NOSjohn

iTrader: (9)

uh huh...yep yep.

93LS1RX7

iTrader: (8)

Sorry to say bud but you are flat out wrong.

A corvette Cd is .32
A Hayabusa Cd is .561

Now yes the frontal area is much less on a bike than a car but that is not the only factors.

Here is an article from a motorcycle magazine comparing motorcycle Cd and their results.

http://myweb.cableone.net/toddshelton/aero.html

This is where most people go wrong, they relate drag to coefficient of drag. The Cd is a constant used to figure out drag which is a factor of Cd and of frontal area.

Drag is proportional to the square of speed, and to the size of the frontal area. The constant of proportionality is called the drag coefficient, or Cd, and is primarily the function of shape (NOT SIZE). It indicates which shape is superior, but does not define the total aerodynamic drag by itself. The product of the drag coefficient and the frontal area,
A, gives the drag.

The shape of a motorcycle is where it gets killed not the frontal area like people think. The tire out there spinning on distrubs the air tremendously. The elbows and person riding disturbe badly. The forks on the bike kill the Cd.

This is a Very common misconception but the reality is a bike is more like a brick going through the air.

A Land Rover Discovery has a Cd of .55 which is still BETTER than a Hayabusa which is the most aerodynamic production bike produced.

Transamula

Wow! learn something new everyday! Who would have thought a Bike is more like a brick! Very interesting topic!

James1

This is true. The bike's shape creates a lot of form drag due to the high concentration of static, high pressures developed in the front of the bike.

BigBronco

iTrader: (2)

yep, i was about to comment on that, but i am still not sure about the drag coefficients and how it all works out....


i will learn a lot more of this soon in more physics through my degree to becoming a Mech Engineer

1gen

iTrader: (1)

just haaaadddd to throw that in...if you paid attention in Physics in HS you'd know that



ps- is it sad that I dont have to click on the smilie anymore to use one?

2002Z06yellow

oh yeah ... especially the webpage that says a 600 bike needs a 600RWHP car to hang in there with it... HAHAH big time.. he ran an 11.9@118 and says he needs a 600 RWHP to keep up with him..

James1

Umm...you learn most of this in Fluid Mechanics.

NicD

iTrader: (7)

Maybe if you understood how differently a bike and a car accelerate you could comprehend this. He ran that 11.9 @ 118 with a 2.2 60'. That ET would not happen in a car with a 2.2 60' and a trap of 118. Besides, now that he got a clutch in the car he has run an 11.4 @ 121 since he can actually launch the bike without fear of toasting the clutch. The page needs a little updating. I would change the 600 rwhp car to 550, but everything else would remain.

2002Z06yellow

550 RWHP trap 130 miles with low to mid 10 sec ETs what are you on about? a 600cc bike will get owned from a roll by Z06... and i do understand how a car and a bike accelerate belive me.. owned both..

929

Again, most of you need to remove your heads from you know what.

Flat out, race someone. Not all bikes are the same, and because one ran shitty, doesn't mean it will do it again with a different rider.

Every bike is different, every car is different. One bike on a certain night may run like crap, but a week later with nothing much done can run totally different. Riders make twice as much a difference when it comes to skill level than it does on a car. Trust me on this, experience first hand has taught this to me.

Bikes at 130mph usually, hit a brick wall....what is it? Yea CD. Whoever posted the CD of bikes, I give kudo's to. Too many people are misconceived on what it takes bikes to run. I've run a few single turbo Supra's here in Austin (almost the Big Single Supra Capital) and right around 125-140 is where they begin to pull good.

Bring my any Z06, Any LS1 for that matter here in Austin...and win or lose, we'll post the vids. I'll be the guinnea pig biker. I want to prove a few people's theories wrong...that's all they are. Theories.

How about it? Anyone in Austin care to take on a bike that runs 10.90/130?

NOSjohn

iTrader: (9)

Hey BUD, did you use to cheat on your Math tests too? Did you even read how they got that number? Let me help:
*Frontal area on the Hayabusa and ZX-12R was measured using Photoshop
images with the pixels set to a scaled size, then counted. The Hayabusa
proves to have a smaller frontal area, but the Cd also shows it has the
superior aeridynamic shape.*

That's real mathmatical ! I would venture to say... it's not very accurate. Of course a 'vette has a low Cd, it was designed (practically) in a wind tunnel. I previously stated F-bod type cars too but I guess you forgot to look on the internet for their Cd?


