[pwatts]

Hi all,

Some may remember my complaint earlier about tiring riding style - all fixed now after a couple 100 miles exercise :-)

Anyhow, has anybody noticed their blades' fuel economy? On my stock 06 blade with my first tank, mostly 'sane' distance riding, I got about 31mpg, which is about right. However, aggressive riding mostly in-town and high-rev riding to "loosen up" the motor (advice from the agents since the previous owner never took it over 100mph), resulted to a sobering 17mpg. Is this a realistic figure?

According to a dyno test the bike is running a bit rich, so BMC, PC3 and 2 Bro's SO will come when funds allow.

PS: I attach a pic of my babe.. you US guys are lucky with your prices, I paid $10k for mine (2006, 2000mi, stock) used, which is a bargain here.. new ones go for over $14k.

[curt248]

Wow! That sounds terrible. I will be interesting to see what others say about the 06 blade.

I have an 01 blade (the 929) and I get 40mpg no matter how I ride it.

The only time it was much different was in the high elevations (7 to 11000 ft) of Colorado mountains where I got 47mpg with a passenger while have the bike pegged quite often.

[curt248]

[2xs]

mine is highly dependand on how i ride it. i have ridden really easy at the speed limit and gotten 300kms on a tank, and then i have ridden really hard and run out at 78 kms

[lanbrown]

My take, if you want fuel economy you do not buy a highly tuned large displacement motorcycle. That is like buying a car with a V8 instead of the 4 cylinder and then complain about the fuel economy.

If you want fuel econmy, try a moped.

If you want to play, you have to pay.

[pwatts]

Hehe I can get 10mpg for all I care.. just curious if riding style has such a big impact on economy - kinda important if you go on a 400mi trip on a road with very few fuel stops!

[curt248]

I was quite worried about taking a trip in the boonies with my bike too. It turns out that, at least in Colorado's mountains, 160 miles in between fuel posed no problems at all.

Even a car (much heavier) with 150HP should get around 30 to 40mpg's. I would think a bike with ~150HP that weighs only 380lbs or so should be able to do better.

Come on blade owners. Post your gas mileage.

[Bryce Auten]

around 28 mpg

[bobfluent]

02 954 and I get around 34 to 40 depending. I agree with the moped comment 100%

[curt248]

Hey Bryce. I just looked at your gallery pics. I like the red and black 01 colors. Did you paint it black as in the other 2 pics?

How did you paint it? Did you have it done professionally or did you do it yourself somehow? If you did it, what did you use.

[Ol' Gravy Leg]

i get about 35mpg with an all stock set up and a fist o' ham.

[lanbrown]

Originally Posted by curt248

Even a car (much heavier) with 150HP should get around 30 to 40mpg's. I would think a bike with ~150HP that weighs only 380lbs or so should be able to do better.

Come on blade owners. Post your gas mileage.

Apples to oranges. One, the gearing on a bike is for performance, not fuel mileage. Next, the engine revs higher than that of a car. If you are going 70 MPH, how many RPM’s are you at on the bike compared to your car? RPM’s use fuel. A bike also runs much richer than a car. A car also has an oxygen sensor, most bikes do not.

Lastly, the aerodynamics of a bike are much worse than that of a car. If you look at some cars, they are below .3 while a motorcycle is typically that of what a truck is. I remembered that from a longtime ago and I did a search and found chart.
Air Drag Coefficients
The current Prius is .19. Here are some more for you:
“0.27 Nissan GT-R 2008
0.32 Scion xB 2008
0.37 Volkswagen Tiguan 2008
0.27 Toyota Camry Hybrid 2007
0.29 Peugeot 308 2007
0.30 Porsche 997 GT3 RS 2007
0.32 MAZDASPEED3 2007
0.26 Mercedes-Benz W221 S-Class 2006
0.27 Honda Civic Hybrid 2006
0.28 Chevrolet Corvette Z06 2006
0.28 Lexus IS 2006
0.29 Porsche 997 GT3 2006
0.30 Koenigsegg CCX 2006
0.30 Hyundai Sonata 2006
0.30 BMW E90 2006
0.31 Toyota RAV4 2006
0.31 Honda Civic 2006
0.32 Volkswagen GTI Mk V 2006
0.33 Dodge Charger 2006
0.33 Audi A3 2006
0.35 BMW Z4 M coupe 2006
0.28 Toyota Camry / Lexus ES 2005
0.29 Porsche Boxster 2005
0.29 Honda Accord Hybrid 2005, 2007
0.29 Chevrolet Corvette 2005
0.291 Toyota Avalon 2005
0.30 Honda Odyssey 2005
0.30 Acura NSX 2005
0.324 Cobalt SS Supercharged 2005
0.35 Jaguar XKR 2005
0.40 Ford Escape Hybrid 2005
0.26 Toyota Prius 2004
0.28 Porsche 997 2004
0.29 Peugeot 407 2004
0.31 Nissan Tiida / Versa 2004
0.31 Mazda RX-8 2004
0.33 Subaru Impreza WRX STi 2004
0.33 Renault Modus 2004
0.34 Aston Martin DB9 2004
0.35 Aston Martin Vanquish 2004
0.39 Dodge Durango 2004
0.28 Volkswagen NewBeetle with wing 2003
0.28 Saab 9-3 2003
0.29 Honda Accord Coupe 2003, 2005-2007
0.30 Honda Accord Sedan 2003, 2005-2007
0.38-0.39 VW NewBeetle without wing or spoiler 2003
0.57 Hummer H2 2003
0.27 Infiniti G35
(0.26 with "aero package") 2002
0.29 Chevrolet Corvette C5 Z06 2002
0.30 Nissan 350Z 2002
0.32 Honda Accord Coupe 2002
0.33 Honda Accord Sedan 2002
0.25 Audi A2 1.2 TDI 2001
0.26 Lexus LS 430
(0.25 with air suspension) 2001
0.27 Mercedes-Benz W203 C-Class Sedan 2001
0.29 Toyota Prius 2001
0.29 Mercedes-Benz W203 C-Class Coupe 2001
0.29 Mercedes-Benz SL (Roof Up) 2001
0.31 Peugeot 307 2001
0.33 Lamborghini Murcielago 2001
0.34 Mercedes-Benz SL (Roof Down) 2001
0.36 Honda Civic 2001
0.30 Mitsubishi Eclipse 2000”

