Gearbox Ratios

Gearbox Ratio - CV Joint  - Erratic Encoder

 Here is a handy calculator to help map between RPM and MPH.

Guessworks - Gearbox & Speedo Ratio Calculator (guess-works.com)

Settings: 165/70 x10 wheels; 1:1 Drop gear ratio, MKIII Cooper S gearbox, 3.444:1 Final Drive

For Jan, this is what it calculates which has been verified using a GPS speedometer.:

Given this, with the ME1616 motor, 45 MPH is easily hit at about 5,000 RPM, well within spec.   Field-weakening is active at these higher RPMs but the responsiveness is decent. from about 20 MPH up to 45 MPH.

Currently just staying in 2nd gear for most city driving, though 3rd gear is quite acceptable and allows speeds up to 60 mph.

Configuration learnings:

1. Low Speed Gains and Speed Mode Gains play a big role in low (below 150 rpm, which is adjustable) performance.  If these gains are too low, the motor is very sluggish starting out but once over the 150 rpm threshold, the primary gains Kp and Ki for iQ and iD become active.  With the Low Speed settings were low, it was taking ~2 seconds to go from 0 rpm to 150 rpm, which is a long time when the traffic light turns green.

2. Observing an electrical hum at low RPM which started once I increased Kp and Ki for iQ and iD.  No obvious side-effects, but audible.  - This is from Kp for iD being set to 8.  Lowered to 2 and hum resolved.

3. Added a cooling fan to the new radiator.  Wired to the same fuse as the one activating the high voltage power (not traction) feed to the Sevcon controller.  This created some noise, and the controller issued a parameter out of range fault, and the Find the Parameter feature identified the Temperate Map Setting #3 as being the issue - It was set to 110C and 0.5 cutback, which should have been well within range.  Disconnected the fan and the fault code resolved.

4. Controller was going in the Motor Temperature Cutback at 80C, though the mapping did not start until 100C.  Tried different mappings but no change.  Activated and deactivated the I2T motor temperature feature and this resolved the issue.  I2T is deactivated and now the motor thermal cutback is operating properly.

5. Receiving Encoder Errors (0x52C1) when coming to a stop and the car rolls backwards a little.  It seems like the error is set (requiring a restart) as soon as the throttle is pushed.  Added shielding to the encode lines to see if helps but did not.  Swapped the encoder with one from another motor I had, and it appears the encoder errors are resolved.    Drove about 6 miles with stops and starts and the motor up to about 80C and not a single encoder error

6. Inner CV Joint alignment.  When the new ME1616 was installed, its increased size shifted the transmission a bit.  Also, the new motor provided an opportunity to realign the transmission.  Well, the first attempt had the transmission about 1/2 inch to far forward.  To shift it back, the transmission had to be raised about 1/4 to allow the motor to avoid a bolt from the suspension tower.  This allowed the motor whole assembly to shift back the 1/2, resulting in a much better alignment of the left inner CV joint.  In looking at the CV joint, the ball bearings were not fully within the joint and under force (like pulling up a driveway), would push out of the joint, slipping, and causing a thump sound as they pushed back into the joint.  With the improved alignment, they now are more in the joint and unable to push out.