Gearhead Sleuthing

[Diablo1]

I believe I've figured out the RSV4 crank design from stop action of the Aprilia engine vid. It's a 180 degree crank with the following firing order:

0....180.....295......475 degrees
This is the same as the new Yamaha Vmax.

You can contrast this with the Desmosedici softpulse engine with 70 degree crank offset:

0....90....290......380 degrees


Remember who told you first.....

[rx7tt95]

According to Two Wheels(UK), the firing order is back left, front left, back right front right with firing intervals at zero degrees, 180, 425 and 605 degrees. A massive 245 degrees of crank rotation without firing.

[Diablo1]

According to Two Wheels(UK), the firing order is back left, front left, back right front right with firing intervals at zero degrees, 180, 425 and 605 degrees. A massive 245 degrees of crank rotation without firing.

If you do the math, you'll see that's two different ways of calling out the exact same firing sequence. The firing intervals are 180, 245, 180 and 115 degrees. But, the firing order is not back left then front left - since there is 65 degree cylinder angle, which is inconsistent with having the 2nd cylinder fire at 180 degrees.

[rx7tt95]

I suck at math I'm just regurgitating what I read in the magazine today. I just double checked (took a picture) so you'll have to take it up with them, LOL. I've not examined the firing order at all.

Also, you may be assuming the animation is actually correct.

[Diablo1]

I suck at math I'm just regurgitating what I read in the magazine today. I just double checked (took a picture) so you'll have to take it up with them, LOL. I've not examined the firing order at all.

Also, you may be assuming the animation is actually correct.

The animation is consistent with the crankshaft picture I saw posted that shows a 180 degree crank. Because of the 65 degree cylinder spread, there are only a few firing order options. One would be big bang with the two cylinders on one side firing 65 degrees apart, and Aprilia did not choose that. The other option that Aprilia chose was conventional with the most even spread of firing pulses. And as you've pointed out, is not very even. Big bang engines, mean big vibration and durability problems, and that's the reason that Aprilia and Yamaha (V-max) would not select that firing sequence.