Wait...let me look something up on the internet...here we go:
http://www.motorcycle.com/mo/mcyam/1996_ace.html

...and I quote," Yamaha claims the fairing fitted to the Ace is the slipperiest ever worn by any of their street bikes, with a drag coefficient of only 0.29..."

WOW! that's 3 hundredths less than a Corvette!

It goes on to state it does very little for improved top speed. As stated before, a motorcycle with a size of "x" needs a certain amount of power "y", very similar to a car of size "x" needing to make power "y" to sustain speed.

Now we're comparing apples to oranges and I hope we dont discuss which is more round. I hate it when I'm "flat out" wrong.

2002Z06yellow

okay 929... you show some spirit that i respect... we should get this over with .. do you think you can drive ur bike down to san antonio? if so me and my roommate will race you .. i have a stock Z06 12.9@114 and i will race you from a 60mph punch up to 170 mph and we will get that on tape.. and then you race my roomate with a cam nitrous trans am 480 from a 60 mph punch to 170 mph .. we will post the results either way.. we need to get this discussion over with...

is ur bike stock? let me konw a day before you come so that my frined can fill his bottle!

2002_TAWS6

Im the room mate and would love to race you if you come to san antonio as well. I really dont care if I get beat - Its a bike man comeon! I do understand you have a bike and coming to san antonio might not be possible. If thats the case its ok I understand. Thanks for offering to race anyway. That is really cool of you to make such an offer

I will also be a true sport. I will meet up at san antonio (cant make it to austin at all) and will get my dyno sheet with me. I dont know about racing to 170mph but I will do it anyway. If I lose and its on tape so be it. The performance will speak for itself and if im not faster then who cares. Keep in mind i will NOT be able to spray in 5th gear (dont want my engine to blow). But if my rpms start climbing in 5th I may spray just a "little" bit. I do not mind having a camera person with me in the car taping me as I hit the button and disarm the nitrous in fifth to prove it.

I make 379.94rwhp without spray - BARELY 380rwhp with a mild cam and bolt ons. I make 482.51rwhp on spray (true 100 shot).

I will give all the details on everything and promise to be a true sport even if I lose. Let me know if you think its fair or not.

Let me know if you can make it to san antonio and we'll plan this out.

Please do not take this in a wrong way. I am not trying to bash your bike. Its an awesome bike and it would be BAD *** if I can beat it WITH nitrous (again I wont spray in 5th).

93LS1RX7

iTrader: (8)

Nope FLAT OUT wrong AGAIN. You need to read the whole context of the text not just pull one part of it out and warp it to make your point. It says the FAIRING has a Cd of .29. NOT THE BIKE (THE FAIRING ALONE). Sure that fairing is more slippery in the air than a corvette but not once it is bolted to the rest of the bike and a rider is put on it. THAT IS WHY IT DOES VERY LITTLE TO HELP TOP SPEED. The Cd of that bike is still HORRIBLE.

I did search the internet for some of the information because unfortunately I dont have access to a wind tunnel to do real world testing so I need to rely on someone else to do that for me but I sure as hell can extrapolate the data I need from the hard facts they give which is much more accurate than I dont get wet in the rain because the bike has a good Cd (Which is completely incorrect to). Other than research scientists everyone merely extrapolates information from previous information. No need to redo someones work.

Here is a tidbit for you FRONTAL AREA HAS NOTHING TO DO WITH THE COEFFIECENT OF DRAG!!!!!!!!! So the photoshop thing is irrelevant, but it is the most accurate way to measure the frontal area of the object. Again showing your lack of understanding.

The coeffiecent of drag is not something you can figure out with a formula. It is a constant value that you can only discover through scientific testing. Using the formula for drag I will explain why a bike HATES high speeds and where the Cd effects it so greatly.

Now that we have discussed Cd and drag here is the one that will really fry your noodle.

