Hi,
I am no electrician and know what I read without always understanding it so
here is a mix of my 'layman' understanding with some 'electrician' terms.
Any non mechanical tacho gets its information from the ignition system pulses
which it reads from the engine coil.
There are two basic types of tacho design known as RVC and RVI - I have no
idea without checking what this means. What I do know is that any RVI type
will not read correctly with almost any (probably every) electronic ignition
system. I think this is because the electronic ignition system modifys the
ignition pulse that the tacho is reading. I recall reading that this is
because the RVI type cannot cope with the faster pulse. For further
explanation ask anybody but me! In the UK at least any RVI tacho can be
converted to RVC at a cost not far off the price of a new cheap tacho. Some
tachos may have the letters RVI or RVC on the face if not if they go wild or
read badly when you fit an electronic ignition system you need the conversion
or a new RVC tacho. I would guess most Sprite use RVI tacho technology as it
is older. I haven't run a standard tacho with electronic ignition.
But, any cheap tacho whether RVC or RVI can be inaccurate simply because they
are built to a price and it is only when you start to get into gear driven or
pro race tachos do you get absolute accuracy - but at a price!.
If anyone wants more info I might have a bit more stuff I can dig out but I am
no electrician. My recomendation would be to fit the electronic ignition and
either fit a modern aftermarket tacho or get the original modified.
Daniel 1312
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