[Karaya One]

Are they answering a question no one asked for motorcycles?

http://www.motorcycle-usa.com/Articl...ID=3909&Page=1

[benVFR]

I knew this was coming... I had been predicting it after a speech their CEO gave last year.

I figured it was going to show up in an even more bastardized version of the VFR motor.

Sucks if it feels/sounds like crap.. I think the idea has plenty of promise for streetbikes.

[Stoneman]

I don't buy into the whole 'fuel efficiency' with this variable cylinder schtik. I mean, just how much horsepower does it take to KEEP a 400 lb motorcycle at 80 once it's reached that speed? I don't buy into any of it...

[hambone]

i could give a shit if its 48 mpg instead of 40, maybe on a goldwing i'd care

[Honclfibr]

Hmm, high gas mileage coupled with on-demand horsepower? Seems familiar...

Oh yeah, they invented that 100 years ago and called it the turbocharger.

[Punjistick]

ducati riders get hassled as it is with the dry clutch "hey dude I think something is wrong with your bike". Imagine what these blackbird riders are gona have to put up with.

[richw]

Another example of

Just cause you can doesn't mean you should.

Proof that Honda has no concept why people buy a hyperbike. There are Europeans that use bikes for commute that might be interested in gas mileage and extra power when you want it.

It would be fun to be at full lean when another cylinder decides to kick in.

[mikeb]

Originally posted by richw


It would be fun to be at full lean when another cylinder decides to kick in.

exactly what i hate about the 02+ vfr's. i was freaked out more than once with the vtec. had to learn to keep the rpm's above 7g's when playing in the twisties.

[benVFR]

Originally posted by Stoneman
I don't buy into the whole 'fuel efficiency' with this variable cylinder schtik. I mean, just how much horsepower does it take to KEEP a 400 lb motorcycle at 80 once it's reached that speed? I don't buy into any of it...

How much HP to keep a 400lb faired bike at 80mph once it's reached that speed?

Very Very little. 10hp? Less? It's a shockingly small #.

The author is dead right Honda should have it operate on all 4-cylinders unless you're cruising.

Also a 30% gain on 40mpg would be 52mpg, not 48mpg. I don't think that's enough of a gain for me either.. but a Blackbird/ZX-14/Busa that got the same fuel economy as a 500-600cc bike like an EX500 or SV650 would be fairly neat IMO.

Of course I think there is something else wrong here.. they could have gotten the same result by just giving it a "real" VTEC system like the cars.

They are also just thinking ahead to the day when gas is so expensive this is the only way anyone will even consider buying an 1100cc bike. What would you rather have, a blackbird that you can afford to fill the tank on, or a 250-500cc bike? They are going to need to make large displacement bikes more expensive if they want to keep selling them at all.

[stoinkythepig]

One of the main reasons I opted for a ZX9R over a ZX12R when I was looking was mileage. Not so much for the cost savings, but for the range. I ride quite a bit and the though of having to gas up every other day just to commute bothered me. I can gas up every third day on my 9R. Oddly, the ZX6R gets about the same mileage as the 9R so there was no incentive to go down 300cc.

The power it takes to go 80 MPH is exactly 1/4 of what it takes to go 160 MPH since drag is a function of the square of speed. So 80 MPH may actually require more HP than you think. If it takes 100 RWHP to go 160, you'll need 25 RWHP to go 80.

My bike is supposed to top out at 169 MPH with 128 RWHP. That means it'll take 28.7 HP to 80. Considering it takes about .08 gallons of gas per hour to make 1 HP, I should be getting about 35 MPG to maintain 80. That's about right.

[richw]

I think air resistance is a forth power function of speed.

2,4,8,16 or

16 times the force at twice the speed

Also at cruise internal motor and drive losses are a big factor.


If they really loved us you would have variable displacement operating at near atmospheric pressure. So at cruise it would be like a 125 cc. There was an operating engines like this for 50 years. I think the crank arms etc to heavy for bikes.

Twer it up to me cars would have 1 motor capable of operating up to 85 on expressways at maximum efficiency and an entire 2nd engine that would clutch in for acceleration

[stoinkythepig]

Originally posted by richw
I think air resistance is a forth power function of speed.

