Tachometer Options

[Moderator]

The Sun Super-Tach II in my MGB was old and second-hand when I got it 25 years ago. Apparently, it's not going to work easily with my new ignition system. (There's a trick for connecting real old tachs involving wiring up a coil from a gutted relay to simulate a coil's inductive spike, but I'm not especially keen to do that.)  Replacing my tach with a newer version of "Super-Tach II" would probably fix the problem too - and they only cost $40.  

But just for the grins I thought I'd ask...  What features do YOU look for in an aftermarket tachometer?

Do you have a strong brand preference?


my starting point:

[Addicted]

Honestly, I'd go to Amazon, search for tachometers, and sort by customer review score.  Then start at the top and look for the price and style that you like.  

I just went through the same type of question looking for an oil pressure gage for my TR7 project.  I went with a VDO that looks original and had good reviews.  I just hacked it up and installed it in my stock TR7 instrumenet cluster last night.  It looks fantastic.  

As for Tach options, I am hoping to use my stock TR7 tack with my V8.  MSD recommended a Dakota Digital tach adapter to bump the 8 cylinder signal down to 4.  Has anyone used one of those tach signal adapters?

[Addicted]

Here's a link to their tachometer signal interfaces.  

http://www.dakotadigital.com/index.cfm/page/ptype=results/category_id=287/home_id=59/mode=cat/cat287.htm

"The SGI-8 Tachometer Interface Unit is designed to allow a factory tachometer to function accurately after performing an engine swap to an engine with a different number of cylinders or tach signal. If you are swapping out a V-6 for a V-8 and you need to recalibrate the tach signal from the V-8 to make it read accurately on the factory V-6 tachometer, the SGI-8 will do the job. The SGI-8 is capable of recalibrating tachometer signals for nearly any engine swap combination."

[Moderator]

Cool.

I've been poking around and considering lots of options. The three small gauges in my dash are from Stewart Warner's "Track Force" series. I bought them years ago from Pegasus Racing.  Apparently that whole model line has been discontinued, but I'm hoping to find a Track Force tach used or new-old-stock somewhere because it would be nice if more of my gauges matched.

[BlownMGB-V8]

It probably doesn't get much better than Autometer but they aren't what you'd call inexpensive.

Jim

[tomsbad6]

hello from the great White North  were driving my little cars just seems like a dream I have 4 feet of snow in my front yard. I do not know what kind of driving you do in your car but in my car readings  the tachometer and driving seems impossible my vote would be hide a good shift light somewhere running off  RPM switch and you'll never have to look for the tachometer while driving again

[Moderator]

Well... not much happened with this from February until today.  I learned Stewart Warner did manufacture a 0-8000rpm electronic tach to match my other gauges, but apparently they didn't make many before going out of business. I've seen exactly one on eBay, but I got outbid on that one.  

So, today I made an adapter to facilitate using my vintage Sun tach indefinitely. I had it together before I remembered to take a photograph... so this snapshot is after the fact. You can't really buy just one transistor, just one resistor, etc. - so I had spare parts and I laid out some of them as examples.  Also, as you can see, I "potted" my adapter circuitry in a 35mm film canister to protect it from vibration. The adapter seems to work perfectly so far!



p.s. See the little circuit diagram on the side of the relay? See how there's a resistor inside, wired in parallel with the coil? If you're making a similar adapter, you'll want to pry open the relay and remove that resistor. I ended up removing everything but the coil.

[BlownMGB-V8]

Are you using the relay coil as a choke?

[MGBV8]

You can't really buy just one transistor, just one resistor, etc.

Sure you can. Awesome source for electronics:

http://www.mouser.com/

We still have an old-time electronics store in Johnson City, TN called L&S Electronics where you can still walk in & buy pieces parts electronics. They have some old used classic stuff like USA Triplett 630 mutlimeters, oscilloscopes, etc.

[DiDueColpi]

I'll second Mouser Carl.
Not necessarily the cheapest, but if you need it they've got it.
I use them all the time.
We've also got a place like L&S called Ungers.
The old guy there still does tube testing etc.
Just like the old Rexall drugstore from when I was a kid. It's always a treat to go into the back for some long forgotten dust covered part. We need to support these old shops.
It's history that's slipping away.

Cheers
Fred

[Moderator]

If my town had an old-time electronics shop to support, I would have. I went to two Radio Shacks and gave up after that. Driving around costs money too!  

On eBay, I paid $0.99 for fifteen transistors, shipping included. Resistors weren't such a screaming deal... $1.99 for ten plus $2.32 shipping. Smaller resistors would have been cheaper, but I figured I might prefer the big 2 Watt resistors for some future project.  I already had all the other stuff.

The coil produces an inductive spike to simulate an ignition coil. I got the schematic <a href="http://www.msextra.com/doc/ms2extra/MS2-Extra_Hardware.htm#tachoout">here</a>.