Notice most of those are far below that of a motorcycle. Add all of the factors in, and a bike is not fuel efficient at all.

[curt248]

I'm not sure if I missed it but what is the coefficient of drag for a sport bike then?

[lanbrown]

Provided in the link, but since clicking might be difficult for some, I will just post the info here:
“Vehicle Drag Coefficient
Description Low Medium High
----------------------------------------
Experimental 0.17 0.21 0.23
Sports 0.27 0.31 0.38
Performance 0.32 0.34 0.38
60's Muscle 0.38 0.44 0.50
Sedan 0.34 0.39 0.50
Motorcycle 0.50 0.90 1.00
Truck 0.60 0.90 1.00
Tractor-Trailer 0.60 0.77 1.20”

There you have it, a motorcycle can be equal to that of a tractor trailer.

This is why when you look at the power to weight ratio that out bikes are drag limited.

[Abjatrer]

Having read ....
Define "motorcycle"
as per definition of "truck".
With or without rider ?
If rider - position, build, rider's D/C, impact of clothing?
Totally standard bike as per off the assembly line? or Modded?


Those stats dont make diddly sense to me. Way too many unknown, unfactored variables. Why can we get 30km/l @ 90 km/h while a 0.27 D/C might get 25km/l @90 km/h?

[lanbrown]

That would be stock and without the rider. The vehicles were put into a wind tunnel and there are no variables. More weight means worse fuel mileage. So if they used a rider, what was the weight? What about the car, more weight means worse fuel mileage. This is why all fuel mileage tests are done with the car stationary. You are trying to make it more complex than it should. Truck would be a large commercial truck, not a light-duty model.

To answer your question, because you don’t know what you’re talking about and don’t understand the mechanical and aerodynamic aspects.

[curt248]

Drag in sports and racing cars

Reducing drag is also a factor in sports car design, where fuel efficiency is less of a factor, but where low drag helps a car achieve a high top speed. However, there are other important aspects of aerodynamics that affect cars designed for high speed, including racing cars. Notably, it is important to minimize lift, hence increasing downforce, to avoid the car ever becoming airborne and instead force the car onto the track -- allowing higher cornering speed for the vehicle. Also it is important to maximize aerodynamic stability: some racing cars have tested well at particular "attack angles", yet performed catastrophically, i.e. flipping over, when hitting a bump or experiencing turbulence from other vehicles (most notably the Mercedes-Benz CLR). For best cornering and racing performance, as required in Formula 1 cars, downforce and stability are crucial and these cars must attempt to maximize downforce and maintain stability while attempting to minimize the overall Cd value.

[edit] Typical values and examples

The average modern automobile achieves a drag coefficient of between 0.30 and 0.35. SUVs, with their typically boxy shapes and larger frontal area, typically achieve a Cd of 0.35–0.45. A very gently inclined windshield gives a lower drag coefficient but has safety disadvantages, including reduced driver visibility. Certain cars can achieve figures of 0.25–0.30, although sometimes designers deliberately increase drag in order to reduce lift.

