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 Post subject: S100 shift cut parameters
PostPosted: Tue Aug 14, 2018 2:44 pm 
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Joined: Tue Jan 16, 2018 9:38 am
Posts: 54
Location: Aberdeen
ECU Model: S100 Pro
Distributor: DTA
Hi All,
I'm struggling to undestand the definition of the shift cut start and end points when setting up the gear position sensor for good shifts.

On my previous system (Xoomshift), there was a +/- tolerance figure to enter and that was it. With the identical gear pot as being used now with the S100, I had this set at 25mV and it worked well with a very stable and repeatable voltage for each gear.

With the S100, I'm using 75mV start and 200mV end - which worked very well with the contactless pot on the busa engines I've setup.

Can someone explain in plain english what the two settings do as I can't understand the description in the manual!

(I had my first failed run of the season yesterday - and with Alex's help reviewing the logged data, the gear pot is the likely suspect. I had loads of false "Shif A" commands logged with each one retarding the ignition accordingly, and 250ms times in the "last 20 shifts" which is the time-out value for a gearchange. Of course, I wasn't trying to change gear...The car basically lost all power and I cruised into Top Ess marshals post.)

I've still to fully investigate the gear pot and test it out, but even if it's goosed and needs replaced, I still need to set up the start and end values to suit.

I've had the odd hicup throughtout the season and often the logging (only at 10Hz) does capture a spurious Shif A trigger so it does indeed look like the gear pot is on it's way out.

Looking through data from earlier in the year, the pot voltage varies by around 17mv but data from yesterday is showing a variation of up to 47mv so perhaps the mechanical interface between gear barrel and pot is slacking off with age.

I'll keep you posted on what I discover once I have the pot and mounting removed.

Cheers
Steve


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 Post subject: Re: S100 shift cut parameters
PostPosted: Tue Aug 14, 2018 4:09 pm 
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Joined: Fri Feb 28, 2014 1:03 pm
Posts: 1139
ECU Model: S40 Pro
Distributor: DTA
Firmware Version: 79
Shift Cut Start point is effectively the dead band around the set value.

Shift Cut End Point isn't used for shifting, but is now used for throttle blip on downshift.

I'd like to change this, and separate out the shift cut start point, and the next gear end point, so that they can be set separately.
That will then allow early removal of the retard.


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 Post subject: Re: S100 shift cut parameters
PostPosted: Wed Aug 15, 2018 2:12 am 
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Joined: Thu Jul 28, 2011 4:10 am
Posts: 872
ECU Model: S100 Pro
Steve, next time I see you I can demonstrate how to find how much that 'shift cut start' point needs to be set at. Principally with engine stopped and in say 2nd gear get someone to pull the car backwards to load the dogs as if the engine was driving the car. Now slowly operate the gear leaver by hand and you will feel the drum rotate and take up the slack in the dogs. Whilst looking at the pot voltage, this will give you an idea of the start point setting, set it at the end of the slop in the system.
As Alex says the start point is also used as the end point which is poorly explained and desperately needs seperating out! They don't need to be the same.
The end point does nothing on shift cut, Allan thought it would be needed so left it in. so leave it at 200mv
To try and prevent false shifts increase the filter setting and up the 75mv

Perhaps an optional safety feature could be added in that a shift would be disallowed if a paddle had not been pulled?

But it does sound like you have a load of slop in the drive to the pot?


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 Post subject: Re: S100 shift cut parameters
PostPosted: Wed Aug 15, 2018 1:48 pm 
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Joined: Tue Jan 16, 2018 9:38 am
Posts: 54
Location: Aberdeen
ECU Model: S100 Pro
Distributor: DTA
Thanks Alex - that makes sense now.

Rob - you did explain this to me previously but i had forgoten the technique - thanks for the details; I'll give this a go. I didn't think the slop I had was much, but with a filter seting of only 3 and the tight 75ms It's obviously too much!

Strangley, it's 3rd gear that give the most slop - perhaps the selector fork pin / barrel slot is looser in that area? I'll maybe have to assemble up a spare half engine casing with gear cluster and selector mechanism and do some bench experiments.....Sounds like a winter project.

So, varying the 200ms "end" value would allow me to fine tune where the blip happens? (Not that it's a problem - I can comfortably come down 3 gears in just over a second).

I plan to make a new "drive" adapter for the pot to remove the slop and will do some fast logging of just the gear stuff at Prescott.

Cheers
Steve


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 Post subject: Re: S100 shift cut parameters
PostPosted: Thu Aug 16, 2018 2:43 am 
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Joined: Fri Feb 28, 2014 1:03 pm
Posts: 1139
ECU Model: S40 Pro
Distributor: DTA
Firmware Version: 79
Sorry, misled you a bit there.

The blip on paddle shift is entirely from the paddle, nothing to do with the pot.
A recent firmware update has added blip based on the pot for use with gear levers.


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 Post subject: Re: S100 shift cut parameters
PostPosted: Thu Aug 16, 2018 1:07 pm 
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Joined: Tue Jan 16, 2018 9:38 am
Posts: 54
Location: Aberdeen
ECU Model: S100 Pro
Distributor: DTA
Ah, ok Alex, no worries.


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 Post subject: Re: S100 shift cut parameters
PostPosted: Thu Aug 16, 2018 2:18 pm 
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Joined: Fri Feb 28, 2014 1:03 pm
Posts: 1139
ECU Model: S40 Pro
Distributor: DTA
Firmware Version: 79
You can already fine tune the blip in the paddle shift parameters.


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 Post subject: Re: S100 shift cut parameters
PostPosted: Thu Aug 16, 2018 4:12 pm 
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Joined: Tue Jan 16, 2018 9:38 am
Posts: 54
Location: Aberdeen
ECU Model: S100 Pro
Distributor: DTA
Thanks Alex.

Well, I've stripped and checked the gear pot mounting/linkage and it's all snug and no slop. So I've fitted the spare (new) pot I have and will run up the engine over the weekend and log some gear changes.

I'll increase the start point to 85mV and the filter up to 6 and see how I get on. does the filtering just smooth the raw voltage the ECU reads?


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 Post subject: Re: S100 shift cut parameters
PostPosted: Fri Aug 17, 2018 2:25 am 
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Joined: Fri Feb 28, 2014 1:03 pm
Posts: 1139
ECU Model: S40 Pro
Distributor: DTA
Firmware Version: 79
SMR wrote:
I'll increase the start point to 85mV and the filter up to 6 and see how I get on.


Remember that the start point is also the end point, so check where the retard is ramping back in. You may need to increase the initial retard as you may be releasing the cut a bit early now.

SMR wrote:
does the filtering just smooth the raw voltage the ECU reads?


Yes


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 Post subject: Re: S100 shift cut parameters
PostPosted: Sat Aug 18, 2018 1:19 pm 
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Joined: Tue Jan 16, 2018 9:38 am
Posts: 54
Location: Aberdeen
ECU Model: S100 Pro
Distributor: DTA
I ran up the engine today on the stands (wheels off) and went up and down the gears multiple times, slowly and quickly and all appears good. Voltage stability of the new gear pot is vastly improved.
Once it's back on the ground I'll check the barrel movement via Rob's method above and then take it from there. Off to look at the 100Hz logging now and see what I can learn.


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