Optimal shift point analysis is just what it sounds like: identifying the shift points to achieve maximum speed. The premise is to keep torque to the ground at its maximum possible value at all times, because this maximizes the tractive force and the acceleration. I didn't invent this, someone else did - if you disagree with the premise, take it up with them, not me. The analysis factors in the engine torque curve, the gear ratios and final drive ratio, and tire size.
With a E153 transmission the gear ratios are:
Ignore 6th gear. There is no sixth gear in a e153.
Typical characteristics for a race tire - this is a Hoosier A6.
Typical 2GR torque curve (from Alex W. dyno chart)
Let's go ahead and digitize this, but with a twist, of extrapolating tq and HP past the 7200 rev limit, with declining torque and hp - in a minute, you'll see why I did this.
And these are the data points
It's elementary to produce a chart showing how fast the engine needs to rev for a given speed in a given gear.
:Ignore 6th gear. There is no sixth gear.
It's also elementary to produce charts of how much torque the engine puts to the ground in every gear - this accounts for the wheel size and for every overall gear ratio including final drive.
Again, ignore 6th gear. I keep repeating this because I know that someone is going to get hung up on 6th gear. Ha ha.
Next the columns for speed and torque can be matched to produce charts of torque versus speed in any gear .
Now the idea is in order to maintain maximum acceleration, you have to maintain the maximum torque at any speed. So you hop-scotch from one gear to the next - in other words, shift - where the torque produced in a given gear becomes less than the torque produced in the next gear. This gives the shift points - with a little bit of programming magic
And with a little bit more magic the shift points can be overlaid on the speed vs rpm chart.
Do you see what I see? 7200 rev limit is definitely an improvement over the factory 6400, but 8000 would be even better, even on stock engine, no camshafts.The 2GR wants to be shifted well over 7000 for maximum acceleration.
I wrote this spreadsheet to help my dyno tuning clients develop their race strategies. Shift points change drastically with different torque profiles and boost profiles. The spreadsheet is completely automated and spits out the shift points given the data for gear ratios, tire size, and torque profile. If there is interest, I can make this available on google sheets.
