Shift cut settings - bike engined car

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John Loudon
Posts: 29
Joined: Mon Jul 20, 2020 3:47 am
ECU Model: S100 Pro

Shift cut settings - bike engined car

Post by John Loudon »

Hi,

Can someone please help me understand what the impact of having gear dependant shift cuts as opposed to general ignition retard settings has. Does the gear dependant settings override the general settings a shown in the attached image for each gear?

I cannot find anything which indicates this in the manual. I have gear dependant settings ticked (although different figures to the attached image)

I have been having paddle shift issues on a bike engine single seater going from 3 to 4, 4 to 5 and 5 to 6 and wondered if it was because of this setting? The first 3 gears are all fine. If I lift the throttle it goes in 4,5 and 6 OK so its like the gears aren't unloading enough for flat shifting in 4, 5 and 6

Any ideas on this please? Should i just untick the gear dependant table and just use the general ignition retard settings.

Engine is a Suzuki GSXR 1000 K8 if that helps

Thanks

John
Attachments
Shift cut setting.JPG
katana
Posts: 455
Joined: Sun Jan 27, 2013 6:08 pm
ECU Model: S60 Pro
Firmware Version: 29

Re: Shift cut settings - bike engined car

Post by katana »

You have retard for 3-4, 4-5 and 5-6 set to zero! I would assume retard is the 'unloader' for shifting. Try adding 40 and see what happens?
John Loudon
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Joined: Mon Jul 20, 2020 3:47 am
ECU Model: S100 Pro

Re: Shift cut settings - bike engined car

Post by John Loudon »

Hi. Thanks for the reply. Those aren't my settings. Its just the image from the manual I used for illustration. My settings are attached but i get your point. This is why I am asking if this table overrides what is set in the general ignition retard section. If they do, then it would explain the issue but if they don't, then I'm on the wrong tack
Attachments
20220506_122653_resized.jpg
David Ferguson
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Re: Shift cut settings - bike engined car

Post by David Ferguson »

Since the Suzuki K8 has a gear position switch (not a variable pot), there might be an issue when you are between gears - it other words it might stop the cut too soon. So, I would consider unchecking "use switch to start, pot to finish".

After that if it still doesn't unload the dogs enough to shift, I would suggest you increase the delay time for gears you feel aren't unloading.

You want to have gear dependent, so you can vary the ign cut time (Delay Time), and the Retard (more retard will make the power after the gear shift smoother (i.e. less harsh) correctly for each shift. Due to the changing RPM drops, and after shift torque not all the timings / retards will be the same
Alex DTA
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ECU Model: S40 Pro
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Re: Shift cut settings - bike engined car

Post by Alex DTA »

katana wrote: Fri May 06, 2022 10:13 am You have retard for 3-4, 4-5 and 5-6 set to zero! I would assume retard is the 'unloader' for shifting. Try adding 40 and see what happens?
No. Those are the ramp in rates AFTER the shift has completed. They are used to minimise wheel spin in lower gears and limit shock loads on the gearbox by ramping the retard in over the specified time. The shock loads will be minimised anyway as retard is used, not cut, in the image posted.

The retard to unload the dogs is in the bottom right corner in the first image, and is a fixed value.
Alex DTA
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Re: Shift cut settings - bike engined car

Post by Alex DTA »

David Ferguson wrote: Fri May 06, 2022 5:02 pm Since the Suzuki K8 has a gear position switch (not a variable pot), there might be an issue when you are between gears - it other words it might stop the cut too soon. So, I would consider unchecking "use switch to start, pot to finish".
If that's the case, then that set up cannot be used for paddle shift. The ECU needs to see the voltage change to initiate the cut/retard strategy.
David Ferguson wrote: Fri May 06, 2022 5:02 pmAfter that if it still doesn't unload the dogs enough to shift, I would suggest you increase the delay time for gears you feel aren't unloading.
There is no delay time, we use the gear pot for closed loop shifting to ensure the gear is selected before the engine torque is returned.
The only way to increase the torque reduction is to increase the ignition retard, or use shift cut to entirely cut the ignition.
David Ferguson wrote: Fri May 06, 2022 5:02 pmYou want to have gear dependent, so you can vary the ign cut time (Delay Time), and the Retard (more retard will make the power after the gear shift smoother (i.e. less harsh) correctly for each shift. Due to the changing RPM drops, and after shift torque not all the timings / retards will be the same
Delay Time is not used in this case, but the others are. These are the settings for AFTER the shift has completed. If shifts aren't happening, changing the settings will have no effect.
John Loudon
Posts: 29
Joined: Mon Jul 20, 2020 3:47 am
ECU Model: S100 Pro

Re: Shift cut settings - bike engined car

Post by John Loudon »

To clarify, I am using closed loop paddle shift with a dual channel non Suzuki gear pot

@Alex DTA - are you saying that the chart is purely for preventing wheelspin at gear changes and nothing to do with shift cut retard for disengaging gears at gear changes?
Rob Stevens
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Re: Shift cut settings - bike engined car

Post by Rob Stevens »

John, post up all your settings as the screen dump you show is confusing. But yes the first column is ignored in closed loop and the next 2 columns relate to the ramp back in, the figures look sensible in the screen dump.
John Loudon
Posts: 29
Joined: Mon Jul 20, 2020 3:47 am
ECU Model: S100 Pro

Re: Shift cut settings - bike engined car

Post by John Loudon »

Hi Rob,

I currently have 65 deg retard and a 20ms retard ramp in time (bottom right). I have not driven it with this yet but previously it was 40 deg and 2ms

My chart settings are as the attached photo below but previously was as my photo in post 3. (In case you cant see the middle figure in the top it is 25 and then 15, 15, 10, 10 ,10 etc

I have copied both of these settings from someone in BHC with a Hayabusa engine who seems to have no issues but have not tried them yet. I am trying to understand what effect the changes will have and if for the better in both the chart and the retard settings for not changing up reliably from 3 to 4, 4 to 5 and 5 to 6


Thanks

John
Attachments
20220506_122812_resized.jpg
katana
Posts: 455
Joined: Sun Jan 27, 2013 6:08 pm
ECU Model: S60 Pro
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Re: Shift cut settings - bike engined car

Post by katana »

Alex DTA wrote: Sat May 07, 2022 2:11 am
David Ferguson wrote: Fri May 06, 2022 5:02 pm Since the Suzuki K8 has a gear position switch (not a variable pot), there might be an issue when you are between gears - it other words it might stop the cut too soon. So, I would consider unchecking "use switch to start, pot to finish".
If that's the case, then that set up cannot be used for paddle shift. The ECU needs to see the voltage change to initiate the cut/retard strategy.
If the K8 GPS is like the Hayabusa one, it should provide what Alex says is a requirement. Switch has 5v In, Ground and different fixed voltage output subject to each gear eg. 1st = 0.75v, N = 1.2v, 2nd = 1.8v, 3rd = 2.5v, 4th = 3.2v, 5th = 3.9v and 6th = 4.7v (voltages are hypothetical for the example)
Even if the DTA is looking for a 'change,' doesn't the null time between gears count as a 'voltage change' as volts will drop to 0v between outputs.
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