| Author | Message | ||
     Okc99 |
Ok, we all know that V-twins sound better and feel better than most 4 cyc bikes of comparable size/weight. But I'm curious if that is really the only advantage? I guess I would like to believe that I'm driving an bike with an engine that is not "old tech" simply for aesthetic reasons of feel/rumble/and sound. My fear is that 4 cyc really are a more efficient design from a true-engineering perspective. I welcome your comments from those of you who are knowledgeable about mechanical engineering from a scientific standpoint. I must claim ignorance on this one because I don't know much about the mechanical efficiency of 2 vs 4cyc in the way that most bikes utilize these designs. Thanks! | ||
| Froggy |
4 cylinder engines are superior in almost every way. I can't type a full argument on my PDA, but there are no 4 bangers that have the sound or feel of the big twin. | ||
| Metalstorm |
To me, the advantage is a flat torque curve with lots of usable power in most of the rev range. I don't like to have to rev a bike to the moon all the time just to be in the meat of the power range. The V-twin lets me ride any way I like from slow cruise in town to bat out of hell in the twisties. | ||
| Okc99 |
Appreciate the responses. But my fear is with the 2nd response: that from a mechanical engineering standpoint, 4 cyc are more "efficient" in the transfer of energy with minimal loss. I guess what we need is a Phd in M.E. to chime in. Any of you out there? | ||
| Mbsween |
A twin is narrower (therefore more centralized) so you have reduced frontal area and you have the potential for a better handling bike. The powerband is the result of the whole package, not just the engine config. Take a twin , make it enormously oversquare and you'll get a bike that makes power in the upper end of the rev range like a 4. Take a 4 lengthen the stroke and give it two big valves per cylinder and you'll end up with a nice torque curve I don't think you can write one off as better than the other. engineering is all about making compromises that work. The Big 4 have the art of the IL4 down pretty well. Then there is that Ducati place. They seem to have a very good handle on high performance twins. And let's not forget the Buell guy, he's just starting in the horsepower race. While I doubt Buell will make race replicas like the Big 4, I'd be surprised to learn that we weren't going to see more power from his Bikes. | ||
| Froggy |
Ock, short answer is yes. Blake will give all the little details  | ||
| Chasespeed |
The 4cyls make more hp, overall. BUT, HP is nothing but a mathematical equation, based on tq and rpm.... Efficient, my 1250 gets 45-55 mpg cruising... My 600RR got a best of 30.... Its more a relative thing, than apples to apples.. For an all around, day to day bike, a healthy v-2, should satisfy just about any street riding urge... For the track, you really do need a L4 do be competitive.... The L4 has MUCH newer tech than the old XL based engines... and PEAK HP will always be superior based on displacement. BUT, peak HP is not always relevant... Chase (Message edited by chasespeed on September 27, 2008) | ||
| Ducxl |
POWER PULSES!!! The duration between the cylinders firing is much farther apart on a VEE-Twin.An inline four has the power pulses spread much more evenly/closely. NOW...While laid down IN the corner,an inline-4 will lose traction and will need to be throttled back in order to KEEP traction. The VEE-Twin with the power pulses much farther apart and can recover from the pulse and have much more throttle applied and KEEP traction. That's why they say VEE-Twins rule the corner and inline fours rule the straightaway Another tidbit i learned from that great man,Kevin Cameron Wanna talk about OVERSQUARE Versus UNDERSQUARE VEE-Twins?? (Message edited by ducxl on September 27, 2008) | ||
| Brumbear |
Baby bull (4cyl) says to daddy bull (twin) hey daddy lets run down the hill and hump a cow in the pasture daddy says no no son lets walk down and hump them all. Steady power delivery starting way down low nothing better | ||
| Reepicheep |
Ugh. Here we go again. You feel horsepower. Peak horsepower is more power, period. Torque is the mathematical abstraction, because without knowing RPM you don't know squat about anything the bike is doing. Horsepower is what is real. What is missed for some of the inline fours is that peak HP is only measuring the bikes power output when it is time to shift (and when you are making a scene)... not the overall drivability at many RPMS. So peak horsepower means little, it is the horsepower curve versus RPM that matters. For street riding, more HP at lower RPMs makes for a more usable bike. For racing, it matters less and peak horsepower is more important, as you are willing to do a lot of unpleasant things to always have maximum performance. People like big bikes like a 'busa because they like the grunt at any RPM. That is not "torque", it is power. And a busa makes so much power everywhere that it makes lots of power at low RPM also. Even when they are not winding it out to 9000 RPM (where they actually make 150 HP), they like having an honest 30 HP at 3000 RPM. It's less shifting and less work. If you look at the power curve versus RPM of an XB12, its not that far from a 'busa, up until the XB runs out of revs. So unless you are always winding your busa out to 8000 RPM, you would be just as well off with an XB motor. An inline four will generally be cheaper to make then a twin, and will generally put out more power per cubic inch. So if you are interested in arbitrarily restricting displacement and seeing what makes the most power, then an inline four is better. If you want to arbitrarily restrict width, a twin is better. I look at the overall package for the task at hand. My 78 HP air cooled twin is really nice and I really like it. I could care less that a 989cc inline four makes more power per cubic inch. | ||
| Ducxl |
An inline four is certainly MORE efficient. It has a lighter reciprocating assembly too. For street riding, more HP at lower RPMs makes for a more usable bike. Maybe.But only if the sound of running at 10000 RPM bothers you.Otherwise,an inline four is perfectly comfortable running at 10000 RPM. I like my original explaination.But an inline four,speaking only about combustion efficiency,is the engine with the advantage | ||
