Why multis are better - Nerd-alert!

[faffi]

No matter how much we love our Guzzi twins, there are benefits to be had by adding a cylinder or two. While it is often said that singles and twins make the most torque, while multis make more peak power, it is my experience that this is not true. Sure, if an engine is too small, you will lose torque by adding cylinders, because there will be too much friction at low rpm that will rob power. However, there were reasons why Suzuki made a 3-cylinder 50cc race bike, and Honda a 5-cylinder 125cc racer; they managed to make more power.

For fun, I compared 4 bikes with roughly 650cc engines where I had access to dyno charts where rear wheel horsepower and torque were measured, despite 650 being on the small side to get full benefits from as much as four cylinders. Finding one of each designed to make about 50 hp is not possible, but I chose the Suzuki DR650 to represent the singles, and the Royal Enfield 650 to represent the twins, since these two are somewhat similar in their claimed max power; 44 PS for the DR and 48 for the RE. I could have chosen the Yamaha MT-07, which is a torque monster for its size, and I do touch on this at the end. To represent the triples, I chose the Triumph Street Triple 675, and the fours are represented by the Kawasaki 636 Ninja.

So how do they compare? Listed figures are taken at the rear wheel and are corrected for ambient temperature etc.

DR650: 35.1 hp @ 6.200 rpm and 32.2 lb-ft @ 4500
RE650: 40.9 hp @ 6.800 rpm and 37.4 lb-ft @ 5100
ST675: 91.1 hp @ 12100 rpm and 43.5 lb-ft @ 9800
ZX636: 108.4hp @ 13200 rpm and 45.8 lb-ft @ 10900

But these numbers do not tell nearly the whole truth. For instance, the DR650 single is the peakiest engine of the bunch, the Royal Enfield has the gruntiest torque curve, and the Speed Triple 675 has the flattest torque curve.

The DR require 2700 rpm to break 25 lb-ft, the RE only 1700 rpm, the Ninja 1800 rpm. The Triple never drops below 35 lb-ft.

To break 30 lb-ft, the DR require 3500 rpm, the Enfield 1900 rpm, the Ninja 2700, the Triple no more than 2100 rpm, which is where the dynograph begin.

The DR hit 30 lb-ft again at 6000 rpm on the way down, the Enfield sit above 30 until 7000 rpm, and the multis never drop below 30 lb-ft again. The Enfield make more torque than the DR's peak from 2000 to 6500 rpm, and make 35 lb-ft or more between 3900 and 5800 rpm. The Triple make 35 lb-ft or more between 2100 and 13000 rpm, and the Ninja do this between 6300 and 14600 rpm.

There are only two bikes that will break above 40 lb-ft, and those are the multis. The Ninja from 7200 to 13500 rpm, and the 675 from 7000 to 12000 rpm.

Now, the MT-07, aka FZ-07, is a twin that will overshadow all of these for normal riding. It make more than 40 lb-ft from 2600 to 9000 rpm, with a peak of 47.6 @ 6500 rpm. Peak power is limited to 67.8 @ 8800 rpm, but most of us will use the midrange the majority of the time, and here the MT-07 rule. It also, along with the 675 to a slightly lesser degree, benefit from more engine capacity at 689cc. However, if Triumph had decided to optimize their triple for torque, I have no doubt that it would have made more power from idle to redline than the Yamaha, while also being more flexible.

This is where more cylinders really start to shine IMO. Even my old Suzuki GS650G and Yamaha XJ750 Seca would take full throttle in 5th gear from their 1100 rpm idle. Without protest, without vibrations or pinging. Not with a lot of acceleration, but without strain. That is what I miss with singles and twins. I do not like the busyness and sometimes buzziness that comes with multis, but I really like their flexibility.

[michaell32]

I like my DR650 but I think its a bad example for a single cylinder since it's unchanged from 1996 for the most part and the other bikes are built with much modern technology and engineering.  The KTM 690/Husqvarna 701 is only 50 more cc's but fuel injected and makes a lot more power.   

[Perazzimx14]

You are comparison is Briggs and Stratton tech to F1 tech (DR650 to a modern Sport bike). It's more than the number of CC's and the number of cylinders.

If it displacement and number of cylinders why is it:

The 2023 KTM 1290 Super Adventure R is still powered by the 1,301cc LC8 V-Twin making a claimed 160 hp and approximately 102 lb-ft of torque, or. Dads old 72 Nova with a V8 305 pumping out a whopping 110 HP getting 8 MPG while my 2017 V6 3.5L/212 cu/in Tacoma has 289 HP and gets 19 MPG.
 

