V12 - do cylinders fire in pairs or staggered?

I've always wondered this, whether in a V12, all the cylinders fire one by one or in pairs? Any 750i/S600 owners out there? :)

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One cylinder at a time. Harley Davidson Motorcycles engine cylinders/pistons both fire at the same time.Unless things have changed lately. cuhulin
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On Oct 6, 7:48 pm, snipped-for-privacy@webtv.net wrote:

Guess what cuhulin? The HD engine fires one cylinder at a time too. If the HD engine had both cylinders firing at the same time, I would imagine that catastrophic engine damage would be the result. The HD 45 degree V Twins connecting rods share a common crankpin. The front cylinder fires, the rear cylinder fires 315 degrees later and the front cylinder starts the cycle over again 405 degrees later. That's what accounts for the HD's distinctive sound, shakiness and sounding like it's out of tune even when running perfectly. As for the V12, I don't know. You can certainly look up firing orders for various V12's on the internet.
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snipped-for-privacy@webtv.net wrote:

True in as much as the ignition system is a waste spark system.
The firing sequence of a H-D V twin is; fire-crank rotates 315*fire- crank rotates 405*fire-crank rotates 315*fire-crank rotates 405* lather, rinse, repeat.
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I guess I was mistaken.I once saw a program on tv about motorcycles, a guy said Harley Davidson motorcycle engine pistons both fire at the same time.I have never owned a Harley Davidson motorcycle before.Well, I have, but that one was a made in Italy one cylinder Harley Davidson motorbike. cuhulin
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On Oct 6, 11:32 pm, snipped-for-privacy@webtv.net wrote:

I think I knew that about Hardley's but I've never owned one. I don't have a spare room/garage to park it in. So I ride a bike I can park on the street, 1975 BMW R90/6. Those bikes had a wasted spark ignition. Altough sometimes I use a substitute electronic ignition that is one cylinder at a time and timed off the crank, not the cam.
So where do you park a V12 car?
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On Tue, 7 Oct 2008, disston wrote:

Right next to the gas pump.
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In article

If it's a modern one, the same place you park any other car. The V12s being built these days aren't all that much larger, physically, than a V8 'cause they use smaller pistons. Just from looking at it, you probably won't be able to tell it's a 12 instead of just a big 8 without counting plug wires/injectors. (Unless, of course, it has a "V12" brag molded/stamped/painted on the valve covers or similar, which SHOULD make it fairly obvious...)
The old 40s/50s vintage 12s, on the other hand, might need an extension on your garage to get 'em inside and close the door.
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What is 720 divided by 12?
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Depends. Here is an article that should help. http://www.enginehistory.org/fo/FO.htm HTH Ben
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Back in the 1960s a used car lot down town had an old 12 cylinder Lincoln car for sale, for $3,500.I tried the car out around the block.The car didn't seem to have much power.Across the street from that used car lot there was another used car lot.They had a 1953 Corvette car for sale for $3,500. cuhulin
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Dean wrote:

I don't know of any common engine, from 4 cylinders to 20, that fires cylinders simultaneously. What on earth would be the point?
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Twice as much "oomph" per combustion phase?
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wrote:

True, but offsetting one bank of cylinders by half a crankshaft revolution means you get 12 small surges of power rather than 6 large ones, so the engine is smoother: the explosions from one bank fill in the gaps between the explosions on the other bank.
Silly question: in a 4-cylinder engine, it's normal to have the pistons at 0 or 180 degrees on the crank shaft, so two are at the top of the travel (one about to do induction, the other about to do power) when the other two are at the bottom of the travel. But would it make the engine smoother if the pistons were at 0, 90, 180 and 270 degrees (though in a random sequence to avoid a travelling wave)?
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Yamaha has a cross plane crank four cylinder engine:
Check the demo at:
http://www.yamaha-motor.com/sport/msite/micro_v1.aspx
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writes:

Yes that's the sort of thing I was thinking of. So it *is* possible - I wondered whether there was some very obvious reason why it wasn't done years ago in the early development of the engine so as to become the standard.
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Mortimer wrote:

