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even or odd fire??
Posted: Thu Dec 09, 2004 2:41 pm
by jiminy14
how do i know if i have an even or odd firing engine??
my firing order is 1,3,4,2 so even??
not sure what this tells MS, but i have been running as even fire.
james
even or odd fire??
Posted: Thu Dec 09, 2004 2:48 pm
by Bernard Fife
James,
Odd-fire or even fire doesn't refer to the firing order, but rather the interval between successive firings.
So if you have a 4 cylinder, and a spark every 180 degrees, you have an even fire. Almost all 4 cylinder engines are even fire.
However some 90 degree V6s, and most V-Twins (usually motorcycle engines), as well as a few others, have 'odd-fire' arrangments.
For example, from 1978 to 1984, the GM V6 (200 and 229 cid) had a semi-even fire sequence, with firing intervals of 132°/108°. It is "semi" because the rod journals are offset, but not quite enough to make for even firing intervals. In MegaSquirt terms, this is an 'odd-fire' engine, because the interval between firing can be either 132° OR 108° degrees.
There's more in this thread:
http://www.msefi.com/viewtopic.php?t=4520
Lance.
Re: even or odd fire??
Posted: Thu Dec 09, 2004 2:55 pm
by efahl
jiminy14 wrote:
> my firing order is 1,3,4,2 so even??
Yes, it's even fire, but not because of the firing order. Odd-fire is what we call engines that have uneven intervals between spark plug firing, the most obvious example is a Harley-Davidson 45 degree V-twin. If your I4 had a twisted crank, you could get it to fire at intervals other than every 180 degrees of crank motion, but that would be insane.
Some other common odd-fire motors are 90 degree V6 motors that use a common crank pin for the pistons on opposite banks (as opposed to the same block containing a crank with offset crank pins that make it into an even fire motor; there was just another thread on this recently, I think it had some pictures or links to some of these).
--
Eric Fahlgren
http://www.not2fast.com/
even or odd fire??
Posted: Thu Dec 09, 2004 3:08 pm
by johnsop1
The only 4 cylinder motors that I am aware of that are odd fire are V4.
So if you have a boxer or an in line you have an even fire motor.
-Phil
even or odd fire??
Posted: Sat Dec 11, 2004 9:38 am
by jiminy14
thankyou guys. i know it was kind of a noob question.
james
even or odd fire??
Posted: Sat Dec 11, 2004 10:06 am
by Bernard Fife
James,
It's a good question, and I will add this material to the manual.
Lance.
even or odd fire??
Posted: Sat Dec 11, 2004 2:56 pm
by KariM
In standard Megasquirt, what does even/odd-fire setting affect, while it's not sequential, and does not handle ignition? This has puzzled me a bit. More averaging to rpm calculation or..?