whats the GT's coefficient of drag rating?
- Thread starter Fast Freddy
- Start date
FordGTGuy
Well-known member
leave it to FordGTGuy to save the day!
article:
http://www.motortrend.com/roadtests/coupe/112_0410_exotic_coupe_comparison/index.html
article:
http://www.motortrend.com/roadtests/coupe/112_0410_exotic_coupe_comparison/index.html
Pipelion
Well-known member
Thanks for the cool post of those three!!!
Allan :biggrin :wink
I read the article before but missed the graph.
Allan :biggrin :wink
I read the article before but missed the graph.
Pipelion
Well-known member
Sorry I'm going to brag,
I know Preston Henn, I'm good friends with his daughter. He's the guy Motor Trend got the Enzo Ferrari from for this test of the three super cars above.
I've been to his house in FL alot, and his old house in Aspen. His daughter just sent me some pics of his latest cars in his collection. He had everything but a Ford GT or a Veron. I haven't asked him yet if he's getting one. The Enzo is his daily driver.
Allan :thumbsup
I know Preston Henn, I'm good friends with his daughter. He's the guy Motor Trend got the Enzo Ferrari from for this test of the three super cars above.
I've been to his house in FL alot, and his old house in Aspen. His daughter just sent me some pics of his latest cars in his collection. He had everything but a Ford GT or a Veron. I haven't asked him yet if he's getting one. The Enzo is his daily driver.
Allan :thumbsup
satx
Well-known member
Fast Freddy said:
I have heard "under .40 Cd". I would like to know the frontal area as well. Interestingly the new viper coupe is more aerodynamic than the Z06 even though it's Cd is higher due to less frontal area. I think given the GT's low height it should have very little frontal area.
analogdesigner
GT Owner
Cd vs. absolute drag
Gentlemen:
Cd is a good marketing person's method of trying to express drag coefficient in their advertisments. Cd is actually a relative number which defines how slippery a given surface is. We need to know what the absolute drag is, as satx asked about, (true frontal area x Cd). I had personally measured the true frontal area of my GT and will have to get my notes from work. I have to believe that the GT's Cd is much lower than 0.4! For a car to go 214 MPH with only 550 RWHP, along with it's frontal area makes me guess that it's much closer to 0.3, than 0.4!
Jay
Gentlemen:
Cd is a good marketing person's method of trying to express drag coefficient in their advertisments. Cd is actually a relative number which defines how slippery a given surface is. We need to know what the absolute drag is, as satx asked about, (true frontal area x Cd). I had personally measured the true frontal area of my GT and will have to get my notes from work. I have to believe that the GT's Cd is much lower than 0.4! For a car to go 214 MPH with only 550 RWHP, along with it's frontal area makes me guess that it's much closer to 0.3, than 0.4!
Jay
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biffom
GT Owner
FordGTGuy said:
Thanks for the link.
After reading the article I'm pretty amazed (and happy) that the GT acquitted itself so well against some pretty heavy duty competition.
Ford really got it right with this one.
Pipelion
Well-known member
The Motor Trend article of the three super cars this above graph came from was truly unfair to the Ford GT.
They used a very small track 3.? miles.
If One of 19 can do 215mph, then it's as fast top end as the Enzo or faster, and probably more stable. The articles' driver said the Enzo was twichy at top end speed. "One" says his GT is stable at 215.
That's why you have to take these magazines' info and opinions with a grain of salt.
There is no winner of the three, each is a very special and unique auto. The Enzo rare, expensive and fast. The Carrera GT one of the most amazing cars ever, with a total package of bundled expertice as well as under statement. And the Ford GT a truly historical resurection of an amazing car made even better, also possibly the fastest and easiest to drive. The Ford GT is also a third the price of the Carrera GT and one fifth the price of the Enzo.
Allan :biggrin
Analog: amen on your post, the Ford GT has to be very slipery to exceed the Enzos' top end speed with less horse power.
They used a very small track 3.? miles.
