Strange engine question

[Lloyd]

Have been discussing engines with someone at work involving essentially a 4 cylinder engine being run as a twin, ie having 1 and 4 firing at the same time. Easy enough to setup but does anyone have any info on these sorts of setups or if its been done to any road engines?

I know a bit about the history of it a couple of years ago with Yamaha running soemthing close to it, but thats all I've heard. Anyone got anything?

[Jdawg]

I remember, maybe not correctly, in the 70's the poms stuck 2 plane (flat plane) cranks in 302 Ford v8s and put them in Capri, might have been Cosworth, so idf they did it to a v8 they must have done it to a 4 pot

[JRS]

flaty plane v8's don't firs 2 cyclinders at one, it just makes each back like a 4 cylinder (2 up 2 down).

i can't see any advantage to the firing 2 cylinders at once idea.
will possibly break the crankshaft. and you'll have to pay big dollars to get a camshaft made to run it.

but the only real way to find ou if it's good or not is to do it. if you can do it is easily as you say. trying it on something cheap and see how it goes.

[toymachine]

A few motorbike manufacturers have done this in racing, not sure about cars though.

[fivebob]

Can't see it ever being used in a road going car engine. It's primary use is to stop wheelspin in high HP race bikes. initially used on the 500GP bikes, and later on the MotoGP by Yamaha, Kawasaki and Ducati. It has also appeared in at least one Yamaha engine in the British superbike series, but is banned in World Superbikes.

I know Ducati went back to the normal firing order, but I'm sure if anyone else is using it in the current 800cc MotoGP, as they aren't at the power levels where it might be useful...yet

[Lloyd]

Fair enough FiveBob, I thought it was mainly for the wheelspin issue but couldn't find any other info on them.

And yes JRS, it would be stressing the crank a fair bit, and the belt/chain driving the cam also being that its trying to open twice the valves without any help from another pair helping to push the cam around.

[79rolla]

get a 3/4k, make a cam and give it a go
im sure it could hack it

it would defiantly be something different if it worked even if only for the novelty facter

[fivebob]

Fair enough FiveBob, I thought it was mainly for the wheelspin issue but couldn't find any other info on them.

Try this google search, there's a few articles on it

The main reason it wouldn't be used in a car engine is that they don't rev high enough, so the wheel has a chance to recover, and on four wheels traction contol is an option. On two wheels it can cause handling problems as suddenly regaining traction tends to result in the rider being propelled over the handlebars

Which is why in the days of Fast Freddie (Spencer), before the big bang engine was invented, he used to ride very high up in the power band. So that, if the wheel did start to spin, the engine started to loose power and the spin recovered in a controlable manner.

[Malcolm]

as far as I know there is no scientific proof of the claimed traction advantages gained from grouping your cylinders to fire around the same time. That doesn't mean it doesn't have an effect, but there's not scientific theory that supports it, and no scientific testing has been conducted to prove there is an effect. I have read a reasonable amount of debate on the subject (has been a hot topic in FSAE circles in the past) and there doesn't seem to be any consesus on it either.

[fivebob]

There may be no scientific theory that fits the observations, but there's plenty of emprical evidence of improved traction and subsequent reduced tyre wear.