Drag Coefficient

[Sasuketr]

Are you driving 45 MPH on the freeway?? My PP GT struggles to give me 19 MPG.

Cruise set between 67 and 72 mph. If you stay right around 2000 rpm thats the sweet spot. But let me tell you i ve been using 93 octane since day 1 including the fill at the dealer.

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[RocketGuy3]

Are you driving 45 MPH on the freeway?? My PP GT struggles to give me 19 MPG.

Are you seriously getting 19 mpg? On the freeway!???

 

[ponyup]

Ford is mum on the GT350 drag coefficient numbers as well...

 

[zxd9]

Found the following discussion. Take it for what its worth. No references as to where the number came from and not current generation.
http://www.mustangevolution.com/forum/f133/t313368/

See post #5 & 8

 

[FoxFan]

Has no one figured this out, yet?

I've built a program that uses an OBDII scanner to determine HP & TQ based on acceleration. It accounts for air resistance, which makes a huge difference in 4th gear, but I'm not at all confident in my guesses of Cd = .355 and more importantly Frontal Area, which I used 25 ft^2.

I think the Cd is in the ball park, but the Frontal area might be on the low side (originally I used 26 ft^2). A fox body LX Hatch is 0.36 & 21-22 ft^2. A Crown Vic is in the neighborhood of 26 ft^2. So, I put the S550 dead in between them. I think the S550 might be just as big, though. They're both big damn cars when you're looking from the inside of a Fox. Anyways, look how close I am... I really wish I could put the cherry on top of this one:

 

[Linkster1666]

The 2011 pulled a 0.38 or so and I saw a number for 2014 at like 0.36. SO! 3% of 0.36 is .01ish, 0.35

A one, A two, A three!! A 0.35, maybe.

 

[FoxFan]

Thanks for that rationale. Makes sense to me. Anything on Frontal area?

 

[kent0464]

Lol! You guys are killing me, back in the 80’s we were happy to get 10-12 mpg with 400 plus horsepower, and you’re fussing about 20+ mpg

 

[FoxFan]

I'm trying to calculate power like a dyno using a $50 OBD2 scanner, and I need the data to get it right.

 

[Linkster1666]

Just look up Drag Coefficient land speed record. The "Frontal area" is just that, the open area on the front of your car. 24+ sq ft. or so.

 

[FoxFan]

Just look up Drag Coefficient land speed record. The "Frontal area" is just that, the open area on the front of your car. 24+ sq ft. or so.

Sorry, I don't think I understand. Are you saying an S550-specific land speed record car, because I cannot find anything on that. Or, are you implying that some land speed car's frontal area is 24 ft^2? My Fox has a frontal area of ~21-22 ft^2. A Crown Vic has a frontal area of 25.5-26.5 ft^2. The difference between the 2 would indicate a ~20% difference in air-resistance at any speed. I figure an S550 to be in that area, so my baseline guess is 24, but did you find actual data on the S550?

 

[Cobra Jet]

For anyone seeking the info:

These (2) links contain the 2014 Press discussions regarding the new 2015 S550 and it’s aerodynamics. The (2) links below will support only the 2015-2017 models.

https://media.ford.com/content/ford...c-testing-helps-the-all-new-ford-mustang.html

https://www.thetruthaboutcars.com/2...o-look-at-the-new-mustangs-slick-aero-tricks/

Those articles and all others online state the 2015 S550 design and drag coefficient is 3% less than the prior model year (so go back to the 2014 findings and reduce by 3%).

——

There was also this article that came out discussing the 2018 redesign (which would also apply to the 2019+):
https://www.fordnxt.com/news/human-engineering-improves-2018-mustang-economy/

——

And lastly (saved best for last), this online blogger has the absolute best tech I’ve seen yet regarding the S550 aero and coefficient data. The very detailed findings is based on his extensive background education and knowledge of the subject matter. Do note he is using a 2016 Mustang GT350R as his subject. This guy needs kudos for sure.

Get something to eat, drink and read:
https://theansweris27.com/shelby-gt350r-mustang-cfd-simulations/

Hope all the above helped!

 

[Linkster1666]

12 MPG, you be dreaming.

Sorry, I don't think I understand. Are you saying an S550-specific land speed record car, because I cannot find anything on that. Or, are you implying that some land speed car's frontal area is 24 ft^2? My Fox has a frontal area of ~21-22 ft^2. A Crown Vic has a frontal area of 25.5-26.5 ft^2. The difference between the 2 would indicate a ~20% difference in air-resistance at any speed. I figure an S550 to be in that area, so my baseline guess is 24, but did you find actual data on the S550?

What I am referring to is the math, calculations that will tell you the frontal area, with that you can calculate the coefficient, but that has already been done up thread.

 

[kent0464]

Hmmm, the best way without a wind tunnel, is to turn the speed limiter off, and see where the mph tops out at. There’s an equation to apply, I forgot where I wrote it down, should be easy to find on google though.

 

[FoxFan]

For anyone seeking the info:

These (2) links contain the 2014 Press discussions regarding the new 2015 S550 and it’s aerodynamics. The (2) links below will support only the 2015-2017 models.

https://media.ford.com/content/ford...c-testing-helps-the-all-new-ford-mustang.html

https://www.thetruthaboutcars.com/2...o-look-at-the-new-mustangs-slick-aero-tricks/

Those articles and all others online state the 2015 S550 design and drag coefficient is 3% less than the prior model year (so go back to the 2014 findings and reduce by 3%).

——

There was also this article that came out discussing the 2018 redesign (which would also apply to the 2019+):
https://www.fordnxt.com/news/human-engineering-improves-2018-mustang-economy/

——

And lastly (saved best for last), this online blogger has the absolute best tech I’ve seen yet regarding the S550 aero and coefficient data. The very detailed findings is based on his extensive background education and knowledge of the subject matter. Do note he is using a 2016 Mustang GT350R as his subject. This guy needs kudos for sure.

Get something to eat, drink and read:
https://theansweris27.com/shelby-gt350r-mustang-cfd-simulations/

Hope all the above helped!

Thanks, I sent that last guy a message. If he's got the car drawn up in CAD, it should be a no-brainer to give its precise frontal area. Hopefully, he replies.

To the other guys, the only math I see in this thread is taking 3% of a proposed Cd for the S197 that I haven't been able to confirm from an official source. There's absolutely nothing regarding frontal area. Trying to do a top-speed run is a ludicrous approach as there are too many variables to account for (wind speed, altitude, air temps, humidity, rolling resistance, actual output from the engine, etc...) to get anything approaching accuracy or precision. I can and have done all that math in the graph above, but it's meant to measure power, not take it as an input. Frankly, I have more faith in ball-parking Cd & Frontal Area as we already have than trying to calculate it in this manner.

So, alright. Thank you guys for the responses. Hopefully, the lead Cobra Jet provided will bear some fruit.

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