Its not all that simple to judge from just from the above info, as the Bore x Stroke, crank, fuelling, head, etc. matter a lot and they all determine the character of the bike.

But simply and generally speaking, the single cylinder should produce higher torque at lower rpm's, if not anything else.

Yes. Generally speaking.

Yes, I meant all other factor being constant. It's the reason why CBR 250 have more torque than N250 but N250 can achieve higher top speed.

Re: Does no. of cylinder makes difference...

I hope I get a reply - thread seems to be dead.

I did go through the thread but most of the discussion was a bit too technical for me to wrap my head around. I did understand that a more cylinders essentially means that we get a much better top end - but that's a result of the ability to rev a lot higher than a single cylinder counter-part - which produce better torque because they have a bigger bore/longer stroke.

Is my understanding correct?

If it is, it leads to my question - single cylinders are more relaxed at top speed than multi(dual essentially)cylinders?

Re: Does no. of cylinder makes difference...

No it is just the opposite I think . Multicylinder are more relaxed at top speed.

Re: Does no. of cylinder makes difference...

Dont they have to rev a lot moe to output the torque required? Why the 'screamer' tag then?

Re: Does no. of cylinder makes difference...

AFAIK, twin cylinders are more relaxed. I guess. Maybe am wrong. Reason being : twice the number of power strokes per time than a single cylinder engine. That's why the 'screamer' tag i guess. Collective rpm of both cylinders of the engine may make it seem that it revs higher. I may be totally wrong so it's better if i join you in asking the same question. LOL!!

Re: Does no. of cylinder makes difference...

I don't know technically, but what I have observed in my life is two cylinders are always better than one in same capacity of engine, in term of top speed, torque and long distance & constant cursing.

Re: Does no. of cylinder makes difference...

Single cylinder - more torque, less hp. Ideal for load pulling (non racing/touring type) activities. Generally vibrate more due to absence of counter balancers.
Multi cylinders - less torque, but lots of hp. Ideal for fast dashes. 2 or more cylinders, hence more RPMs. Torque usually comes higher in the rev band, which in itself is in proportion to the number of cylinders, hence the tag "screamer".

But practically, its all about the engine's configuration. A HD Fatboy and a Ducati Panigale are both double cylinder bikes (V twin and L twin respectively). You get the drift.

Re: Does no. of cylinder makes difference...

Power is a factor of both torque and rpm. Multicylinders have a momentum advantage to singles. This may or may not allow them to rev higher, that's a different question.

Its true that they have to rev more to get the same torque usually, but Multicylinders anyways usually allow for a higher rev limit, because each cylinder is smaller in size, and this allows shorter stroke value for each cylinder.
If the stroke value is smaller, it has to travel lesser per rpm... That means lesser friction.

Take an example of CBR 250 & Ninja 250:
CBR 250 is one giant cylinder of 250~ cubic centimeters of combustion space.
Ninja is two smaller cylinders of 125~cc each, which empower the same crankshaft.

Stroke values are smaller in each cylinder of Ninja, at 41.2 mm.
While in the single cylinder CBR, it is 55mm or so.

It means for 1000 revolutions of each of these machines, Ninja's twin pistons travel 41.2 metres each, while CBR's single piston travels 55 metres alone.
Less travels for a particular rev or rpm, means lesser friction, further means you can rev them higher.
Yes, to get the same torque.



OT and unrelated to the question:

When it comes to revs, larger engines are at a disadvantage, because they do have bigger stroke values, which means more piston travel & more friction. Let's take 3 examples of 4-cylinder engines (All are 4's):

ZZR250: Revs upto 19000 rpm.
R6 (600cc): Revs upto around 16000 rpm.
S1000RR: Revs upto 13000~ rpm or so.


As they increase cubic capacity (cc) of engine, each cylinder gets bigger with bigger stroke value, and more piston travel per rpm. And they don't have a choice except to increase cylinders, beyond a point.

My point is that if you create a square single cylinder 1000cc engine, it won't rev beyond 2000 rpm or so, because piston will travel a long distance just for 1 stroke. Friction will kill the engine beyond a certain speed.
Yes its true, that this engine will give solid torque and can have a really low idle rpm. But otherwise, what will you do with this engine? Fit it in a car?



