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V Twins, Triples, Inline fours - Noob Question

Discussion in 'General Motorcycling Discussion' at netrider.net.au started by oliver, Jun 15, 2008.

  1. I've read various posts about riders singing the praises of V twins, others swear by Inline fours, and yet others reckon that triples are the bees knees.
    But for a Noob it is all a bit confusing. What are the characteristics/positives/negatives of the the various engine layouts???

  2. Generally speaking:
    For a given size engine, the fewer the cylinders, the stronger the low-rpm power and the weaker the high rpm power.

    There are exceptions, of course...

    Single cylinder bikes (usually dirtbikes) have prodigious amounts of power at low rpm, and are mechanically very easy to service - one carburettor, one sparkplug.

    Twins are common on road bikes and tend to be tuned for strong midrange power. They sound very cool too.

    Triples are fairly rare and blend some of the "twin" low-to-midrange torque and some of the "four" top-end power. Also, they only require a single counterbalancer to eliminate vibration.

    Fours are very common, and tend to be better suited to high-rpm power, but lose a little bit of low-end power typically. They require two counterbalancers to eliminate vibration.
  3. Why do shoe shops sell all sorts and shapes and types of shoes? Because what suits some people, doesn't suit others.

    So let's assume your interest is academic, since you're going to be limited in choice for the first year or more of your riding, and deal with the concepts involved.


    V-Twins have fewer cylinders than most other bikes (except singles, natch) and deliver their power in steady pulses. The bigger the capacity, the bigger the pulses. Big Ducatis are almost erotic as a result :LOL:.


    Despite the current success of Triumph's triples, no-one else is building to this specification, so they either know something, or are ignoring something! A triple is slightly wider than a twin, and narrower than a four (at the crankshaft level) and delivers its power in an odd, staggered manner.

    In-Line fours

    In-line fours make up a huge section of the market, for several reasons, all the subject of interminible debate. For every one person who says thst it is the best layout for power, smoothness and economy, you'll find someone else who'll say it's just that the Japanese are lazy and can't be bothered innovating.

    Ultimately, as we always say, ride them all, study up, and make your choice on what you LIKE, not what someone else says is good or bad.
  4. Just to nitpick; Triumph's "Urban Sports" range have the pistons moving 120 degrees apart, so they deliver power "evenly" like a four that's revving at 3/4 the speed.

    I can't remember the type of triple which went "1-2-3-pause", which is I think what you're describing? :-k Hopefully I haven't misunderstood. :)
  5. Yep, Purely out of Interest. Thanks for the explanation :grin: .
  6. Don't take TOO MUCH notice of what I say; most of the bikes I know something useful about are already PAST the wreckers :LOL:!!!!
  7. I think I vaugely remember reading something about some of the lateest Benelli's being Triples also

    Edit - Just read above post :LOL: :LOL:
  8. Yes but Benelli don't make their own engines. They outsource them from Suzuki, Ducati, Triumph and maybe some I've missed. no one uses the rotary car engine bar Mazda but it's still a cracking engine.
  9. You're talking about learner bikes so the concepts of engine layout is more exaggerated. Eg. yes twins have great low down power, so a gpx250, vtr250, zzr250 will pull from lower revvs than a cbr250rr, bandit 250, 250 hornet, etc.

    But when you get to a certain CC the rules stop applying.. eg. my vtwin 650, good low down torque but a 1000cc i4 obliterates it.. My bike pulls well from 4000rpm and I cruise comfortably there. Riding yak's 954, it pulled with that same power from 2000rpm! :S

    Conclusion? I want an i4 ;) Keeping the twin though too.
  10. There was one. A Laverda 973cc engined bike built back in the early 70's. It was an inline triple with a 180 degree firing order (720 degrees in a 4-stroke power cycle, eh), and operated much like an I4 with one cylinder chopped off. ie. 1-2-3-pause.

    Vast, vast majority of triples have a 240 degree firing order (120 degree crank spacing) though..

