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What is the power delivery difference between a Vertical Twin and V Twin

21K views 72 replies 40 participants last post by  Mike K. 
#1 ·
Just a quick question. What is the seat of the pants difference between a Vertical twin and a v twin. Does a v twin have a lower center of gravity? Can you compare the two?

Also what are the advantages of a chain drive. I hear all the advantages of the other drive systems but have not heard any for the chain drive.

Thanks for your insight.

Dave
 
#2 ·
I'm no mechanic and not a gearhead, so I don't know the answer for the vtwin and vertical twin thing. Seems the vertical twin is usually capable of producing more power than a comparable sized vtwin though.

Chains seem to be advantageous for big, powerful, engines. Seems all the highly modified big hp bikes I see have chain drives. Maybe they are cheaper to manufacture as well, particularly to shaft drives? Personally I prefer the low maintenance, quietness and smoothness of a belt or shaft drive (seems a little clunky sometimes), but I don't ride big hp machines. Love the belt drive Harleys.
 
#3 ·
Just from a physics standpoint, there is no difference in the power that could be delivered from the two engine types if the displacements were the same, fuel and exhaust systems (including valves, porting, etc.) were comparable, etc.

In theory, a V-twin could have a lower center of gravity, but that's not a guarantee that a finished design would, necessarily; and it doesn't relate to power.

Now, from a practical standpoint, I once read that it's easier to design a vertical parallel twin to handle sustained power from a cooling standpoint than it is for a v-twin, because the back cylinder of the vee won't receive as good air flow and must therefore be babied a bit...but I don't really know if the fellow knew what he was talking about, and in the coming era of all-liquid-cooled engines, it won't be a factor anyway.

As for drive methods, I agree with Sponger that Harleys' belt drive is very nice, and that one of the big reasons chains are still around is that they are cheaper than the other two methods.

Chains are also a lot less massive than shafts for a given power handling capability, and are less subject to certain kinds of physical damage than belts. Plus, modern construction techniques make chains sturdier and lower maintenance than they were in the "olden days."
 
#4 ·
Well, if you set it up like Ducati does, then you can actually get a much more progressive torque curve. Thats why Ducatis were spanking the 4 cylinder Japanese competition for so long, they could power out of a turn much, much earlier without upsetting the bike. They certainly weren't putting out more power, but they delivered it in a smarter way.
 
#68 · (Edited)
V vs Parallel twins.



A V twin would have only one advantage to my mind. The staggered firing gives a better delivery of power to the road under maximum conditions, without breaking traction. As mentioned by the commie, LOL I believe that the intake angle and single carb, along with Harley's push rods and heating of the air cooled rear cylinder.of Harley's, continues to make them handicapped. We should also note that 270° cranks seem to give more torque as well, even in a vertical twin.
As far as chains Vs belt, one small stone caught under the belt gave my mate a twin belt drive and we had a time and a half limping him home. If you are a road rider, I have found no major set backs with a shaft drive. As a road racer, the torque effect when switching corners, and powering out of corners can be very tricky at times. I can get over 40,000 miles on a chain before it needs replacing. My ZX14 has over 35,000 on the original chain. I guess you are spoiled for choices in todays world.
 
#5 ·
Chains are cheap, simple to work on, and strong. Shaft drives weigh more. When you are talking about building a truly fast bike, weight is your number one issue. When you are talking about a manufacturer building a bike for under $10k a $20 chain that works wonderfully, its a no brainer. At the end of the day Triumph has its share of bean counters happy to shave a little here or there in the pursuit of profit margins.
 
#6 ·
It was once pointed out to me (by Kevin Cameron) that a vertical twin is,in effect,only a very narrow angle V twin, and a boxer twin(ala BMW)is nothing but a very wide angle V twin. Ducati-90 degree,Harley-45deg, Triumph- 0deg, BMW-180deg. Power production is a factor of bore and stroke,breathing,and cam timing,not really angle of the cylinders.

However,power delivery is affected by the offset firing order of the Harley engine, which has a 270 degree firing order(as does the America,Speedmaster,and Scrambler,along with some of the Japanese V twins,and the Dreer Norton). This means that you get two close together power strokes,then a relatively long time between two more close power strokes. This is a big boon in low traction situations, and is the official reason that Harley has dominated dirt track racing for so many years.(The AMA rule book is the real reason,but that is for another post)

I am a Harley owner,and it might interest some of you to know that the rear cylinder actually runs a few degrees hotter than the front!