Some examples of Cd follow. Figures given are generally for the basic model. Some "high performance" models may actually have higher drag, due to wider tires and extra spoilers.
Production cars Cd http://en.wikipedia.org/skins-1.5/co.../sort_none.gif Automobile http://en.wikipedia.org/skins-1.5/co.../sort_none.gif Year http://en.wikipedia.org/skins-1.5/co.../sort_none.gif 0.7 to 1.1 typical values for a Formula 1 car (downforce settings change for each circuit)
0.7 Caterham Seven
0.6 + a typical truck
0.57 Hummer H2 2003 0.51 Citroën 2CV 1948 0.48 Volkswagen Beetle [6]
0.46 Ford Mustang (coupe) 1979 0.45 Dodge Viper RT/10 1996 0.44 Ford Mustang (fastback) 1979 0.44 Peugeot 305 1978 0.44 Peugeot 504 1968 0.44 Toyota Truck 1990 0.425 Duple 425 coach
(named for its low Cd by coach standards) c.1985 0.42 Lamborghini Countach 1974 0.42 Triumph Spitfire Mk IV 1971 0.42 Plymouth Duster 1994 0.40 Ford Escape Hybrid 2005 0.40 Nissan Skyline GT-R R32 1989 0.39 Dodge Durango 2004 0.39 Triumph Spitfire 1964 0.38-0.39 VW NewBeetle without wing or spoiler 2003 0.385 Nissan 280ZX 1978 0.38 Mazda Miata 1989 0.374 Ford Capri Mk III 1978 0.372 Ferrari F50 1996 0.37 Renault Twingo
0.37 BMW Z3 M coupe 1999 0.37 Volkswagen Tiguan 2008 0.36 Citroën CX (named after the term for Cd) 1974 0.36 Citroën DS 1955 0.36 Eagle Talon 1990s 0.36 Ferrari Testarossa 1986 0.36 Ford Mustang 1999 0.36 Honda Civic 2001 0.36 Opel GT 1969 0.355 NSU Ro 80 1967 0.35 Aston Martin Vanquish 2004 0.35 Dodge Viper GTS 1996 0.35 Jaguar XKR 2005 0.35 Toyota MR2 1998 0.35 BMW Z4 M coupe 2006 0.34 Aston Martin DB9 2004 0.34 Chevrolet Caprice 1994 0.34 Ferrari F40 1987 0.34 Ferrari 360 Modena 1987 0.34 Ferrari F430 F1 1999 0.34 Ford Sierra 1982 0.34 Ford Puma 1997 0.34 Honda Prelude 1988 0.34 Mercedes-Benz SL (Roof Down) 2001 0.34 Peugeot 106 1991 0.338 Chevrolet Camaro, 1995 0.33 Audi A3 2006 0.33 Citroën SM 1970 0.33 Dodge Charger 2006 0.33 Ford Crown Victoria 1992 0.33 Honda Accord Sedan 2002 0.33 Lamborghini Murcielago 2001 0.33 Mazda RX-7 FC3C 1987 0.33 Peugeot 206 1998 0.33 Peugeot 309 1986 0.33 Renault Modus 2004 0.33 Subaru Impreza WRX STi 2004 0.324 Cobalt SS Supercharged 2005 0.32 Buick Riviera 1995 0.32 Dodge Avenger 1995 0.32 Honda Accord Coupe 2002 0.32 McLaren F1 1992 0.32 Mercedes-Benz 190E 2.5-16/2.3-16
0.32 Nissan 300ZX 1989 0.32 Peugeot 406 1995 0.32 Peugeot 806 1994 0.32 Scion xB 2008 0.32 Suzuki Swift 1991 0.32 Toyota Celica 1994 0.32 Volkswagen GTI Mk V 2006 0.32 MAZDASPEED3 2007 0.31 Audi A4 B5, 1995 0.31 Citroën AX 1986 0.31 Citroën GS 1970 0.31 Eagle Vision
0.31 Ford Falcon 1995 0.31 Holden Commodore 1998 0.31 Honda Civic 2006 0.310 Lamborghini Diablo 1990 0.31 Mazda RX-7 FC3S 1986 0.31 Mazda RX-8 2004 0.31 Nissan Tiida / Versa 2004 0.31 Peugeot 307 2001 0.31 Renault 25 1984 0.31 Saab Sonett III 1970 0.31 Toyota Avalon 1995 0.31 Toyota RAV4 2006 0.31 Volkswagen GTI Mk IV 1997 0.30 Acura NSX 2005 0.30 Audi 100 1983 0.30 BMW E90 2006 0.30 Hyundai Sonata 2006 0.30 Honda Accord Sedan 2003, 2005-2007 0.30 Honda Odyssey 2005 0.30 Koenigsegg CCX 2006 0.30 Mitsubishi Eclipse 2000 0.30 Nissan 180SX 1989 0.30 Nissan 300ZX 1983 0.30 Nissan 350Z 2002 0.30 Porsche 996 1997 0.30 Porsche 997 GT3 RS 2007 0.30 Saab 92 1947 0.295 Ford Falcon 1998 0.291 Toyota Avalon 2005 0.29 Alfa Romeo 155 1992 0.29 BMW 8-Series 1989 0.29 Chevrolet Corvette 2005 0.29 Daewoo Espero 1990 0.29 Dodge Charger Daytona 1969 0.29 Honda Accord Hybrid 2005, 2007 0.29 Honda Accord Coupe 2003, 2005-2007 0.29 Honda CRX HF 1988 0.29 Lancia Dedra 1990 0.29 Lexus LS 400 1990 0.29 Lotus Elite 1958 0.29 Mazda Millenia 1995 0.29 Mazda RX-7 FC3S Aero Package 1986 0.29 Mercedes-Benz SL (Roof Up) 2001 0.29 Mercedes-Benz W203 C-Class Coupe 2001 0.29 Peugeot 308 2007 0.29 Peugeot 407 2004 0.29 Peugeot 607 1999 0.29 Porsche Boxster 2005 0.29 Porsche 997 GT3 2006 0.29 Subaru XT 1985 0.29 Subaru SVX 1992 0.29 Toyota Prius 2001 0.29 Chevrolet Corvette C5 Z06 2002 0.28 Lexus IS 2006 0.28 Mitsubishi Diamante 1995 0.28 Porsche 997 2004 0.28 Renault 25 TS 1984 0.28 Rumpler-Tropfenwagen 1921 0.28 Saab 9-3 2003 0.28 Toyota Camry / Lexus ES 2005 0.28 Chevrolet Corvette Z06 2006 0.28 Citroën XM 1989 0.28 Volkswagen NewBeetle with wing 2003 0.27 Volkswagen Passat B5(sedan) 1997 0.27 Honda Civic Hybrid 2006 0.27 Infiniti G35
(0.26 with "aero package") 2002 0.27 Mercedes-Benz W203 C-Class Sedan 2001 0.27 Toyota Camry Hybrid 2007 0.27 Nissan GT-R 2008 0.26 Alfa Romeo Disco Volante 1952 0.26 Hotchkiss Gregoire[citation needed] 1951 0.26 Lexus LS 430
(0.25 with air suspension) 2001 0.26 Mercedes-Benz W221 S-Class 2006 0.26 Opel Calibra 1989 0.26 Toyota Prius 2004 0.25 Audi A2 1.2 TDI 2001 0.25 Honda Insight 1999, 2003, 2005 Concept/experimental cars Cd http://en.wikipedia.org/skins-1.5/co.../sort_none.gif Automobile http://en.wikipedia.org/skins-1.5/co.../sort_none.gif Year http://en.wikipedia.org/skins-1.5/co.../sort_none.gif 0.25 Dymaxion Car 1933 0.25 SmILE (an experimental car) 1996 0.22 Citroën ECO 2000 Concept 1981 [7] 0.212 Tatra T77 1935 0.20 Loremo Concept, 2006. Planned production 2009 0.20 Opel Eco Speedster Concept 2003 0.195 General Motors EV1 1996 0.19 Alfa Romeo B.A.T. 7 Concept 1954 0.19 Dodge Intrepid ESX Concept 1995 0.19 Mercedes-Benz Bionic Concept [8](based on the boxfish) 2005 0.168 Daihatsu UFE-III Concept 2005 [9] 0.16 General Motors Precept Concept 2000 0.159 Volkswagen 1-litre car Concept 2002
2009 (Planned production) 0.14 Fiat Turbina Concept 1954 0.125 Sunraycer, solar race car 1987 0.12 Reflex 1000, solar cycle 1996 [10] 0.117 Summers Brothers Goldenrod Bonneville race car 1965 0.11 Aptera Motors Typ-1 2008 (planned) 0.08 Fortis Saxonia (Shell Eco-marathon) Concept 2007 0.075 PAC-Car II (Shell Eco-marathon) Concept 2005 0.07 Nuna, World Solar Challenge winner 2001-2007
[edit] Selected Photographs