If One of 19 can do 215mph, then it's as fast top end as the Enzo or faster, and probably more stable. The articles' driver said the Enzo was twichy at top end speed. "One" says his GT is stable at 215.
That's why you have to take these magazines' info and opinions with a grain of salt.
There is no winner of the three, each is a very special and unique auto. The Enzo rare, expensive and fast. The Carrera GT one of the most amazing cars ever, with a total package of bundled expertice as well as under statement. And the Ford GT a truly historical resurection of an amazing car made even better, also possibly the fastest and easiest to drive. The Ford GT is also a third the price of the Carrera GT and one fifth the price of the Enzo.
Allan :biggrin
Analog: amen on your post, the Ford GT has to be very slipery to exceed the Enzos' top end speed with less horse power.
BlackICE
GT Owner
Just think what the GT would have done if it had decent set of tires and a pulley swap. I think it would have trashed the other cars! I never did like Goodyear street tires they leave alot to be desired. When I see a treadwear rating of 220 I know a lot of perfomance is left on the table. The GT suffered by not being able to come out the the turn as fast as the others cars, better tires would have help a lot there, even without more power from a pulley swap.
Some nice R compound tires (treadwear < 100) will transform the car to a new level.
BlackICE
Some nice R compound tires (treadwear < 100) will transform the car to a new level.
BlackICE
analogdesigner
GT Owner
Correct!
Allan and BlackICE,
You analysis is correct...
Ford was very clever in selling the GT "AS-IS," allowing the adventurous to find another 50-150 RWHP.
I will try to accurately compute the GT's true Cd this weekend. Also, I live only two miles from the Swift Engineering (rolling floor) wind tunnel, so I may be able to set up a tour for us "fellow" GT owner's someday. This is where the real aerodynamic testing and tweaking was done during the GT's development a couple of years ago. The other companies could only dream that they could have this kind of setup...
With the Ford's lateral g-rating of only 0.91 (according to Motor Trend) makes something very wrong! This car should be closer to 1.0 than 0.9... Was it's alignment checked before tracking the car?
The Motor Trend article is interesting, however, just as in politics, you can sculpt a dog into a rocket-sled. All three cars are winners anyway.
Jay
Allan and BlackICE,
You analysis is correct...
Ford was very clever in selling the GT "AS-IS," allowing the adventurous to find another 50-150 RWHP.
I will try to accurately compute the GT's true Cd this weekend. Also, I live only two miles from the Swift Engineering (rolling floor) wind tunnel, so I may be able to set up a tour for us "fellow" GT owner's someday. This is where the real aerodynamic testing and tweaking was done during the GT's development a couple of years ago. The other companies could only dream that they could have this kind of setup...
With the Ford's lateral g-rating of only 0.91 (according to Motor Trend) makes something very wrong! This car should be closer to 1.0 than 0.9... Was it's alignment checked before tracking the car?
The Motor Trend article is interesting, however, just as in politics, you can sculpt a dog into a rocket-sled. All three cars are winners anyway.
Jay
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BlackICE
GT Owner
Yes, look at the exits speeds on the turn,
Exit Speed Top Speed
Ford GT 178 200.1
Carrera 192 201.5
Enzo 200 211.0
Starting at a 12 mph disadvanged to the Carrera and 22 mph to the Enzo the GT didn't do too bad. Its cornering has to be better on that track to beat the others cars. Tires and maybe a suspension tuning would so the trick.
I used to drive a Vette on the track and its stock specs were not bad, but not the best in class. Some other cars of the time like the NSX posted better specs. When I put racing compound tires on the car it was much better in the corners and braking. It was like a different car. The Vette came with Goodyears with treadwear 220 the NSX came with tires with a treadwear of 120. The NSX owners were complaining about how the rear tires only lasted less than 10k miles. I had over 30k on the tires with still a lot of tread on them!
It is amazing that the GT does so well handicaped by the poor tire choice.
