Speedo Fix for Transaxle Transplant

[MD]

A good number of twin spark transxales are being fitted to earlier 116 chassis only to come unstuck with the speedo not functioning. This is because the nature of the (Jaeger)sender unit signals being incompatible with the earlier (Veglia)speedo head.

To overcome this problem it is possible to do a signal conversion using this device, a Dakota SGI-5 unit.
It is available from the USA at this site:

http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=126/category_id=311/home_id=59/mode=prod/prd126.htm

Keep this in mind. There a two Jaeger senders. Early and late. The early one is a two wire job and uses a supplemnetary device in the guise of a black box under the 75 back seat. The box and the sender have to be wired up in series to the Dakota together to provide the correct input signal.

The later Jaeger sender is a three wire device and is meant to do away with the black box because it now incorporates the black box components inside the upgraded sender itself.

Ultimately both combinations produce the same signal output.

[AR116]

The other possible option is to modifiy the pinion shaft in the gearbox to suit the jaeger sensor that is commonly used in 116 cars such as Alfetta/Giulietta. This requires some machining, where a gear is made to suit the speedo gear for the jaeger sensor.

This saves lots of time from using devices to convert signals from one sensor type to the other, especially if you spend hours trying to make it work and it still fails.
This modification will work to a high accuracy, as when the car left the production line. It will look like a factory mod.
My 1984 Giulietta has a TS gearbox and I wil be doing this modification soon, as i believe this is the best solution to my problem instead of buying universal kits.

regards;
marco.

[MD]

Angelo,

With all due respect, I think you got some of those facts a bit wrong.

The earlier boxes started with a gear driving a very long cable to a mechanical speedo head.
This was later modified by the fitment of a Veglia sender to match the Veglia electronic speedo head. The original gear drive had a mechanical converter (which was availble in different ratios as well) that did the actual mechanical driving of the Veglia sender . A bit like a bicycle generator ( don't take this too literally).

The Jaeger sender is a completely different sender unit to the Veglia one and is energised by a completely different method.

Having said that, I beleive what you had intended to say is that the orignal Veglia sender could be fitted to the twin spark box making it 100% compatible with the Veglia speedo head by installing the original speedo shaft from the earlier boxes making it drive like it use to.

Not the other way round.

The Dakota answer is far simpler and less work.

[116gtv]

thanks for taking the time to post this Mike, will come in handy sooner or later 

[MD]

Thanks Martin. My single intention is to save some grief for people doing these conversions. When I did mine the quest to solve the problem took me two years of leaning on electronic engineers and technicians mates to decode the signal and try to restructure it to make it work with the old Veglia head. This was a rubber boot talking to an empty egg carton or may as well have been 'cause the old and new are like night and day in their differences.
Ultimately, I managed to cobble a circuit together that worked but unknown to me, at the same time, a young Brisbane engineer and Alfa enthusiast solved his own problem in a better way with a more stable circuit. This circuit was ultimately refined. A small batch of converters were made using German VDO gear with the view to market them. Unfortunately due to the high cost of the VDO unit, it just could not compete with the US product that came on stream not long after. Nevertheless, I know one or two things about this problem as a result of all the research which hopefully I have now passed on.

[scuzzyGTV]

Whilst this is a brilliant thread, there is always the problem of people like me, who are really not electronically minded. i'm struggling to understand how this works.

if i may, i'll make myself look stupid: we are talking about running a mechanical speedo from an electronic signal?

you plug this device into the ts 'box and add a few wires (i know it's more involved than that, but i'm a simpleton) to the original alfetta speedo head unit?

insert laughter here

thanks in advance.

scott

[MD]

Early Alfetta GTVs have a purely mechanical speedo head that requires a mechanical speedo cable to drive it.

Later cars have an electronic speedo head that is driven by the same "gears" (if you like ) instead of a cable. Coupled to these gears is an electronic signal generator ( sender) fitted to the gearbox. This sender makes signals that the electronic speedo head can read and make a display.

The twin spark box has an electronic sender that makes signals intended for a later design electronic speedo head. The signals that it sends cannot be read by the original electronic speedo head in the GTV because they are not compatible.

Installaing the Dakota SG-5 makes the translation so that the twin spark sender will drive the GTV speedo head.

If you cannot understand the above, I am at a loss as to what else I can say to you.

[scuzzyGTV]

thanks for that, i can completely and comprehensively understand that. makes so much more sense now.

[Paul Gulliver]

The rubber boot can now speak to the egg carton . Thats all you need to know. Thank you Dakota.

[martym00se72]

So, I just passed up on the option of an LSD today because issues like speedo and shift linkage may be a bit beyond me - and then I read this thread... Would this 'black box' solve the speedo issue, leaving just the issue of the linkage? Is that (shift linkage) easy to overcome for someone who is pretty new to this game? Should I be reconsidering that LSD??? (83 GTV6 BTW)

[MD]

Maybe the question is : Why do I really need an LSD in the first place? If you cannot simply and clearly answer that then perhaps you are just beating yourself up for little gain ??

[martym00se72]

There is that, which is largely why I passed up on it - wasn't on the priority list, just on the nice to have list. The suspension (and what looks to be original shocks) beckons for poly and Koni's...

[Mike]

I have also been looking into this issue.  There is a Jaycar kit according to an electrical engineer mate of mine that may also work.  I am not sure if he has taken into account the rubber boot issue though...  Still it was about 70 dollars.  I'll dig up the details he gave me and throw them up here.  May be of interest.  By the by, For those with mechanical speedos as I have in my GT, they can be swapped with the electrical speedos if you get one of a donor car, the only issue then is that you forgo the original miles (not sure if they are easliy revised).  You probably also find yourself in the situation where you are wanting to retain a blue faced dial instead of the black later version.  This is all interchangable with care.  The only other thing I have noted is that the electronic speedo is deeper than the mechanical one, so may need a mod or two to fit.

Now I'm off ot check out MD's kit!  Sounds interesting to say the elast.

[MD]

Sorry Mike. Been there. We couldn't make it work. Real pity. Still got the gizmo on the shelf.

There is a VDO unit made in Germany that can be used to do the translations but at last enquiry it was $220 AUD plus other components to go with it and labour on top to make it and test it and calibrate it.

However ,by all means have a go. You may just crack the davinci code. 

[Darryl]

MD, I don't suppose anyone has put a CRO on the output of the SG-5 to see what it produces that approximates the original transducer well enough to make the original speedo happy?