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[feeutfo]

never paid much attention to firing orders, mainly because i always assumed we already had something like or similar to this already.

Sincere appologies for the cheesy presentation

http://www.youtube.com/watch?v=UvTXMtTTKQw

[feeutfo]

just me then...
sometimes used on v8s apparantly. Needs 4 pots to work/balance. Seems to work, both Rossi and Spees(well he was until if binned it at Assen) doing well in their respective championships.

[Kevin Wood]

Hmm. Interesting.

It results in an odd firing order so it's not going to be a refined engine. I guess on a bike that matters less than getting the best out of the strength of the engine internals, which is what they imply is the advantage.

Most V8 engines have a crossplane crank, in fact. It's interesting that the more extreme V8 engines go back to a flat plane crank because it is easier to make them strong and they don't need such large counterweights to keep them in balance.

Kevin

[Kevin Wood]

The other important advantage of a flat plane V8 is that the firing order means that a cylinder from each bank fires alternately, which is exactly what happens on the GM V6. This keeps the exhaust system simple because you don't get adjacent cylinders firing in quick succession and the exhaust can scavenge the exhaust gases more effectively. It is also why you keep the exhausts from each bank separate rather then join them with a "balance pipe".

Unfortunately, the "burble" of a V8 comes from the unevenness of the firing between banks, so flat plane V8s lose that.  Not that that would discourage me from owning a Speed Eight (reliability would though ).

Kevin

[feeutfo]

the bike media describe it more as a triple, rightly or wrongly, with the 4th cylinder firing as a fill in to keep momentum. They played with a "big bang" 4 that didnt really work too well. I guess this is a development of that. Theory being the tyre gets 2 or 3 bigger pulses , depending on firing order, giving it time to recover(grip) between pulses. Rather than equaly phased pulses of the flat plane.

Cross plane 4 gives v twin grip and grunt rather than peaky slides of the fours while still retaining a high rev limit and top end horse power that twins can only dream of. For bikes it appears the best of 3 worlds.

Your way ahead of me on the v8s, the noise of the yamaha is lovely. Cross between a triple and a twin with the the revs of a four. I just might wet myself if another bank of 4 cylinders where added, what a symphony that would be.... Cant see the bank firing order staying the same though sadley...??

I think if the cruiser bike world can work with harleys they can work with anything. Cars are another matter imho. For the road esp, Ascari A10 for fun days, one day i hope.

Back to my first thought though, the balance within
the four pot cross plane, with firing of the next cylinder over coming the up/compression stroke and so on.... My assumption was firing orders where along those lines already, clearly not.

Interesting...:-)

[Kevin Wood]

Back to my first thought though, the balance within
the four pot cross plane, with firing of the next cylinder over coming the up/compression stroke and so on.... My assumption was firing orders where along those lines already, clearly not.

Almost every other 4 cylinder engine looks like this:



So one cylinder is on the compression stroke while the other is on the power stroke and the other two are induction and exhaust. Problem is you get a big dead zone at TDC and BDC where nothing moves and because of the rod angles the piston speeds aren't matched and don't balance out. In any case, it's the first half of the power stroke that produces the highest torque and the last half of the compression stroke that requires the greatest torque so the whole lot relies on a 'kin great flywheel to keep it running.

Bah! 4 pots. Who needs them?  

Not sure about the torque delivery. I would have thought that was more down to the cams than the number of cylinders, firing order, etc. but I know root F.A. about anything with 2 wheels.

Kevin