An interesting question is, why don't we have really short stroke and large bore singles for big capacity engines?
A:- Well, beyond a point, big boreXshort stroke system won't work at full efficiency, probably due to some Principles of air dynamics. Also big bores generate tremendous heat.

In short, if you want to create a reliable 1200cc engine for a motorcycle to be sold in market, then it has to be multicylinder & not a single.. Its not a choice. Its a mandatory progression.

Re: Does no. of cylinder makes difference...

I guess I can add some confusion with my half understanding...
A 4 stroke engine has 1 power stroke to three dead strokes to complete a combustion cycle.
A Twin cylinder engine has TWO POWER strokes to Two dead strokes , and a Four cylinder engine has no DEAD stroke at all.
This explains why a Twin cylinder can build power faster than a single cylinder.
Torque, and power is proportional to Piston Velocity. Hence a Long Stroke engine generates more torque than a short stroke for the same revs. but the longer stroke does not allow the engine to rev to same RPMs as a short stroke ,due to the higher Piston Velocity and time for each cycle...A single cylinder Karizma 223cc has good torque from lower RPM since it is a longer stroke engine...as compared to a Pulsar 220 engine which is comparatively shorter stroke ...
There are much more variables to an Engine's function , power delivery , etc., which more knowledgeable members can clarify..
Hope I had confused enough.

Re: Does no. of cylinder makes difference...

[MENTION=32286]psr[/MENTION] sir & [MENTION=50548]samrat[/MENTION]h619 I am loving the discussions. As far as my understanding goes (which is no where close to you people), psr sir comparison between P220 & Karizma is a comparison between over square engine & under square engine. If we see the scenario in high revving multi cylinder engine all of them are of over square (bigger bore) nature. The reason for this is I believe is
1. In high revving inline configuration where the cylinders are placed close to each other, a under square (longer stroke) will generate more friction & hence more heat ( from 4 cylinders) as if the present under square set don't generate enough.
2. A bigger bore area (in over square engine) helps to give a better head area/space for more valves (4 valve) which are necessary for high rpm. A under square (longer stroke) engine will have a smaller bore i.e a smaller head space.
3. An under square set up has a longer crank throw (which has to tolerate higher stresses as rpms increase). High rpms would make the case worse.

Re: Does no. of cylinder makes difference...

Interesting thread...

Adding further info for readers like me...

Inline 4 : Here they're coupled(pair) with 180⁰ offset to other pair. We can assume for "no dead stroke" engine(as a whole), if one is doing power-stroke its pair ought to be on intake. And when one is doing exhaust, the pair ought to be on compression.

However, Wiki says Inline-4 fire with 180⁰ offset. Inline-four engine - Wikipedia

Firing Orders: Firing order - Wikipedia (no two at the same time)





Flat (Boxer): I don't think they employ this in motorcycles.



And then there is V4, couldn't find any animation. : V4 Engine - Wikipedia

Also the go-betweens Inline 3 (Straight 3) with 180⁰ or 120⁰ offset. I3 Engine - Wikipedia

Re: Does no. of cylinder makes difference...

Well, why don't companies bring out an engine which has no dead stroke, and at every stroke of the whole engine, we have one cylinder doing the power stroke?
The only reason i can fathom is, according to the above animations, two power strokes are better than just one, even if it means the presence of dead strokes. But why not an engine like the one [MENTION=32286]psr[/MENTION] sir said?

Sent from my C5502 using xBhp Connect mobile app

Re: Does no. of cylinder makes difference...

I was also thinking the same...

Re: Does no. of cylinder makes difference...

check out the firing order in the same animation post, there are no dead strokes in any of the mentioned engine configuration, for 4 cylinder 4 stroke engine, all pistons undergo one powerstroke for one rotation of crankshaft with no dead strokes. Most of the engines are of order 1-3-4-2 meaning for a 360 degree rotation of crankshaft (Each cylinder powers 90 degree of rotation so 90x4=360 degree) the first cylinder fires first and rotates crank by 90 degree then the 3rd fires and rotates another 90degree then the 4th cylinder fires adding another 90degree rotation and then 2nd cylinder thereby completing 360 degrees. This process repeats