Hi everyone,

In reading a recent post I ran across something about which I'd like
to learn more.
What does odd fire and even fire engines mean?
I have a very basic understanding of engines firing in a
specific sequence, but what do these terms mean?

Also, please excuse my use of capital letters in my screen name.
I was very new to computers when I started on here and didn't
realize that could be offensive. If someone could explain how
to change it, I will.

Dean

yea odd-fire is a refrence to the firing order sequence of the engine,
heres the link brando posted http://www.gnttype.org/general/v6hist.html

Does not answer his question.


This doesn't either.

Rockets: They used a different crankshaft design and replaced the the V8 distributor with one designed for the V6.

I'm working on a more specific answer.

Norm

Thanks Norm- I was also working on one, but I will let you take care of it, as school leaves me little time to compose-

Andrew

I was thinking This one would save me a little time, but it was no more than a sidebar.

Added the tidbit, about the distributor, above while you posted.

Norm

http://www.novak-adapt.com/knowledge/buick_90_v6.htm
http://home.off-road.com/~merls_garage/oddfire.html

Already checked both, since they are at the top of Google's returns. They did not have what I needed.

They are, however, about as accurate as one will find on the internet.

Norm

Firing order has nothing to do with it.

Odd-fire and even-fire (231's) have the same firing order, 1-6-5-4-3-2.

It is odd-fire, because of the crankshaft design is derived from the V8, instead of being redesigned to suit a 6 cylinder engine. This is from Wiki, and I can't think of a better way to say it- Article can be found here



Then this-



Hope this helps-

Andrew

Hi everyone,

Thanks for the replies.
Right, the link posted by 91parkave did not answer my question,
in fact it prompted it. I had already seen that when Brando posted it.
Norm, Andrew, please don't go out of your way or spend too much
of your time on this. unless you want to know more about it.
I see it is more complicated than just the firing order, involving the
crankshaft etc. That's way above my level and I never plan to be that deep into the Reatta engine. I'd be lost in there forever.

yea what are you r trying to know because from the 2 links i posted and other reasearch is that they have diffrent firing impulses , and various engine parts

odd fire:
The cylinder numbering for the odd-fire V6 is 1-3-5 from the front down the driver's side, and 2-4-6 down the passenger side. The firing order is 1-6-5-4-3-2.
The Dauntless 225 and the odd-fire Buick 231 have a crankshaft with three journals that are offset at 120 degree intervals.Looking at the front of the crankshaft you would see the front journals at the noon position on a clock, the middle journal at the eight o'clock position, and the rear journal at 4 o'clock.
Each of the three journals are shared by two pistons. The front journal is shared by cylinders 1 and 2, the middle shares 3 and 4, and the rear shares 5 and 6. Keep in mind that this means if one piston is fully extended towards the cylinder head, the other piston that shares that journal will not be.
This is a 90 degree V6, meaning that the two banks of cylinders are at 90 degrees to each other. Most V8 and some other V6 engines are also built at 90 degrees, but logic would dictate that 60 degrees would be more natural for a V6. For example the 2.8L V6 used in some late model cars is a 60 degree engine.
Since each journal is shared by two pistons, if one piston is fully extended towards the cylinder head the other piston sharing that journal will not be. For example, with number two fully extended number one will not be fully extended until the crankshaft rotates another 90 degrees (since the cylinder banks are at 90 degrees to each other).
The distributor shaft and rotor will make one complete rotation for every two rotations that the crankshaft makes.
Since an engine crankshaft always rotates twice per ignition cycle, most of the information here is presented as 0 to 720 degrees rather than just 0 to 360. The 720 degrees represents two complete rotations of the crankshaft.
As the crankshaft rotates, zero degrees is the beginning of the firing order cycle. This is actually when ignition takes place on the last piston and is also equal to 720 degrees in the rotation cycle.



even fire:

In mid-1977 the 231 was converted to "even-fire" (120 degree spaced firing impulses) by changing the crankshaft, camshaft, distributor and (presumably for increased volumetric efficiency) the cylinder heads and intake manifold.

andrewk: Thanks.

ROCKET: You're welcome.

Norm

I will skip your giberish and move on to your, rude and unnecessary, cut and paste.


It does not tell us what changes were made. Without knowing the changes, we cannot know the difference.


This one shows us the changes, and the difference, although, I question the use of the word "smooth".

In addition, the camshaft lobes were repositioned to the new valve timing requirements.


I do not believe it was changed, at that time. I will confirm, after I verify it.


Presumably?

If a change was made, it was for a different purpose. I will verify when I check the validity of the distributor statement.

Norm

So arent you the on ewho preaches about quote this quote that? Anyways.....The odd fire was fitted with the electronic disrubitor its last year in production, also i have found that even fire is not exactly "true" in its meaning. besides from what i seen is the diffrence in Crankshafts mainly. but heres another tid bit for the even fire

While the 90 deg. - V8 engine produces a natural even-fire engine with each cylinder firing at 120 deg. intervals the 90 deg. - V6 engine is an odd-fire engine. In the odd-fire mode V6 engines typically run rough with excessive vibration. The odd-fire V6 operation was improved substantially by modifying the crankshaft. Each pair of adjacent connecting rods shared a crankshaft throw with the two journals offset by 18 deg. This offset produced a firing sequence of 132 deg./108 deg. or a semi even-fire sequence throughout the firing order. It also required that connecting rod lower ends be 0.050" narrower than the small block V8 engines to provide for a thrust bearing between adjacent connecting rod journals.

I follow the established protocol. You are still unable to act like an adult.


According to andrewk's post that would be '76. Use of HEI began in '73 CA, and '74 (or was it '76) 49 state, in all GM gas vehicles.

If you are right, you were wrong when you said:

And, I was right when I made the correction.

I will verify it anyway.


If it is not, would it make your first post any less than BS?


Not true. They fire at 90° intervals, not 120°. I suggest you check your source(s) with a BS meter.


It is, but, as already stated, after '76, 90° V6 is even fire.


Sounds familiar. Why am I thinking Chev V6? I will check it with my crank grinder, when he gets back from lunch.


I still think you should verify your source(S).

I will compliment you on your ability to "Google" for answers that have already been posted. Does it involve using keywords culled from those answers?

Norm

i dont even have to quote you, as a matter of fact for someone who is checking with their crank grinder and someone who was searching through the net themselves, you dont know jack shit about these either, i contributed facts from the net, nobody i can think of dumps b.s about buick odd-fire and even fire engines that i can think of. Once again you also distort me when you quote and still talking about b.s statments when you have nothing to put fourth but the same info from other people. Because if you had personal experience you would have posted it already. Otherwise youre getting all your info second hand, so i dont see how you can talk shit about something posted when youre not sure as you stated, about the subject.........