Auto Shift points - what should they be?
Thread Starter
Team Owner
Joined: Oct 2000
Posts: 29,937
Likes: 22
St. Jude Donor '03-'04
Cruise-In 1-2-3-4-5 Veteran
Auto Shift points - what should they be?
Technical guide, team.
Suppose you were fiddling with the shift points on your auto trans. You have a dyno printout that shows your current torque peak and your current horsepower peak.
Where do you want your transmission to upshift for best ET? Should it shift on the torque peak, after the torque peak, on the horsepower peak, after the horsepower peak?
I've always wondered about this.
Suppose you were fiddling with the shift points on your auto trans. You have a dyno printout that shows your current torque peak and your current horsepower peak.
Where do you want your transmission to upshift for best ET? Should it shift on the torque peak, after the torque peak, on the horsepower peak, after the horsepower peak?
I've always wondered about this.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Re: Auto Shift points - what should they be? (Matt Black)
Ideally, you want to shift as many rpms over peak horsepower, as it will fall back to after the shift. It will take a little experimenting, but if the HP peak is at 5000 rpms, and a 5400 rpm shift point drops the revs to 4600 after the shift, you've got it nailed. Actually rather than the same number of revs above and below peak, you want the HP to be at the same levels before and after. This will put the peak power in the middle of the operating curve, and give you the highest average power.
Melting Slicks
Joined: Jun 2001
Posts: 2,525
Likes: 1
From: Sarasota, FL
Re: Auto Shift points - what should they be? (CFI-EFI)
I have heard that you want your shifts to land your rpm at about 400-500 rpm below peak torque. Some of the gurus will chime in shortly I am sure.
Team Owner
Joined: Nov 1999
Posts: 26,679
Likes: 17
From: This vette goes to 11 Milford MA
St. Jude Donor '03-'05
Re: Auto Shift points - what should they be? (CFI-EFI)
I guess it depends on how many RPM's the motor drops between shifts. On my stock 88, leaving it in D, it shifts right where the motor runs out of breath at 4,800 RPM's and runs 14.0@98 allllll day. If I shift it manually at 5,200, it is wheezing and not pulling but drops the right into the sweet spot of the engine's powerband when it shifts and runs 13.9@101. Its not that its making more power at 5,200, I can almost guarnatee it isn't, it just drops the motor rpm to where it wants to be. You have to experiment and find out what works best.
Safety Car
Joined: Feb 1999
Posts: 4,724
Likes: 16
From: Little Elm TX
Re: Auto Shift points - what should they be? (Matt Black)
As already said, to determine where your best shift point is.... you have to know what your slap back rpm is.... for example if you shift at 5800 rpm and it lands at 4400 rpm in the next gear, you have a 1200 rpm window.... with that in mind, get your motor dynoed.... cut out a little piece of paper thats the length of 1200 rpm on your dyno sheet and move it around until you find the 1200 rpm window that provides your best average HP.... there is a problem with this though, if you determine such as the above example that a 6300 rpm shift seems to give the best average HP.... but you find out when you actually go out and do it that your motor noses out too hard right before where you want to shift... you have to back out of it. Most cars like to be shifted right before they nose out..... you have to rev your motor once to find that limit..... its their, we all have it. Mines at about 6000 rpm.
good luck
Beach Bum
good luck
Beach Bum
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Thread Starter
Team Owner
Joined: Oct 2000
Posts: 29,937
Likes: 22
St. Jude Donor '03-'04
Cruise-In 1-2-3-4-5 Veteran
Re: Auto Shift points - what should they be? (Beach Bum)
Thanks, team.
I'm so picky about technical details, I may have to go and buy some realtime monitoring software and record a few runs to see the exact shift points. I've never actually been able to concentrate on the tach needle when I'm at WOT.
More training, grasshopper...
I'm so picky about technical details, I may have to go and buy some realtime monitoring software and record a few runs to see the exact shift points. I've never actually been able to concentrate on the tach needle when I'm at WOT.
More training, grasshopper...