Engine design

[Scab]

From an engineering point of view, is there a "preferred" engine design? I have noticed the proliferation of he V-twin engine in so many motorcycles that are sold in the U.S. Is there an engineering reason for this? Or is this just what the market requests? Are there mechanical benefits to the V-twin? Is the V-twin more cost-effective to manufacture?

 

[SkooterG]

V-Twin = Torque, pretty exposed cylinders for the cruisers, copy Harley designs, lower frequency vibration (than inline 4) for 'feel' and 'sound'. It's a less advanced engine than other designs, but that's what the cruiser crowd wants.

As far as cost it may be cheaper, I don't know. I am sure there is plenty of $$$ going into R&D to build a better mousetrap (V-Twin) than the next guy.

 

[wfooshee]

V-twins are pretty narrow, too. Even counting those big chrome pipes and air intakes on the sides.

 

[Bungie]

From an engineering point of view, is there a "preferred" engine design? I have noticed the proliferation of he V-twin engine in so many motorcycles that are sold in the U.S. Is there an engineering reason for this? Or is this just what the market requests? Are there mechanical benefits to the V-twin? Is the V-twin more cost-effective to manufacture?

Kay, I've still got one of those big *** VTwins (05 Kaw. Meanstreak 1600cc). Around town, the torque is awesome, MUCH better than the FJR. It doesn't really matter what your gear your in, twist the wrist and it jumps ahead. Even on the highway, if I set the throttle lock on the FJR, it'll lose 5-8km/h going up hills (at a higher rpm than the Streak) and gain a simlar amount going downhills. The Streak might vary +/- 3km/h MAYBE.

They get pretty similar gas mileage as well. Seriously, for an all around engine in the real world, that big VTwin beats the I4 in the FJR. But ring down the engine room on the FJR and put the spurs to it and you tend to forget all about the VTwin

All that being said, I haven't been on the Streak in about 3 weeks.

 

[Checkswrecks]

From an engineering point of view, is there a "preferred" engine design? I have noticed the proliferation of he V-twin engine in so many motorcycles that are sold in the U.S. Is there an engineering reason for this? Or is this just what the market requests? Are there mechanical benefits to the V-twin? Is the V-twin more cost-effective to manufacture?

Sure there's a prefered engine design. You tell me what you want your engine to be optimized for, and we can figure out which design would be prefered for the application.

Harley factory people have said for many years that they know they could develop an ***-kicking 4-cylinder, but that they know their market. Their market is all about "The Ride" and subjective stuff like feel and hearing the words "potato - potato - potato" over and over. Or we could use a single cylinder design, perhaps. Little single lungers are optimal for small-cc scooters because they give a lot of torque, but they're probably not what you'd want for a sport-tourer or World Cup GP racing.

Then we can get into displacement, water or air cooled, transverse or V, yada yada yada...

Clear as mud, right?

 

[Knifemaker]

Sure there's a prefered engine design. You tell me what you want your engine to be optimized for, and we can figure out which design would be prefered for the application.
Harley factory people have said for many years that they know they could develop an ***-kicking 4-cylinder, but that they know their market. Their market is all about "The Ride" and subjective stuff like feel and hearing the words "potato - potato - potato" over and over. Or we could use a single cylinder design, perhaps. Little single lungers are optimal for small-cc scooters because they give a lot of torque, but they're probably not what you'd want for a sport-tourer or World Cup GP racing.

Then we can get into displacement, water or air cooled, transverse or V, yada yada yada...

Clear as mud, right?

+1 or Gunny or whatever...

From a pure engineering view , the "ideal" motor would be the simplist. Less moving parts means less things to go wrong. I was always told a 2 stroke single was the easiest to build and used the least amount of parts.

Those of you whose butt finaly stopped vibrating after all these years from riding an old Suzuki TS400 back in the day will understand that the ideal single two stroke should also be fairly small.

Another good design keeping with the KISS principle would be the rotary engine. I heard it is making a comback...

KM

 

[radman]

A big part of the VTwin thing is, of course, Hardley® wannabe's that can't afford the real thing, or for whatever reason, prefer the rice equivalent. Though they aren't. But anyway, the preponderance of choppers, customs, etc is because of S&S and RevTech, who make complete, ready to run engines, and Baker, who builds transmissions, 4, 5, and 6 speeds. With a driveline, the rest is relatively simple. From an engineering aspect, inline 6's, and V12's. Perfect primary balance, 7 main bearings, nice sound and, in the case of the V12, smooth tremendous torque output in proportion to displacement like no other.

 

[S76]

I guess everyone has their own preference.

If I was building an air compressor, tractor, roto tiller, or log splitter I would go with the V twin. But on a bike I want an engine that has good midrange, low vibration, and a high red line.

Kinda like an FJR engine.

But that's just me, you know.

 

[Rolavine]

[

+1 or Gunny or whatever...

