A while back, I mentioned a new ignition which had an onboard tach.
I have now tried two of them and they work quite well.
They are std now on the new ROTO engines .
The unit has 30 degrees advance built in and uses a magnet pickup just like most other setups
The factory says a "Hall type"
The magnet is reversed polarity from magnets used in my ZDZ engines (drat!) but I am a gonna fix that!
The cap and base are much like that used on th ZDZengines - that is, the same short spark plug is completely enclosed and shielded.
(It is interchangable with ZDZ setups in this respect )
It is also beautifully machined and braided.
Anyway - the unit simply records highest rpm in a run (from the time the ignition is switched on to switched off.
So on a test stand or in flight - it records and you can read after running the engine
The readout is a 1/4" dia LED that simply appears to glow but when you place a tach in front of it -- the tach reads 1/2 of the peak rpm reached.
I checked this feature and it is pretty close - reading the prop at 6600 will give a reading of 3300 on the LED.
As far as I know , these ignitions are NOT available as a seperate unit .
They are a part of the new ROTO engine package.
That doesn't stopa rabid engine freak
I have put small block Chevs into Austin Healeys so this swap job should not require too much work -
Looks to me like a new magnet- a couple of holes in the crankcase and Bob's your uncle!
I hope this feature catches on with other ignition folks - I really like it .