4 piston v twin
 

Is there such a thing? Think instead of a straight crank 4 cylinder, two vtwin cranks in parallel timed so one piston is firing when the other crank is in the middle of its downstroke/up.

Edit: ive found this.
http://thekneeslider.com/archives/20...linder-engine/


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Re: 4 piston v twin
 

so its basically a v4 with each bank of cylinders firing at the same time? sounds interesting

Re: 4 piston v twin
 

http://www.youtube.com/watch?v=TSJNFUkN2Dw

Here it is being fired up.....

Re: 4 piston v twin
 

so what you want is a twin crank v4?

i know that the old RG500 was a twin crank configuration but not in a V.

Re: 4 piston v twin
 

Does it mention firing order? I couldn't see where it did, so I'm not sure where you get that idea from. Essentially as it's two engines with cranks on a common axis it could be arranged in any manner the builder desires. 180° or 360° would be the most obvious balance wise, but 0°, (or 720° - depending which way you look at it :)), is possible as is anywhere in between. A 180° crank would have the pistons rising and falling alternately, (better balance but the firing pulses are uneven), 360° crank has the pistons rising and falling together but out of phase, (ie one is risng on compression the other on exhaust, then falling on power the other on induction), I've never encountered a V4 engine where the cylinders in any given bank are in phase, I can't see any benefit in doing so. Considering the propensity for Harley motors to shake I should imagine that the engine would be arranged as 180°.

It's not really twin crank as in RG500, RD500, KR250/350 or for that matter Ariel Square Four, as its cranks are side by side rather than tandem, which is to say it's two cranks joined together end to end rather than geared together on separate axis.

Side note: VFR750/800 are 180° cranks, RC30 has 360° cranks, the two of the obvious ways of arranging a V4.