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Posted by: Wasa914 Oct 20 2003, 11:49 PM

I'm a newbie to contribute but I have received a bunch of information from this board in the past which I am very grateful. Just wanted to share what I learned.

I am using a VDO electronic speedometer and have seen alot of innovative ways to send the electronic signal via the 901 trans. My solution is to cut off the slotted key end of the speedometer cable that fits the angled trans cable driver. Drilled out the cable hole and sodder in a shortened square key drive that is in the standard GM VDO sender. I had a machinist do this and make a bushing that will center the slotted cable end in the GM sender. The GM sender has a threaded nut that will fit the 901 angled cable driver which is amazing because I thought it wasn't meteric. Hopefully this picture will appear.



Philip
'73 914 still in transformation

Posted by: 914Timo Oct 21 2003, 12:18 AM

Great info. Many thanks.

Posted by: kafermeister Oct 21 2003, 05:40 AM

Did you make the adapter piece in the middle?

Posted by: John Jentz Oct 21 2003, 09:59 AM

What happened to the picture? All I get is an X.

Posted by: Wasa914 Oct 21 2003, 10:15 AM

Sorry about the picture. This digital thing is new to me. I'll try to reformat it.

The middle piece is the end of the speedometer cable attached to the square key that comes with the GM sender.

Philip

Posted by: Wasa914 Oct 21 2003, 12:57 PM

This is my try at reformatting the picture.
\
Philip

Posted by: Wasa914 Oct 21 2003, 12:58 PM

I'll have to start a new topic and post it.

Philip

Posted by: seanery Oct 21 2003, 01:16 PM

here it is.


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Posted by: SirAndy Oct 21 2003, 01:27 PM

that's schweet!

i already have the elec. speedo (actually my 944 speedo is both!), that seems like a good/easy solution.
how do i adjust a elec. speedo for different tire sizes?

Andy

Posted by: ss6 Oct 21 2003, 02:35 PM

Search the Pelican 911 board for "speedo" and / or "calibration", plenty of how-to's there.

Posted by: Lawrence Oct 21 2003, 02:38 PM

Is the signal for an electronic speedo sent via wire or some type of wireless comm?

If it's wire - what's the overall benefit for our cars? After all, we still have an ugly cable beneath, just waiting to be cut by debris, burnt by exhaust, etc.

Curious,
-Rusty

Posted by: SirAndy Oct 21 2003, 02:55 PM

less rotating mass

Posted by: sleepdoc Oct 21 2003, 04:12 PM

Hi nice tinker!

Please tell us a bit more about the centering bushing. A pic would be great.

And do I understand correctly that the smaller square drive key part came with the sender part?

thanks Mark

Posted by: sleepdoc Oct 21 2003, 04:22 PM

Hi,

One more question.

The GM sender is a 16 pulse per revolution.
This recent post

http://www.914world.com/bbs2/index.php?act=ST&f=2&t=5400&hl=speedo

suggests that the 911 VDO speedo wants 8 pulses. Are you using a programable speedo? or is this setup working with a 911 speedo correctly?

thanks Mark

Posted by: Wasa914 Oct 21 2003, 11:31 PM

The bushing is a hard plastic. It not only centers the slotted key, it also seals between the sender and angled cable drive. The small square key came with the sender and was almost cut in half, then solder to the cable end. The long axis play is not limited, there is 2 to 3 mm of play. I will try to enclose a picture.


Attached image(s)

Posted by: Wasa914 Oct 21 2003, 11:47 PM

I forgot. The sender is for a programable VDO speedometer and not for a 911. Hopefully this is a better picture.


Attached image(s)

Posted by: sechszylinder Oct 22 2003, 02:01 AM

hi Philip,

this is a great setup, but I have a question concerning the sender: Is this part made by VDO or GM ?


Benno

Posted by: Wasa914 Oct 22 2003, 07:58 AM

Benno,

The sender is made by VDO and made to fit all GM trans. In the first posted picture, the blue box has the part number on it.

Philip

Posted by: 914Timo Oct 29 2003, 02:37 AM

Nobody seem to answer to the sleepdoc´s question. If this GM sender gives 16 pulse per revolution, but
the 911 VDO speedo needs only 8 pulses per revolution, doesnt the speedo show double the speed ??