http://upload.wikimedia.org/wikipedi...rstati on.jpg

2.1 - a smooth brick


http://upload.wikimedia.org/wikipedi...px-Lotus79.jpg

0.7 to 1.1 - typical values for a Formula 1 car


http://upload.wikimedia.org/wikipedi...icerOnBike.jpg

0.9 -a typical bicycle plus cyclist


http://upload.wikimedia.org/wikipedi...px-Super_7.jpg

0.7 - Caterham Seven


http://upload.wikimedia.org/wikipedi...505_scania.jpg

at least 0.6 - a typical truck


http://upload.wikimedia.org/wikipedi...-Hummer_H2.jpg

0.57 - Hummer H2, 2003


http://upload.wikimedia.org/wikipedi...roen2cvtff.jpg

0.51 - Citroën 2CV due to the mudguard, despite the round roof


http://upload.wikimedia.org/wikipedi...stacionado.jpg

0.48 - Volkswagen Beetle due to the mudguard, despite the round roof


http://upload.wikimedia.org/wikipedi...le425Coach.jpg

0.425 - Duple 425 coach


http://upload.wikimedia.org/wikipedi...ach_LP500S.jpg

0.42 - Lamborghini Countach, 1974


http://upload.wikimedia.org/wikipedi...tfire_MKIV.jpg

0.42 - Triumph Spitfire Mk IV, 1971-1980


http://upload.wikimedia.org/wikipedi...MiataGreen.jpg

0.38 - Mazda Miata, 1989


http://upload.wikimedia.org/wikipedi...arp.850pix.jpg

0.38 - Rolls-Royce Silver Seraph, 1998 [1]


http://upload.wikimedia.org/wikipedi...-amoswolfe.jpg

0.374 - Ford Capri Mk III, 1978-1986


http://upload.wikimedia.org/wikipedi...errari_F50.jpg

0.372 - Ferrari F50, 1996 high drag due to aerodynamic aids and cooling ducts.


