Fuel Difference between Riding at Gear 5 (100km/h) or Gear 5 (60km/h)

[gohjlb]

I wanna to ask if there is any difference between riding at gear 5 maintaining at (50km/h or 60km/h) aNd riding at (100km/h)

 

Does riding faster save you more fuel????

 

Coz i find out when i ride faster, my fuel tend to save more. is that true?

[xavw]

I'm no expert, but what I know is that start-stop traffic consumes more petrol compared to cruising at expressway. And there's an optimum point of fuel consumption different bikes at a cruising speed, where the engine works the least to maintain speed and forward momentum. The bike's RPM would probably offer a clue. Anything beyond that forces the engine to work harder, consuming more petrol, especially at very high RPM. So it does not mean that faster automatically equals to less petrol.

[Hydher]

of course. might be error in ur calculations

Edited January 23, 2011 by Hydher

[biting_point]

travelling at a higher speed doesnt actually yields better FC..

 

for example:

Bike A travelling at 60kph, FC is 18km/L

Bike A travelling at 80kph, FC is 21km/L

Bike A travelling at 100kph, FC is 16km/L

 

at different speeds, your air/fuel ratio will be different..

at 80kph, air/fuel yields best mixture..

at other speeds, the mixture maybe too rich (wasting fuel), or too lean (normally at higher speeds)

it also depends if your bike had a ram air intake..

normally for a average capacity bike/car, travelling at constant 80kph yields best FC..

 

to prove you wrong, try travelling NSHW at 140kph and calculate your FC..

you'll be shock..

[Wormwood]

Correct me if I'm wrong, but I seem to believe that the less you open throttle, the better your fuel consumption. In that case, travelling at 60kph would consume less fuel than travelling at 80kph if your bike could cruise at that speed without opening throttle much. But the reverse would be true if travelling at 60kph would require you to open throttle more, such as when going up a slope (in which case shifting to a lower gear would help you save fuel).

 

Usually, the more you open throttle, the higher the RPM. However when travelling upslope low RPM does not mean lower fuel consumption if you're in 5th gear.

[NightPhantom]

travelling at a higher speed doesnt actually yields better FC..

 

for example:

Bike A travelling at 60kph, FC is 18km/L

Bike A travelling at 80kph, FC is 21km/L

Bike A travelling at 100kph, FC is 16km/L

 

at different speeds, your air/fuel ratio will be different..

at 80kph, air/fuel yields best mixture..

at other speeds, the mixture maybe too rich (wasting fuel), or too lean (normally at higher speeds)

it also depends if your bike had a ram air intake..

normally for a average capacity bike/car, travelling at constant 80kph yields best FC..

 

to prove you wrong, try travelling NSHW at 140kph and calculate your FC..

you'll be shock..

 

i agree totally.

[arthur_chan]

Correct me if I'm wrong, but I seem to believe that the less you open throttle, the better your fuel consumption. In that case, travelling at 60kph would consume less fuel than travelling at 80kph if your bike could cruise at that speed without opening throttle much. But the reverse would be true if travelling at 60kph would require you to open throttle more, such as when going up a slope (in which case shifting to a lower gear would help you save fuel).

 

Usually, the more you open throttle, the higher the RPM. However when travelling upslope low RPM does not mean lower fuel consumption if you're in 5th gear.

 

it depends on the makeup of the engine, some engine's optimum performance is @ 80km/h, some 60km/h, however anything above or lower will be wasting fuel, my friend's car best fc is @ 80km/h.

 

however u're right in RPM value, low RPM not necessary = good fc. my bike's RPM seems constant throughout to 100km/h, however my best fc is around 50-60km/h.

[-Gu0Zz-]

Lower CONSTANT RPMS with CONSTANT velocity(no net acceleration) will always result in better fuel economy. that's when the force from the tires is equal to the frictional forces.

 

Power and torque and rpm is directly proportonate so u can think of it as each turn of the engine produces that amount of force at that RPM. And power is the rate of doing work. Assume the torque(force) remains constant, The engine produces more power by increasing the RPM, hence using lower rounds per min to maintain a constant velocity always results in lesser energy used.

 

Of cos, there are other considerations such as Richer fuel to air mixture that will result in more % of unburnt fuel, hence may result in lower economy at lower RPMS. Fuel injection systems should be able to provide the most optimum ratio to minimise unburnt fuel. So lower RPMS should always be equal to less fuel burnt.

[DeusExMachina]

Actually, your mileage... or best mileage... is a function of two things.