| Chasespeed |
orque is the mathematical abstraction, because without knowing RPM you don't know squat about anything the bike is doing. My bad.... posting while distracted... had something in mind... just didnt make it to the page... ANYWAY, what drives YOU, what are you going to enjoy more? THATS what is really relevant to YOU. If you wannt a 4cyl, get one... Chase | ||
| Rich |
My 4cyl. will cruise at 90 and deliver 40mpg while doing it. My Buell will jump it out of the hole, though. And with the Buell, I can rip on it more often, 'cause it won't do 90 in first gear. | ||
| Danger_dave |
>>Horsepower is what is real.<< 'Torque is what you ride with' - EB. I fully understand all of it - but the torque figure is FAR more important than the horsepower number to me too. | ||
| Bandm |
You feel horsepower. Peak horsepower is more power, period. Torque is the mathematical abstraction, because without knowing RPM you don't know squat about anything the bike is doing. Horsepower is what is real. Reep you have it backwards, torque is a measure of force, horsepower is a mathematical abstraction. Torque x RPM divided by 5250 equals horsepower. You feel torque. Peak torque is more power, period. Horsepower is the mathematical abstraction, because without knowing RPM you don't know squat about anything the bike is doing. Torque is what is real. Mark (Message edited by BANDM on September 27, 2008) | ||
| Brumbear |
that smart talk is a load a HOOEY I got an I4 and a Twin and the twin is 10 times more fun period the power comes in low and stays and pulls like a train and it is user freindly no surprises the I4 is a pain in the arse for my rotundness in the turns and the motor is squirlly turn the revs way up and it gets fun but I don't run alot of straight lines bye the way the KZ 1000 is turning 89HP stock mine has jetted carbs dyna he ign and a header so I would think the XB and KZ are almost dead even POWER wise | ||
| J2blue |
For bonus points tell us why more cylinders per given displacement is more efficient at producing horsepower than fewer cylinders of equal displacement? For bonus, bonus points: why would you not want a motorcycle that produces 100hp at 1000rpm? (Message edited by j2blue on September 27, 2008) | ||
| Teddagreek |
How about V4's  | ||
| Bandm |
525 ft lbs x 1000 rpm divided by 5250 equals 100 hp. 525 ft lbs torque is why. | ||
| Danger_dave |
And flat sixes are good as well. The Rune engine is a torquey peach. Bore x Stroke makes for interesting discussion too. | ||
| J2blue |
Remember when Wiley Coyote tried to use a catapult to catch that inline 4 called the Road Runner? Talk about a tank slapper. | ||
| Blake |
There is no meaningful and honest technical generalization concerning the efficiency of two cylinder versus four cylinder engines. A high revving short stroking engine will be less efficient than a lower revving longer stroking engine. There is no free lunch. A turbo-charger is the closest you can get to that. Now, all else being equal, an engine with more cylinders will be capable of generating more power than one with fewer cylinders. If you want to characterize that as efficiency, then there you go. Efficiency can mean many things, efficiency of design, material, maintenance, parts, operation, fuel, cost... What kind of efficiency are you talking about? | ||
| 4cammer |
"I guess I would like to believe that I'm driving an bike with an engine that is not "old tech" simply for aesthetic reasons of feel/rumble/and sound. My fear is that 4 cyc really are a more efficient design from a true-engineering perspective." Are you worried that you might have purchased the wrong bike? If you are concerned with having the most up to date spec sheet figures a XB based bike is not what you want. You do realize the engine design can trace its roots to the '50's, right? Any company can make a nice inline 4. Making one w/character is a whole different matter. | ||
| Ducxl |
Cool discussion.I hesitate to say but my passion for building engines comes very close to surpassing my passion for riding motorcycles.Engines are fun machines. | ||
| Ft_bstrd |
If there is no way to produce an engine with two cylinders that produces the same power as four cylinders given equal displacement, I think you have your answer. I guess the question is whether there is a perfect number of cylinders. Four is where we are now. Triumph does three. Would a V-4 be better than an inline 4? Would a V-5 be better than an inline 4? What about the Motoczysz design? I just can't believe that the IL4 is the final word in engine design. | ||
| J2blue |
It is gross over-generalization, but for a given displacement more cylinders can produce more horsepower, yet fewer cylinders can produce more torque. That is my layman understanding of the subject. Wikipedia has some great articles on the science of combustion engines that anyone interested should check out. If you know how both torque and horsepower contribute to the motion of a bike than knowing the trade-offs between engine designs can tell you what you want, when, and where. It isn't surprising to me that a lot of engineers are attracted to V-twin based bikes for their personal ride. It provides a nice compromise of power and rideability. But those same engineers will tell you without checking their slide rules who can run the fastest top speed given enough distance and it won't be the V-twin. | ||
| Ducxl |
The Desmosedici is an excellent example of a four cylinder engine with the torque characteristic of a twin and the Horsepower of a four. | ||
| J2blue |
Besides cylinders engines have valves, cams, etc. All impact performance. I did say "gross over-generalization".  | ||
| Firebolt020283 |
Ok this topic is confusing me, I just can not see how you can figure a IL4 is better than a v-twin for a motorcycle engine. Now I will give it to you that they can give more Hp at the same displacement, But we see it time and time again when you put a t-twin and a IL4 with the same HP ratings the v-twins seem to be the better bike. | ||
| Firebolt020283 |
also I have never ridden a bike with a v4 but I would think that, that would be the best compromise of the 2. Why are there not that many v4's? What Bikes use v4s besides the v-max and the duc Desmosedici? |