[faffi]

Those a fair comments, although FI does not make more power than carbs, but they do compensate much better for temperature and altitude etc. I included the DR and the Royal Enfield because both have four valve heads, both are tuned for good torque and not much power, and both are air cooled.

I did think about comparing the KTM 690 to the MT-07 / FZ-07, because they would sit closer to the two sportbikes in comparison. So we can do that now.





Again, adding a cylinder also add power and torque and broaden the useful range of revs where most will ride, but the single does make impressive max power and torque.

[faffi]

The KTM 1290 Super Duke R


Suzuki Hayabusa


My cousin has a 2023 1290 Adventure R, and the power doesn't really start to build until 4000 rpm and doesn't begin to impress until 5000 rpm, and sitting in top gear under 4000 rpm just hammer the whole driveline. The Busa can be ridden from idle in top without protests. And, like with the 690, try and ride for 50,000 miles and check the condition of the KTM engines vs the Japanese engines. KTM have managed to extract a lot of power for singles and twins, but it does come at a cost, both in longevity and also usefulness in daily city commuting. Admittedly, KTM have upped the quality a lot over the years, but they are still demanding more attention than average.

[Vagrant]

You must have had a very boring day.
It's time for you to go for a ride and quit thinking.

[Perazzimx14]

The KTM 1290 Super Duke R


Suzuki Hayabusa


My cousin has a 2023 1290 Adventure R, and the power doesn't really start to build until 4000 rpm and doesn't begin to impress until 5000 rpm, and sitting in top gear under 4000 rpm just hammer the whole driveline. The Busa can be ridden from idle in top without protests. And, like with the 690, try and ride for 50,000 miles and check the condition of the KTM engines vs the Japanese engines. KTM have managed to extract a lot of power for singles and twins, but it does come at a cost, both in longevity and also usefulness in daily city commuting. Admittedly, KTM have upped the quality a lot over the years, but they are still demanding more attention than average.

There are always tradeoff's in performance vs longevity. A NHRA top fuel car pumping out 12,000 HP and speeds over 300 MPH is good for less than 1 mile before needing rebuilt verses a Camry that is 180 HP and will last for 400K. Good/Fast/Cheap pick any two.

Personally I prefer the single and twin cylinder motorcycles and their power output. I also don't care about peak HP at 27 million RPM. I care about usable HP and good power delivery in a sensible RPM range which is what singles and twins tend to do. 

I have had very limited experience on I4 motorcycles but can say i did not like any of them. You had to spool the engines up to 7000+ RPM before they started making power.

[sign216]

The only time I like a lot of cylinders is in my car.  Cycles, simple is more enjoyable.  Car vs bike are two different worlds, with different attributes.

[blu guzz]

I just got off of my 1400 Eldo and it is only about 85 hp at the rear wheel and only about 80 something pounds at 2750 and up, but it's fun.   

[kingoffleece]

The day I need charts, graphs, and hp wars to tell me I'm riding a "better" machine is the day I stop.
The only metric that matter is operator satisfaction with the machine.  That will differ with the individual.

[Huzo]

You must have had a very boring day.
It's time for you to go for a ride and quit thinking.

If it weren’t for people thinking, we wouldn’t have any bikes. It’s entirely possible he can do both.

[faffi]

I prefer singles and twins myself, and I also prefer an engine that feels eager vs one that is fast but feels gutless. For instance, my son's MT-07 feels like a rocket, while my brother's 955i Triumph feels rather slow, yet in any kind of performance comparison, the latter just kills the Yamaha. My KZ1300 DFI was the same thing; was fast, felt slow.

However, what I prefer does not prevent me from acknowledging facts. And as those numbers show, at any rpm the Hayabusa produce more power than the Duke. And it will probably go 4 times as far between rebuilds. I would still rather have the KTM, but it doesn't have the better engine.

[Kev m]

The problem is the narrow use of the term "better" which in and of itself means nothing until it is qualified.

Multis are not "better" enough in anything that matters to me, ergo the "facts" are irrelevant.

Tastes are subjective.

[Frulk]

I really like my 2013 CB1100. Its performance numbers on paper don’t tell the whole story. It has very usable torque at all RPMs but you don’t need to go above 5K to tap into it. I like to lug it around town because you can just roll the throttle and have torque when and where you need it without shifting. That engine is WAY under stressed.

[faffi]

The problem is the narrow use of the term "better" which in and of itself means nothing until it is qualified.

Multis are not "better" enough in anything that matters to me, ergo the "facts" are irrelevant.

Tastes are subjective.

The title was chosen to provoke. And as you say, what is better or worse can always be debated, because priorities vary. If you like the workout from chopping trees with an axe, it does not matter if a chain saw can do the same job much quicker.

