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1913 buick firing order


dnoznesky
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Isn't 1-3-4-2 the only possible firing order on a four cylinder in line motor?<P>For balance the 1 & 4 pistons move up and down together. Likewise the 2 & 3 move up and down together. If you fire #1 first, then you have to fire #4 third. So you get a 1-?-4-? firing order. Now, since you have fired a cylinder in the front first, you want to fire a cylinder in the back next. The only possible cylinder would be #3. Thus, 1-3-4-2 is the only possible order.<P>I think there might be two possible orders for a six cylinder motor. I haven't thought about any V, flat or eight cylinder engines (because I don't have any).

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As long as you don't put in special balance shafts, there are a limited number of configurations you can build a in-line engine. On a four cylinder you have to have the front & rear pistons move together and you have to have the center two pistons move together. Otherwise the engine will be horribly unbalanced.<P>As long as the pistons are moving together that way you must have #1 and #4 fire one revolution apart. Likewise you must have #2 and #3 fire one revolution apart. So your choices are 1-3-4-2 and 1-2-4-3.<P>On some more thought: 1-2-4-3 and 1-3-4-2 both have the same dynamic power balance problem: Sequential power strokes in adjacent cylinders. Two power strokes in the front of the engine, then two at the rear. So they are both equally bad (and therefore equally usable).<P>In general, you want to spread the load from front to rear evenly during a complete cycle (two rotations) of the engine. So generally if you fire in a front cylinder on one spark you want to fire on a rear on the next. Note that you cannot do that for a in-line four, but you can for a in-line six.<BR><table border="1" cellspacing="0"><BR><tr><td>Option 1</td><td>Option 2</td><td>Comments</td></tr><BR><tr><td>1-?-?-6-?-?</td><td>1-?-?-6-?-?</td><BR><td>On a six, starting with #1 (Again for balance #1 and #6 move together, #2 and #5 move together and #3 and #4 move together)</td></tr><BR><tr><td>1-4-?-6-3-?</td><td>1-5-?-6-2-?</td><BR><td>Picking the two possible rear cylinders for spark number two</td></tr><BR><tr><td>1-4-2-6-3-5</td><td>1-5-3-6-2-4</td><BR><td>Since we have now fired in the rear, we want to pick a front cylinder next. There is only one choice left</td></tr><BR></table><P>So, does anyone know of a in-line four that does not have either a 1-3-4-2 or a 1-2-4-3 firing order?<P>How about a in-line six that does not have either a 1-4-2-6-3-5 or a 1-5-3-6-2-4 firing order?<P>I'd love to be proved wrong. Learning is always fun. smile.gif<P>By the way, the Chrysler product flat sixes used 1-5-3-6-2-4, and a quick look under the hood of my 1991 Jeep 4.0L in-line six looks like a 1-5-3-6-2-4 as well.<p>[This message has been edited by TodFitch (edited 08-31-2000).]

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Tod<P>You have given this A LOT of thought, and I'm sure you are right. I just don't know why exactly. Please don't take this as sarcastic or argument. It is not intended as such. I am just very curious and want to learn. I just love philisophical discussion.<P>First, the assumptions:<P>4 cylinder, 4 stroke, therefore each cylinder fires 180 degrees apart.<BR> <BR>Why can't 1 & 2 move together and 3 & 4 move together resulting in firing orders of 1-3-2-4 or 1-4-2-3? <P>Or, 1 & 3 move together and 2 & 4 move together resulting in firing orders of 1-2-3-4 or 1-4-3-2?<P>To minimize the number of times two adjacent cylinders fire sequentially, 1-3-2-4 or 1-4-2-3 would be best, as it happens only once. This would also give a better front/rear distribution in that you fire a front then a rear, a front then a rear. I'm sure there is a reason that this is not done. It is probably balance, as you have already cited, but I don't really understand why. <P>Could you please explain why these other two crank configurations are not able to be properly balanced?

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Model A Hal,<P>Also no argument or sarcasm intended either. <BR>I love wondering why things were built the way they were. I first wondered about why certain pistons moved up and down together when I was on a tight deadline to get my engine together and had some new pistons that did not meet their weight specs. I also had no idea of where to remove material without weakening the pistons. I finally noticed the #1 & #6, #2 & #5, and #3 & #4 arrangement on the crank. I then took the two pistons that were closest to the average weight and put them in the #1 & #6 positions. The next best pair I put in #2 & #5. Finally the lightest and heaviest pistons I put in #3 and #4. I also alternated the heavy one of each pair from front to rear. The result was that each throw of the crank had equal weight and the mass at the front of the engine matched the weight at the rear. The engine ran smooth even though the pistons were officially out of spec. So much for the triumph of logic and tight schedule over doing the job right smile.gif<P>I have not actually gone back to old college mechanical engineering texts to verify alot of my thoughts, so I could be wrong.... Also I often make assumptions about how manufacturable something might be (a dangerous thing for me as I have never worked in a foundry or production machine shop environment). Some of this is "hand waving" arguments, so bear with me.<P>If pistons #1 & #2 are on the same throw and pistons #3 & #4 are on the opposite throw then your recipicating mass is such that the engine will want to rock front to back: Mass (pistons, connecting rods, etc.) moving up in front at the same time as other mass is moving down in the back. On the next stroke the reverse. That front to back rocking will cause lots of vibration in the engine.<P>As to having #1 and #3 move together and #2 and #4 move together: I don't know, it might work. However, generally main bearings are placed where the throw crosses the center line. I suspect you would need more main bearings to keep from whipping the crank around. That costs more money. Also, lurking in the dregs of memory from college is knowledge that some seemingly symetrical shapes are not stable when you spin them on their axis. I suspect this might be one of them. That would take more research to find out. In any event, the power strokes you get in that combination are still two front, two rear giving the same vibration characteristics you would have with a cheaper crank, so there is no real benefit.<P> smile.gif Boy, I love this kind of discussion! Thanks for asking! smile.gif<P>Anybody out there with fresh mechanical engineering knowledge that could give us more info?

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Gee Tod, Looks like it's just you and me.<P>Thanks for the explanation. I had not thought about rocking the engine front and rear. Makes sense to me. I was only thinking about rotational balance. <P>While we are on balance and firing order. Have you ever read how Harley Davidsons fire?<BR>It is a 45 degree V-two four stroke. Both connecting rods are attached to the same throw, but both cylinders fire at the same time on every revolution. Let's say we are firing at full advance, which I think is 30 degrees BTDC. Let's look at the rear cylinder first. The front cylinder fires at the same time, but it is 75 degrees BTDC on the exhaust stroke, therefore a "harmless" spark. 405 degrees later, the front cylinder is 30 degrees BTDC and both plugs fire again. This time the rear cylinder is 15 degrees ATDC. I would assume that the intake valve is already open and wonder why the spark doen't try to ignite the fuel. My guess is that since there's no compression and relatively little fuel, the conditions are just not right to support combustion.<P>Anyway, if you been keeping track of the degrees of rotation, you realize that it is only 315 degrees until the next time the plugs fire. This 315, 405, 315, 405 is what gives Harley Davidson the distictive sound that some of us love (others hate) so much. grin.gif

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Yeah, I think that the fuel/air mixture needs to be compressed before the spark will do its job. So you are really only getting two power strokes from that Harley. But they are definitely not 180° apart!<P> smile.gif I guess I was wrong about requiring the engine to be balanced: Harley proved you can market an unbalanced engine and make it a selling point.

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