gear detection setup.

[stevieturbo]

Ive tried this a couple of times with the M800pnp following the instructions, but it just doesnt seem to work right ?

It isnt essential that it does work, but I'd like it to.

Ive entered the ratios, and using Digital input 1 as the road speed sensor ( LG Speed ) which is hooked up to the OEM speedo drive on the front diff/gearbox ( Subaru )

Any pointers ?

Gear method 1
Ive tried entering the maths in the help file for tailshaft speed cal, doesnt seem to work for me
3.9 diff, 225/45x17 tyres = approx -300 value

In gear ratio's, should I enter the diff value, or 1 ?

[Greenlight]

I've tried it too.

It has never worked for me either.

I even sent the file to Motec for them to look at and let me know what was wrong.

They made a few suggestions. I tried everything they recommended (and more), but still "no dice".

[SportsCarRacer]

Works fine for me....calcs reliably and quickly after change. Using dig1, with digital input going in. Was using hall effect on tailshaft, but now using factory mazda sensor, mag, after is is filtered by the cluster from mag signal to 5v dig signal.

I have made it work in many cars...in fact, every car i tune....

Are you sure your signal is a nice square wave going into the dig1? Have you looked at it with a CRO?

Else, it just works...i'll try to past some settings, because your setup would be analagous to mine (ie: measuring speed prior to final drive ratio, ya?)

T.

[MarkMc]

As long as you can provide the correct gear ratios and tyre diameter and the number of teeth, etc there should be no problems. I, also have set this up many times without problem.

The ECU is fairly tolerant of mistakes and will choose the closest gear even if its calculation is a little out (i.e. you tyre diameter is not quite correct). If you have something miles out it will not work.

If you include the actual ratios and you can verify that the wheel speed reads correctly then it should not be too hard to work out. Better still if you can also provide data logging with the speed and RPM this can help to be able to verify the ratios are correct.

[stevieturbo]

So in the case of a typical Subaru with 17" wheels, and speed measured on Dig 1 from the factory speedo location...what should the settings be ?

Is that deemed a tailshaft speed measurement ? It would be taken off the mainshaft, but before the actual crownwheel as far as I know.

I do have an ok speedo signal, and it is accurate ( although TBH it is quite an erratic one when looking at logs, although it maybe just has poor resolution. Not actually sure how many teeth/pulses the sender has )

[OmarK]

Below are the instructions from the help menu in the digi1 speed measure parameters to come up with calibration number. Depending on which WRX you have the calibration number will be different.

FOR SPEED MEASUREMENT

Enter the number of pulses per (Display Unit / 10).
Display will be in Display Units / hr.

eg. If the display is to read in km/hr then enter the number of
pulses per km/10 (ie. per 100m).

FOR WHEEL SPEED MEASUREMENT

Calculate the calibration factor as follows :

1(a) Measure the rolling circumference

Measure how many times the wheel rotates over a measured
distance (eg. 100m) then divide the distance by the number
of rotations then convert the answer to the desired speed
units (ie. km or miles).

eg. 52.5 rotations over 100m and the speed is to be
displayed in km/hr

rolling circumf. = 100 / 52.5 = 1.905 metres = 0.001905 km

1(b) or Calculate the rolling circumference

Multiply the rolling diameter of the wheel by 3.141 (PI)
then convert the answer to the desired speed units (ie. km
or miles).

eg. Rolling Diameter is 0.62 metres and the speed is to be
displayed in km/hr.

rolling circumf. = 0.62 x 3.141 = 1.947 metres = 0.001947 km

2. Calculate the Calibration Factor

Calibration = Number of Teeth / (10 x Rolling Circumf.)

eg. For a rolling circumference of 0.001947 km, 24 teeth and
km/hr speed units.

Calibration = 24 / (10 x 0.001947) = 1232

Note : If the speed is measured on the tail shaft then the
calibration number should be multiplied by the diff ratio.

Note : If the front and rear wheels have different circumferences
or a different number of teeth then separate calculations
must be done for the front and rear wheels.

Note : The time measurement resolution of the speed measurement
system is 1usec. This limits the resolution to which the
ECU can measure wheel speed at high speed. The more teeth
on the measuring wheel the less resolution at high speed
but the faster the update rate at low speed.

For example a 60 tooth wheel at 300km/hr would typically
have a resolution of about 1km/hr. If the number of teeth
were 12 then the resolution would be 0.2km/hr. At lower
speed the resolution is proportionally higher.

[stevieturbo]

The subaru sender has no visible teeth in the sender unit. IS the 24 you used just a generic number for the purposes of the maths, or do you know how many pulses per rotation the Subaru sender has ?

A simple drive along in each gear and hit "calibrate" function would be easier lol after inputting ratios etc.

thanks

Stevie

[OmarK]

The 24 teeth is just for demonstration only, the calibration number on a standard factory car is 264.