[Mk2] [Turbo] Rev 1 tubby standalone speedo and P/S issues

[Mike N]

I though I should start my own thread on this one instead of tagging on to someone elses post.

I have been fitting a standalone VDO electronic speedo during last night & today, but still want the P/S to continue working.

I also have an aftermarket steering wheel fitted, that prevents the P/S from working untill the car is driven forward about ten feet.

I think that both issues may be related?

The car is a Rev 1 tubby - cable driven into a Hunter double drive which converts mech drive into an electronic pulse for the aftermarket VDO Speedo.

Any thoughts or help on the OE wiring to keep the PAS as it should would be apreciated. Are there some cables that need joining together to bypass the above?

Thanks
Mike.

[toxo]

The P/S needs both the speed signal and the steering wheel position signal to function correctly, but as you're finding, without the steering pos. signal it works once it realises the vehicle is going along. Without the speed signal it doesn't function at all

I guess you have an aftermarket boss which has removed the steering wheel position sensor? There's a ring gear on the end of the stock boss that goes through a 'reader' to calculate turns of the wheel.

I helped someone else out with a similar problem here, maybe that will help you:

http://www.imoc.co.uk/forums/viewtopic.php?t=133166

Be careful with the signal you send to the PAS as it also goes to the ECU. It will need to be correct for some things to work - the steering assistance provided varies dependant on your speed, and cuts out all together past 50mph. When people fit rubbish speedo converters this causes the PAS to assist all the way up to 80mph which can make for a light front end amongst other things. It's also this signal that the ECU uses for applying the speed limiter etc. So it can be desirable to send a different signal to one than to the other, or to use a clamping delimiter like Stef's ones.

[Mike N]

Thanks toxo,

I had a look through the link.

So I need to get an original steering wheel & cut out that senser and fit it to my Ford steering boss.

As for the speed sensor that is normally at the back of the OE speedo, I will cut up an instrument cluster leaving the OE speedo attached and fit it under the dash out of sight, but plumbed into the loom along with the speedo drive attached to ensure it sends the correct signal to the P/S ECU.

I cant post pics here, but could email some if anyone would like to see my way around the P/S problem now that I know what I'm looking for, or take a look on www.banham200.co.uk in Mike's gallery. I will post some up there later today most probably.

Cheers so far!
Mike.

[Mike N]

Update,

All of the above has worked out fine except:-

Due to the VDO speedometer having an electronic feed, it goes to max (150mph) as soon as the P/S starts working and when the steering wheel is turned, even though the car is doing 5 mph in first gear! The P/S signal is basically messing up the signal to the speedo.

On to plan B tommorrow.

[Stef Derner]

How many pulses per rev of the cable does your VDO signal generator send out? You could slave this to your ECU if it is four per rev.

The ECU gives out 5V, this is grounded by the reed switch in the rev 1 speedo, four times per revolution of the speedo cable. The ECU then sends out the signal to the power steering. I don't see how this can be screwing up your VDO speedo unless you are getting crosstalk between the cables. Try to route the VDO speedo cables separately to the rev 1 speedo head and make sure there is a screen between them.

150mph sounds like a lot of pulses though, on a rev 2 MR2 speedo that would be about 140Hz.

[Mike N]

I dont know what the signals per revolution are, I will ask at VDO, I thought is was 4 though.

The electronic drive goes from the OE cable into the Hunter drive box and through that into the OE speedo, the VDO runs great when the power steering doesnt. IE when the veh is safely jacked up and chocked on the driveway or the OE speedo is disconected.

I tried to move the OE speedo away from the VDO unit (12 inches or so) but I still had the same problems.

My next plan may well be to remove the VDO speedo internals and fit a UK spec MR2 head into the casing through the VDO speedo card, a bit of jiggling I know, but thats kit cars! At least then I will know the speedo is correctly geared and that the P/S works properly.

Mike