MoTeC Global Forum

Having some difficulties getting Gear Detection to work properly on a 2006 USDM STI. I have my gear ratios set properly, but the only way I can get gear detect to work (somewhat) correctly is with a tailshaft speed cal setting of "1.2"... which I think is just a coincidence - my settings are likely off elsewhere and I'd really like to learn how to do this correctly.

The speed measure signal on this car comes from a geared shaft driven by the front differential. Front differential speedometer gear is 25 teeth, speed measure sensor gear is 19 teeth. Pulses per speed measure sensor rotation are unknown.

I've narrowed the potential problems down to a few settings (not listing the ones with obvious settings):

Gear Detection setup
(Gear Method set to "1 - Speed")

Tailshaft Speed Cal (currently set to 1.0... setting this to 1.2 gets detection somewhat accurate)
Tailshaft Speed Source (set to DIG3... but maybe this should be set to 0: "calculated from drive speed"?)

Gear Detection gear ratios
(1st - 6th ratios set to transmission ratios, 7th - 10th set to "0")

Diff Gear Ratio (set to 1.00... but the VSS is not measuring tail shaft speed)

DIG3 - Speed Measure parameters
(Measurement Type set to "1 - Speed")

Calibration (set to 264, which is the default setting in all Subaru base maps I have found)

On a friends car with pnp, this was something I could never get to work either. I tried many different settings...but it never showed the correct gear.

Here was a working setup on an EVO9 with a similar VSS setup-

Gear Method = 1
Tailshaft Speed Cal = -265.4
Tailshaft Speed Source = 0

Gear ratio setup-

enter all gear ratios incl. diff ratio.
If a primary reduction is used calculate it.

Must turn TC on to calc drive and driven speeds.

Got it sorted (biggest changes in BOLD):

Gear Detection setup
Gear Method = 1 (Speed)
Tailshaft Speed Cal = 5.0 (will probably change to 5.3, see below)
Tailshaft Speed Source = 3 (DIG3 - Speed Measure)

Gear Detection gear ratios
1st - 6th ratios = (transmission gear ratio)
7th - 10th ratios = 0 (off)
Diff Gear Ratio = 3.9 (front diff. ratio)

DIG3 - Speed Measure parameters
Measurement Type = 1 (Speed)
Calibration = 242 (adjusted until speed matched OEM dash read-out)

Speed measurement calibration was the first adjustment made. 241-242 both gave good values between 30-60 mph; 20 mph and below was a hair off, but the reason for this is noted in the MOTEC help files. If wheel/tire size changes, this must be re-calibrated.

Initially setting the Diff Gear Ratio to the front diff. ratio (3.9) would cause me to always show 6th gear when the vehicle was in motion. The problem was I was not adjusting the Tailshaft Speed Cal value to compensate for the number of pulses per rev -AND- the gearing between the front diff. and vehicle speed sensor. My speed measurement was also off by around 10%... but this was not causing the bulk of the problems.

The VSS (19-tooth gear) on this car is driven by a plastic (25-tooth) gear below the ring gear the front diff. The VSS rotates 25/19 = 1.316 times per front axle rotation. Since the OEM VSS provides 4 pulses/rev, the Tailshaft Speed Cal value is 1.316 x 4 = 5.264, rounding to 5.3. The '5.0' value listed above was a guess while I was testing that worked fairly well. 4.0 and 6.0 were completely off, so 5.2-5.3 will likely be the optimal value.

Next thing I'm going to try to do is convert the output from kmh -> mph. I *think* all I will need to do is change the Speed Measure Cal to '150' and adjust the input setting from kmh to mph.

I should note, TC is disabled on my tune, but R drive/ground and L drive/ground will still calculate.

I made one mistake on my previous post - converting to mph from kmh requires speed measure calibration to be MULTIPLIED by 1.609 giving a value of '388'. I mistakenly divided by 1.609 and the value of '150' is incorrect!

This has now all been changed and tested - it works great!

Your TC/setup/ slip calc mode is = 0? My ground and drive speed were always 0 whenever Slip Calc Mode was 0.

Correct.

Ground Speed will not calc/log w/o TC enabled.
Wheel Speed will not calc/log w/o TC enabled.

-however-

R Ground Speed
L Ground Speed
R Wheel Speed
L Wheel Speed

...all log accurately regardless, and the data is the same in my case.