From a pure engineering view , the "ideal" motor would be the simplist. Less moving parts means less things to go wrong. I was always told a 2 stroke single was the easiest to build and used the least amount of parts.

Those of you whose butt finaly stopped vibrating after all these years from riding an old Suzuki TS400 back in the day will understand that the ideal single two stroke should also be fairly small.

Another good design keeping with the KISS principle would be the rotary engine. I heard it is making a comback...

KM

Yes, electric induction motor is pretty near perfect, just wire, armature and bearings, that Tesla was one smart fellow. And now with superfast analog digital microcontrollers and mosfets with on resistances as low as wire we are all set to bemoan the lack of any good batteries or equivalents. What we need is a really great fuel cell and I don't mean a jug that holds some extra gas for you bike.

 

[rivgar]

I don't know about the R & D cost factor, but 90 degree v-twins (more proper L=twins) are naturally balanced because of the crankshaft angles. The are no need for counter balancers on a 90 degeee twin. They are also much more narrow than an I4 so the bike can be built with a narrow profile, however the length of a L-twin usually requires a longer wheelbase. Examples of L-twins that I am familiar with are all of the Ducati line, Honda RC-51, and the Suzuki TL and SV series.

I have a Suzuki TLR which is a load of fun on a spirited ride. It is very different than the FJR but differences are often a good thing.

 

[MotorToad]

There are tons of issues with engine design and packaging. One wives' tale I'd like to get out of the way first, though, is "torque." Twins make about the same torque as an inline-4, they just stop making power sooner so without that huge rush at the top they feel torqueyer... torquier... whatever. Check the charts between the RC-51 and 999 vs. GSX-R1000 and ZX-10R. Having a much narrower operating band it's easier to tune out the valleys in the torque so twins usually don't have as much of a hit at 4k rpm like the i-4s do.

Another is that the vibrations are at a lower frequency. Both I-4s and V-2s have perfect primary balance and a secondary imbalance. The only time there's a difference in the frequency is in the 4-6,000 rpm band where the i-4 is making power and the V-2 is making shrapnel. I think the magnitude of the imbalance is less with a twin than a 4, but I don't know that as fact. The direction is slightly different but a secondary imbalance is defined as twice engine speed so there's no difference in frequency over the same rpm.

Twins are way thinner, but they're also a lot longer. This limits swingarm length and handling, and rider comfort. Compacting the twin to 75º or 60º requires a power-sapping and heavy system of counterbalancers. Compacting it more to, say, 45º makes it an unbearable lump with, honestly, no good qualities as an engine (its qualities as a replacement for an off-balance washing machine or paint shaker should be obvious). Twins also require twice as many head castings and twice as many cams. They're smaller and simpler castings, but I'm not sure if it's enough to make up for being twice as many, so I think cost is a toss-up. Also, the space taken up by two heads exacerbates the packaging problems.

V-4s have the good qualities of both engines, with the bad qualities of both engines. Narrower but longer, more power but more of the expensive components. They're better balanced, though, hence their popularity in MotoGP. Also, V-4s (and twins for that matter) can't get as much advantage from a "stacked" gearbox like what all the new sport bikes have.

IMO the best design for a street bike is the I-3 that Triumph uses. They get about the same fuel economy as I-4s, good top end with a smooth torque curve, perfect primary and secondary balance, and they're more compact than either other design. They only down side is that they need a counterbalancer to cure crankshaft wobble.

Here is one of my favorite web sites ever. The 180º twin has the same balance as an I-4, and the 90º twin is pretty obvious. Also, it shows a 60º twin so you can compare that to the 90 twin knowing that the further ou go from 90º, the worse the balance is.

 

[JRO]

From an engineering point of view, is there a "preferred" engine design?

Yes! There is.

The turbojet.

 

[charismaticmegafauna]

From an engineering point of view, is there a "preferred" engine design?

Yes, depending on the engineer and his/her employer. If no constraints where applied it would most likely be a multi -- anything from an in-line 3 to a V-8.

I have noticed the proliferation of the V-twin engine in so many motorcycles that are sold in the U.S. Is there an engineering reason for this?

Probably. One, it's a cheap way to get more than a single; and, two, alot of the American market isn't very discriminating (engineering-wise).

Or is this just what the market requests?

There's much truth to that -- in America. Companies take funds out of engineering and put that money into marketing -- (sad to say) it benefits the bottom line. Many (lemmings) just get what someone tells them to get.

Are there mechanical benefits to the V-twin? Is the V-twin more cost-effective to manufacture?

Yes, it's cheap to manufacture (generally speaking) -- especially the H-D type (w/knife & fork connecting rod). The only real benefit is the one twins have over singles in breathing -- more piston area, valve area for either same displacement or similar packaging (space used).

 

[rockmurf]

Wait a minute. Who asked this fairly intelligent question? Is someone staying at scab's house or broke into his computer because this cannot have come from the scab I met at eom. Now what is up with this. Not to hijack someones thread but whad up?

 

[Scab]

A temporary moment of lucidity.