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Gear Detection


SimonR32
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Just want to confirm something with gear detection and voltage tolerances. It's for a PPG sequential with a rotary position sensor, so when in gear the voltages are fairly accurate, usually +/- 0.02V. 

Originally I had the voltage tolerance much lower, +/- 0.05V but the ECU and dash were registering neutral so I've raised to +/-0.27V which is basically half the difference between the smallest gap in driven gears. I can actually increase it to +/-0.29V if needed as it still sees neutral between some gears for a very short time.

This tolerance fixes the neutral readings between gears but it concerns me that the ECU will register the next gear during a driven up shift too early (0.27V before it's fully in gear) and engage torque too early causing premature dog wear and or mis-shifts.

I guess my question, is it better to have a large window so the ECU doesn't register neutrals or small window so the ECU knows exactly when the gear has made it fully into the next gear?

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You are correct, the tolerance setting will affect the point at which torque reintroduction occurs.  Which option is correct will depend on how fussy the gearbox is but you may have to put up with a short period of "gear zero" in between gears if reintroducing torque while it is still shifting causes a problem.  My gut feeling is since you have six gears + R & N, the spacing between each barrel position is close enough that it will be perfectly happy with a fairly big volt tolerance there.

I have tuned a couple of cars with closed loop gear cut systems and in those I have a big enough tolerance that we dont really see gear zero at all during a shift.

 

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1 hour ago, Adamw said:

You are correct, the tolerance setting will affect the point at which torque reintroduction occurs.  Which option is correct will depend on how fussy the gearbox is but you may have to put up with a short period of "gear zero" in between gears if reintroducing torque while it is still shifting causes a problem.  My gut feeling is since you have six gears + R & N, the spacing between each barrel position is close enough that it will be perfectly happy with a fairly big volt tolerance there.

I have tuned a couple of cars with closed loop gear cut systems and in those I have a big enough tolerance that we dont really see gear zero at all during a shift.

 

Thanks for the reply. Is there any issue with seeing gear zero during changes or just ?

Another option would be to lower the voltages of each driven gear by say 0.2V so there is still a big enough window to see the gear correctly but effectively will delay the torque introduction until 0.07V before the gear is full engaged (rather than 0.27V)

or am I totally overthinking it? I just want the dogs (and gears) to be as safe and long lasting as possible

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2 hours ago, SimonR32 said:

Is there any issue with seeing gear zero during changes or just ?

No from a functionality perspective, just it might be distracting to the driver to see a flash of zero and the logs wont look as nice.

 

2 hours ago, SimonR32 said:

Another option would be to lower the voltages of each driven gear by say 0.2V so there is still a big enough window to see the gear correctly but effectively will delay the torque introduction until 0.07V before the gear is full engaged (rather than 0.27V)

or am I totally overthinking it? I just want the dogs (and gears) to be as safe and long lasting as possible

Yep you could do that too but I havent needed to on the cars I have played with.  You are not going to hurt it with a few test shifts so try it and see.  If it is not cutting for long enough it either wont engage or you will get a big clunk.

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