Rather perplexing...

[UncleBob]

Originally Posted by 2.2 Straight six

according to VW, it's a VR5 (vee straight 5) the cylinders aren't in line, so it's a V, regardless of it being a single-bank engine.

http://www.motoczysz.com/main.php?ar...turn_path=news

I guess you'd call this engine a V4 then. Its a twin crank engine also, btw, cranks rotate in opposite directions. Another GP bike

[UncleBob]

after doing a search on the VR5 (I'd never heard of it) you are right, its a V5. From your discription, I thought you were discribing something more like what I posted above

[GreyGoose006]

now big bang engines are pretty cool.
i kinda wonder who was cracked out enough on caffine and sleep deprivation to think of that.

[UncleBob]

nothing too difficult about MAKING a big-bang motor, just requires different cams....what was perplexing was the REASON why it worked so well.

The thing that got engineers thinking so hard about it, was why relatively underpowered V twin race bikes were constantly beating the I4's on the track. The V2's couldn't match the I4's on the straights, but the V2's would consistantly get away with earlier full throttle coming out of corners, that the I4's, if they attempted the same level, would lose traction and high side violently.

So some smart cookie started looking at the dynamics of traction on a milisecond level. The simple question was, what causes traction loss? Its not just the power, obviously, as the above example shows.

But when you graph the individual power pulses between the two engine designs, not too shockingly, the V2's power pulses are half as often as a traditional I4. What this created was time for the rear tire to recover between pulses. Where as the I4 hits so frequently, the tire couldn't recover, and would cause a chain reaction that would make it step out.

So they made the I4 (and V4) to match the V2 closer in power pulses. 1 & 4 have the same power stroke together, ie, they are basically the same cylinder, working in unison. Same for 2 & 3. Same power, but completely different sound and traction quality. But the reliability suffers severely. The cams were a major problem, because its opening too many valves at once, lots of cam chains were breaking and cams snapping in half from all the stress. The load on the crank is much harder too. Even the chain and sprockets take a lot more abuse because of this.

Some of the newer ideas on this (which I assume was partially why honda went with the V5 originally) was to make "little bang" engines, where the pulses are slightly more staggered to spread it out just a little bit, to increase longevity

[GreyGoose006]

well thats what i was thinking...
if you have an I4 crank, all the crank parts will be split by 180*
in an I2 they are on the same side.

why not have a big bang I4, but instead of having them all on the exact same side, spread them out by 10 degrees or so.

less stress in one shot.

i guess thats what a little bang is tho...

too bad someone else thought of it first.