Using the formula for drag we can see some interesting things. Lets compare a corvette to a Hayabusa at 75 mph and at 150 mph.

D = Cd * A * .5 * r * V^2
D= Drag (not including FORM drag for now at least)
Cd= Coefficient of Drag
A=frontal area
r= Air density (1.2 kg/m^3 constant)
V= velocity

Example 1:
A corvette traveling at 75mph (33.582 meters/second) with a frontal area of 2.048 m^2. The drag on this car is:
D=.32 * 2.048 * .5 * 1.2 * 33.582^2
D=443.45

Example 2:
A motorcycle traveling at 75mph (33.582 meters/second) with a frontal area of .313 m^2. The drag on this motorcycle is:
D=.516 * .313 * .5 * 1.2 * 33.582^2
D=118.82

Example 3:
A corvette traveling at 150mph (67.056 meters/second) with a frontal area of 2.048 m^2. The drag on this car is:
D=.32 * 2.048 * .5 * 1.2 * 67.056^2
D=1768.09

Example 4:
A motorcycle traveling at 150mph (67.056 meters/second) with a frontal area of .313 m^2. The drag on this motorcycle is:
D=.516 * .313 * .5 * 1.2 * 67.056^2
D=435.73

As you can see the drag(without form drag) on the corvette is ALWAYS higher than the drag(without form drag) on the motorcycle. Now you are thinking this guy just proved himself wrong. But you are wrong there. The rub is when you bring form drag into the equation which relates to the Cd. The reason why a motorcycle loses to a car when speeds get high is .................turbulence.

At low speeds turbulence doesnt matter a whole lot cause the air is able to flow fluidly wherever it wants now at high speeds turbulence becomes a major concern particularly for a motorcycle. A motorcycle doesn't share the shape of your car: a motorcycle and rider have a very irregular shape and generate turbulence (and therefore additilonal drag) by design! The windshield, front fairing, gas tank, and tail sections of the motorcycle (and virtually every part of the rider) all have aerodynamically abrupt shapes -- these shapes do not taper together like an aeroplane wing. Areas of low pressure behind the abrupt shapes of the motorcycle cause the airflow to collapse into the space, creating vortices and increasing the form drag.

Form drag is the aerodynamic resistance to the motion of the motorcycle through the air. As air flows around the bike, local velocities and pressures change as a function of the motorcycle's shape. The change in flow is apparent from the size and type of wake left by the object. The flow change and wake produce forces that can be summed to determine the total force opposing the motion (this is why drag slows you down!) (TOTAL DRAG INCLUDING FORM DRAG, I told you it was coming.) This source of drag depends on the shape of the motorcycle and is the most-commonly engineered parameter in the drag equation. Form drag is why riders will crouch behind the windshield of the motorcycle while traveling at high speeds.

Form drag is much less significant on a car because everything is smoothly tucked away, relative to a motorcycle. The flow is much less turbulant than a motorcycle.

THUS THE MOTORCYCLE LOSES THE HIGH SPEED BATTLE.

Maybe this can become a sticky so no one ever has to type all that again.

NOSjohn

iTrader: (9)

It looks like you're arguing with yourself now...haha. You can talk about Cd, force of drag, drag queen...whatever you want. My point was this:

As stated before, a motorcycle with a size of "x" needs a certain amount of power "y", very similar to a car of size "x" needing to make power "y" to sustain speed.

ANY vehicle will lose acceleration ability at high speed, that is a law of nature. That's all, end of discussion.

93LS1RX7

iTrader: (8)

No your point WAS what I quoted right here. Now that I have proven you wrong you have moved on to a new topic.

No **** as speed increases power to increase the speed increases more that wasnt the discussion. But you are still wrong in saying it a motorcycle and car are similar at high speeds. Turbulence comes into the picture on a bike in a big way.

I am not argueing with myself I am just trying to inform people of the facts instead of the
that you are spewing. Maybe I should argue with myself though it would be much more mentally challenging than the one legged man in an *** kicking contest you have proven yourself to be.

Now thats all end of discussion

Class dismissed Biatch

99-LS1-SS

Blah blah blah.

This post needs to be locked down.

NicD

iTrader: (7)

Sure.

MillaTK