I bought a 911 electronic speedo for my conversion that I really want to use. Initially I heard that it was compatible with the Subie VSS in the trans. Since then I have learned that the speedo is 8 pulses per revolution and the Subie is 4 pulses. Is there any way to correct this easily?

I found a couple of options but was hoping for something simpler, and of course CHEAPER :

Convert to GPS:

Livorsi Marine

A little pricey at $179

Universal Speedo Signal Interface

USSI

$84.95...probably the way to go...

Unless there is a simpler way I am not aware of? Just need to double the trans signal to 8X or halve the speedo output to 4X....easier said than done I'm sure.

I don't think it's as easy as flipping a switch or soldering in some resistors.

Honestly, if $85 makes sure that you don't accidentally fry your speedo...I'd say that's worth it.

Not my money though, so I can't say for sure.

It probably wouldn't fry, but it would read wrong...like 50% off...I can't do that much math while driving....

You have a schematic of this 911 speedo?

Install a new VSS wheel with 8 flags on the CV joint with a Hall sensor.

Not a bad idea at all

Another way using one ic chip.

http://freecircuitdiagram.com/2010/05/30/f...bler-with-4011/

Thanks very much for the input!

Sorry Tim, I don't have a schematic for the speedo. It's a 160 mph 80's VDO.

Like both of 904svo's ideas.. Thank you! I'll look into them.

The speedo is triggered by a switch closure, you don't need to use a hall effect switch and it makes it easier since you don't need to supply power to the sensor. I used 8 magnets on the cv joint and a magnetic switch to drive the speedo.

http://phoenixhobbies.com/html/elec_speedo.html

I just did this for about $40. I used this CV grease rind, embedded magnets and used the stock VW sensor on a bracket. I plugged the zerk fitting holes so they didn't hit the sensor. Super easy!

http://www.pacificcustoms.com/ac501930gr.html

Click to view attachment

I just read that thread title "Speedo Dilemma" and had a TOTALLY different vision, and not a pretty one, of a problem with swimwear. Way too early, so careful with that word "Speedo", it can do harm.

Thanks guys for the additional feedback...Paul I followed your build for years BTW....my inner CV is a Subie so I would probably have to do a trigger wheel if I went that way....

And DB - didn't even realize that when I wrote it. No "Speedo" pics will be posted...no worries.

Find a spot on your inner Subie CV and drill some holes. My magnets are 3/16" di and 3'8" long. I will send you some if you can use them. Just drill 4 holes and epoxy them in.

Thanks Mike. I would need eight for the 911 speedo though, right?

You might need 12. 8 for the 911 speedo and 4 for the ECU. You could use both sides of the tranny. Like I said, if you can use them, I'll send you 12.

Thanks Mike. Once I figure out what I'm doing I'll let you know. Really appreciate the offer and help.

I use one of these on my Boxster trans setup. I'm not sure of the pulse output of my factory sending unit, but this is easily calibrated 500-399,999 pulses per mile.
http://www.egauges.com/vdo_ind.asp?Type=Sp...&PN=437-151

I have that programable VDO speedo in my car too, easy, cheap (cheaper on e-Bay) and works great. If you're really determined to use that 911 unit you might also look for a motorcycle "speedohealer" like this:



They're a bit expensive (I think $50 is the lowest price I've seen) and I'm not sure about the range, but call Healtech, who make the most popular one, and see what they can do for how much. Bikes use them because they change sprockets and such a lot, and I seem to remember the bike-motor-into-car people used them to match different engines and gauges. I like the magnets idea best but this might work, I don't know, maybe worth checking.

I spent $20 dollars at the bike shop, got a programable speedometer. Mounted the magnet on the CV, and built a mount for the pickup off the trans flange. Extend the wire and a little math, accurate speedometer.

It would also track the number of calories I burned

Ha ha ha, calories per mile? Very cool, I imagine we could all use one of those.