http://upload.wikimedia.org/wikipedi...S23_Pallas.jpg

0.36 - Citroën DS, 1955, relative high drag despite the aerodynamic headlights, due to the rough windshield-roof transition.


http://upload.wikimedia.org/wikipedi...TAROSSA-02.jpg

0.36 - Ferrari Testarossa, 1986


http://upload.wikimedia.org/wikipedi...an_2001-05.jpg

0.36 - Honda Civic, 2001


http://upload.wikimedia.org/wikipedi...rcx1silver.jpg

0.36 - Citroën CX, 1974 (the car was named after the term for drag coefficient)


http://upload.wikimedia.org/wikipedi...-NSU_Ro_80.jpg

0.355 - NSU Ro 80, 1967 despite the edgy front


http://upload.wikimedia.org/wikipedi...px-Audi_TT.jpg

0.35, Audi TT, 1998 [2] much drag despite smooth shape, the similar 2007 version has 0.30 [3]


http://upload.wikimedia.org/wikipedi..._Viper_GTS.jpg

0.35 - Dodge Viper


http://upload.wikimedia.org/wikipedi...de-gallery.jpg

0.342 Pontiac Trans Am 1982 [4]


http://upload.wikimedia.org/wikipedi...ierra_2.0L.JPG

0.34 - Ford Sierra, 1982, at least one combi in this gallery! The passat 2003, has 0.32


http://upload.wikimedia.org/wikipedi...arking_lot.jpg

0.34 - Ferrari F40, 1987


http://upload.wikimedia.org/wikipedi...onvertible.jpg

0.34 - Chevrolet Corvette Z06, 2006


http://upload.wikimedia.org/wikipedi...California.jpg

0.338 - Chevrolet Camaro, 1995


http://upload.wikimedia.org/wikipedi...Citroen_SM.jpg

0.33 - Citroën SM, 1970 low drag despite edgy front


http://upload.wikimedia.org/wikipedi...ickRiviera.jpg

0.32 - Buick Riviera, 1995


http://upload.wikimedia.org/wikipedi..._AX_red_vl.jpg

0.31 - Citroën AX, 1986 low drag due to down pulled hood


http://upload.wikimedia.org/wikipedi...sa_special.png

0.31 - Citroën GS, 1970


http://upload.wikimedia.org/wikipedi...x-R25white.jpg

0.31 - Renault 25, 1984


http://upload.wikimedia.org/wikipedi...px-Sonett3.jpg

0.31 - Saab Sonett III, 1970


http://upload.wikimedia.org/wikipedi..._silver_vl.jpg

0.30 - Audi 100, 1983 smooth nose to flow transition


http://upload.wikimedia.org/wikipedi...s3_black_l.jpg

0.30 - BMW E90, 2006


http://upload.wikimedia.org/wikipedi...e_911_Gris.jpg

0.30 - Porsche 996, 1997


http://upload.wikimedia.org/wikipedi...1950saab92.jpg

0.30 - Saab 92, 1947 - developed using wind tunnel testing


http://upload.wikimedia.org/wikipedi...-1991CRXSi.jpg

0.29 - Honda CRX HF 1988


http://upload.wikimedia.org/wikipedi...rear_right.jpg

0.29 - Subaru XT, 1985


http://upload.wikimedia.org/wikipedi..._silver_vl.jpg

0.29 - Lancia Dedra, 1990-1998


http://upload.wikimedia.org/wikipedi...lite-%2760.jpg

0.29 - Lotus Elite, 1958


http://upload.wikimedia.org/wikipedi...opfenwagen.jpg

0.28 - Rumpler Tropfenwagen, 1921 thin tires have low aerodynamic drag


http://upload.wikimedia.org/wikipedi...oyotaCamry.jpg

0.28 - Toyota Camry and sister model Lexus ES, 2005


http://upload.wikimedia.org/wikipedi...sche911997.jpg

0.28 - Porsche 997, 2004, and that with the wide tires


http://upload.wikimedia.org/wikipedi...enault25ts.jpg

0.28 - Renault 25 TS, 1984, low drag despite its overall edgy shape


http://upload.wikimedia.org/wikipedi...sportsedan.jpg

0.28 - Saab 9-3, 2003


http://upload.wikimedia.org/wikipedi...px-Audi_A2.jpg

0.28 - Audi A2, 1999 [5]. Note the Kammback shape.


