Electromotive DIS tach output voltage?

Don't know the voltage, but when I did mine I used an adapter that can be bought directly from MSD. Without the adapter the tach would read twice the actual RPM. It was kind of cool to see it rev so quickly though. If you need the p/n let me know and I'll see if I can dig it up.

Henry

 

Dan
Tach output is a 12v square wave. Older tachs use voltage. There is an amplifier. If you check the Electromotive site, you can download hte manual or call Nick (sponsor), he sells the tach corrector.
Philip

 

I got an MSD amplifyer from summit racing--all is fine on my TEC3 now

 

I'm trying to fix this problem also . . . P/N?

Thanks,


Sean

 

Dakotadigital.com has what I need! Found it mentioned in another thread after some searching.

Sean

 

Sean,

So you are good to go?

 

Some chatters had problems with this unit . . . I couldn't find an MSD product that seemed correct so I was going to give it a try . . . be nice to have another alternative if I have problems.

Thanks,

Sean

 

Sorry, I just went through my old receipts and all it says is "tach adapter". I know it is a MSD unit.

 

Thanks for checking . . . I've got a direct number for a decent tech at MSD so he should know what it is.


Sean

 

The tach adapter I have fitted to the HPV-1 on my 1978 GTS is MSD PN 8920 (at least that's what it says on the cover). This adapter is really an amplifier that conditions the DIS tach output for the car's tach. Works great.

Bill

 

Bill,

Was your tach reading double rpm from the DIS output before you put the adapter on?


Thanks,

Sean

 

Sean,

No, my tach was not reading at all when I initially installed the system.

It is my understanding the MSD tach adapter only changes amplitude of the tack signal from the DIS so that the tack can read and understand the resulting signal.

The double reading of rpm is a different issue. It means there are too many pulses reaching your tach. Electromotive makes an internal change to their DIS during manufacturing for the twin distributor Ferrari 308 series, effectively halving the number of pulses sent out on the tach circuit. As I recall, the tach takes it signal from only one coil in the OEM installation. I ordered my system directly from Electromotive some years ago and told them it was for a US spec 308. You may want to contact them directly to see if they can rework your system to give the appropriate pulse count. I suspect the system you are using was meant for a standard V8 where only one distributor was originally used.

Alternatively, maybe someone can provide a divide by two circuit that can be wired in?

I hope this helps.

Bill

 

If you have an 8 cylinder HPV-1 or HPX-1 that was not purchased for a Ferrari application, it will not send out the correct tach pulse, the Ferrari tach is a 4-cylinder tach, thus you need a 4-cylinder tach output on your direct coil ignition. The kits that we sold for the Ferrari application were all modified for a 4-cylinder output. You can also send your unit to Electromotive & they can modify it for a 4-cylinder tach output.

If you are having a problem with the signal coming out of a TEC3 or HPX or HPV-1, you can use a MSD 8920 TAC amp. It will work with your OEM tach.

 

Yep, that's what I did. I sent the unit back to Electromotive and they modified it. It cost abour $35, but that was over 10 years ago.

 

Thanks all . . . that clarifies it.

I'm using a Haltech ECU so I'll give the Dakota digital tach box a try. Supposedly it conditions the signal from any engine for a 4 cylinder tach.


Sean