2,4,8,16 or

16 times the force at twice the speed

Also at cruise internal motor and drive losses are a big factor.


If they really loved us you would have variable displacement operating at near atmospheric pressure. So at cruise it would be like a 125 cc. There was an operating engines like this for 50 years. I think the crank arms etc to heavy for bikes.

Twer it up to me cars would have 1 motor capable of operating up to 85 on expressways at maximum efficiency and an entire 2nd engine that would clutch in for acceleration

Sorry, just the square.

See : http://www.seed.slb.com/qa2/FAQView.cfm?ID=858

You have described a hybrid vehicle pretty accurately.

[TheIglu]

Honda should just buy a KLR650, call it the blackbird and it'll sell great.

70+ MPG in mine, jetted, WOT 90% of a 280 mile ride. I love my KiLaR

Fuck gas, they should get goin on Diesel! It's already proving reliable and fast recently....

[richw]

You are more are both 1/2 right

Time the 4th dimension..............

Power

The power required to overcome the aerodynamic drag is given by:

P_d = \mathbf{F}_d \cdot \mathbf{v} = - {1 \over 2} \rho v^3 A C_d

Note that the power needed to push an object through a fluid increases as the cube of the velocity. A car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7.5 kW) to overcome air drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW). With a doubling of speed the drag (force) quadruples per the formula. Exerting four times the force over a fixed distance produces four times as much work. At twice the speed the work (resulting in displacement over a fixed distance) is done twice faster. Since power is the rate of doing work, four times a work in half the time requires eight times the power.

It should be emphasized here that the drag equation is an approximation, and does not necessarily give a close approximation in every instance. Thus one should be careful when making assumptions using these equations.

[stoinkythepig]

Originally posted by richw
At twice the speed the work (resulting in displacement over a fixed distance) is done twice faster. Since power is the rate of doing work, four times a work in half the time requires eight times the power.

The only work here is overcoming the drag. The velocity is not really work since without drag, the bike would maintain the same velocity indefinitely. It only takes work to attain the velocity in a drag free world, not to maintain it.

I still think HP requirements are proportional to drag, in water too, BTW.

[zombie]

I'm diggin this technical conversation as I have never really understood the horsepower thing , but you guys are putting it in language I can understand.
When I was a motorcycle courier and fuel mileage was an issue I rode a honda CX500 and got 45-50mpg and my other bike was a triumph trident 750 that got shite mileage but it wasn't why I rode it , I just liked it plain and simple

[Stoneman]

Okay. So say, 20-30 HP to KEEP a motorcycle traveling at 80MPH. Keeping in mind that it's simply MAINTANING the speed once it's reached with all 4 cyliders, wouldn't 4 cylinders have less work to do than 2 to keep that speed? And wouldn't that result in better mileage?

I'm still not buying into this as a mileage savings step. I'm seeing this so-called technology as a way to passify...

[richw]

The efficiency of a
gas engine goes up with the cylinder pressures..

A small engine with an open Throttle runs near atmospheric pressure. The higher pressure in the cylinder increases the amount of energy converted to mechanical force rather then heat.

A large engine operating with a closed throttle is running a high vacuum that results in lower cylinder pressure and reduced efficiency. Additionally the larger area has a cooling effect on the charge and also poor flame propagation.

Diesels are efficient because there is no throttle. They always have atmospheric on the intake stoke and vary power by the amount of fuel injected.

So more theory then reality if you turn an 1100 into a 550 it would be more efficient then a low stressed 1100. It would not be as efficient as a well tuned 550 because of the thermal losses of the dead cylinders.


Note We will assume that the fuel air ratio is adjusted for efficiency that is different from either lower pollution or maximum power. When it comes to old air cooled engines like a triumph there was actually additional gas squirted by the main jet to cool the piston top by evaporation.

[benVFR]

Rich is pretty much dead on..

This is one of the big factors behind variable valve timing & lift, the move to throttle by wire, etc..

They are all there to maximize the flow/pressure of air into the cylinders at cruise speeds, etc.. for maximum efficiency.

And besides we know the car folks are loving the variable cylinder technology aren't they?