    There are two other aspects here as well, that being the stroke length and the firing frequency. The lesser cylinders for the same capacity means a bigger diameter piston, but you can't just make the piston too huge in proportion to the stroke length, and so the stroke is longer too. This tends to boost both the engine braking and the lower regions of the torque curve but the engine can't rev as quickly with a longer stroke as the piston speeds become too high and conrods start to fatigue and break as a result.

    V2's actually have a very uneven firing order, but this has benefits in helping the tyres to "cool off" and regrip the road better as the power pulses are less frequent.

    The same goes for the triples which have supurb traction on the edge under a wide throttle allowing for quick corner exits.

    Also, less cylinders means less crackshaft rotational mass which actually can be felt in how easy a bike is to turn into a corner due to the gyroscopic precession effect.

    There's lots of subtle things. It's hard to put this into context with racing. Less cylinders means longer strokes means lower top rev rate means less power at the same capacity, which is why a 600cc four, a 675cc triple, and a 750cc twin all make about the same power.

    The other problem with racing though is that the racing codes are driven by dollars and are quick to snuff out anything too unfair by punishing them with added weight. In SuperSport, the 675cc triples carry an enforced 4kg weight penalty even though they're not even dominating, while the 750cc twins have an enforce 8kg weight penalty which explains why the Ducati's pretty much fell by the wayside in World Supersport.

    At the end of the day, if you ride hard enough and long enough, you'll start to develop an idea of the characteristics that you like in an engine, and that's what means the most to any one person, that they feel like they're at one with the machine.
  11. A few more bits and pieces.

    The fewer the pulses of power per cycle the better the tractability. The tire has a longer period of time to recover and conform to irregularities in the road between pulses. i.e. for a given amount of power an i4 would spin up well before a single. Then you've got things like big-bang engines which make a twin behave more like a single, and a v4/i4 behave more like a twin.

    The ratio of stroke vs bore (distance the piston moves vs the diameter of the piston), the weight of moving parts, the porting, etc etc has as much to do with power delivery and character as the engine configuration. An "over square" single which has a stroke shorter than its bore is wide for example may well rev out to 13k rpm, while a long stroke twin may redline at 8k rpm.

    Physical dimensions. A single, vtwin can be quite skinny. A vtwin will hold its weight lower than a similar parallel twin. etc etc.
  12. singles putt

    twins thump

    triples burble

    fours sing

    thats all you need to know :grin:
  13. Interesting topic, thanks for posting!!

    All the above talk about twins seems to be about v-twins, how does a parallel twin (i.e. my bike) compare?

  14. More information about each engine config here: http://en.wikipedia.org/wiki/Category:Motorcycle_engines

    That's more of a straight-up discussion of the engines themselves, rather than how they apply and feel to the rider on the road.

    Parallel twins have bad mechanical balance and thus are naturally buzzy. The only naturally balanced twin configuration is the flat twin/boxer.

    Aside from the manufacturing costs, there doesn't seem to be any good reason why we don't see a very narrow angle V6 being used more frequently, which is basically 6 cylinders staggered such that the overall width is no wider than a regular I4. Most racing codes apply hefty weight penalties for 6 cylinder engines and this would seem to be the predominant reason for why we aren't seeing them used in motorcycles.
  15. Vertical twins are pretty good these days, with balance shafts and all.... Now my old 650 Yamaha vertical twin, that WAS a different story :LOL:.
  16. Stew, a small, narrow-angle V6 would be sweet, but it'd be a cow to change the plugs :LOL:.
  17. Just for the sound alone,the v6 Laverda,shame they ran out of money
  18. ...and servicing/rebuild costs for the road going versions perhaps?
  19. Maybe. Couldn't imaging that it'd be too dramatic since pulling the engine head off is a pretty rare occurrence, valve adjustments not withstanding.

    Just to be clear, I'm talking about the 6 cylinders in the same physical bank, much like the VR6 engine used by Volkswagon.

    ie. http://en.wikipedia.org/wiki/VR6

    Could do the same thing with any number of cylinders really, but a VR6 engine would have the potential to surpass I4's dominance within a fixed capacity limit.
  20. and one of the best sounding V6s out there!!!!