are cut off. Otherwise the unburnt fuel will wash does the bores.
The AFR goes lean during shifts because the injectors are cut off. This is normal - the AFR is meaningless when combustion does not occur.
Added fuel and allowing combustion, even with ignition retard, will result in a higher MBEP, and the rev hang will be worse.
So the short answer is that it does not make sense to keep the injectors open upon overrun, for the reasons outlined above.
Hondata
Re: Overrun - Ignition
I'm talking about the "Overrun fuel cut" per gear delay table. Right now I have to set it very low to prevent rev hang.
I appreciate all your points but I can tell you that in practice, the mixture does not go "so rich that combustion does not occur". The minimum IPW set in the ECU is generally a lot lower than what is applied even during very high vacuum decel in a low gear. Subarus have this set to 0.5ms and even with injectors about twice the size as stock, I see about 0.8ms during high rpm decel in a low gear which results in the lowest MAP.
I have been tuning Subarus for almost 10 years and I regularly tune cars where some of the customers want the fuel to stay on during throttle lift. I can tune them so after you lift from high rpm, the car continues to fire the injectors so I retard timing in that RPM range and the AFR runs basically 14.7 with retarded timing all the way down to near idle where I ramp the timing up again and normal operation resumes. I do not get rev hang while employing this strategy. I do get rev hang if I leave the fuel on and not retard timing.
I also leave the fuel on the entire time when tuning the leftmost column of a VE map on Speed Density tunes.
I agree the AFR is meaningless when combustion does not occur but I'm talking about the lack of response when they come back online again.
I completely disagree with "Added fuel and allowing combustion, even with ignition retard, will result in a higher MBEP, and the rev hang will be worse."
I do not get rev hang when employing this strategy on 2.5L Subarus with a DBW throttle. Also, BMEP is directly proportional to ignition timing advance. Reducing advance reduces BMEP.
In short, I have used this strategy several times and it works fine. All I ask is that Hondata let me tune the same way on my S2000. Will you please let me do so?
I appreciate all your points but I can tell you that in practice, the mixture does not go "so rich that combustion does not occur". The minimum IPW set in the ECU is generally a lot lower than what is applied even during very high vacuum decel in a low gear. Subarus have this set to 0.5ms and even with injectors about twice the size as stock, I see about 0.8ms during high rpm decel in a low gear which results in the lowest MAP.
I have been tuning Subarus for almost 10 years and I regularly tune cars where some of the customers want the fuel to stay on during throttle lift. I can tune them so after you lift from high rpm, the car continues to fire the injectors so I retard timing in that RPM range and the AFR runs basically 14.7 with retarded timing all the way down to near idle where I ramp the timing up again and normal operation resumes. I do not get rev hang while employing this strategy. I do get rev hang if I leave the fuel on and not retard timing.
I also leave the fuel on the entire time when tuning the leftmost column of a VE map on Speed Density tunes.
I agree the AFR is meaningless when combustion does not occur but I'm talking about the lack of response when they come back online again.
I completely disagree with "Added fuel and allowing combustion, even with ignition retard, will result in a higher MBEP, and the rev hang will be worse."
I do not get rev hang when employing this strategy on 2.5L Subarus with a DBW throttle. Also, BMEP is directly proportional to ignition timing advance. Reducing advance reduces BMEP.
In short, I have used this strategy several times and it works fine. All I ask is that Hondata let me tune the same way on my S2000. Will you please let me do so?
Re: Overrun - Ignition
Here are the 3 tables I modify for Subarus...
I am SURE a similar table(s) exists in the Honda ECU. Either it's a simple 2D RPM based table or maybe it's a 3D RPM vs Load table. Not sure if Honda uses different tables for neutral/in-gear and above/below speed threshold etc.
I am SURE a similar table(s) exists in the Honda ECU. Either it's a simple 2D RPM based table or maybe it's a 3D RPM vs Load table. Not sure if Honda uses different tables for neutral/in-gear and above/below speed threshold etc.