http://upload.wikimedia.org/wikipedi..._G35_Sedan.jpg

0.27 - Infiniti G35, 2002 (0.26 with "aero package")


http://upload.wikimedia.org/wikipedi...mry_hybrid.jpg

0.27 - Toyota Camry Hybrid, 2007


http://upload.wikimedia.org/wikipedi...-Benz_S550.jpg

0.26 - Mercedes-Benz W221 S-Class, 2006, low drag despite wheelarches an a large grill and a Mercedes sign in the airflow


http://upload.wikimedia.org/wikipedi...-Lexsls430.JPG

0.26 - Lexus LS 430, 2001 (0.25 with air suspension)


http://upload.wikimedia.org/wikipedi...-Prius2004.JPG

0.26 - Toyota Prius, 2004


http://upload.wikimedia.org/wikipedi...el_Calibra.jpg

0.26 - Vauxhall Calibra, 1989 even the transition from the bumpers to the head light is smooth


http://upload.wikimedia.org/wikipedi...2_L_Silber.jpg

0.25 - Audi A2 1.2 TDI, 2001, low drag despite wheelarches, due to down pulled hood and fastback


http://upload.wikimedia.org/wikipedi...sight-2703.jpg

0.25 - Honda Insight, 1999, low drag due to down pulled hood and fastback


http://upload.wikimedia.org/wikipedi...atra_T_77a.jpg

0.212 - Tatra T77 a, 1935 low drag despite an edgy windscreen-roof transition.


http://upload.wikimedia.org/wikipedi...20px-GM_EV.jpg

0.195 - General Motors EV1 (electric), 1996


http://upload.wikimedia.org/wikipedi...enz_Bionic.jpg

0.190 - Mercedes-Benz Bionic (concept), 2007 low drag despite a relative blunt back end


http://upload.wikimedia.org/wikipedi..._Wallpaper.jpg

0.11 - Aptera Motors Typ-1 (2008 planned)

[dattaway]

My bikes:

150cc scooter, 80mpg
cbr600f4, 48mpg
cbr1000rr, 40mpg
ZX14, 30mpg
Prius, 62mpg

The Prius coasts for quite a while. Even though it weighs a great deal more than a bike, it feels that it slips through the wind much more efficiently. No bike air brake parachute like my bikes. I have also noticed it has very low drag on the tires for a car too. Very little engine run time if the car is in the city. That's where it shines.

[bladeracer]

My 929 gets roughly 13.5kpl in general usage around town - our Suzuki Swift gets the same. With all running costs included it costs four times more to run one of my bikes on the road than it does my car.
On the track I'm not sure (no instruments) but it's not real good - well under 10kpl and probably under 8kpl.
On the open road with a throttle lock at 120kph gets around 22kpl.
I have had just on 30kpl out of it when almost out of fuel and trying to get to the next fuel stop.
Be aware that if you have lowered gearing your odometer reads high by the same percentage as your speedo.
Since I can never recall how many litres are in a _US_ gallon I haven't bothered trying to convert and all my vehicles run 98RON.

[Abjatrer]

Originally Posted by lanbrown

To answer your question, because you don’t know what you’re talking about and don’t understand the mechanical and aerodynamic aspects.

OK. If you say so. Thank you.

[ghbzorro]

There have been some interesting statements made.

Originally Posted by lanbrown

Apples to oranges. .. RPM’s use fuel. ... the aerodynamics of a bike are much worse than that of a car. ... a bike is not fuel efficient at all.

Hmmm. RPMs use fuel? Simplistically looking at it, I suppose I agree. More revs means more air means more fuel and consequently it means more power.

But back when I was in school I remember doing some specific fuel consumption (sfc) testing in the mech lab, and it seems to me that for most throttle positions on most of the engines we tested they did tend to improve (i.e. lower) their sfc as the engine speed increased at first. Then, at about the time the torque began to reduce, the sfc began to worsen. Best sfc occurred when minimizing the sum of heat losses and mechanical (friction) losses. For the tests I performed as part of a course back then (Ford V-8, some ancient diesel and a Honda 750-Four) we kept the revs down because of difficulties adjusting the brake and scale, if I remember correctly.

So lower revs do not always mean lower sfc.

And different engines had different revs at which the most efficient point was reached. So Engine A at, say, 6500 rpm can have a lower sfc than Engine B at 4500 rpm.

So the fact that bikes are often running at higher revs than cars has basically no relevance.

As for bikes having poorer aerodynamics than a car, using just the drag coefficient for comparison is an oversimplification. After all, when was the last time you saw a bike with the same frontal area as a car? It is the product of drag coefficient and frontal area (times square of the speed) that determines aerodynamic drag force and therefore horsepower required at a given speed.