It's my opinion that the only reason that Harley developed a belt drive for their big cruisers,back in the late 70s, is that the parent company,AMF, would not fund what would have necessitated a complete re-design of their power-plant to accommodate a shaft drive.They came up with so many reasons(excuses) that a belt was better than a shaft,that now that they can afford a shaft,they are not about to eat their words,and build one. Now, of course, if you have a big cruiser,and you don't have a belt,you're just not cool. For a big cruiser,or touring bike,a shaft is better in every way. For almost every thing else,a chain is the way to go. It will stand up to dirt,rocks,and mis-alignment(read:ham fisted owner abuse)much better than a belt.
For a pampered bike, a belt is a lot less maintenance than a chain.
:chug:
Cheers!
Bruce
 
#62 ·
Well said Bruce. I like your choice of classics. I remember my first Norton, it was vastly more torquey than my Triumph and only 100cc bigger. Parallel twins were cool but eventually the V, the 180, and the 90 became more powerful. I love my Boxer for its torque delivery and shaft drive. But it's a complicated system, the Triumph is simple old school cool.
Happy Trails
 
#7 ·
Some good replies here. I believe the V design lends itself to really good low end "grunt", but not necessarily high hp numbers. The torque curve is where we live in the real world anyway. A good illustration I once heard was that in using boxing as an illustration, hp would be how fast you can hit and torque would be how hard you can hit. I don't believe a big twin Harley has much if any hp advantage over my 790 cc's but it produces quite a bit more torque. The R3 has both in spades.
 
#8 ·
On 2007-06-07 06:58, 1962gypsy wrote:
Some good replies here. I believe the V design lends itself to really good low end "grunt", but not necessarily high hp numbers. The torque curve is where we live in the real world anyway. A good illustration I once heard was that in using boxing as an illustration, hp would be how fast you can hit and torque would be how hard you can hit. I don't believe a big twin Harley has much if any hp advantage over my 790 cc's but it produces quite a bit more torque. The R3 has both in spades.
Oh, that's because the R3 has the bestest, mostest and fastest engine design, the beautiful TRIPLE!!! Sorry, I will scuttle back to our forum... :razz: :wink:
 
#63 ·
Howdy Austin, I noticed your Triumph appears to have a dual disc up front, is that correct? Triumph doesn't have much repensentation in the Central Texas area. I applaud your indivuallity. Long live Triumph.
But back to the question at hand, I think you misunderstand the previous response.
I'm so glad to have purchased one of the last air cooled Triumphs. I believe they will be coveted like the air cooled Porsches. Hopefully.
Happy Trails
 
#11 ·
On 2007-06-07 08:24, sweatmachine wrote:

You're wrong, Harley uses a 45 degree V twin, which would be 315 degrees, not 270.

360-45 = 315.
So Harley is really using a single pin for both con-rods on the crank? I mean, I know that the purists say a Vee is only a "Twin" if it has a single pin, but I figured Harley and everybody else were probably using two pins now so that they could set the firing interval independent of the Vee's angle.

Keep in mind that you can set firing interval to anything you want on any engine type as long as each piston has its own pin on the crank, hence the way that Triumph is using 270-degree timing on parallel twins. At the point that firing interval is being set completely independent of the engine's design, there ceases to be any real difference among the different engine designs except in terms of how much counterbalancing is needed and how the engine cools. Of course, since counterbalancing takes some HP, it's still true that a naturally-balanced engine design can generate more HP than one that requires a lot of counterbalancing.

On the other hand, even BMW's R-series boxer engines, which are the most perfectly-balanced natural engine design, now use counterbalancers, which seems incredibly stupid to me. At the point that every engine is counterbalanced, I guess that ceases to be much of a concern too.

Once you can build a 45-degree Vee-Twin with a 360-degree firing interval and a Parallel Twin with a 270-degree firing interval, much of the inherent difference in the engines is gone. Hell, if the Japanese wanted to, they could set up one of their I-4 engines to exhibit the exact same power characteristics as a Ducati - set cylinder 1 and 4 to fire together, and 2 and 3 to fire 270 degrees later, lean the engine 45 degrees forward of vertical and tune the counterbalancers to produce a forward "kick" at the moment that 2 and 3 fire and an upward "kick" at the moment that 1 and 4 fire. I'll bet they could make it exhibit *exactly* the same characteristics.

