Fords new Anti-Ecomodding Car

[Hubert Farnsworth]

Originally Posted by rmay635703

But do you? This forum is about aero.


Thats why assuming a CD of 0.14 and a frontal area of 16sqft results in a much better result that all here would appreciate far more than a CD of .38!

200hp for 200mph, Now that would be an achievement I could take to the bank!

The published drag coefficient for the outgoing Mustang GT500 is around 0.38, the newer one may be a little bit sleeker, but yes if you were to reduce the frontal area or the drag coefficient it would become much more aerodynamic and would also require less power to travel at the same speed. However unless you were able to use unlimited resources to mass produce this mythical car with a drag coefficent of only 0.14 and a frontal area of just 16ft as a single seater, or perhaps a tandem two seater it might be possible to achieve higher speeds with less horsepower, however given the constraints placed on manufacturers by the governments as well as the demands of consumers for more comfortable as well as powerful cars they tend to not do this except as a technological show piece/ concept car, although currently the limit was nearer to 0.18 or 0.2 on the show circuit for their high mpg concepts, however none of those had barnstorming performance.

As I was trying to illustrate earlier the road load power required to overcome the aerodynamic drag force is a function of the vehicle's speed to the third power. This has been proven to be reasonably accurate.

The road load force calculation looks like this:
frl1=fr*w*cos(phi)+0.5*cd*(rho)*(af)*vm.^2 + w*sin(phi)

Where frl= road load force, fr= rolling resistance coefficient, w= weight in newtons; i.e. the mass in kilograms* the gravitational constant of 9.81 m/s^2, phi being the grade the vehicle is on in radians + 1/2* the drag coefficient * the density of air* af= frontal area *vm (the velocity in m/s^2) + the weight in newtons * the sine of the grade angle in radians

To calculate road load power you multiply the road load force equation by the velocity in meters per second and the result is in Watts or Kilowatts in the S.I. unit system, however if you used the English units you would end up with horsepower.

I might not know the best way to reduce the aerodynamic drag of a vehicle, having only touched upon the fundamentals in my automotive mechanical engineering coursework, but I do understand that a smaller frontal area, cleaner air flow and a smaller stagnant pocket of air behind the car can help it slip through the air better. My car had a damaged under tray, the bolts that held it on had been broken in half, so I had to improvise by making an air dam to help prevent it from flapping while in motion, and do you know what, it actually helped regain some of the lost fuel efficiency, it would be better if I could actually take the car and put it on a lift and drill out the bolts and replace them so that the under tray is also properly installed while still being removable for oil changes and the like.

[redyaris]

A Cd of 0.38 for production a car is poor. My Yaris is at 0.29 in stock configuration and as modified it may be as low as 0.26 the same as a Prius. The honda insight is at 0.25. For your home work, answer this; if it takes 600 hp to push the car like a mustang with a Cd of 0.38 to 200mph how much HP would it take to push a car like the honda insight with Cd of 0.25 to 200mph? you may only use information from this website.

[wdb]

I like the bits in the article about how the car is safe to drive. I'm sorry, but no car is safe at 200MPH on public roads in the hands of Joe Testosterone.

Granted, cars really have gotten easier and safer to drive at high speeds. I can't imagine driving my old '66 Beetle at a sustained 75mph; the thing was floaty at 55, had tires the width of pencil lead, and steering as precise as the Titanic's. Stopped about as well too; the puny drum brakes faded away during stops from 60. In contrast, my Honda Fit will hum along at 75 all day, safe as houses. I haven't done it, but I don't doubt that the little guy would top 100. In the 60's that kind of speed was possible only in muscle cars, sports cars, and the like.

People used to brag about topping 100. These days soccer moms hit 100 in the passing lane while taking junior to piano lessons.