Honda knows what they're doing.. just a question of whether or not they get all the kinks out before they release it. I hope they do.

If they wanted to "passivate" us they'd just stop selling anything over 500cc. Or go to the government.

BTW efficiency and cleanliness go together. Pollution is best fought by raising combustion temperatures, which implies lean running. Maximum power comes at a lower temperature & richer mixture, but the increases in efficiency over the years has more then made up for the loss of a few horsepower due to leaning out the mixture.

They still have to make it ride nicely though..

[Stoneman]

Originally posted by richw
A large engine operating with a closed throttle is running a high vacuum that results in lower cylinder pressure and reduced efficiency. Additionally the larger area has a cooling effect on the charge and also poor flame propagation....

...So more theory then reality if you turn an 1100 into a 550 it would be more efficient then a low stressed 1100. It would not be as efficient as a well tuned 550 because of the thermal losses of the dead cylinders.

Okay. By that equation, overdrive wouldn't improve fuel economy then. I'm not talking about OD from a transmission stand-point. Rather, the point of OD is to make your engine work less hard, maintanign desired speeds at lower RPM's. Now that - in theory - is supposed to increase your fuel economy. So you have that same (assumed) big engine MAINTANING a certain speed, yet it's turning lower RPM's therefor resulting in lower cylinder pressure. Going by your the above theorie(s), OD should result in LOWER gas mileage...

(I know what I'm trying to say, just not sure it's coming through my fingertips correctly)...

Bottom line is I still say it's a crock of shit. When REAL WORLD, long term tests start coming in on ALL these types of engines I'd be willing to bet all the nay-sayers (such as myself) are gonna be standing over here saying we told you so...

[RandyO]

[quote]Originally posted by stoinkythepig
It only takes work to attain the velocity in a drag free world, not to maintain it.



not true, there is a power requirement in addition to friction losses, not much, I am not sure it is worth computing in aerodynamics but I certainly compute the velocity losses in fluid dynamics when I spec a pump.

yes, fluid dynamics are the same as aerodynamics just with different coefficients of friction

it's best just to say that losses due to aerodynamics are exponential with speed rather then linear with speed

[richw]

Overdrive works

The losses in the motor are related to engine speed. Friction, pumping losses, fluid and oil drag all go up with rpm. So if you travel at the same speed with the engine turning slower then there is less motor sacrificial losses.

2ndly as described above the slower engine is operating closer to atmospheric pressure and thus operating more efficiently.

[benVFR]

Dead Simple..

OD works cause you're turning fewer RPM, firing the fuel injectors less often.

Cylinder deactivation works because you're firing fewer cylinders.

Two separate variable, both concepts can and are used together.

[stoinkythepig]

[quote]Originally posted by RandyO

Originally posted by stoinkythepig
It only takes work to attain the velocity in a drag free world, not to maintain it.



not true, there is a power requirement in addition to friction losses, not much, I am not sure it is worth computing in aerodynamics but I certainly compute the velocity losses in fluid dynamics when I spec a pump.

yes, fluid dynamics are the same as aerodynamics just with different coefficients of friction

it's best just to say that losses due to aerodynamics are exponential with speed rather then linear with speed

The losses you are calculating are still based on friction or drag. My point was that with no drag, objects in motion tend to stay in motion (Newton's First Law). In space, once an object has attained a velocity, it tends to maintain that velocity with no more force added.

HP (in its true definition) is based on the ability to displace a specific weight object against the drag of gravity (hence the use of weight, not mass) at a specific speed, not just displace an object.

[RandyO]

Originally posted by stoinkythepig
The losses you are calculating are still based on friction or drag. My point was that with no drag, objects in motion tend to stay in motion (Newton's First Law). In space, once an object has attained a velocity, it tends to maintain that velocity with no more force added.

HP (in its true definition) is based on the ability to displace a specific weight object against the drag of gravity (hence the use of weight, not mass) at a specific speed, not just displace an object.

the calculation I an talking about has not to do with friction, but it does have to do with gravity, cause gravity 32ft/sec/sec is in the calculation

I supose in space it wouldn be there, and on the moon the 32# would be different,

BUT we are on earth, gravity is always there