Difference between "Inline Twin" and "Parallel Twin"?

[aargee]

Gives me an immense pleasure sharing my knowledge that a fellow XBHPian taught me when I was new in this forum

Take an example of two cylinder engine; A parallel engine goes firing for every 360 degree rotation, while an inline goes firing for every 180 degrees.

Means, on an inline engine, when one piston goes up, the other comes down. But in the case of parallel, both goes up & down together.

Additional information - Straight-two engine - Wikipedia, the free encyclopedia

Ninja 250R, Triumph Bonneville are some motorcycles running on parallel twin.

[niks_devil666]

If its just this diff (180 and 360 degree offset), then why don't they exist , or do they ?

[ken cool]

Take an example of two cylinder engine; A parallel engine goes firing for every 360 degree rotation, while an inline goes firing for every 180 degrees.

Means, on an inline engine, when one piston goes up, the other comes down. But in the case of parallel, both goes up & down together.

Additional information - Straight-two engine - Wikipedia, the free encyclopedia

Thank you!

[aargee]

Thank you!

No problem Sir, pleasure is mine.

If its just this diff (180 and 360 degree offset), then why don't they exist , or do they ?

Are you asking if they (which one?) exist or do not exist? I didn't understand the point. Pls elaborate.

[Andante]

If its just this diff (180 and 360 degree offset), then why don't they exist , or do they ?

The major point why you will generally only find inline twin engines is that the dynamic balance of a inline twin is much better than a parallel twin. A parallel twin has a dynamic balance that is the same as a single cylinder engine as the pistons move up and down together. In an inline twin they move in opposite directions thus canceling out some of the second degree vibrations that a single cylinder (and a parallel twin) engine would have. An inline twin does have a sideways rocking vibration around its central axis, but that's a much less then any vibration from having your pistons move together.

[aargee]

Last weekend I was explaining this to one of our member & he felt asleep ; worst part being, I too felt sleep & the difference being that he was co-passenger while I was driving

Anyway, that conversation left me with a question - Which one generates more torque? In my thoughts, its the parallel twin due to the double punch, but the top end or the maximum speed will be a limit. While an inline lacks the punch as much as a parallel twin but has a very good top end. Is this really true? Can someone help me understand the technicalities pls? Tks.

I think we're completely off topic; Mods - requesting to create or merge with an existing thread. Thanks.

[Samarth 619]

Last weekend I was explaining this to one of our member & he felt asleep ; worst part being, I too felt sleep & the difference being that he was co-passenger while I was driving

Anyway, that conversation left me with a question - Which one generates more torque? In my thoughts, its the parallel twin due to the double punch, but the top end or the maximum speed will be a limit. While an inline lacks the punch as much as a parallel twin but has a very good top end. Is this really true? Can someone help me understand the technicalities pls? Tks.

I think we're completely off topic; Mods - requesting to create or merge with an existing thread. Thanks.

sorry for OT.

Actually, it depends on cylinder firing orders too.
In 4 stroke engines, every cylinder fires on 720 degrees of crankshaft turn.

For multi cylinder engines, irregular or close pulses result in more low end torque or more sound, while evenly spaced firing pulses result in higher revving...

Hence, for a modern parallel twin, it is possible to fire 360-360 degrees to high rev it, like Ninja 250 does, and so it produces more power too than a single cyldnr 250 does...

[Andante]

sorry for OT.

Actually, it depends on cylinder firing orders too.
In 4 stroke engines, every cylinder fires on 720 degrees of crankshaft turn.

For multi cylinder engines, irregular or close pulses result in more low end torque or more sound, while evenly spaced firing pulses result in higher revving...

Hence, for a modern parallel twin, it is possible to fire 360-360 degrees to high rev it, like Ninja 250 does, and so it produces more power too than a single cyldnr 250 does...

Actually, ninja uses a 180 deg crank throw for it's pistons, so they don't move together. Ninja has a typical inline twin engine which fires the cylinders right after each other. A parellel twin as you describe would not be able to rev as high, since the second order vibrations would shake the engine to bits.

[niks_devil666]

^ so ninja is an inline twin but called as a parallel twin by the manufacturer?

[aargee]

Actually, ninja uses a 180 deg crank throw for it's pistons, so they don't move together. Ninja has a typical inline twin engine which fires the cylinders right after each other. A parellel twin as you describe would not be able to rev as high, since the second order vibrations would shake the engine to bits.

With due respects, glad if you can check this out - kawasaki ninja - Bajaj

Actually, it depends on cylinder firing orders too.
In 4 stroke engines, every cylinder fires on 720 degrees of crankshaft turn.

Got you, learned something new today. Thanks.

Hence, for a modern parallel twin, it is possible to fire 360-360 degrees to high rev it, like Ninja 250 does, and so it produces more power too than a single cyldnr 250 does...

I couldn't understand this; could you elaborate pls?

[Andante]

^ so ninja is an inline twin but called as a parallel twin by the manufacturer?

With due respects, glad if you can check this out - kawasaki ninja - Bajaj


Got you, learned something new today. Thanks.


I couldn't understand this; could you elaborate pls?

Uhm... now I'm confused. I thought it was an inline twin. I could very well be mistaken.

Edit:
Seems I was right. I found some pics of the crank from an older model on ebay and it has a 180 deg crank throw. Also on wikipedia it say inline twin. We all know how accurate companies and their marketing departments are.

[tanay]

We should ask here:

http://www.xbhp.com/talkies/desi-bikes/12801-long-term-plan-cbz-250r.html

On page 2, the valve pics show the valves of the 2 cyls in different positions...perhaps that makes it inline?

[aargee]

Seems I was right. I found some pics of the crank from an older model on ebay and it has a 180 deg crank throw. Also on wikipedia it say inline twin. We all know how accurate companies and their marketing departments are.

^^^ Strongly disagree

Are you saying the one you found on the wikipedia written by someone who's not even been associated with Kawasaki & an old model of crankshaft found on ebay are right or the manufacturers are right?

[Andante]

^^^ Strongly disagree

Are you saying the one you found on the wikipedia written by someone who's not even been associated with Kawasaki & an old model of crankshaft found on ebay are right or the manufacturers are right?

How about this then? OEM Parts Kawasaki Ninja 250R (EX250-JAF) 2010 CRANKSHAFT - Cheap Cycle Parts

If you take a careful look at the diagram you'll notice there's only one crankpin visible.

And the ebay link: EX250 crank

Yes I know it's an EX250 (which is a 250r) crank from 2007, but i don't think Kawasaki would have changed the crank throw in the latest incarnation.

[cool_dude_sunn_y]

With due respects, glad if you can check this out - kawasaki ninja - Bajaj

I completely agree with Andante, and the proof is that i recently stripped down the whole 2009 engine and pistons do fire one after the another.