[Hubert Farnsworth]

Originally Posted by redyaris

A Cd of 0.38 for production a car is poor. My Yaris is at 0.29 in stock configuration and as modified it may be as low as 0.26 the same as a Prius. The honda insight is at 0.25. For your home work, answer this; if it takes 600 hp to push the car like a mustang with a Cd of 0.38 to 200mph how much HP would it take to push a car like the honda insight with Cd of 0.25 to 200mph? you may only use information from this website.

Given we actually used the powertrain out of an insight (the original 3 cylinder ima insight, not the new one) in one or several of my automotive powertrain courses to power other theoretical range extended electric vehicles I happen to already have some of this information, however it is not difficult to calculate if you plug the numbers into the equations I provided.

The insight weighs 848kg empty with a/c a full tank of gas, and a 5-speed manual transmission, now assuming a minimal load of just a 150 lb/ 68kg driver the car would then weigh in at 916 kg.

Density of air is considered a constant for the range of speeds we would be considering, as the air flow is still sub sonic, and therefore the density used is 1.225 kg/m^3

The frontal area is 1.84 m^2 using 80% of the height and width information made available to me.

200 mph is approximately 322 kph, which works out to 89.44 m/s

On level pavement the road load force to over come the combination of rolling resistance and aerodynamic drag (this is the best case scenario, adding in any minor grade resistance and the power required to maintain this speed increases substantially

plugging in these numbers into the earlier equation, after converting units to their proper format the road load force is approximately 2295.0 N, to calculate the road load power required this is multiplied by the speed the vehicle is traveling, 89.44 m/s and gives a required road load power of 204 kW. 1 Horsepower is equal to 746 watts or 0.746 kW so to determine the road load power required one must divide 204 over 0.746 hp/kW. Therefore the required road load power is 273.5 at the wheels.

Now assuming a theoretical driveline with only a 10% loss (eta/efficiency= 0.9) from the engine to the wheels an insight would require the road load power divided by the efficiency (Prl/eta) 273.5/0.9 or 304 hp at the crankshaft in order to power an insight to this speed, this assumes you can package enough gearing/ engine within the original weight constraints of a gen 1 insight

However if the driveline is only 80% efficient the power required from the engine in order to go this speed increases to 342 horsepower ( a driveline loss of 20%)

Of course an actual insight capable of traveling at 200 mph while weighing around the same as stock seems unlikely.

On a counter point though, according to car and driver the 2011 Mustang GT500 only had a drag coefficient of 0.36, not 0.38, and I guess I shouldn't trust the online calculators, but instead run the numbers through my own matlab script that solves the equations correctly.

The GT500 would require only 343.8 kW to over come the road load force on level pavement at 200 mph, that works out to just 460.9 horsepower at the wheels, also assuming a 150 lb/68 kg driver. This means that for a driveline loss of just 10% the power required by the engine on level pavement is 512 hp or 382 kW. Would it benefit from being more streamlined, yes it could get away with less power on level pavement, I'm using the current mustang information as I am unable to get a hold of the information for the 2013 but I anticipate it to be roughly similar.

Again if the driveline were only 80% efficient in translating the power from the engine to the wheels the Mustang would require 429.75 kW or 576 hp, still shy of the 650 the engine is capable of cranking out, however the supercharger is stealing some power in order to run itself, however that should be accounted for in the resultant power from the crankshaft.

[redyaris]

Game On
The best car in the catagory; Eco-unfrendly
The Criterian are:
Price under $50,000
Sales of over 6000 units / month
Capable of 155 mph top speed
Not subject to Gas guzeler Tax

The next game is; can you find a eco-frendly versions that meet the above criterian?

[Cd]

.38 is truly bad. That's about the same as the Cd on a Ford Lightning pickup.



( Nevermind the CDxA, just talking the Cd here )

[Hubert Farnsworth]

I'm pretty sure the mustang gt500 was purposely un-aerodynamic in order to generate enough drag to prevent the car from being capable of being faster than it already was, given the fact that the outgoing car was limited to 155 mph as opposed to the 2013 which with its 5.8L supercharged engine is supposed to be capable of over 200 mph.