Could somebody confirm this sender really works with 911 speedo ?? I mean, is there anybody who have this combo in his/her car ???

I just would like to know this for sure before I go and by one.

Posted by: sechszylinder Oct 29 2003, 02:50 AM

hi timo,

I guess that it will double the readout, if you double the pulse count.
Philip is using the programmable VDO speedo which needs 16 pulse per revolution.

To half the pulse rate is pretty easy using a small electronic circuit.

benno

Posted by: Steve Oct 29 2003, 05:03 PM

I got a degree in electronics 20 years ago and pretty much forgot everything.
Do you by chance know the components and schematic required to drop it from 16 to 8?

thanks,

Steve

Posted by: sechszylinder Oct 30 2003, 03:18 AM

hilow steve,

you could simply use a 74ls74 d-flip-flip . You have to convert the voltage level coming from the sensor
to TTL-Level. The output of the flip-flop must be converted to 0-12v level to drive the speedo. Here you
can use a 2n2222.
Another idea is to use a small microcontroller, so you can something more than only half the puls rate. ...

benno

Posted by: ss6 Oct 30 2003, 10:57 AM

Been watching this thread with a little curiosity, since I posted a how-to a few weeks ago on rigging a 911 speedo with a homebuilt sender.

A GM/VDO sender will cost at least $75, you'll have fab an adapter to attach it to the tranny right angle drive, and now it looks like you may have to build a circuit to divide the pulse train in half. To each his own, but why is this more desirable than a $30 sender and hacksawing some scrap iron?

Posted by: sleepdoc Oct 30 2003, 05:58 PM

Hi ss6,

Some solutions are completely functional and cheap.
Some solutions are beautiful, engineered, funtional, and expensive.
Some solutions appeal because they are elegant.

Many of the mods we do to our teens are of the first variety
like the BMW320 front calipers.

Some for the fortunate are of the second type like James' beautiful
RennShift.

This mod is just plain elegant, using off the shelf parts in a mix and
match way to get rid of a long revolving cable and an old and cranky
mechanical speedo. (I have to rap mine just so to get it started).
It also offers the advantage of allowing the adjustment of the new
speedo for different wheel size with a signal adjuster like this.
http://www.abbott-tach.com/era.htm .And with this ratio adapter
a later model porsche electronic speedo will work correctly.

Desireable ? It is in the mind of the desiree. There is no question
that your solution is functional and is a very impressive piece of
engineering and I followed your thread closely, but I was already
trying to find a sensor that would fit on the 901 speedometer
output, and Wasa914 verifying that the gm sender physically
attaches to the 901 makes me want to opt for the drill, cut solder,
etc instead of the cut grind bend bolt etc.

You da man! with the custom sensor and the metal fins.I was wowed
at your solution and would have implemented it if this other idea had not
surfaced.

I appreciate both you and Wasa914 posting your stuff, what an incredible resource this is.

best Mark

Posted by: Steve Nov 1 2003, 12:33 AM

WOW $145.00 for the ERA controller.
It looks like a perfect solution for electronic speedo's but why so expensive??
This web site is a wealth of information and I appreciate all the help and diferent ways of doing it.
I just won an Electronic 911 speedometer off of ebay.
I still have my TI TTL cook book from college.
I will look up the 74LS74 in my book.
I will also visit my local radio shack and check out my options.
I also love the ingenious way of bending scrap metal and using a sensor.
I remember something similiar to this in the early 80's for cruise control.
Except they had a conductive strip that wrapped around the axle.
This strip had metal pieces sticking out similiar to SS6's solution.
It would be interesting if you could use one of the cruise control kits and kill two birds with one stone.
So many choices so little time and money.

regards,

Steve

Posted by: ss6 Nov 1 2003, 08:08 AM

You don't need the ERA controller if you're willing to open up the speedo and tweak the pot inside.

Posted by: Steve Nov 1 2003, 10:20 PM

If you use the GM sender with the 16 pulses can you tweek the 911 speedo to work with it since the 911 speedo is expecting 8 pulses??

regards,

Steve

Posted by: ss6 Nov 1 2003, 11:12 PM

Steve,

I don't know if the 911 Speedo has enough adjustment range to accommodate 2:1+ "tweakability", kinda doubt it without changing some its timing circuit components.

Suggest searching the Pelican 911 bbs for speedo calibration, those guys have been up and down that topic at least once.