Dino Tacho and MSD 6A ignition

Why do you want to use an MSD box? At a fairly low rev point they go to single spark anyway.

While some people on the Pantera forum have found MSD boxes to be reliable, many guys carry a spare in the car because failure rates are pretty high.

Yes, you will need an adaptor because of the wave form of the impulse from the box.

 

yakks21,
Are you triggering the MSD with points? Try putting the brown wire from the tach directly to the points connection at the distributor and see if the tach works then. If that doesn't work, perhaps Adrian LeHanne will chime in. I haven't tested the output of the tach output on the MSD to see what it looks like, so I can't comment on that output. However, if enough current is going to the points, the square wave produced at the points should be strong enough to trigger the tach. Fred

 

I am using an MSD 6AL-2 in a Marelli box with no tach adapter and it works fine, just did a 2000+ mile R/T to Monterey;
1) the grey wire is my tach output but length adds resistance so shorten the wire length as much as possible.
2) Sounds like you've checked tach output at the gray wire of the MSD, right? Now make the same measurement behind the dash. many times wire between tach and box will have unseen breaks.
3) Make sure the rear of your tach has clean connectors, especially the Tach input, Ground and 12V which all have spades that tend to corrode

 

Also have had an MSD (with its guts put into a Dinoplex enclosure) with no changes to distributor (i.e., still points based) and NO tach adapter. Has been super reliable for the last 4 years.

 

Yes, the signal to the points should work, providing MSD designed in enough current to the points. I use a 35 to 40 ohm resistor (18 ohms on 6V units) to ensure there is enough current to keep the points clean and this is small enough that when the points open that the signal is strong enough for any tachometer that requires a 12V square wave. MSD would need a separate tach output to simulate the points because it can be triggered magnetically too. Also the multiple sparks at low rpm means that would have to be factored out of the equation. That makes for some extra complication to achieve the same result a piece of wire does with a more simple system triggered only by the points. On some cars, it's very important that enough current is run through the points or otherwise a greyish paste will form that insulates them. I don't know if the Dino is one of those cars, or how much current the dinoplex or the aec103 put through the points, but I know that it should be at least 400milliamps to work universally.
A word of caution. You need to be careful that if you switch back to standard ignition that the tach signal does not experience the high voltage it would see if connected to the points. I would attach it upstream to the MSD points wire, so that it is out of the circuit if switched to standard ignition should you go with this method. I do not own a Dino, so I can't say for sure. I haven't run across a tachometer yet that would fail if subjected to the higher voltage signal when it was meant for a 12V square wave, but it's probably not worth chancing it on a car of that calibre with inflated parts prices. The Veglia tachometers of the same years on Fiat Spiders would only accept the higher voltage of the Kettering system and need a tach adapter of some sort if the only output is a 12V square wave. I'm surprised the Veglia tach in the Dino does not accept both kinds of signals, but some VDO tachs of the era were the same (12V square wave only). Amazingly, some of the best tachometers were the early AC tachometers that went into GM cars of the early sixties. They would accept any voltage and were self powered from the trigger wire. Anyway, good luck with it, Fred

 

Jakxx21,
Not sure exactly what you would like drawn. The points only see high voltage when they have to break coil current. The coil is an inductor. The high voltage (about 200 volts or more) is from self induction. It's exactly the same sort of thing (to use an analogy) as water hammer. If you slam a downstream valve closed very quickly stopping a column of water moving in a pipe, the pressure at the valve will rise much higher than the pressure required to move the column of water in the first place. When points are only used to trigger a CDI or other electronic ignition, there is no inductive component that would cause self induction and raise the voltage, so the voltage only rises to battery voltage when the points open. Adding inductance is like making the water pipe longer in the analogy. The inductance is a bit like giving the electrons more mass. Does my poor analogy make sense? Tell you what, email me with a more descriptive request, and I'll get back to you. If it looks useful for the forum, you can repost it here. My email is [email protected] Thanksgiving here in Canada, so I'll be up to my armpits in Turkey tomorrow, so if I'm slow replying, that's why. Thanks, Fred

 

My apologies-- I assumed you we no longer using the points and had replaced them with a more accurate system. I have only bad memories of points and condensers.

 

What Fred isn't telling you is he makes one of the best, if not the best replacement points CD ignition unit that replaces the Dinoplex plug and play. I'm not buying or selling. I just want as many vintage Dino and Ferrari owners to know what he's doing for us. We're fortunate to have Fred and Adrian on this board.

I have on of the first Winterburn CD ignitions on my Dino http://www.ferrarichat.com/forum/206-246/276251-rebuilding-dinoplex-aec103a-10.html

My ignition is stock with points and have had ZERO issues with it. Totally reliable and starts right up hot or cold.

Freeman

 

Adrian LeHanne has been down this road before. If you can't find a substitute tach, Adrian has designed a board that you can build. Tacho Circuit Board Replacement for Classic Tachometers

 

Where are you?
RHD or LHD?
Got any photos of the rear markings on yours?

It makes a difference because there are some replacements that won't have US lighting legends on the lower face. You can still use the tach movement but your scope of work changes. You can find these for about $100 but I think the scaling resistor needs changing?

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Just swap the tach modules, only three screws hold them in.

What are the markings on the case? 30,000 or 16,000?
This appears to be the scaling factor from V to RPM and is probably a Volt divider circuit so the addition of a resistor could make a common Fiat part usable for our cars. Thx, wasn't sure where you were, wanted to tinker on this as I have extra instruments.

 

I have not seen an unmarked Tach before, but anything goes in Dinoland.

The photo of the tach next to the Dino tach says Fiat and I got it from a 2000 or 124 for under $100, that is where you get another module.
I was hinting at canniballizing and modifying it to fit yours

 

I can't say for all Fiats, but my brother in law has a 1971 Fiat Spider. Of course, the tach is meant for 4 cylinders, so if you can find a Fiat tach for a 6 cylinder car, that would be best. The point of my message is that the early Fiat Spider tachs would only trigger from a high voltage and would not accept a low voltage square wave. The later Fiat Spider tachs (I do not know the transition model year) would trigger from both types of signals. The newer tachs have a shorter case (not as deep). The same situation probably exists for Fiat 6 cylinder cars, but who knows until you try one. My brother in law was insistent that he keep the original tachometer when I installed his Cd ignition, but the tach would only work with the switch on the CD box selected to standard ignition, so I devised a simple tach adapter that would allow it to work when selected to CD as well. Unfortunately, that simple circuit will not work with an MSD ignition. So, if you do get a tach movement that only accepts a high voltage signal, but fits inside your original case, you could use it with the correct MSD tach adapter. Getting the right movement is the better option though. Good luck, Fred

 

No, It has to be for the same rpm range and number of cylinders or the calibration will be too far off if you are using your original faceplate. I do not know the inner workings of those tachometers, so I can't say whether they can be calibrated for different numbers of cylinders or sweep on the dial. 10000rpm! You are unlikely to find another tach movement designed for that. You may have to inspect the innards of more than one tach. Also, it is very likely that your tach can be repaired without replacing all of the electronics if the mechanical portion is in good shape. Fred