1964 Ford Falcon ute (Ranchero) - calculating Cd via coastdown tests

[64Falcon]

And the coastdown figures are in.
For a frontal area of 1.847 M^2 I get a Crr of 0.024 and a Cd of 0.386
Which doesn't come as any surprise, although .45 wouldn't have surprised me either. I did the tests beside the airport, so I had accurate temperature, humidity and pressure off their website, and a flat section of road without too much traffic. For speed measurements I used my dads vericom VC200 performance computer and a digital camera, which gave me speeds accurate to .1 for the first 60 seconds after take off and .2 for the next minute. Although none of that means that the 0.386 is necessarily accurate, but it at least takes human error out of the equation.
Now its time to try and get that figure down a bit, and still keep my '64 looking like a '64

[MetroMPG]

64 Falcon: hope you don't mind I split this off into a new topic in the Aerodynamics forum. It might be be overlooked by others who haven't followed the original "Hello!" thread.

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Did you use the Instructables method & spreadsheet for your calculations?

[64Falcon]

Yeah, I did it all off the Instructables stuff, which is how I ended up here. I was working out my own formulas before I found that, so then I just double checked things against my own formula (I couldn't let them go go waste).

I'm guessing this is where a lot of my drag is coming from


So here is the start of an aluminum belly pan. I've still got a lot more to do, but its a start, and its up high enough that it doesn't really stand out until you look from a distance.

[jazzie604]

underbodies on those things definitely cause a lot of drag. I was watching an episode of "horsepower" and a professional tuner found nearly .5 sec in the 1/4 and a whole lot of stability by adding some under panels.

[MetroMPG]

Do you have a tonneau cover on the back? That will improve aero without changing the exterior looks too much.

[64Falcon]

I'll have to keep an eye out for "Horespower" although being in Australia I tend to miss out on a lot of those sorts of shows.
No tonneau cover yet, I have to get one made since they are different to the Rancheros, but a friend of mine is a motor trimmer so it shouldn't be too far off, she's got the material there for it, but it's waiting in line for her to finish a wedding dress.
I'm still messing around with clearances for suspension travel with the front pans, but I should have things ready for another test run later this week, weather permitting.
I cant think of much else I can get away with on the aero side of things, I'm trying to work out how to block off the sides of the grill so the air flows over or under the car rater than straight into the front bulk head which is completely flat, which I don't believe would have an effect on cooling, since we get a lot of 100+ days over here, I don't want to get in the way of the radiator.

[64Falcon]

Its all finished, with grill block and a belly pan back to the end of the trans. No photo's at the moment, but everything worked out pretty good and you cant see any of it when its on the road.
Unfortunately time and weather stopped me from getting in a set of coastdown figures. However I did have time to do a mileage run before the rain set in.
I drove my usual 104k's (64 miles) 32 out and 32 back to the same gas station, where I put in 7.95L. Which works out to 30.5 MPG. Last time on the same road I got 25 MPG, so I'm pretty happy with the aero mods.

[SVOboy]

Sounds like you're doing pretty good. That's a respectable improvement!