[wdb]

Ah, the Lightning. What a beast. Ford was going to run A/C through the intercooler to cool the intake charge, back a few years, but never did it. I wonder if the A/C parasitic losses were greater than the gains from the cooler charge.

Oooops, there I go salivating over high performance again. I'll cover my butt by saying that the concept would work on turbo/supercharged vehicles of any HP.

[RH77]

Originally Posted by redyaris

Game On
The best car in the catagory; Eco-unfrendly
The Criterian are:
Price under $50,000
Sales of over 6000 units / month
Capable of 155 mph top speed
Not subject to Gas guzeler Tax

The next game is; can you find a eco-frendly versions that meet the above criterian?

This challenge has been haunting me since I read it.

After combing the database and top speeds, the answer:

It doesn't exist in the U.S. or Canada.

Using the EPA Fuel Economy Figures spreadsheet, I input 25 mpg as a benchmark of "Eco-Friendliness". The following "sporty" cars meet this, your requirements, and all but 155 mph top speed, in order of Top-Eco by combo mpg:

VW Jetta (Sedan, Wagon); 2.0L I-4 Diesel (Auto-6/Manual-6)
Audi A3; 2.0L I-4 Diesel (Auto-6)
Mini Cooper (Most of Varieties with noted engine); 1.6L I-4 (6-speed manual)
Subaru Impreza (Sedan, Wagon); 2.0L H-4 (CVT) (Manual slightly lower FE)
VW Jetta and GTI: 2.0L I-4 Turbo (Auto-6) (GTI Manual slightly lower FE)
Mazda3: 2.0L I-4 (Auto-5)
VW Jetta (and Wagon) and GOLF: 2.5L I-5 (Auto-6 and Manual-5)
Scion tC: 2.5L I-4 (Auto-6/Manual-6)
Acura TSX: 2.4L I-4 (Auto-5)
Audi TT Coupe Quattro, Roadster Quattro: 2.0L I-4 Turbo (Auto-6)
Audi A4 and A5 Cabrio: 2.0L I-4 Turbo (CVT)
Audi A4/A5 Quattro: 2.0L I-4 Turbo (Manual-6)
Mercedes-Benz C 250: 1.8L I-4 Turbo (Auto-7)
Honda Civic Si: 2.4L I-4 (Manual-6)
Lexus IS250/250C: 2.5L V-6 (not I-6 for 2012) Auto-6
Mazda MX-5 / Miata; 2.0L I-4 (Manual-6)

Missed the mark because of price:
Porsche Panamera S Hybrid (scratches head) at 25 MPG combined
Mercedes-Benz S 350 Bluetec 4Matic: 3.0L V-6 Diesel (Auto-7) at 25 combined
Infiniti M35h Hybrid 29 MPG combined

OK, so the definition of "Sporty" or "Fast" are based on my scan of the cars listed -- maybe 0-60, slalom, or "fun-factor". Granted, a Diesel Jetta might not be all that fun, but add a 6-speed manual and a twisty road, and it gets better.

Click to access the 2012 spreadsheet of FE results from the EPA. Sort it. Crunch it. Cross-reference it. Look up 0-60 times and prove me wrong. Or add, "hey the Chevy Sonic is lots of fun to drive!"

RH77

[TheEnemy]

Originally Posted by redyaris

Game On
The best car in the catagory; Eco-unfrendly
The Criterian are:
Price under $50,000
Sales of over 6000 units / month
Capable of 155 mph top speed
Not subject to Gas guzeler Tax

The next game is; can you find a eco-frendly versions that meet the above criterian?

My wifes 05 Accord is limited to 145, with a few aero tweeks and removing the govoner it should be able to break 155 easy enough. Though I doubt you would seriously call it sporty even though it does pretty good.