another tach question

[alantf]

Yes, but how does it differentiate between a two cylinder & a single cylinder? Surely the twin cylinder only needs to fire each cylinder once every two revolutions, whereas a single cylinder needs to fire every revolution. Doesn't that mean that a rev counter designed for a twin will show double the revs when fitted to a single? Or am I missing something? :??:

[blaine]

Originally Posted by alantf

Yes, but how does it differentiate between a two cylinder & a single cylinder? Surely the twin cylinder only needs to fire each cylinder once every two revolutions, whereas a single cylinder needs to fire every revolution. Doesn't that mean that a rev counter designed for a twin will show double the revs when fitted to a single? Or am I missing something? :??:

I don't know how to explain it.I know that a lot of people used aftermarket tach's designed for duel-fire,Harleys,me included.If you come across a simple method of explaining the concept,I would love to here it,as I never understood this fully. :??: It's one of those"I don't how it works,I just know it works".
:2tup:

[alantf]

Mmmmmmmmmmmm I'll have to accept that it works But I recall a posting some time ago when a guy set his tickover to 1400 revs (using a tach) but was still having problems. He posted a video, and upon listening to it, it sounded as though it was reving at 700. It was thought at the time that his rev counter was showing double the actual revs. :??:

[mrlmd1]

If I am correct, a dual fire ignition fires on every revolution of the engine, even though the power stroke on a single cylinder 4 cycle is every 2 revs. It counts every spark. A 2 cylinder engine also fires every revolution, same number of sparks. Is that clear enough?

[alantf]

Sorry This old brain can't get it's head around this

[blaine]

Originally Posted by mrlmd1

If I am correct, a dual fire ignition fires on every revolution of the engine, even though the power stroke on a single cylinder 4 cycle is every 2 revs. It counts every spark. A 2 cylinder engine also fires every revolution, same number of sparks. Is that clear enough?

You are correct.Dual fire ignition systems fire both spark plugs from a single coil at the same time.(Two plug wires from one coil).The majority of the spark energy goes to the cylinder under compression while a small portion goes to the cylinder on the exhaust stroke causing a small wasted spark. Single fire ignitions separate the firing pulses,(Two seperate coils) only firing the cylinder under compression. The main advantage of dual fire systems is simplicity and low cost. The advantage of single fire systems are smoother engine operation and the elimination of the popping that sometimes occurs when long duration camshafts are used. There is no horsepower advantage with single fire ignition systems. My older EN450 has single fire ignition,wile the newer Vulcan has a duel-fire ignition.
:cool:

[mrlmd1]

Under "How To's", in the "Add a Tachometer" thread, on Aug. 23, 2010 I posted

"If you want to go a different route, ie, a small electronic tach + hour meter, look at Tiny Tach.
http://www.tinytach.com/tinytach/index.php
They can be bought for as low as $40 from eBay and Amazon and other places, are easy to hook up with an inductive coil wire wrapped around a spark plug wire, have an internal battery supposedly guaranteed for 5 years and are totally waterproof, small enough to be mounted anywhere. I saw them on a jetski forum and another bike forum and they seem to work just fine." These require no wiring, no amount of genius to install.

Like all over here, Search is your friend. There are multiple threads on tachs.

Go back to that thread started in Aug 2007 by quimrider, you'll see a detailed pictorial of his installation step by step, and I believe on page 3 you'll see another explanation of a dual fire ignition. Basically whenever the piston is at TDC the coil delivers the spark, whether it's in the compression stroke or the exhaust stroke, ie. there is a spark for every revolution of the engine and that's what that tach is counting. OK? If the engine was a single fire ignition, ie, only firing on the compression stroke at TDC, it would be much more costly as then you also have to sense not only the flywheel position but the cam position. Nothing is lost by shooting off a spark on the exhaust stroke also and it's easier and cheaper to do. So again, Dual fire tachs work on the GZ.