However, my point was not about tastes or preferences - as mentioned, I prefer singles and twins (and find fours to be stressful just by the way they sound) - but that when it comes to flexibility and power, more cylinders (to a point) have the upper hand. If that matters.

[s1120]

I prefer singles and twins myself, and I also prefer an engine that feels eager vs one that is fast but feels gutless. For instance, my son's MT-07 feels like a rocket, while my brother's 955i Triumph feels rather slow, yet in any kind of performance comparison, the latter just kills the Yamaha. My KZ1300 DFI was the same thing; was fast, felt slow.

Thats the thing right there. Its the feel. Unless your racing, ill take a bike that feels stringer in the power range used, over a more powerful engine, that feels kinda flat. I think a lot of us like a little crudeness in the power delivery. Ive always said its a lot more fun to ride a slow bike fast, then a fast bike slow.

[Huzo]

A motorbike is designed to make you feel good.
If it feels better, then it ACTUALLY is….

[kingoffleece]

What he said

[faffi]

On topic, somewhat https://www.youtube.com/watch?v=qQAhuL5Ow1M

[MerleLowe]

This is a gross generalization, but more cylinders of smaller capacity allow the engine designer to use a shorter stroke for the same displacement.  Power (in general again) is made by increasing the number of combustion events within a given time.  The shorter stroke allows higher RPM due to lower piston speeds and inertial forces.  The use of smaller cylinders makes for smaller valves, also lowering inertial forces permitting higher speed operation.  Now that the reciprocating assembly and valvetrain can withstand higher speed operation, you can optimize the tuning to move more air/fuel mix at those high RPMs.  More bangs = more power all else being equal.

Torque comes from cylinder pressure and displacement.  You'll notice that most modern engine designs make similar torque numbers for like CCs with very different peak HP numbers.  WHERE that torque peak occurs is a different matter.  Notice that most 1000cc engines come in a bit above 70 lb/ft but at very different engine speeds.

In practice, inline 4s for motorcycles are generally (there it is again) quite oversquare with relatively large valve area.  This makes for a relatively high flow cylinder head with lots of valve area.  In that case you can still use somewhat mild cam timing and still get good cylinder fill at high speeds without killing cylinder pressure at lower RPM.  The end result is a very wide torque curve but with a peak relatively high up the RPM scale.

Also in practice, twins end up with longer strokes, higher piston speeds and lower redlines.  The tuning is then (generally again) optimized for lower-speed operation.  This means often the rider is running the engine closer to the torque peak and gets fast strong response to throttle inputs.  This is interpreted as "torquey" since it is so immediately available. 

That's when aesthetics comes into play.  You might prefer the running characteristics of a lower-hp engine that gives the feel, sound and throttle response that you prefer.  Just know that the choice can greatly affect performance.  The extreme end of this would be the current HD and Indian air-cooled v-twins.  Peak torque is at very low speeds.

[Perazzimx14]

Can someone define "better" as it pertains to this thread?

[MerleLowe]

Can someone define "better" as it pertains to this thread?

The Tao that can be told is not the eternal Tao.
The name that can be named is not the eternal name.
The nameless is the beginning of heaven and earth.
The named is the mother of ten thousand things.
Ever desireless, one can see the mystery.
Ever desiring, one can see the manifestations.
These two spring from the same source but differ in name;
this appears as darkness.
Darkness within darkness.
The gate to all mystery.

― Laozi, Tao Te Ching

So, the better that is defined better is not the true better but is the origin of the full garage.

 

[Perazzimx14]

The Tao that can be told is not the eternal Tao.
The name that can be named is not the eternal name.
The nameless is the beginning of heaven and earth.
The named is the mother of ten thousand things.
Ever desireless, one can see the mystery.
Ever desiring, one can see the manifestations.
These two spring from the same source but differ in name;
this appears as darkness.
Darkness within darkness.
The gate to all mystery.

― Laozi, Tao Te Ching

So, the better that is defined better is not the true better but is the origin of the full garage.

 

 Wadda bout less is more?

[MerleLowe]

Wadda bout less is more?

I think that would be a Zen thing.   

jokes aside, you're right, faffi didn't say what "better" means.

[MerleLowe]

Ah!, I was wrong, here is the "better" from faffi's initial post. 

"This is where more cylinders really start to shine IMO. Even my old Suzuki GS650G and Yamaha XJ750 Seca would take full throttle in 5th gear from their 1100 rpm idle. Without protest, without vibrations or pinging. Not with a lot of acceleration, but without strain. That is what I miss with singles and twins. I do not like the busyness and sometimes buzziness that comes with multis, but I really like their flexibility."