A spreadsheet, to explain torque/HP, shift points, etc...
Thread Starter
AudiWorld Super User
Joined: Apr 2002
Posts: 3,384
Likes: 0
A spreadsheet, to explain torque/HP, shift points, etc...
Simply plug in numbers from the torque curve for any engine. (It comes with numbers for the very torque-y 1.9 TDi engine) It will compute horsepower (I could have set it up so you plug in HP, and it computes torque, but figured this way would make Jim TT happy)
Also plug in gear ratios (it will handle 5 gears), final drive ratio and tire diameter.
It will then give nice charts for HP and torque. It will also compute rear wheel torque (proportioal to acceleration, as I stated in my original post on HP vs. torque) at speed based upon engine torque and the given drivetrain ratios. It will also show HP at speed.
Notice that the shift points given by either method (calculating torque from the engine through the drivetrain, or simply looking at the HP through each gear) are IDENTICAL (at 23, 41, 64 and 87 mph, for the data given), and correspond to maximizing the horsepower in each gear and NOT the torque.
ALSO NOTE THAT ONLY IN FIRST GEAR DO WE EVER DRIVE THROUGH THE TORQUE PEAK, NOWHERE ELSE IS IT IN ANY WAY SIGNIFICANT - the torque peak is simply not used for maximum acceleration in any gear other than first. I also explained why this is so in my original posting. In the given data, driving through the torque peak makes us go from 8-13 mph faster than we other wise would, but so little time is spent there anyway that it makes very little overall difference to acceleration.
With the given engine, peak torque could be cut by almost 15% without significantly affecting maximum acceleration.
Another way of looking at it is that torque determines the _shape_ of the acceleration curve, but HP determines the _height_. Maximizing acceleration means we want it as high as possible.
Horsepower on the chart has been scaled by a constant only so that it is more legible. It's not important how high it is (on the chart), we're interested in where the crossover points are, which is where we should shift.
(you may need to right-click, "save target as..." or your browser's equivalent in order to download it.)<ul><li><a href="http://www.flatsurface.com/shift_point.xls">HP/Torque/Shift point spreadsheet</a></li></ul>
Also plug in gear ratios (it will handle 5 gears), final drive ratio and tire diameter.
It will then give nice charts for HP and torque. It will also compute rear wheel torque (proportioal to acceleration, as I stated in my original post on HP vs. torque) at speed based upon engine torque and the given drivetrain ratios. It will also show HP at speed.
Notice that the shift points given by either method (calculating torque from the engine through the drivetrain, or simply looking at the HP through each gear) are IDENTICAL (at 23, 41, 64 and 87 mph, for the data given), and correspond to maximizing the horsepower in each gear and NOT the torque.
ALSO NOTE THAT ONLY IN FIRST GEAR DO WE EVER DRIVE THROUGH THE TORQUE PEAK, NOWHERE ELSE IS IT IN ANY WAY SIGNIFICANT - the torque peak is simply not used for maximum acceleration in any gear other than first. I also explained why this is so in my original posting. In the given data, driving through the torque peak makes us go from 8-13 mph faster than we other wise would, but so little time is spent there anyway that it makes very little overall difference to acceleration.
With the given engine, peak torque could be cut by almost 15% without significantly affecting maximum acceleration.
Another way of looking at it is that torque determines the _shape_ of the acceleration curve, but HP determines the _height_. Maximizing acceleration means we want it as high as possible.
Horsepower on the chart has been scaled by a constant only so that it is more legible. It's not important how high it is (on the chart), we're interested in where the crossover points are, which is where we should shift.
(you may need to right-click, "save target as..." or your browser's equivalent in order to download it.)<ul><li><a href="http://www.flatsurface.com/shift_point.xls">HP/Torque/Shift point spreadsheet</a></li></ul>
Thread
Thread Starter
Forum
Replies
Last Post
[not Steve] Trac
A4 (B5 Platform) Discussion
7
Nov 21, 2000 02:17 PM
19, acceleration, calculating, calculator, curve, horsepower, hp, maximum, point, points, ratio, shift, spreadsheet, tdi, tire, torque, vs
