Metro aerodynamics

[omgwtfbyobbq]

Your decrease in CdA wrt to your increase in mpg depends on your average speed. at a ~35mph average, I figure you've dropped CdA to ~.27-.3 to see a ~12% increase in FE. If your average speed is lower, then you've managed to drop the CdA even more.

[MetroMPG]

The speeds all the tests were done at were between 88-95 km/h.

[MetroMPG]

According to the aero & rolling resistance tool I made from Dan's spreadsheet formulas:

http://metrompg.com/tool-aero-rr.htm

I've would have reduced my Cd from .34 to .294 to see a 12% FE gain @ 55 mph @ 15C ambient.

[omgwtfbyobbq]

That sounds about right! Of course, you can't just sum up FE increases, they are cumulative. If that calculator is right, I should see +15mpg@50mph average from LRR tires/proper pressure (of course that's my dumbass fautl for not mindin' my units), and +24mpg@50mph if I can magically cut my CdA in half. I like that calculator.

[MetroMPG]

+15 mpg? Do you mean +1.5?

[omgwtfbyobbq]

Nope, +15 if I can drop on overinflated LRR tires with a 0,0,0 alignment because I'm hoping it cuts my Crr in half. At least by my reasoning, because on the beater I currently have, all the tires are mismatched and from the junkyard, I never checked pressure because I severely underestimated the impact of rolling friction, and the alignment is so bad I've had two blow out because of wear/nasty camber (wore to the metal on one side, tons of tread on the other), so god knows what toe and caster is. In any event, given my current ~55-50mpg@45-50mph average, new LRR tires, overinflation, and proper alignment should make a world of difference.

edit- by never I mean I've inflated to the sidewall pressure on each tire three or four times over the 8 months I consistently drove it. Each time, especially the last long trip. I noticed a significant increase via my butt dyno in how I was able to accelerate, especially at lower speeds uphill, so I'm guessing I've been really negligent and can hopefully see a big improvement.

[MetroMPG]

You should fill out your garage/car info. Sometimes hard to recall exactly what everybody's driving if it only gets covered in their original intro thread.

[omgwtfbyobbq]

Wow, I never even bothered with an intrductory post! In any event, now that I've been pretty much stationary I haven't driven it for the last month or so. My pickup gets half the mileage, but at less than 200 miles per month, I'm paying an extra $12 so I don't go deaf due to my ghettotastic glasspack exhaust. Of course that's what I get for a few hundred dollar car, but I'll hopefully swap out the engine, put it into my $75 clean version, get nice LRR tires, and start driving it again.

[MetroMPG]

I realized today that if I put front wheel skirts on the car it'll look like a shoe.

[MetroMPG]

That's probably what made me think of it. But more of a sneaker look, not a high-top.