[ This message was edited by: lindsayt on 2007-06-07 11:01 ]
 
#48 ·
Single Pin Honda=sucky

I own a few single pin shadows-that fact totally ruins what could have been a great bike. Honda went to a single pin crank to make the bikes sound more like Harleys and as a result made them vibrate and shake badly as higher speeds. I have a dual pin bike, a Suzuki S50 and the smoothness is so apparent compared to the single. My quest for a smoother bike led me to a Thunderbird 1600.;)
 
#13 ·
On 2007-06-07 11:00, lindsayt wrote:
Hell, if the Japanese wanted to, they could set up one of their I-4 engines to exhibit the exact same power characteristics as a Ducati - set cylinder 1 and 4 to fire together, and 2 and 3 to fire 270 degrees later, lean the engine 45 degrees forward of vertical and tune the counterbalancers to produce a forward "kick" at the moment that 2 and 3 fire and an upward "kick" at the moment that 1 and 4 fire. I'll bet they could make it exhibit *exactly* the same characteristics.
Or, you could take a Triumph 360 motor, time it to fire at 45 degrees, remove the counterbalancers, limit the hp, add 300lbs of junk, and it'd be just like a Harley! :-D
 
#14 ·
> I believe the V design lends itself to really good low end "grunt", but not necessarily high hp numbers.

That's the kind of voodoo and horsefeathers they might like you to believe, but it has virtually nothing to do with the vee. The HP-to-torque tradeoff is principally a function of how the designer chooses to achieve a given displacement...bigger piston & shorter travel for greater torque, the opposite for greater HP. The power delivery curve is set by the factors we call "tuning," including valve and ignition timing, carb needles & jets or FI mapping (as applicable), etc.

As for 360 or 270 or 315 degree ignition sequencing, that's significantly more horsefeathers than voodoo. The sound is different, not much else.

You don't measure the output of an engine as peak power available in just part of a single crankshaft revolution. The combined flywheel effect of all parts in the engine--and when in motion, the gearbox, drive train, rear wheel, and inertia of the rest of the bike and rider too--average everything out over time anyway. Power out of the engine=total power contributed by all cylinders, less mechanical losses. There's no mysterious boost because of when those pulses of power occur in one cylinder relative to another.
 
#17 ·
On 2007-06-07 16:09, Joe-Dirt wrote:
I converted to a 520 chain on my Sportster. I don't miss the belt whatsoever. :wink:
Kick A$$! That is one sexy bike! Please tell us what all you've done to it!
 
#19 ·
I'm no tech'...... have no idea what the particulars are, never tore down an engine, and don't understand anything written in posts prior.

But I put significant mileage on a Sportster 'Sport' 1200cc V-twin, quite a few miles on a couple newBonneville 790 parallel twins, and 60,000 miles on a R1150RA Beemer horizontally opposed twin.

I have an intense fascination for the little Ninja 650 parallel twin....... It's not as a good a machine as the ever-popular SV650, and I wouldn't expect that it would stand up as well to the punishment I gave the Beemer. But it's really captured my interest..... and I blame my time in the saddle of the Bonnevilles for that.

The V-twin was visceral, the Boxer's pulses were comforting and really hooked up with the road, and the parallel twin was extremely linear.
 
#20 ·
On 2007-06-07 16:11, lindsayt wrote:

Kick A$$! That is one sexy bike! Please tell us what all you've done to it!
Thanks! The mods include: Crossroads Performance rearsets, Stuntme clipons, Trak-Tek fork brace, 1200S rear shocks, Excel rims (19x2.15 front 18x4.25 rear) that I laced with Buchanan stainless spokes, headlight eyebrow mounted under top clamp, gauges mounted to top clamp, HD accessory bikini fairing, trimmed cam cover, trimmed sprocket cover, Renthal 520 sprockets, Vance and Hines SS2R exhaust, and rear frame fender struts cut off. I couldn't find a tail that I liked, so I made the seat/tail section, with a lot of helpful input from a Sportster forum. It has underseat storage and uses an integrated LED tail light for a GSXR. Lots of mods still to do, but it's a blast to ride!

With the chain, I've noticed no real difference in driveline lash or noise from the belt.

My S4 has a 14,000 rpm 4 cyl., so it's quite a difference in power delivery (and power) from the Sportster. :)
 
#21 ·
My limited experience with motorcycle engines has led me to some simple (perhaps overly simple) conclusions. The cylinder configuration has very little to do with power out put. Harley's new 96 cubic inch motor puts out only 60 or 65 horsepower. Meanwhile my 500cc parallel twin (30.1 cubic inch) makes 45 HP. The reason has more to do with valve train and cam configurations. My 500 is designed to operate at a sustained rpm of 4,000 to 6,000. Harley, with the old push rod and rocker arm style valve train is designed for sustained rpm of 2,000 to 3,000 and therefore cannot approach the rpm range of other more modern designs. Since Horse power is measured as a known weight (1 pound) being moved a known distance (1 foot) in a known amount of time (1 second) yeilds a known horsepower (1 HP) the speed at which a motor turns (combined with proper torque, and valve timing) has a direct bearing on the horse power out put of the motor. (The higher revving the motor is capable of, the higher the horsepower potential) I say potential because other factors come into play.