BlackICE
Exit Speed Top Speed
Ford GT 178 200.1
Carrera 192 201.5
Enzo 200 211.0
Starting at a 12 mph disadvanged to the Carrera and 22 mph to the Enzo the GT didn't do too bad. Its cornering has to be better on that track to beat the others cars. Tires and maybe a suspension tuning would so the trick.
I used to drive a Vette on the track and its stock specs were not bad, but not the best in class. Some other cars of the time like the NSX posted better specs. When I put racing compound tires on the car it was much better in the corners and braking. It was like a different car. The Vette came with Goodyears with treadwear 220 the NSX came with tires with a treadwear of 120. The NSX owners were complaining about how the rear tires only lasted less than 10k miles. I had over 30k on the tires with still a lot of tread on them!
It is amazing that the GT does so well handicaped by the poor tire choice.
BlackICE
analogdesigner
GT Owner
Alignment, tires, etc...
Yes,
If memory serves me, the earliest NSX's were lucky to get about 4,000 miles out of a set of tires. If I were to track my NSX, I would set the alignment to the '91 settings (or even more radical) for best handling. I have my 2000 NSX set to the very conservative "2000" setting at a big loss in cornering capability. It's really amazing what a slight alignment tweak can do to a good chassis design. When aligned to the original '91 settings, it's like the damn thing is attached to a rail...
If the GT was setup in the same way as the NSX was back in '91, it would be one hell of a ride!
BlackICE said:
Yes,
If memory serves me, the earliest NSX's were lucky to get about 4,000 miles out of a set of tires. If I were to track my NSX, I would set the alignment to the '91 settings (or even more radical) for best handling. I have my 2000 NSX set to the very conservative "2000" setting at a big loss in cornering capability. It's really amazing what a slight alignment tweak can do to a good chassis design. When aligned to the original '91 settings, it's like the damn thing is attached to a rail...
If the GT was setup in the same way as the NSX was back in '91, it would be one hell of a ride!
Pipelion
Well-known member
BI & AD,
Good points,
Remember too in the Motor Trend testing, only the Enzo was given a fast exit on both ends of the track, due to weather. They thought the Enzos' test would be called due to rain. So they told the driver to blast it both ways. This gave the Enzo more speed into both ends of the track. You can't change the rules 2/3rds through the test. It's no longer a fair comparison.
But the major flaw was too small a track for high speed testing. Any track shorter than the Italian 8 mile, becomes an acceleration test vs a top end test.
Still was cool to read how each car is different, as well as not many times these three cars blast around a track together. Each are very cool cars.
Allan
Good points,
Remember too in the Motor Trend testing, only the Enzo was given a fast exit on both ends of the track, due to weather. They thought the Enzos' test would be called due to rain. So they told the driver to blast it both ways. This gave the Enzo more speed into both ends of the track. You can't change the rules 2/3rds through the test. It's no longer a fair comparison.
But the major flaw was too small a track for high speed testing. Any track shorter than the Italian 8 mile, becomes an acceleration test vs a top end test.
Still was cool to read how each car is different, as well as not many times these three cars blast around a track together. Each are very cool cars.
Allan
SLF360
GT Owner
BlackICE said:
Fully agree, and I think I mentioned this in one of my very first 'impression' posts last year, so did ENZOBTR aka Karl..
Let me get unpopular and (hopefully) provocative here: Somehow the forum is sooo US... :usa
All the tech posts are about HP and power, nothing (!) so far about setup improvement, apart the setup posting from BaronDave..
Then, the only one seriously working on shocks and rims and tyres is Mr. Denmark, JasonW 101. :thumbsup That means 100% of all Danish GT owners work on steer in and handling improvements, while a mere 0,00025% of US based owners are on it !
Welcome BlackIce to get on the subject. You alone might double the GT's forum US R&D quota. Power I think we have under control by now, and real good improvements identified and ready available. Street handling needs setup and tire improvements ! Let's go, boys !
stefan
PS: Don't get me wrong: I am only being selfish here... want to make sure I'll get the most out of our GT's...
