SDV - SVA on Monday Help!!

[Salty]

Hi Got SVA on monday morning can any one help!!...

I set speedo up ages ago (SDV so (on westfields advice) sensor taken of front of prop as it comes out of gearbox). I tested it roughly and was at the time happy as it registed about 10 mph up my short drive.

The problem is today was the first time I tested it on the road (copper who lives on the corner on holiday) and it went of the guage. Have any other SDV Builders sucsesfully mounted the sensor here ? If not has anyone mounted sensor taking reading from  propshaft to dif bolts and if so do they have the figure to be used when calculating the pulse setting..

Yep i know ive left it a bit late................

Dave

[Stevo]

This has been asked a couple of times and I think that most people mount the sensor at the diff end of the prop as the gearbox end moves around too much / has too much metal flying around to give a decent reading. Also I think that some people had problems with interference from other wires in the loom and had to route seperate wires to the back of the speedo itself.

I used a bike sensor with magnets on the rear drive shafts and this works well.

The speedo calcs are fairly easy to work out but even then mine still under read at SVA, but the tester adjusted it for me.

good luck for Monday.

Stevo

[Salty]

Cheers Stevo,

I think i'll try running some sepearte wires first if that fails I'll try mounting furtherback and take reading from dif bolts (spoke to westfield today and all they advised was get it as close as you can to the prop without hitting it!!

I all else fails i'll say at the test that is was working fine ! better to pay the 30 quid or so for the retest than to cancell at this stage...

[NEW SS1]

A speedo isnt required for an MOT.. is it required for SVA test?

Mine has not speedo and went straight through the MOT but as I am the 4th owner of it I've no idea about SVA tests.

Dan

[Barry Ashcroft]

Yes a speedo is required for sva and it must not underead you are allowed a slight overead.

Salty what is the transducer attached to is it attached to the gearbox so can move with it to keep the distance constant or is it attached to the chassis if so the distance between prop and trans will alter with movement. Mine is fitted over the rear lobro joint bolts and has to be so close that it nearly touches in order to work properly.

Barry  

[miserableoldgit]

Mine's a Pre-lit with live axle; Westfield told me to mount mine off the chassis rail beneath the gearbox end of the propshaft and sense off the lobes of the Hardy Spicer joint.

Distance from sensor to joint = 3 mm

Movement of rear of gearbox on monting = +/- 12 mm

First sensor lasted all of 500 yards!   Second sensor now mounted off tailshaft of gearbox on homemade clamp.

Works fine up to 80mph then it goes all wobbly, but then so do I at that speed!

[Salty]

Barry,

It is attatched to the chassis rail behind the gearbox that crosses the transmission tunnel and so yes it is rigid. I see where you are coming from though, I might try to fabricate a bracket that moves with the gearbox and so keeps the gap constant.

although at 120 tomorow night i might try anything...............

Dave

[david matthias]

Hi

My SDV has a bracket welded to the chassis as in the photo from Barry. I fitted the sensor there & it then senses of the bolts that hold the lobro to the diff so there is no movement between the two. It is also where the wires appear out of the loom. The sensor I used meant that it almost had to touch the bolt heads a real fiddle to get right but ok in the end. The Calculation I used is the one for true speed although westfield initially said use the 3% higher figure. Having used the true speed figure at sva it read 1mph over all the way up.

worth mentioning that I have aetb instruments but I'm fairly certain the settings are the same.

Calcs to be 3% fast

195/50 tyres inflated to 20psi rolling circumference 69.3"

revs per mile 914

369087 divided by 69.3" = 5325.93

number of pulses to be entered into speedo 005326

Calc for true speed

195/50 tyres inflated to 20psi  rolling circumference 69.3"

380160 divided by 69.3" = 5485.71

number of pulses to be entered into speedo 005485

hope that helps

David  

[wookie]

depends what drive shafts you have, mine are the pop-in type for rear drums, i used the diff to prop bolts to pick up the signal from, the gearbox end i tired and wiped out the transducer with the movement of the gearbox on its mount, plus there really wasn't much of a good signal to pick up from.

[Salty]

Just Finished,

Bag of tools and bits filled, and the Car is as ready as its gona be for SVA in the morning.

I moved the sensor and made up a bracket so it now picks up Dif to propshaft end of propshaft. Speedo now seems a bit more realasistic (ie doesnt show 140 in first)

Out of interest does anyone know the ratio of a standard seira dif, just so I can check my calculations....

Cheers

Dave