[Andy@Ross-Tech.com]

I had a chance to do some more logging last night and plotted out full pulls in 1st, 2nd, and 3rd.



Acceleration is maximized by the following shifts:

1>2: 6600 rpm (42 mph)
2>3: 6400 rpm (64 mph)

Where the curves cross is where the acceleration in two gears is equal. For example, at 40 mph, the MCS could be in 1st, 2nd, or 3rd gear. The acceleration at that speed is:

1st: 0.29g
2nd: 0.28g
3rd: 0.23g

The greatest acceleration at that speed is achieved in 1st gear.

Now, at 45 mph, the MCS could be in 1st, 2nd, or 3rd gear. The acceleration at that speed is:

1st: 0.25g
2nd: 0.28g
3rd: 0.22g

The greatest acceleration at that speed is achieved in 2nd gear.

The point where the curves cross is where you should shift, such that you are always in the gear that yields the greatest acceleration.

[Grinder]

Thanks for the info and great plots!

[bigbaddaboom]

Smart, thanks for that Andy!

[toofast]

What about the other 3 gears???????????

[Grinder]

Maybe he took 'em out for weight reduction!

[Andy@Ross-Tech.com]

I have 3 more gears ?!? I've only been using the first three all this time!

According to my calculations, 7,000 rpm in each gear relates to:

1: 44.24 mph
2: 70.42 mph
3: 93.59 mph
4: 114.59 mph
5: 138.32 mph
6: 169.33 mph

I need to find a different test track for the top 3 gears.

[minimini36]

Great graphs Andy!

I took a different approach to determining the optimum shift points. I constructed two tables. The first table shows the speed in each gear at each engine speed from 4000 rpm to the 6950 rpm fuel cutoff in 250 rpm increments. These speed calculations are based on a 72.7 inch rolling circumference for the tire. This was verified using a GPS to check the speed at 5000 rpm in 4th, 4000 rpm in 5th and 3000 rpm in 6th gear. The second table shows the engine torque in NM at the same engine speeds. It also shows the torque available at the wheel in each of the gears at these engine speeds. The torque values were taken from the graph in the MCS Powertrain article that was posted here on MINI2.com. If you look at the first table at 6950 rpm in first it is 41.9 mph. If you next find this same speed in second gear it is about 4500 rpm. Now you can compare the torque values at the same engine speed and gear. In all cases the value in the lower gear is equal to or greater then the value at the lower engine speed in the next higher gear. The torque curve is very flat for this engine with 76% of the maximum torque available from 1800 to 7000 rpm. Our numbers appear pretty close since mine is just an approximation. I am curious how you measured your acceleration since the graph shows the car still accelerating well past 7000 rpm in first gear. Have you removed the 6950 rpm rev limiter (fuel cutoff) or is this a measurement or graphing inducted error. Were you recording the speed change to determine the acceleration or were you using a data acquisition system with an accelerometer? Keep up the good work.

[minimini36]

I am new to posting pictures so here is my second attempt at posting the tables. If it does not work look here.

[minimini36]

BruceK
Thanks for getting the picture inserted into the post The first time I included the path on my PC thinking it would upload it for the attached file. The second time I included the link to where I had just uploaded it to the gallery. What did I do wrong?

[Andy@Ross-Tech.com]

Quote:

Originally posted by minimini36
Great graphs Andy!

I took a different approach to determining the optimum shift points. I constructed two tables. The first table shows the speed in each gear at each engine speed from 4000 rpm to the 6950 rpm fuel cutoff in 250 rpm increments. These speed calculations are based on a 72.7 inch rolling circumference for the tire. This was verified using a GPS to check the speed at 5000 rpm in 4th, 4000 rpm in 5th and 3000 rpm in 6th gear. The second table shows the engine torque in NM at the same engine speeds. It also shows the torque available at the wheel in each of the gears at these engine speeds. The torque values were taken from the graph in the MCS Powertrain article that was posted here on MINI2.com. If you look at the first table at 6950 rpm in first it is 41.9 mph. If you next find this same speed in second gear it is about 4500 rpm. Now you can compare the torque values at the same engine speed and gear. In all cases the value in the lower gear is equal to or greater then the value at the lower engine speed in the next higher gear. The torque curve is very flat for this engine with 76% of the maximum torque available from 1800 to 7000 rpm. Our numbers appear pretty close since mine is just an approximation. I am curious how you measured your acceleration since the graph shows the car still accelerating well past 7000 rpm in first gear. Have you removed the 6950 rpm rev limiter (fuel cutoff) or is this a measurement or graphing inducted error. Were you recording the speed change to determine the acceleration or were you using a data acquisition system with an accelerometer? Keep up the good work.

Good eye! I inadvertently used the wrong data and ended up with a screwy 1st gear plot. Here is a corrected (and whimsically enhanced) version.



I am using a prototype data logger program that is currently set up to record wheel speeds from the DSC system through the diagnostic port. The sample rate is quite good (about 13 samples/second so far) and of course the program is a work in progress. I derived acceleration from the average rear wheel speed change over time.

[DEye]

And for us Nosy types , could PM me what the cable spec is to connect to the Diag port, please.

Realizing that anything I do could render the MINI very UNHAPPY !

And what software are you using to gather the data ?

[gowest]

minimini36, I find both charts usefull but I wish your chart extended down to at least 2500 rpm where the supercharger seems to start really being useful or maybe even as low as 2000 rpm.