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Tiny tach? Rpm gauge

Has a anyone used one of these on the aircraft motor , it's simple to hook up but I am confused about the settings I have a 0320, so a 4cylinder should have 2 sparks per Revolution correct ?
Instructions are straight forward
Ground to engine block
Red wire wraps around your spark plug wire. If I use the other settings I get readings that aren't right at all
So I get left with a 180 option which is the 2 sparks per revolution and that's the one that makes sense to me
 

John Fenner

Well-known member
Spark plug wire? No,, red wire should go to accessory power, black wire to ground, and the trigger wire can be hooked to the P-lead of the magneto, they do not fire twice per revolution.
 
John thanks for the reply, this one I have is different it only has 2 wire one white for ground and the red one that gets wrapped around the sparkplug wire,
I called and talked to them at tiny tach told him the application and I know I have the right one. Well hope so anyway.
But it has different settings and
Some of the settings throw out numbers that just can't be true.
So far I narrowed it down to the 180drgree setting which is 2 sparks per if I use the 4 sparks per the numbers are wayyyyyyy of and it tells me I have 100rpm at idle and that's a lie just no way.
 
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Slidin Gator

Well-known member
What type of ignition system are you using and what type of plug wires?

Each plug on a magneto ignition fires 1 time for every 2 revolutions. Electronic ignition solutions vary, depending on how the timing trigger is derived. Pacemaker ignitions fire each plug 1 time for every 1 revolution.
 
Ok so the 720° setting is where I'm suppose to be at if it fires 1 time for every 2 revolution.

Here's the order
720°- 1 for every 2 revolution
360° - 1 for every revolution
180° - 2 sparks per revolution
120°- 3 sparks per every revolution
90°-4 sparks per revolution
60°- 6per revolution
45°-8 per revolution
 

Slidin Gator

Well-known member
The 720 deg setting is what I would expect to be the correct setting and your idle is likely somewhere between 400-700 RPM.

However, note the points in the instructions about noise potential as the red and white wires at the end of the coax are basically antennas. Unshielded mag ignitions systems generate a lot of RF noise, all along the length of the wires. It is very possible that the readings are off due to noise from other plug wires.

Route both red and white wires as far away from any other plug wires as possible, do not run them in parallel with plug wires, cross at right angles. Wrap the red wire near the plug so it is separated from the rest of the plug wires.
 
Damn that's awesome you did that test like that, I would have never guessed the mags give off that much noise To a collar. Makes alot of sense though
 
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