speedo drive output

[GrahamU 5]

Hi,

 

How many turns does the speedo drive do for 1 revolution of the diff/driveshaft.

 

I've just bought an 02s that doesn't have the speedo drive and I'm thinking of converting to speedo from the abs

[GrahamU 5]

So the 02s box I bought of ebay turned out to be an 0a4 5 speed... grrr, and theguy of ebay would only refund the price of the box if I returned it and not the shipping costs so I would be £100 down on a box I gave 200 for so I have decided to try it unless another 6 speed comes my way.

 

The 0a4 doesn't have a speedo drive either so I still needed to know the output from the VSS.

 

So I had a play with a VSS today, unfortunately the car is in the garage in bits so I didn't get any live data so what I have found was done on the bench.

 

Started of by powering the VSS on a 12v supply and monitored the signal pin on a osciloscope, got nothing at all no matter how fast I span it.....

 

School boy error, the VSS signal line gets the voltage from the cluster (5v I beleive) and as the sensor turns it shorts the signal line to ground, giving you a square wave pulse.

 

For one revolution of the VSS you get 4 pulses.

 

Fitted the VSS back to the gearbox and turned the output shafts together, tried this several times to be sure and got a constant 10 pulses per full revolution of the driveshafts

 

With 205/40/17 tyres fitted I will get 859.9 revolutions per mile (figure taken from http://www.rimsntires.com/specs.jsp?item=Wheel-Tire size comparer&sw1=205&ar1=40&bd1=17&rw1=7.5&et1=51&sw2=195&ar2=50&bd2=15&rw2=7.0&et2=45&text1=&text2= ) so I should see 8599 pulses per mile.

 

So my next challenge is to convert the output from an ABS sensor to give me the same ammount of pulses.

 

 

If someone has found anything different to this I would be interested to know as I wont know if I got it right till the car is back on the road

 

 

Update:

 

Using a signal generator and a simple transiator switching circuit, I put a square wave signal into the cluster ans found the following:

 

Most odviously I noticed the Hz setting on the signal generator matched the KPH seen on the speedo, so 10Hz = 10KPH, 100Hz = 100KPH &160Hz - 160KPH

 

Converting that to MPH:

160KPH = 100MPH so 100MPH = 160HZ

 

1Hz = 1 Second so 100MPH there are 160 pulses in every 1 second

 

That means 160x60=9600 pulses in 1 minute

 

and 9600x60=576000 pulses in 1 hour @100mph (continuous)

 

so 576000/100=5760 pulses in 1 hour @ 1mph (continuous)

 

Working that back, there are 888.3 revolutions of a 195/50/15 tyre in 1 mile

 

then 5760/888.3=6.48 pulses from the VSS for 1 revolution of the wheel (not the 10 I thought above)

 

 

I hope I have it right this time

Edited February 16, 2013 by rado20vT

[science 0]

Would love to see this work out, but wouldn't it be easier to re-case the gearbox, or fit the diff speedo gear and machine the case to accept the VSS?

 

Also, what are the ratios like on the LHE box? O2S ratios are a bit short for turbo motors.

 

---------- Post added at 2:31 PM ---------- Previous post was at 2:23 PM ----------

 

and theguy of ebay would only refund the price of the box if I returned it and not the shipping costs so I would be £100 down on a box I gave 200

 

Was he business seller if so Distance Selling Regulations should apply. £200 would have been a right bargain had it been O2S, I haven't seen one on eBay for less than £400 in the last year.

[GrahamU 5]

Hi Science,

 

The ebay guy looked to be some sort of part time breaker, only had one car in his barn that he was stripping and a few parts from previous cars, sounded like a traverler when I spoke to him so didn't reallywant to persue it. But yeah, 200 would have been the bargain of the year for an 02s 6 speed

 

have thought about the re-casing the box but I've never stripped a box and dont want to pay for someone else to do it. I work in electronics so making a circuit to do this wont be to bad.

 

The box I got is a LHW, ratio's are similar to a mk3 tdi box, see below

 

Final 3.64 1st Gear 3.778 2nd Gear 1.944 3rd Gear 1.185 4th Gear 0.815 5th Gear 0.625

 

60 in 5th would be 1959 revs (with the 205/40/17 I have)

 

Looks ok in gears 1 to 3 with 96mph @ 600rpm in 3rd but 4th and 5th are quite tall, I'll see how it goes when its running

 

02s tdi box would work ok I think, these are the gearings I've found so far

 

code final 1st 2nd 3rd 4th 5th 6th

gqm 3.389 3.7778 2.2667 1.524 1.1071 0.875 0.725

gqp 3.647 3.7778 2.2667 1.524 1.1852 0.9667 0.82

gxv 3.9375 3.7778 2.2667 1.65 1.2692 1.0345 0.8649

hyg 3.647 3.7778 2.2667 1.524 1.1852 0.9667 0.8158

jau 3.647 3.7778 2.2667 1.65 1.2692 1.0345 0.8649

jcl 3.389 3.7778 2.2667 1.524 1.1071 0.875 0.725

jcn 3.647 3.7778 2.2667 1.524 1.1852 0.9667 0.725

jcp 3.9375 3.7778 2.2667 1.65 1.2692 1.0345 0.8649

jcq 3.647 3.7778 2.2667 1.65 1.2692 1.0345 0.8649

jwn 3.647 3.7778 2.2667 1.524 1.1071 0.875 0.7333

jxr 3.647 3.7778 2.2667 1.524 1.1852 0.9667 0.8158

jxp 3.647 3.7778 2.2667 1.524 1.1852 0.9667 0.8158

jyg 3.647 3.7778 2.2667 1.65 1.2692 1.0345 0.8649

jyj 3.647 3.7778 2.2667 1.524 1.1071 0.875 0.7333

jyl 3.9375 3.7778 2.2667 1.65 1.2692 1.0345 0.8649

kvt 3.647 3.7778 2.0625 1.4545 1.1071 0.875 0.725

kvv 3.647 3.7778 2.2667 1.524 1.1852 0.9667 0.8158

kvw 3.647 3.7778 2.2667 1.524 1.1071 0.875 0.7333

kvy 3.647 3.7778 2.2667 1.524 1.1852 0.9667 0.8158

kvz 3.9375 3.7778 2.2667 1.65 1.2692 1.0345 0.8649

kwa 3.647 3.7778 2.2667 1.65 1.2692 1.0345 0.8649

kwb 3.647 3.7778 2.1176 1.36 1.0294 0.8571 0.7333

mcb 3.647 3.7778 2.0625 1.4545 1.1071 0.875 0.7333

mdp 3.647 3.7778 2.0625 1.4545 1.1071 0.875 0.725

mue 3.647 3.7778 2.0625 1.4545 1.1071 0.875 0.725

muf 3.647 3.7778 2.0625 1.4545 1.1071 0.875 0.725

[science 0]

Nice list! Many codes I haven't seen before.

 

I've gone with the longest box i could find GQM.

With the VR6 there's lots of driven comparisons on people changing final drives to 3.6 or 3.9 ratio, as it just so happens the gears 1-4 are similar variations;

 

Gears 1-3 will be aprox of having 3.9 final drive

Gear 4 equates to 3.6 final drive

Gear 5 is same as VR6

Gear 6 is for cruise.

 

It should equal rapid acceleration in the vr6 plus a nice overdrive gear.

 

Somewhere, I've got a ton of graphs I made before deciding on this box which really shows the difference (for standard wheels).

I really should get on with this build its almost been a year now.