 

- Fuel consumption vs engine rpm

- gear ratio vs distance travelled

 

Your engine consumes fuel at a given rate depending on rpm. Think of it this way; it consumes X liters per minute at Y rpm. Don't bother abt the speed of the bike yet. Just talk abt the engine only.

 

We take things like air temp, air pressure, etc out of the picture to simplify matters. So, ppl are saying that the lower the rpm, the better yr mileage? Not necessarily true.

 

If u travel at 3000rpm at gears 1 or 6, it makes a lot of diff. But that's common sense right? Ok, that one is too obvious. Any idiot also can see that.

 

But consider that your fuel consumption is not linear vs your engine rpm. To give an example, yr engine does not consume 1 liter every min at 3000 rpm, and 2 liter every min at 6000 rpm. Actual consumption would look more like a curve.

 

So at 6th gear, travelling at say... 80kph at 3000rpm may not necessarily give u more mileage than 100kph at 4000rpm. Fuel consumption may not be linear, but yr speed at a certain gear is.

 

 

If u know yr fuel curve, then u can put it against distance travelled (speed) and find the best mileage.

 

Conclusion: Going slower doesn't always give u better mileage.

Edited January 26, 2011 by DeusExMachina

[CSV]

yeah, i am curious about this as well. i always find myself in a dilemma to shift up or stay at the same gear when my rpm is neither here nor there. i usually shift up to lower the noise and vibration.

 

so lets say at 60km, my revs are around 5-6k in gear 3. optimum shift point is 6-7k.

 

i usually shift early to maintain at that same speed of 60km. so is it better to shift up whenever possible or stay in same gear?

[DeusExMachina]

yeah, i am curious about this as well. i always find myself in a dilemma to shift up or stay at the same gear when my rpm is neither here nor there. i usually shift up to lower the noise and vibration.

 

so lets say at 60km, my revs are around 5-6k in gear 3. optimum shift point is 6-7k.

 

i usually shift early to maintain at that same speed of 60km. so is it better to shift up whenever possible or stay in same gear?

 

Shifting early will definitely save you more fuel, provided you don't knock the engine.

 

The best fuel mileage can be had by cruising at a constant rpm in top gear at the optimal speed. But WHAT is that optimal speed? You won't know unless you know your bike's fuel curve.

[jonnyboy]

i believe it's got to do with air/fuel ratio settings and engine rpm, e.g. at Y setting optimal fuel efficiency is at X rpm, so play around with the gears to maintain X rpm to your required speed. but i think it only applies to higher speeds, sekali your optimal rpm is like 10,000rpm then you'll be like dragging 1st gear everywhere in housing estates hahahaha

[zyrofillica]

no one brought up air resistance? As u increase ur speeds above 80km/h, air resistance actually becomes a major factor when determining fuel consumption. especially so for non sport bikes

[Makiyo Ng]

Hi all, actually best FC will be maintain speeds between 80-90km/h at top 5th or 6th gear....Ride save man...

[Pandoras Kitten 3]

Lower CONSTANT RPMS with CONSTANT velocity(no net acceleration) will always result in better fuel economy. that's when the force from the tires is equal to the frictional forces.

 

It will also depend on engine design.

 

Phantom going 60kph can probably sip fuel forever because the RPM will be very low and it's a four stroke, which produces usable torque at relatively low revs.

 

125Z going 60kph is totally wasting fuel because 2 strokes are inefficient at low revs due to engine design. A 2 stroke is most efficient and powerful when its compression is aided by exhaust resonance, so a 125Z gets the best fuel economy (39.1km/l in my case) when riding at a constant 6,000 RPM on the highway. How fast that is, depends on sprocket ratio. For best efficiency, try 6,000RPM at 130kph but sadly top-speed optimised ratios is not practical in Singapore traffic and there is also the aero drag increasing exponentially after a certain speed.

 

How about my current 4 stroker going high speed? Find the sweet spot in the powerband, tweak sprocket ratios, and find a compromise speed where the engine is producing high torque and the speed is low enough that there's less penalty from aerodynamic drag. Currently 43km/l at 85kph (actual car speed).

[Dranjo]

There are many consideration for FC. As a rule of thumb, highway travelling at constant speed gives u best FC. If you keep accelerating and braking than your FC is definitely bad. If you hav a rev meter. Monitor the rpm and i would say most bike if you maintain it at 5000rpm at highway travelling would give you gd FC vs travelingn time.

 

If your consideration is just FC alone. Lower RPM at high gear would give you the best FC. That's my take. I did tried travelling at 140km/hr for 1hr straight with a FZ6 and the FC is about 20L/km.