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Etb speedo pluses
James300481 - 24/4/17 at 08:45 PM

I'm trying to work out how many pulses to set my etb speedo to.

I need to know the speedometer drive ratio for the standard mt75 sensor.

Haas anyone got any idea?

feckn7 - 24/4/17 at 09:34 PM

The number of pulses will be affected by your diff ratio, wheel size and tyre profile

David

James300481 - 24/4/17 at 09:39 PM

It's a standard 7" sierra diff (either 3.6 or 3.9) and with 195 50 15 tyres.

I contacted etb but they said I needed the speedometer drive ratio to work it out.

mcerd1 - 24/4/17 at 10:02 PM

I believe ford used several different speedo drives depending on what was needed for the car
so which version of the MT75 have you got ? (i.e. what was the donor and what diff ratio did it have? )

failing that you'll count the number of turns to be sure....

quote:
Originally posted by James300481
It's a standard 7" sierra diff (either 3.6 or 3.9)


those diff ratio's are +/- 8% different to each other on there own (that's a lot of error on a speedo)

you need to count the number of turns of the prop you get for one complete turn of the wheels (mark them with chalk to make it fairly accurate)

[Edited on 24/4/2017 by mcerd1]

James300481 - 24/4/17 at 10:06 PM

It's a sierra 2.0 estate mt75, originally had a 7.5" diff but have changed it for a 7"

James300481 - 24/4/17 at 10:38 PM

It's a sierra 2.0 estate mt75, originally had a 7.5" diff but have changed it for a 7"

Huttojb - 25/4/17 at 12:00 AM

Contact ETB - very helpful, I contacted them early this year and they was helpful with lots of information

mcerd1 - 25/4/17 at 06:06 AM

Btw What kind of speed sensor are you using?

quote:
Originally posted by James300481
It's a sierra 2.0 estate mt75, originally had a 7.5" diff but have changed it for a 7"


The size of the diff doesn't matter - there are equivalent ratios in each size

What's important is the ratio as its the only thing that affects the number of pulses per mile you'll get

[Edited on 25/4/2017 by mcerd1]

James300481 - 25/4/17 at 08:55 AM

Contacted etb and the said that they need to know the speedometer drive ratio to work it out.

It's a standard sierra mt75 speed sensor.

The plan was to find out the pulses for both diff ratios and see which one worked on the rolling road when I have it setup in a couple of weeks.

mcerd1 - 25/4/17 at 11:31 AM

quote:
Originally posted by James300481
Contacted etb and the said that they need to know the speedometer drive ratio to work it out.
It's a standard sierra mt75 speed sensor.


All they really need to know is the number of pulses the sensor will give per turn of the output shaft - which depends on the sensor and the speedo drive gear inside the gearbox (which in turn depends on the donor cars diff ratio and tyre size)

if no one else here knows how to ID these on the MT75, then I guess you should be able to hook up the sensor up to a multimeter (or smililar) and count the number of pulses for one turn of the prop.


quote:
Originally posted by James300481
The plan was to find out the pulses for both diff ratios and see which one worked on the rolling road when I have it setup in a couple of weeks.

there is really no need - as above just count how many turns of the prop it takes to get one turn of the wheels - if its close to 4 its a 3.92, if its close to 3.5 then its a 3.62




your tyres should be around 889 revolutions per mile according my calc (or 892 according to some online calcs - but this varies a little with different tyres, some makes even tell you what this is)

then just multiply this number of turns of the wheels in a mile by the diff ratio (probably 3.92 or 3.62) and then multiply again by the number of pulses per turn of the propshaft - and then you have the number of pulses per mile for the ETB gauge

[Edited on 25/4/2017 by mcerd1]

loggyboy - 25/4/17 at 12:38 PM

Just drive it and see what it reads, compare to a GPS reading and adjust, might take 2-3 tries to get it spot on.

big_wasa - 25/4/17 at 05:18 PM

As above.

I can't remember the numbers but I guessed a number for the dip switches. I drove it for a mile using a sat nav. I then worked out the percentage I was out and moved the switches the same.

Job done

se7ensport - 25/4/17 at 05:28 PM

A ford gearbox should normally put out 1000 revolutions per mile, the sensor I'm using puts out 8 pulses per revolution, I've set my speedo to 8000 and just tested it on axle stands; shows approx 62 mph in forth at 3000rpm... this is now close enough to test with a gps and calibrate / fine tune.