What is the best RPM's to shift a 180TT?
04-10-2001, 06:51 AM
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Re-post of how to calculate shift points
<ul><li><a href="https://www.audiworld.com/forum/m/tt/msgs/37587.phtml">https://www.audiworld.com/forum/m/tt/msgs/37587.phtml</a</li></ul>
04-10-2001, 10:07 AM
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Excellent, Jim. Here's an empirical method recommended by Hypertech...
for their automatic transmission shifting point programming. It'll work for manual too. It really just measures the real-world results of Jim's calculation method. You don't have to know the torque numbers either.
Equipment: stopwatch and extra person to measure
OR video camera pointed at gages and stopwatch for analyzing data.
First gear is so short that this method is difficult for 1-2 shift. Do it last.
1) Find mph that corresponds to the approximate shift point...say mph in 2nd @ 6000 rpm. You will accelerate from say 2500 rpm in 2nd and shift at say 5500 rpm exactly. Shifts should be repeatable, not 'power shifts'. Repeatability is critical.
2) Observer watches only the speedo. Start watch at some 10 mph increment which is above the 2500 rpm start speed, but below say 4000. You are looking for steady-state wide open throttle acceleration.
3) Driver accelerates, shifts at target point, and goes 10-20 mph beyond shift speed in 3rd. Observer stops watch exactly at a 10 mph mark on speedo. Record time. Repeat this over same stretch of road (important) 3 to 5 times. Throw out slowest and fastest times and average the others. This is your segment time for a 2-3 shift at a given rpm.
4) Repeat for shift rpm 500 higher, etc. until you get to redline. Compare segment times. Quickest indicates the best shift point, at least for 500 rpm increments. I doubt you'll find much difference in less than 500 rpm increments until you get into the top 2 or 3 gears. 5-6 is probably unimportant to most folks, so I'd consider using the same as 4-5.
5) Try 1-2 last when observer is well practiced.
6) If you use the video camera you can do it alone, and repeat each run to help eliminate stopwatch clicking errors. Talk to note which gear and which shift rpm you are using.
You may find that empirically derived shift points for lower gears are lower than what is predicted by calculations. This is due to driveline inertia and more losses due to lower gearing. IMO, you may find that short shifting a TT in the lower gears is faster.
This is fun to do, easy on the car, and if you control the conditions by using the same piece of roadway, very accurate.
My automatic(!) C5 does a 3-4 shift above 140, so I've not bothered to test there.
My $.02
Equipment: stopwatch and extra person to measure
OR video camera pointed at gages and stopwatch for analyzing data.
First gear is so short that this method is difficult for 1-2 shift. Do it last.
1) Find mph that corresponds to the approximate shift point...say mph in 2nd @ 6000 rpm. You will accelerate from say 2500 rpm in 2nd and shift at say 5500 rpm exactly. Shifts should be repeatable, not 'power shifts'. Repeatability is critical.
2) Observer watches only the speedo. Start watch at some 10 mph increment which is above the 2500 rpm start speed, but below say 4000. You are looking for steady-state wide open throttle acceleration.
3) Driver accelerates, shifts at target point, and goes 10-20 mph beyond shift speed in 3rd. Observer stops watch exactly at a 10 mph mark on speedo. Record time. Repeat this over same stretch of road (important) 3 to 5 times. Throw out slowest and fastest times and average the others. This is your segment time for a 2-3 shift at a given rpm.
4) Repeat for shift rpm 500 higher, etc. until you get to redline. Compare segment times. Quickest indicates the best shift point, at least for 500 rpm increments. I doubt you'll find much difference in less than 500 rpm increments until you get into the top 2 or 3 gears. 5-6 is probably unimportant to most folks, so I'd consider using the same as 4-5.
5) Try 1-2 last when observer is well practiced.
6) If you use the video camera you can do it alone, and repeat each run to help eliminate stopwatch clicking errors. Talk to note which gear and which shift rpm you are using.
You may find that empirically derived shift points for lower gears are lower than what is predicted by calculations. This is due to driveline inertia and more losses due to lower gearing. IMO, you may find that short shifting a TT in the lower gears is faster.
This is fun to do, easy on the car, and if you control the conditions by using the same piece of roadway, very accurate.
My automatic(!) C5 does a 3-4 shift above 140, so I've not bothered to test there.
My $.02
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