Speedometer...

graham-e · Posted: Thu Jul 15, 2010 11:16 am Post subject: Speedometer...

Just been thinking about what I'm going to do with my dashboard. I wondered if the RJES speed sensor could also be used to drive a digital speedo?

Cheers, Graham.

ElusiveStranger · Posted: Thu Jul 15, 2010 3:10 pm Post subject:

Yes, it's what Brantz make them for!
4 pulse/wheel rev at 5V.

Put that pulse into a box containing "Electrickery(TM)" and you can get a speed reading.
After all Speed is proportional to wheel RPM

Even better, get a car based PC, plug it into the ECU and have a full on Digital Dash. I did exactly that for testing/diagnosis on my set up

ODB-I will give you:
Injector Pulse Width
Coolant Temp
Speed
RPM
Throttle Posn etc

It used to be called "Monitor Select" on the now defunct VWRX site
But Brent Wiede has a linky:
http://www.weidefamily.net/vanagon/Files/B10ScanTool/b10scan.html

Building a TTL -> RS232 interface isn't too difficult
HTH

Edit:

Picture, from Brent's pages:

_________________
The advice you receive on here is worth the paper it's written on.
Your experiences are worth shed loads to others, including the f'ups - live and learn.
Wouldn't YOU rather learn by someone else's mistakes? So would they.

'78 Bay, 2 litre 091 box, EJ20 NA & the ashtray's on the 'right' side.
I don't lean forward for hills any more Grin

Bugger, missed out on "Live fast, die young"

graham-e · Posted: Mon Jul 19, 2010 9:51 pm Post subject:

Interesting stuff..
Bought a car PC job off eBay for £30 so might have to give it a go!
Cheers

graham-e · Posted: Mon Jul 19, 2010 10:27 pm Post subject:

Does anyone know If the signal from the sensor going to give the correct speed output signal to the ECU or Speedometer? Or will it need calibrating?
Thanks, Graham

ElusiveStranger · Posted: Tue Jul 20, 2010 8:54 am Post subject:

If you're talking about the s/w up there ^^^.... when I did the maths, a Leggy has roughly the same tyre radius of a T2. It was something like 5% out IIRC

I can't remember exactly as it was a fair while ago

2πR
πD
_________________
The advice you receive on here is worth the paper it's written on.
Your experiences are worth shed loads to others, including the f'ups - live and learn.
Wouldn't YOU rather learn by someone else's mistakes? So would they.

'78 Bay, 2 litre 091 box, EJ20 NA & the ashtray's on the 'right' side.
I don't lean forward for hills any more Grin

Bugger, missed out on "Live fast, die young"

rjes · Posted: Wed Aug 04, 2010 10:31 pm Post subject:

Yes. The sensor will drive an electronic speedo. I assume you mean an aftermarket, (i.e. multi purpose) speedo? If so, that's easy, as the speedo will have some calibration adjustment to account for different speed sensor specs and tyre sizes, and ytou will be able to set it using something like sat nav as a speed reference.

If you mean an electronic speedo from another production car, you will need to fit a speed signal calibrator between the sensor and speedo / ECU, and set it using an accurate speed reference such as sat nav. I can get the calibrators to order (actually I think I have one in stock somewhere).

If you are thinking of using a Subaru speedo, it needs to be from about 1998 or later (from a car with a 3 wire speed sensor screwed in to the gearbox, not a 2 wire sensor or speedo cable). Some of the other Subaru gauges (particularly the fuel gauge) are far more complex to get working correctly in a VW than the speedo.

The Brantz sensors which Elusive mentioned are intended for Vauxhall / Ford applications, and do not fit the VW cable properly. You have to modify the cable to make them fit. The sensors I stock fit with no mods. I stock sensors to fit bays and T25's, with two options on number of pulses per turn for each (4 pulses per turn is close enought to keep a Subaru ECU happy, but not accurate enough for the speedo).
_________________
Regards,

Richard,

R J Engineered Solutions
Quality Subaru Powered VW Components
www.rjes.com

Doghouse Rielly · Posted: Sun Aug 29, 2010 12:16 pm Post subject:

I have seen beetles with dakota digital dashes
thinking of puting one in my bus they do a variery !
any one done this

rjes · Posted: Sun Sep 05, 2010 2:31 pm Post subject:

I'm not familliar with the details of the Dakota Digital dashes, but they more than likely need a digital speed signal, and have means of calibrating the display to suit the sensor built in. If so, the sensors I keep in stock should be suitable.
_________________
Regards,

Richard,

R J Engineered Solutions
Quality Subaru Powered VW Components
www.rjes.com