I would say that bikes ARE aerodynamic, but that their drag coefficient can be improved. I would also say that bikes ARE fuel efficient. Do the same trip at the same speed, same passing of other vehicles, same accelerations and decelerations with one driver/rider only. You will burn more fuel in a car.

Originally Posted by lanbrown

This is why when you look at the power to weight ratio that out bikes are drag limited.

Not sure what this is trying to say. Kind of a non sequitur. I like peanut butter, do you ski? Perhaps it is a reference to top speed. All vehicles are either drag limited or rpm limited. What else is there?

Originally Posted by lanbrown

More weight means worse fuel mileage. This is why all fuel mileage tests are done with the car stationary.

To answer your question, because you don’t know what you’re talking about and don’t understand the mechanical and aerodynamic aspects.

I agree that, assuming you are not on a long down-hill run, more weight means worse fuel mileage. Repeatedly accelerating more mass means creating more kinetic energy. But how does this relate to testing technique?

My understanding was that the excuse given for stationary tests on a dynamometer (besides the chance to provide optimistic results) is that it ensures that no variables like different head- or tail-wind speed would skew the results and it allowed a closely-controlled and repeatable stop-and-go test to be perfomed.

Frankly I am not sure how they determine the wheel torque needed during the simulated trips, except to calculate it from the vehicle's weight and reported drag coefficient, I suppose. So I guess I don't know what I'm talking about either.

[bladeracer]

Originally Posted by ghbzorro

There have been some interesting statements made. I would also say that bikes ARE fuel efficient. Do the same trip at the same speed, same passing of other vehicles, same accelerations and decelerations with one driver/rider only. You will burn more fuel in a car.

I disagree.
I drive a 1300CC Suzuki Swift which gets the same fuel economy as my 929 on the road. The engine is bigger than my 929 but only revs half as high producing less than half the power. Also, the car carries five humans and pulls a trailer with two bikes although that does drop the mileage a lot :-)
Perhaps you drive a truck or a V8?

[lanbrown]

Originally Posted by ghbzorro

There have been some interesting statements made.



Hmmm. RPMs use fuel? Simplistically looking at it, I suppose I agree. More revs means more air means more fuel and consequently it means more power.

But back when I was in school I remember doing some specific fuel consumption (sfc) testing in the mech lab, and it seems to me that for most throttle positions on most of the engines we tested they did tend to improve (i.e. lower) their sfc as the engine speed increased at first. Then, at about the time the torque began to reduce, the sfc began to worsen. Best sfc occurred when minimizing the sum of heat losses and mechanical (friction) losses. For the tests I performed as part of a course back then (Ford V-8, some ancient diesel and a Honda 750-Four) we kept the revs down because of difficulties adjusting the brake and scale, if I remember correctly.

So lower revs do not always mean lower sfc.

And different engines had different revs at which the most efficient point was reached. So Engine A at, say, 6500 rpm can have a lower sfc than Engine B at 4500 rpm.

So the fact that bikes are often running at higher revs than cars has basically no relevance.

As for bikes having poorer aerodynamics than a car, using just the drag coefficient for comparison is an oversimplification. After all, when was the last time you saw a bike with the same frontal area as a car? It is the product of drag coefficient and frontal area (times square of the speed) that determines aerodynamic drag force and therefore horsepower required at a given speed.

I would say that bikes ARE aerodynamic, but that their drag coefficient can be improved. I would also say that bikes ARE fuel efficient. Do the same trip at the same speed, same passing of other vehicles, same accelerations and decelerations with one driver/rider only. You will burn more fuel in a car.



Not sure what this is trying to say. Kind of a non sequitur. I like peanut butter, do you ski? Perhaps it is a reference to top speed. All vehicles are either drag limited or rpm limited. What else is there?



I agree that, assuming you are not on a long down-hill run, more weight means worse fuel mileage. Repeatedly accelerating more mass means creating more kinetic energy. But how does this relate to testing technique?

My understanding was that the excuse given for stationary tests on a dynamometer (besides the chance to provide optimistic results) is that it ensures that no variables like different head- or tail-wind speed would skew the results and it allowed a closely-controlled and repeatable stop-and-go test to be perfomed.

Frankly I am not sure how they determine the wheel torque needed during the simulated trips, except to calculate it from the vehicle's weight and reported drag coefficient, I suppose. So I guess I don't know what I'm talking about either.

If both engines were put under the same load and one was a 1-liter engine and the other a 2-liter but the one liter was spinning twice as fast (double the RPM’s of the 2-liter) then their air intake would be equivalent between the two. If the fuel ratio was the same then the fuel used would also be equivalent. The real differences that come into play is engine design though.

So yes it was a simplistic view but for most part true.
The point about drag limited top speed, you look at the power to weight ratio and it is better than most cars, but other cars can go faster than we can. Their aerodynamics are better and they are able to better use their power as well as have more power to push their speed higher. A motorcycle has far less frontal area though.

[curt248]

Hey ghbzorro. I have a question for you.

Is that the formula then? Frontal area times coefficient of drag to get the full resistance.

