6% Improvement from... 3 aero wheel covers?

[t vago]

So I did something very strange today...

Ordered a set of 4 15 inch aluminum pizza pan covers, some zip tie anchors, and some zip ties from Amazon.com last week. Got them in a few days ago, but didn't do anything with them until today.

Spent this afternoon figuring out how to attach them to my rims. It was a bit of a challenge on the rear, since the brake drum backing plate pretty much covers the entire area of the wheel. There's like a 1/2 inch gap between the backing plate and the hardware.

Finally ended up using the anchors in a star pattern on the pans, drilling a hole to one side of each of them, and zip-tying the pans to the wheels in a star pattern. I did both rear wheels, but only the left front wheel. I ran out of time, for one; and I wanted to make sure that the front brake hardware would not chop up the zip-ties to the point where the left front pan would fly off and become a pizza pan of death.

Drove into work with 3 of the pans installed, and figured that if I would have optimistically improved my C(d) by 5%, then I would see a corresponding reduction in fuel consumption from 2.78 to around 2.6 (figuring this out in my head as I was driving).

Well, I did not get 2.60 gallons consumed.

I got 2.62, instead. That works out to 22.5 MPG, or a 6 percent increase from what I got yesterday. That's pretty impressive, and I am looking forward to seeing what sort of improvement I'll get from installing that 4th pizza pan.

[Weather Spotter]

Cool improvement!

It sounds reasonable depending on how bad the rims were for aero.

[cfg83]

t vago -

6% better implies 21.2 MPG the day before. Pending long-term verification, that's a 1+ MPG improvement. Below it says that you should be seeing a 0.01 Cd gain :



I think 0.01 Cd improvement usually results in a 1 MPG gain on average, so I think your results are in line with what you should expect.

CarloSW2

[t vago]

It just seems so high, though. I would have expected somewhere around 2% improvement. Then again, these are some aerodynamically ugly wheels I'm correcting. Wheels really affect FE that much?



Eh... I'll do a comparison tonight when I drive back. The commute to work is a net 300 foot decrease in elevation, which makes my to-work FE higher than my to-home FE.

[cfg83]

t vago -

It's a fair question. Getting 1+ MPG even fits the downhill commute, so I am hoping for sub 1.0 on the way back. When aerohead reads this he will have the real stuff.

CarloSW2

[Weather Spotter]

Well On the areo trix the smooth wheel covers got me 1.5 MPG from a base of 33 MPG

[t vago]

I consumed 2.76 gallons getting home.

So...

Before:
W: 59.0 miles / 2.76 gallons = 21.4 MPG
H: 59.2 miles / 2.85 gallons = 20.8 MPG
T: 118.2 miles / 5.61 gallons = 21.1 MPG

Now:
W: 59.0 miles / 2.62 gallons = 22.5 MPG (+5.3%)
H: 59.2 miles / 2.76 gallons = 21.4 MPG (+3.3%)
T: 118.2 miles / 5.38 gallons = 22.0 MPG (+4.3%)

Okay, maybe not a 6% increase, but still...

[Weather Spotter]

If that is the case it would not matter how many he has on, one would give the same result as 3 or 4.

[t vago]

@Old Tele Man: I don't think so. My commute consists of about 3% in-town driving, and the highways are pretty much dead at 1 am. This enables me to set the cruise to 7 MPH over the highway speed limit, so I can focus on scanning ahead for deer and Toyota trucks going at 20 MPG without their lights on (yes, I actually saw that last night), without trying to consciously keep a steady speed.

[t vago]

Now I go out and install the final aero wheel cover. FE should go up slightly, I think.