Board logo

SVA retest fail
richwill - 29/4/09 at 11:39 AM

Car failed on retest this morning due to the vapor speedonot being calibrated corrrectly. I had asked for this to be done yesterday while it was on a rolling road. The guy assured me that it was reading correctly when i collected it.
However when the guy tested it this morning the readings were all over the place.
The readings were actually dropping as the speed was increased on the rollers.

Does anyone have any ideas?

I have shortened the speedo sensor cable and resoldered it. Would that be a problem.

irvined - 29/4/09 at 11:41 AM

What type of sensor are you using?

nitram38 - 29/4/09 at 11:46 AM

Where is your sensor located?
Remember that your diff will vary the speed on your rear wheels on rollers as one plays catch up/lead etc.

richwill - 29/4/09 at 11:47 AM

I have fixed the magnet to the rear drive shaft and mounted the sensor on a bracket fixed to the diff casing.

mad4x4 - 29/4/09 at 11:51 AM

Really needs to drive off the Propshaft as on rolling roads boath wheels could turn at different speeds due to the Diff.

I set mine up on the Prop then put the teh speedo in claibrate mode and drove it 1 mile on GPS then checked it against GPS.
(on private roads - offcourse)

tomgregory2000 - 29/4/09 at 12:07 PM

bracket flexing too much and not picking up on magnets

bbwales - 29/4/09 at 01:35 PM

I had the problem when i fitted the pick up and magnet to the diff, I had to move it to the drive shaft. apparently the system couldnt count quick enough, once fitted to the drive shaft it did resolve the problem.

Regards

Bob

02GF74 - 29/4/09 at 01:41 PM

quote:
Originally posted by mad4x4
Really needs to drive off the Propshaft as on rolling roads boath wheels could turn at different speeds due to the Diff.


yes they can. SVS has separate rollller for each wheel. I had draging brake which messed up the speed; sensor was on rear RH wheel.

I had to get document from a rolling road, has 1 roller, for the speedo.

since the test, I found out the cause of the dragging brake.

wilkingj - 29/4/09 at 01:48 PM

Yep... do it on the propshaft, or you could be going faster round the corners! (or slower)

I ended up with a electronic sensor in the gearbox (Rover LT77). which works well after I calibrated it.
I measures the tyre circumference, did the maths on the gear ratios, worked out mph per 1000 rpm in top gear. Then fiddled with the switches on the speedo until I got the right reading.
SVA Man said it was spot on at 30 AND 70. which surprised both of us.


Definately agree.... on the propshaft.

richwill - 29/4/09 at 01:54 PM

looks like i will be repositioning the set up to the propshaft then.

watsonpj - 29/4/09 at 04:41 PM

I hade the same problem at my SVA worked fine at low speeds and then got steadly more inaccurate and then at 50 dropped to nothing. The cause was the separation of the sensor to the magnets. I adjusted closer for the next test and stiffened the bracket (it was bouncing around by about 1-1.5mm ) and it was fine