7 replies to this topic

[Leykor]

Quick question regarding a 998cc mini 4 cylinder engine.

How many sparks occur per revolution?

My understanding is that once the distributor has fired 1-3-4-2 then the engine has performed only one revolution?
I have come across some conflict in that maybe two sparks constitute a full revolution and that the full 1-3-4-2 distributor spark cycle turns the engine two revolutions?


Thanks.

[jaydee]

How many sparks occur per revolution?

It depends on the engine being 2 or 4 stroke

My understanding is that once the distributor has fired 1-3-4-2 then the engine has performed only one revolution?

Thats correct, A series engine is 4 stroke

I have come across some conflict in that maybe two sparks constitute a full revolution and that the full 1-3-4-2 distributor spark cycle turns the engine two revolutions?

Two sparks per turn are 2 strokes engines

Hope this helps.

[lrostoke]

Just trying get my head round this isn't it two sparks per revolution for a 4 cylinder mini engine from the coil. So each cylinder only fires once every 2 turns

eg take TDC as the firing point for cylinder 1

180 degrees after No 3 fires

back to TDC and cylinder 4 fires

180 degrees after No 2 fires

thats 2 full turns before your back to cylinder 1

suck squeeze bang( spark) blow

Edited by lrostoke, 22 December 2009 - 03:38 PM.

[jaydee]

Yeah i get what you mean, trying to explain it better:
a cycle is made of 4 strokes, to complete the four strokes, the crankshaft does 2 turn.
One cycle is one revolution for the camshaft, thats why one turn on the cam is two turn on the crank.

Edited by jaydee, 22 December 2009 - 03:53 PM.

[Guess-Works.com]

When related to RPM, there are 2 sparks per revolution of the crank...

The cam turns @ 1/2 the speed of the crank on a 4 stroke engine, the dizzy turns at the same rate as the cam.

[Sprocket]

One full four stroke 4 cylinder engine cycle is 720 degrees, meaning that there will be four spark events per two revolutions. divide that by two to give you two spark events per revolution. One at TDC and the other at BDC

[newdawn1st]

Worth a read >>Car Bible<<

[Sherlock]

This is how I was taught: A single cylinder 4 stroke engine fires once every 2 revolutions, in mathematical terms that is 0.5 times per revolution, so the formula for determining how many times your engine fires per revolution is 0.5 X the number of cylinders.