Basically rpm is revolutions per minute (number of events over time) and horsepower is movement over time. Acceleration is also movement over time.

Kinda muddies these waters I know, but V-twin, parallel twin, Boxer, inline triple, or even radial, each configuration has benefits, and draw backs. All seem to work well, and all have their own following.

Keith
 
#22 ·
Great responses here. Thank you everyone. Guess what I am looking for is all about the valve system and not the configuration. I have heard many on this forum state that they have more power with their "little" 865 than most Harleys on the road with their 96ci. Thought this was a simple " oh yeah a vertical twin is a better configuration and will have more power in a smaller engine" but I had forgotten that the Triumph engine is very modern with overhead cams. Much different than the big Harley engine with pushrods and a single pin. The 45 degree was originally done to fit the engine in a bicycle frame and the single pin design was done to save money starting with the first successful Harley twin in 1909. I find it funny that the Harley is known for it's V twin which it did not do successfully until 1909 (even though they tried in 1904) but Triumph had a successful twin in their second year (1903). This just made me think that maybe the vertical twin was a better design.

As always the experience from this forum has given me a lot to think about. Thank you so much for sharing your experience and knowledge. Motorcycles can be just machines on two wheels but it is the people like you that make this a wonderful family.

Dave
 
#23 ·
You're wrong, Harley uses a 45 degree V twin, which would be 315 degrees, not 270.

360-45 = 315.
You're quite right, of course.Realized my goof as I was falling asleep last night. I tried to come back to sneak in a fix tonight,but it was too late. Thanks. :moon:

I stand by the rest of my bullshyte!

:chug:
Cheers!
Bruce
 
#24 ·
"I had forgotten that the Triumph engine is very modern with overhead cams. Much different than the big Harley engine with pushrods and a single pin."

And neither distinction has anything whatsoever to do with the horsepower or torque generated. Think compression and cam timing and you'll be on the right track.

"don't you have it backwards there Diego?

Long Stroke = more torque lower

Short Stroke = more hp higher"

Actually, it's neither and another common fallacy. Both long and short stroke engines of equal displacement will produce the same cylinder pressures during the power stroke for the same swept volumes and induction efficiency.

While the pistons in a longer-stroke engine are smaller in diameter and, therefore, experience less force from the same cylinder pressure (force = pressure x area) the crank arms are longer and have a greater mechanical advantage. The converse, of course, is true of the short stroke large bore engine. The net result is that equal displacement engines of unequal stroke lengths experiencing the same cylinder pressures (dependent on induction efficiency and cam timing) will produce the same torque at the crankshaft.

Stroke, however, is not an isolated variable; it affects the design of many other engine components and most importantly the available valve area. But again it comes down to cam timing, valve area, and compression ratio.

Oh yeah, one of the most important advantages to short stroke engines, and the reason they can rev so high, is that the short stroke helps keeps piston velocity below the 4,000 to 4500 fps danger zone.

A long stroke Harley has a very low rpm limit (because of piston velocity) and is designed with very mild cam timing to take advantage of its limited low-rpm power band. Our short stroke Triumphs can rev to 8,000 rpms and beyond and come with cams that can make power near the top of our rev range.

And think about this....

A triumph twin spinning at 8,000 rpms has more swept volume than a 96 inch Harley spinning at 4,000 rpms and so all else being equal (which of course it is not) would make more horsepower at those respective rpms.

[ This message was edited by: Jimbonnie on 2007-06-08 10:52 ]
 
#25 ·
comparing comparably sized engines on comparably sized motrcycles, e.g., H-D 883 Sportster v. Triumph 865 Bonneville, the Bonnie's acceleration wins out because of the weight advantage; the Bonnie is only 451 lb. while the Sportster is 563 lb. (both dry wt.).

Thus, the power to weight ratio considerably favors the Bonnie.

So does the riding experience, having owned and ridden both.

ride on

rick
 
#26 ·
Yeah. Unfortunately the Sportsters gotten really heavy with the new rubber mounted frame; I think it's gone up something like 50 lbs. But I guess they had to do something to make the vibration more tolerable; I wish they'd counterbalanced it like the softail motors and kept the frame light.
 
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