Hornet - Overdrive Gear. How does it work?

Snax

Snax

Snax

Soldato
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Please excuse my ignorance.

On my hornet, I believe 6th gear is an overdrive gear.

I understand the concept of this - cruising gear, but in practse Im ot sure how it works.

Lets say I get to 70mph in 5th and switch up, I have to open the throttle more to maintain that speed. I thought opening the throttle increased fuel injection to the engine, so would this basically mean 6th gear is a waste of time? Or is there something cool and technical that adjusts the fuel consumption to make it more efficeint even after you open the throttle more?
 
Hmm I'm trying to get my head around what your saying there :p

If you drive my car at say 2000 rpm in 3rd your doing say 40mph

but if you slip it into 4th and keep at 40mph your revs will be lower, therefore using less fuel.. surely the same applies for your bike rather than having to rev it more to maintain that speed ?
 
it doesnt rev more. The revs do drop. However in order to maintain speed, you have to open the throttle more.


From my understanding (from wikepedia), the overdrive gear has very low torque, which explains the need to open the throttle more to keep the speed up.
 
Snax said:
it doesnt rev more. The revs do drop. However in order to maintain speed, you have to open the throttle more.


From my understanding (from wikepedia), the overdrive gear has very low torque, which explains the need to open the throttle more to keep the speed up.
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how much do they drop? maybe they are dropping too much (ie 6th is too long for 70mph?)

same effect of changing into 5th at 30mph, i need more gas to keep it going. sounds the same thing your suffering?
 
Overlag said:
how much do they drop? maybe they are dropping too much (ie 6th is too long for 70mph?)

same effect of changing into 5th at 30mph, i need more gas to keep it going. sounds the same thing your suffering?
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that is exactly what it feels like. I find it hard to understand why Honda would include it. Very odd
 
who knows, guess they just mean 6th on your bike is along way away ratio wise to 5th, errr or something, but I've not heard of it before on a bike
 
The 6th cog will have a have been made specifically harder as it would be expected to be in use more due to it being the highest gear and therefore the one you would cruise in most.

Its not an overdrive, its simply top.
 
By definition an overdrive gear has a ratio higher than 1:1, so the output from the gearbox is turning faster than it's input.

To propel a vehicle along at a given speed, you require a certain amount of power. By changing up to a higher gear, you slow the engine down. To maintain the same power (and therefore road speed) you now require the engine to produce more torque (since power = torque * rpm), which you achieve by opening the throttle more.

This gives a higher volumetric efficiency (less pumping losses) and a higher effective compression ratio and hence higher thermal efficiency. The engine is also turning more slowly so frictional losses will be lower. The result is improved economy.
 
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by saying the 6th is an overdrive.to me means that
top speed is achieved in 5th , 6th is there for economy, engine revs less to achieve a suitable(not top speed) cruise... therefore using less fuel....

bullit
 
Didnt know bikes had that, my 6th still pulls lol, top gear on all the bikes ive ridden still achieved more of a top end than 5th.
 
Dogbreath said:
By definition an overdrive gear has a ratio higher than 1:1, so the output from the gearbox is turning faster than it's input.

To propel a vehicle along at a given speed, you require a certain amount of power. By changing up to a higher gear, you slow the engine down. To maintain the same power (and therefore road speed) you now require the engine to produce more torque (since power = torque * rpm), which you achieve by opening the throttle more.

This gives a higher volumetric efficiency (less pumping losses) and a higher effective compression ratio and hence higher thermal efficiency. The engine is also turning more slowly so frictional losses will be lower. The result is improved economy.
Click to expand...


pure genius. That would make sense.

so throttle position isnt a good indicator of fuel consumption in this case?

Incidentally, thanks for all the help thus far. I cant go and test, because the bike is being services atm!
 
Fireskull said:
Didnt know bikes had that, my 6th still pulls lol, top gear on all the bikes ive ridden still achieved more of a top end than 5th.
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Ditto. My TT has a ratio in 6th great than 1:1 so it's bound to still pull. Maybe he's modified the sprockets? That would affect the ratios wouldn't it?
 
Freefaller said:
Ditto. My TT has a ratio in 6th great than 1:1 so it's bound to still pull. Maybe he's modified the sprockets? That would affect the ratios wouldn't it?
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It would but depends on what way, if hes got smaller sprockets could be why 6th gear feels flat, more top end just going to take longer to get there lol
 
i havent modified the sprockets. I know the bike was dynoed by the previous owner to help maximise a K&N air filter and remus can.
 
I just checked the service manual

it lists ratios as 5th at 1.200 (24/20)

6th is 1.086 (25/23)
 
Considering the bike will do about 140mph (if you hold on tight), 6th gear at 70 is not stressing it at all.. don't expect much torque. If you have to open the throttle more in 6th than 5th just to MAINTAIN a constant speed of 70 then there must be something wrong with your bike or you are simply mistaken.
 
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