Using a tach/dwell meter on a Rotary
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Using a tach/dwell meter on a Rotary
I'm trying to use a tach/dwell/voltmeter to adjust the idle speed on my rotary. The tach meter has scales for 6 and 8 cylinder engines (for 4 cyl multiply the 8 cyl reading by 2). Of course there is no 2 rotor scale!
Here is how I figure to convert the reading for the rotary. Would like it if someone who knows could double check me.
I think the meter measures coil pulses (sparks) per minute (frequency). I'm just talking here about a single coil operation--the leading coil for a rotary. For a piston engine, every 2 revolutions gives one spark per cylinder. Thus an 8 cyl engine will have 8 sparks per 2 revs.
In a rotary engine, the rotor rotates at 1/3 the output shaft rpm which equates to the rotor rotating 1 rev in 3 output shaft revs. Also, each rotor rev has 3 sparks.
This gives 3 sparks per 3 output shaft revs or 2 sparks per 2 output shaft revs (per rotor).
Since the engine has two rotors, we should measure 4 sparks per 2 output shaft revs.
In my opinion, it looks like I use the 4 cyl scale (multiply 8 cyl reading by 2).
Hooked it up and using the 4 cyl scale appears to match closely with the in dash tach--so this looks right.
Scott
Here is how I figure to convert the reading for the rotary. Would like it if someone who knows could double check me.
I think the meter measures coil pulses (sparks) per minute (frequency). I'm just talking here about a single coil operation--the leading coil for a rotary. For a piston engine, every 2 revolutions gives one spark per cylinder. Thus an 8 cyl engine will have 8 sparks per 2 revs.
In a rotary engine, the rotor rotates at 1/3 the output shaft rpm which equates to the rotor rotating 1 rev in 3 output shaft revs. Also, each rotor rev has 3 sparks.
This gives 3 sparks per 3 output shaft revs or 2 sparks per 2 output shaft revs (per rotor).
Since the engine has two rotors, we should measure 4 sparks per 2 output shaft revs.
In my opinion, it looks like I use the 4 cyl scale (multiply 8 cyl reading by 2).
Hooked it up and using the 4 cyl scale appears to match closely with the in dash tach--so this looks right.
Scott
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datfast1
Old School and Other Rotary
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06-20-19 10:53 PM