If its a 2-stroke engine, then yes you'd want 90-degree spacing. But in a 4-stroke, each cylinder only fires every other crank rotation so you have to have pairs of cylinders moving together. The inline 4 moves the middle 2 and outer 2 together, which minimizes primary imbalance but leaves a HUGE second-order imbalance. The block tries to "bounce" up and down parallel to the cylinder bores twice per revolution, which is why so many I4 engines have balance shafts turning at twice crankshaft speed. The opposed 4 is a FAR superior layout balance-wise, but packaging constraints have made the I4 dominant in the marketplace. Personally, I gladly pay the extra fuel for a v6 or I5 just to get away from the horrors of inline-4 balance. Even an inline 3 would be better. I hate inline 4s.
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Apart from a Citroen GS in the early 1980s which had a 4-cylinder boxer (horizontally opposed) engine, I've never driven anything except an inline 4, so I've nothing to compare against. 6- and 8-cylinder engines here in the UK are confined to large executive cars which are waaaaaaaaaay outside my price range.
Why is an inline 4 so bad compared with even an inline 3, and why should the *apparently* balanced configuration of two pistons going down as two pistons come up be so bad? I'd have thought an odd number of cylinders would be unbalanced. My mother has a Daihatsu with an I3 engine, and that sounds very rough at high engine revs and the car feels as if it has the tremors at idling speed.
Do all I4s have 1 and 4 moving together and 2 and 3 moving together? Wouldn't 1+3 and 2+4 do equally well in preventing a standing wave? Would it improve or worsen the imbalance that you describe?
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Mortimer wrote:

Well, an I4 isn't a disaster in any way, so don't read too much into my comments. Pretty much any number of cylinders arranged in line can be first-order balanced (in-balance at the same frequency as the crankshaft rotation speed) with crankshaft counterweights. Its the higher-orders that get more difficult. I'm not sure what the dominant vibration for an inline-3 is, but for an inline 4 its the second order (twice the crank speed) that cannot be cancelled directly using counterweights on the crankshaft. The engine tries to "bounce" up and down in the same plane as the cylinders, but at twice the crankshaft speed. An inline 6, by the way, is perfectly naturally balanced at all harmonics. So is a 60-degree V12. V8s and v6s lie in between, their natural imbalances are higher than the 2nd order (ie. 3, 4, or more times the crank rotation speed) and so they are less noticeable than an I4. The problem with the I4 is that the primary residual imbalance is at such a low frequency that it can be felt easily. The plus side is that its very easy to correct with balance shafts, but of course that saps a little bit of engine power away. Obviously its not a big enough drawback to prevent the I4 from being one of the most common engine types in the world. Packaging counts for a lot when it comes to actually putting an engine in a car. The cool thing (to me) about flat-4s like Subaru and Porsche is that the crank is SO light weight compared to an I4 of the same size and power. It looks like a bent steel bar with no counterweights at all, until you look closely and see the VERY small counterweights at each end which cancel the vibration due to the pistons on opposite sides of the engine not being directly aligned with each other.

I'm guessing that's the same (or similar) engine to the old Geo Metro that was sold in the US. The I3 has some roughness due to simply having fewer power pulses per crank rotation, but the mechanical balance is as good or better than an I4. The other thing is that the Daihatsu engine is geared toward economy (both in manufacture and in operation) so its not very optimized for creature comforts. Personally, I like the inline 5s that GM, Mercedes, and Acura have used over the years. Good compromise between fewer cylinders for economy, and avoiding the I4 vibration issue.

I don't think that would change the 2nd order "bounce" motion at all, but it would ADD a tendency for the engine to rock back and forth at crankshaft speed (or maybe 2x speed). Pairing 1 with 4 and 2 with 3 at least keeps everything in one plane of motion.
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Don Bruder wrote:

Which only makes the power delivery less smooth. If you're gonna do that, one bigger cylinder makes more sense. Adding cylinders and making them fire sequentially, even if the spacing between firings isn't even (ala the Dodge Viper V10) makes for less vibration and torsional loading on the crank than fewer, bigger power pulses. There does come a point where crank length makes adding cylinders impractical, but a V12 isn't close to that. EMD made a 20-cylinder medium-speed diesel for locomotives and ships for a while in the 70s and 80s, but it proved less reliable than a higher-powered V16 because the crank and case (there isn't really a "block" in that kind of engine) had flexing problems. Especially in locomotives, it was pretty good in ships (I've ridden on a ship powered by 2 of them).
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