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californiacuda
GT Owner
- Oct 21, 2005
- 919
Very good point. I guess most of us Americans have to try to compensate for our shortcomings in the size and power area. :lol
californiacuda
GT Owner
- Oct 21, 2005
- 919
I have been trying to calculate to Cd of the GT based on the 874lbs at 200mph published in the MT article. Please feel free to comment and make changes. I am not an engineer or a math guy, but if we can get the frontal area and the Cd, then we can do many other calculations. So Here Goes.
These equations were taken from M3Forum which referenced Puma Racing.
Rolling resistence(lbs) = vehicle weight(lbs) x 0.012 to 0.015
= 3468(car)+170(driver) x 0.013
Rolling resistence = 47.294
Air resistance(lbs) =frontal area(sqft) x Cd(drag coeficient) x
0.00256 x speed squared(mph)
874 = 20sqft(estimate) x Cd x 0.00256 x (200x200)
874 = Cd x 2048
Cd = .43
Power (bhp) = total drag (rolling res+air res) x mph/375
= (47.294 + 874) x 200/375
bhp = 491
These equations were taken from M3Forum which referenced Puma Racing.
Rolling resistence(lbs) = vehicle weight(lbs) x 0.012 to 0.015
= 3468(car)+170(driver) x 0.013
Rolling resistence = 47.294
Air resistance(lbs) =frontal area(sqft) x Cd(drag coeficient) x
0.00256 x speed squared(mph)
874 = 20sqft(estimate) x Cd x 0.00256 x (200x200)
874 = Cd x 2048
Cd = .43
Power (bhp) = total drag (rolling res+air res) x mph/375
= (47.294 + 874) x 200/375
bhp = 491
Jason Watt
Had both, sold both
Well thanks for the Thumbs up Stefan!!
I'm improving the suspension on my GT, because I believe that the car will really
ome to life with stiffer springs and roll-bars.
Just look at the Top-Gear feature where "The Stick" guns the GT around their small test track.
Understeeeeeeeeeeeeeeeeeeeeeeeeeeer big time!!!!
And when he slams the brakes the front splitter nearly touches the floor.
I'm having 3-way adjustable shocks made to be able to tune it for both road and track...
BTW: I wonder what sort of topspeed the GT will do when its got 700HP?? :eek
I'm improving the suspension on my GT, because I believe that the car will really
ome to life with stiffer springs and roll-bars.
Just look at the Top-Gear feature where "The Stick" guns the GT around their small test track.
Understeeeeeeeeeeeeeeeeeeeeeeeeeeer big time!!!!
And when he slams the brakes the front splitter nearly touches the floor.
I'm having 3-way adjustable shocks made to be able to tune it for both road and track...
BTW: I wonder what sort of topspeed the GT will do when its got 700HP?? :eek
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Jason Watt
Had both, sold both
centerpunch said:
Tires with more grip will increase the body roll and make the car fell even more hmmm.... "water bed with a lot of power-ish"
Black2003Cobra
Well-known member
Yeah, that’s how I would do it. I was actually just doing that same thing from that 874 lb drag force number published in that article above. I went about it basically the same way, and your numbers seem pretty close mine. Here’s my engineering take on it.californiacuda said:
F = 0.5*ρ*Af*Cd*v²
or
Cd*Af = 2*F/(ρ*v²)
Assuming RH = 0%, an atmospheric pressure of 990 mbar, and an ambient temp of 25 °C, I get an air density at sea level of ρ = 0.0722 lb/ft³, or 0.002244 slugs/ft³. So using F = 874 lbs and v = 293.3 ft/s (= 200 mph), I come up with
Cd*Af = 9.05 ft²
So if Cd were 0.4, that would mean a frontal cross sectional area of ~22.6 ft².
Does that area seem right to you guys? (Seems that could be meas’d indirectly by taking a picture of the car from the front.)
Conversely, if I use 20 ft, I get Cd = 0.45, which seems kinda high, but is close to the other numbers being kicked around.