fuel consumption

[leolion]

Sorry for being a muppet but at a steady 55mph what would be more economical,1 cyl,2cyl,3cyl or 4 cyl?

[RhynoCZ]

Would those hypothetical engines have the same power output?
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[Nobby the Bastard]

[leolion]

[Nobby the Bastard]

[P.]

[The Shaggy D.A.]

[Easy-X]

For fuel efficiency you might want to start with the power to weight ratio rather than the number of cylinders.

For example, of the bikes I'm looking at the moment:

Honda Rebel: 33.5kW for 190kg = 176W per kg

HD Street 750: 43kW for 223kg = 192W per kg

Kwak Vulcan S: 45kW for 229kg = 192W per kg

This is only a basic starting point but it gives you a ball park before you get into how well the engines are tuned.

Also consider that every bike has a certain amount of unavoidable "dead weight" (e.g. the rider but also little niceties like wheels and fuel tank, brakes etc.) before considering the engine weight. The proportion of dead weight vs engine power mostly favours the bigger bikes but lets have a look at something much bigger:

HD Fat Boy: 64kW for 304kg = 210W per kg

So for almost 100kg more weight there's barely any substantial usable power gain. It still looks like the Fat Boy might be a better bet from just the numbers but then you have to take into account it wants high octane fuel...
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[temeluchus]

aerodynamics and rolling friction is the bigger factor on cruising fuel economy than weight. It's why a lot of cars cruising on the motorway are more economical than many bikes.

Weight affects economy when you are braking and accelerating.
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Some shite cruiser. Now with guns and FREEDOM!

[stinkwheel]

A late 80's, piston ported 100cc 2-stroke should return considerably in excess of 100mpg at 55mph.

A C90 would also be well up there pushing 3 figures too.

A "vanilla" 350 bullet would be returning mid 80's mpg and should mamage to do 55mph under most circumstances.

So on that basis, a single cylinder.

But do you want to ride one of those bikes?
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[trevor saxe-coburg-gotha]

[Robby]

The one with the most efficient engine, that is working at its optimum efficiency around 55mph.
I could now spout all kinds of barely understood shite about peak torque, pumping efficiency and specific fuel consumption. Even if I was accurate on the numbers, it wouldn't translate into real-world use.

At 55mph, just about anything you might be considering will return in excess of 70mpg. Fuel burn not worth measuring beyond that point.

[1198]

To help / confuse you more, if this is in ‘whats cheapest to go to work on’ you need to start considering running costs too.
Are you able to service it yourself? Are tyres cheap? What’s the depreciation like? Insurance?
A brand new bike that does 80-100mpg but costs you a large percentage of the total purchase cost over a couple of years and which you had serviced by a franchised dealer (for the warranty) would most likely be more real world money out of your pocket than a bike a few years older that does say 50-60mpg but only loses a few hundred pounds at most in depreciation (if at all) and is serviced by Fred the local motorcycle dealer...

[ThunderGuts]

Fuel has a fixed quantity of energy available per litre (or gallon if you prefer). The majority of fuel burned in even the most efficient engine is still waste heat, but this proportion increases with inefficiency.

I'm not convinced that number of cylinders is the biggest factor, but typically 4 pots tend to be more performance orientated than 2 pots (not always, but typically).

Fuel injected will be more efficient than a carb'd bike as the former should provide the fuel quantity needed more accurately. Faired bikes should be more slippery in the air, so should be better. Weight is largely irrelevant at a constant speed on the flat.

Just look at the book figures and see what they suggest . . . don't expect to get the figures they quote, but they're reasonable for a like-for-like comparison.
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TG.

[chickenstrip]

Hello Mr. Leopussy

How do you propose to get any fun out of life?
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Chickenystripgeezer's Biking Life (Latest update 19/10/18) Belgium, France, Italy, Austria tour 2016 Picos de Europa, Pyrenees and French Alps tour 2017 Scotland Trip 1, now with BONUS FEATURE edit, 5/10/19, on page 2 Scotland Trip 2 Luxembourg, Black Forest, Switzerland, Vosges Trip 2017
THERE'S MILLIONS OF CHICKENSTRIPS OUT THERE!

[The Shaggy D.A.]

[The Shaggy D.A.]

* Green Swarfega. Not orange.
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Chances are quite high you are not in my Monkeysphere, and I don't care about you. Don't take it personally.
Currently : Royal Enfield 350 Meteor
Previously : CB100N > CB250RS > XJ900F > GT550 > GPZ750R/1000RX > AJS M16 > R100RT > Bullet 500 > CB500 > LS650P > Bullet Electra X & YBR125 > Bullet 350 "Superstar" & YBR125 Custom > Royal Enfield Classic 500 Despatch Limited Edition (28 of 200) & CB Two-Fifty Nighthawk > ER5

[chickenstrip]

[leolion]

[P.]

[leolion]

its painful spending a fiver in 30miles though i thought id achieve much better than that.

[chickenstrip]

[chickenstrip]

[leolion]

[chickenstrip]

So given we know that you're not caning it everywhere (not even faintly close ), have you considered your bike might have a problem that needs addressing, rather than you going off and considering a different bike to reduce your fuel consumption?
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Chickenystripgeezer's Biking Life (Latest update 19/10/18) Belgium, France, Italy, Austria tour 2016 Picos de Europa, Pyrenees and French Alps tour 2017 Scotland Trip 1, now with BONUS FEATURE edit, 5/10/19, on page 2 Scotland Trip 2 Luxembourg, Black Forest, Switzerland, Vosges Trip 2017
THERE'S MILLIONS OF CHICKENSTRIPS OUT THERE!