When I read an article about the busa vs the zx14 in the wind tunnel they talked mainly about the coefficient of drag. They mentioned that the reason for the difference in the coefficient was due to the greater frontal area of the zx14. They even took pictures of the two bikes and photoshopped the area to calculate a true frontal area. It sounded like the frontal area was a factor in the coefficient of drag not the other way around.

Could you explain this please?

[ghbzorro]

Originally Posted by curt248

Hey ghbzorro. I have a question for you.

Is that the formula then? Frontal area times coefficient of drag to get the full resistance.

When I read an article about the busa vs the zx14 in the wind tunnel they talked mainly about the coefficient of drag. They mentioned that the reason for the difference in the coefficient was due to the greater frontal area of the zx14. They even took pictures of the two bikes and photoshopped the area to calculate a true frontal area. It sounded like the frontal area was a factor in the coefficient of drag not the other way around.

Could you explain this please?

The formula is actually Drag = Drag coefficient x 1/2 fluid (air) density x frontal area x velocity squared. The people writing the article were confused. What they should have said was that drag coefficient x frontal area of one bike was less than that of the other bike, or perhaps more understandably, that at the same test speed one bike had lower drag than the other. I've seen the term drag coefficient improperly used a lot, because it has a "scientific" sound to it.

I found a fairly good explanation here: Shape Effects on Drag

Hope that helps.

[curt248]

Cd = D / (.5 * r * V^2 * A)

It looks the the Cd (coefficient of drag) formula does include the frontal area (A). According to this formula, if the frontal area increases the Cd will decrease (since A is in the denominator). This doesn't make sense intuitively. If the frontal area is bigger like in a MAC truck, then it's Cd is smaller? What exactly is Cd measuring then? I know it's the formula, but what is it in practical terms? Is the Cd just the amount of additional resistance from the effectiveness of wind flowing over the object after the initial hit (frontal area)?

So what is the drag? Is the drag the ultimate in determining the total amt of resistance on a moving object. If so, maybe they should be talking about drag as opposed to Cd.

I'm still a little confused.

[ghbzorro]

Originally Posted by bladeracer

I disagree.
I drive a 1300CC Suzuki Swift which gets the same fuel economy as my 929 on the road. The engine is bigger than my 929 but only revs half as high producing less than half the power. Also, the car carries five humans and pulls a trailer with two bikes although that does drop the mileage a lot :-)
Perhaps you drive a truck or a V8?

Yeah, truck back home is a 2000 K-3500 Crew Cab with 6.5 turbo-diesel. Miss that thing! But that's another story. Now back to the issue.

I would be willing to bet that on average the 929 gets ridden faster than the Swift gets driven. If driven beside each other I would expect the Swift to burn fuel faster. It might have a pretty aerodynamic shape, but I would estimate that it has at least 3 times the frontal area, and maybe more.

Or maybe I should ask you how long your front wheel bearings have been seized and calipers seized/brakes dragging while pulling you and your parachute, LOL.

Final comment is that you shoudn't confuse the maximum power with the actual power produced at a given engine speed and throttle position. So while the 929 might be capable of higher power, I would expect that it would be producing less than the Swift at a given speed.

Wish we could do a real test!

[ghbzorro]

Originally Posted by curt248

Cd = D / (.5 * r * V^2 * A)

It looks the the Cd (coefficient of drag) formula does include the frontal area (A). According to this formula, if the frontal area increases the Cd will decrease (since A is in the denominator). This doesn't make sense intuitively. If the frontal area is bigger like in a MAC truck, then it's Cd is smaller? What exactly is Cd measuring then? I know it's the formula, but what is it in practical terms? Is the Cd just the amount of additional resistance from the effectiveness of wind flowing over the object after the initial hit (frontal area)?

So what is the drag? Is the drag the ultimate in determining the total amt of resistance on a moving object. If so, maybe they should be talking about drag as opposed to Cd.

I'm still a little confused.

Drag is the resistance to movement. So therefore IF the drag at a given speed was the same for two vehicles, but one vehicle had twice the frontal area as the second, then its drag coefficent must be one half that of the second vehicle.

Any more clear?

[ghbzorro]

Originally Posted by curt248

Cd = D / (.5 * r * V^2 * A)

That formula can be re-written as D = Cd * 0.5 * r * V^2 * A so that it is more obvious that other things being equal, larger A (area) makes larger D (drag) or resistance.

[curt248]

So my thinking is correct. It's not the Cd that is important but the actual drag that requires HP or overcome wind resistance.

The Cd is just a relative value. To compare the overall drag for two vehicles on the basis of their Cd values, they would have to have the same frontal area. This explains why a MAC truck can have a Cd of .5 while a bicyclist has a Cd of 0.9. The MAC truck has lots more resistance because it has a much greater frontal area. If the bicyclist could be big enough to have the same frontal area as the MAC truck the MAC truck would be more efficient.

Am I on the right track?