Pertronix ignition & tach operation

[Certified Lotus]

I switched to a Pertronix ignition in my 64 Elan twin cam but had to have my tach rebuilt to handle the signal. I'm wondering if the same situation is true with my 72 twin cam Europa? I've read a number of posts and can't find anything definitive on the subject. Some say it works without modification and others say not.

Anyone have the facts?

[LotusJoe]

The short answer is yes.The Smiths Tach takes it's signal from the hot side of the coil. See the following wiring diagram.

http://www.lotus-europa.com/manuals/misc/electrical/tcfedc.gif

I replaced mine with an Elliot Tach from Banks Europa.

[BDA]

It seems to be variable. My engine was built with an Allison optical ignition. The stock tach I had didn't like it one bit and would bounce horribly over about 3000. When that ignition failed, I replaced the Allison unit with a Petronix ignition including their coil and the tach stopped bouncing. I've heard of others who say the Petronix caused their tach to bounce. I have no explanation for you, but that's been my experience. In thinking about what differences I might have that would make it work, the only thing I can think of is that I have an electronic revlimiter and an electric fuel pump cut off. I don't think they would change the signal to the tach in any way.

Maybe the answer is in Joe's long answer.

[jbcollier]

I don't have a RVC tach in mine but I have installed Pertronix in other cars with Smiths RVC tachs and had issues.  I modified the wire loop as outlined in the instructions below and the tach then worked fine.

https://jbcollier.smugmug.com/Lotus-Europa/i-Q2Vvtvd/A

[EuropaTC]

I cheated and modified the internals on my tach, but this topic has been discussed in depth on the Lotuselan.net forum. One solution I've seen mentioned several times is to take the +12v feed from a separate switched source rather than the coil terminal. I've no idea if it works but several have claimed to have solved the problems, so if I were doing it now I'd try that before doing anything else.

There's also an internal board you can fit to the existing tach mechanism that solves the problem.

https://www.spiyda.com/magento/index.php/smiths-rvi-rvc-conversion-board.html

Brian

[2766R]

Possibly another option:  http://www.nisonger.com/electric-tachometer-conversions.htm

If and when I get my TCS running again, I may consider updating the tach with them.

[Certified Lotus]

Yes, I have had tach'S converted by Nisonger before. They do very good work. Give yourself time, they have a 6 to 8 week turn around but are more than willing to turn around in a week if you pay them a hefty surcharge.

[jbcollier]

I bought all my gauges from them.  Good to deal with.

[Roger]

The Spiyda conversion is very easy and a fraction of Nisonger's cost.  I have done both.