Downshift vs upshift delay

'Microsquirt' Transmission Control development and support.

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LT401Vette
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Downshift vs upshift delay

Post by LT401Vette »

Using a 4L80e that used to be controlled by a TCI, but is now using a MicroSquirt with the Trans code.

If driving along at 40 MPH in 4th gear and I mat it, I expect it to go straight to the lowest gear that meets the downshift/upshift window, hence straight to 1st gear. In this scenario the TCI controller would go straight to the desired gear on downshift.
However, it seems that is will go 4th --> 3rd, wait min shift time, go 3rd --> 2nd, wait min shift time, then finally go to 1st.

It seems stepping 1 gear at a time leaves the trans doing shift, shift, shift, so you don't start accelerating forever when you add in the final shift completion time so it can start accelerating.

Adjusting the min shift time is a double edge sword. On the upshift at WOT I can't make it too short or it will skip gears especially if tires are spinning.

Is there a way to make it shift straight to the desired gear on downshift?
Phil Tobin
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LT401Vette
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Posts: 12698
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Re: Downshift vs upshift delay

Post by LT401Vette »

Looking at how the old TCI was setup, it looks as though it generally went gear by gear with min shift time too, but it has WOT downshift. So once in WOT mode, it would jump straight from 4th to 1st instead of taking a couple seconds to get there.

It is much nicer having the MicroSquirt in there as it is integrated with the ECU for Data logging, spark retard, etc.
Now I just need to get it setup to work as well.

With the gearing in my car, 1st gear goes to over 60 MPH, so 4th --> 1st shift are common. As it seems I really need the min shift time up at .8 or so to stop skipping through 2nd. That makes for long downshifts.
Phil Tobin
EFI Analytics, helping to simplify EFI
Next Generation tuning software.
Supporting all MegaSquirt versions and firmwares.
http://www.TunerStudio.com
http://www.efiAnalytics.com/MegaLogViewer/
Support the firmware running your engine:
http://www.msextra.com/doc/donations.html
jsmcortina
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Re: Downshift vs upshift delay

Post by jsmcortina »

Good question. I'll have a think about that. I wonder what other customers are doing?

James
I can repair or upgrade Megasquirts in UK. http://www.jamesmurrayengineering.co.uk

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