bethel
06.06.2021 16:10:50
Four Cylinder bike engine, with twin coils, you can only take the sensor off ONE coil, so, again, would be getting one pulse a rev, and would give half rev reading. [links]
See full version: Tachometer on a single cylinder engine (pitbike)
Four Cylinder bike engine, with twin coils, you can only take the sensor off ONE coil, so, again, would be getting one pulse a rev, and would give half rev reading. [links]
1/ Piston falls, half a crank rev, sucks in charge
2/ Piston rises, half a crabk rev, compresses charge
BANG. we want a spark to set fire to the charge!
3/ Piston falls, half a crank rev, Combustion.
4/ Piston rises, ghalf a crank rev, Exhaust, gasses pushed out the pot ready to do it again. more
You need two pulses per revoilution to make it calibrate, SO, you make a 'dummy' ignition trigger, that gives two pulses per rev.
So, a two stroke single, one spark per rev, a two stroke twin, two sparks per rev. A four stroke twin, one spark per rev, a four stroke 'four' two sparks per rev, etc. more
four stroke engine has four 'strokes' perfoming the four 'phases' of the 'Otto cycle', suck, Squash, Bang, Blow. more
The TachMatch TM-03 accepts most standard tachometer inputs. If you have a standard coil and points ignition, connect TachMatch to your coil. If you are using an aftermarket system to control the coil, such as an MSD, TachMatch accepts its tachometer output signal. If you have a typical GM HEI ignition, the HEI tachometer output signal drives TachMatch. If you are driving your tach from an ECU, the TachMatch provides an internal pull-up resistor for compatibility.
If your tachometer is designed for a different number of cylinders than your engine, The TachMatch TM-03 can change the frequency appropriately to correctly drive your tachometer. By selecting how many cylinders your engine has (1-8), and how many cylinders your tach expects (1-8), a wide variety of ratios are available, anywhere from 1:8 ratio to an 8:1 ratio.
TachMatch is a solution for making your tachometer work, when things just don't match up like they did at the factory.
Re: Tachometers - will automotive tachs work or strictly marine? more
Automotive tachs work off the ignition system and are "cylinder based". Outboard tachs could care less how many cylinders the engine has since these tachs operate by counting the pulses from the stator (charging system). If the auto tach will recognize the very different pulse shape then you can do the math to equate the number of cylinders on an auto engine to 6 pulses per rev from most outboard stator systems. If the auto tach doesn't recognize the wave shape then this is all a moot point. [links]
I have an 85hp Evinrude V4.
Re: Tachometers - will automotive tachs work or strictly marine?
If both cars has a distrubutor and the tach signal comes from a single coil that feeds all plugs, then the math is obvious. Again, it depends. more
So, what to do? Hook up the tach to the 4 cylinder engine in the normal way. Listen to the engine idling - does it sound near normal speed? If so, look at the tach. If the tach reads about half speed, say 400 rpm and you'd expect 800 rpm, multiply by 2, or move the selector switch to register the correct speed. My very old fashioned tach has a selector switch for 4, 6, and 8 cylinders and expects to see pulses from s single coil feeding all sparkplugs. It was made before auto engines began using one coil to fire two plugs simultaneosuly. [links]
It all depends o n where the tach is getting its trigger signal.
do you multiply by 2 or devide by 2 ? I can't remember and i can't find my paper work. Thanks in advance.