hubcaps, taped smooth vs none vs standard

[2000mc]

finally tested a missing link that had been bothering me. i couldnt find where someone testing smooth hubcaps compared them to regular hubcaps, only to no hubcaps at all. tested at 65mph using SG2. 3.6mile test section each way. run 1 and possibly even #2 might need to be thrown out, coolant was up to regulating temps for a few miles before start of test, but im guessing not everything was sufficiently warmed up.

#1 taped south: 34.1 north: 39.7
#2 taped south: 34.1 north: 40.9
#3 none south: 34.4 north: 39.8
#4 none south: 34.4 north: 39.8
#5 taped south: 35.6 north: 40.8
#6 none south: 35.4 north: 39.8
#7 taped south: 35.6 north: 40.3
#8 none south: 35.6 north: 39.0
#9 standard south: 35.9 north: 40.3
#10 none south: 35.7 north: 39.7
#11 standard south: 36.3 north: 40.2

wind didnt seem to be a factor, but i recorded it anyway, readings from weatherbug. the road tested on runs dead straight, from nnw to sse
before #1 45f, wind sw@4, gusting sw@8
between #1-2 45f, wsw@1, wsw@11
2-3 46f, wsw@4, wsw@11
3-4 47f, s@3, wsw@11
4-5 49f, wsw@3, wsw@11
5-6 48f, sw@2, wsw@11
6-7 49f, w@4, s@10
7-8 48f, sw@6, wsw@10
8-9 49f, nw@3, wsw@10
9-10 49f, wsw@4, ssw@11
10-11 50f, nw@1, ssw@11
after #11 51f, n@2, ssw@11

taped


none


standard


havent teased out results yet, and figured you guys like raw data better anyhow

[igo]

Thanks for testing! Looks like a minimal difference...with such a little mpg difference it's hard to make a conclusive result.

[JRMichler]

Nice job of testing. Looks like the effects of warmer outside temperature and/or oil temperatures warming up are greater than the effect of aero hubcaps.

Some good follow up tests would be the effect of outside temperature and the effect of driving time (warming of engine oil, tranny oil, and differential oil) on mileage.

[2000mc]

Statistically speaking, is it fair/legal to break this up into mini test sets? Looking at run4,5,6 as an individual test, and then 5,6,7 and 6,7,8 and so on? can I use, or is there an easier way, to use the "none" condition like a moving baseline for the test?

[2000mc]

Originally Posted by JRMichler

Some good follow up tests would be the effect of outside temperature and the effect of driving time (warming of engine oil, tranny oil, and differential oil) on mileage.

And tire temps

Unfortuneately I have run into this before, I thought my car plateau'd after about 30min from a previous test. Also why I started with multiple runs without changing the test, thought I was golden after runs 3,4 came in with the same result, but that faded when I ran #6. At this point, I'm guessing my mileage could keep climbing at an incredibly slow pace for as long as I could take sitting in it for a day. Maybe I'd hit the ceiling faster if it was 105f day, but then I'd want to run the a/c anyway.

[aerohead]

I have some data from both GM and Subaru I'll dig out.

[2000mc]

taped 2,37.5
none 3,37.1
none 4,37.1
taped 5,38.2
none 6,37.6
taped 7,37.95
none 8,37.3
standard 9,38.1
none 10,37.7
standard 11,38.25

i think that chart is as much as i can pull out of it

[aerohead]

Fuji researched wheel cover drag with respect to their Subaru XT.
*The ventilated flat disc,when taped closed,revealed a delta Cd 0.002,for an overall drag reduction of 0.69% (and no brake cooling).
--------------------------------------------------------------------------
John Shinella,of Pontiac styling, researched wheel cover drag in the Lockheed Marietta wind tunnel during development of the Trans Am Firebird of 1982.
*The car,@ Cd 0.32,with no covers
*with ventilated flat discs dropped to Cd 0.296
*TAPING over the vents produced Cd 0.290
*Shinella's ventilated convex covers showed Cd 0.287
--------------------------------------------------------------------------
So,taping was good for delta Cd 0.006,which cut overall drag by 2.02% (a 1% increase in mpg @ 55-60 mph).
--------------------------------------------------------------------------
The difference between no wheel covers,and Shinella's covers is a 10.31% overall drag reduction.(5% MPG @ 55-60 mph).
A set of MOONs would come in at a little lower drag and mpg increase.

[Xist]

Originally Posted by aerohead

A set of MOONs would come in at a little lower drag and mpg increase.

Yes, well, we need to engineer out their tendency to be abducted by UFOs!

[aerohead]

Originally Posted by Xist

Yes, well, we need to engineer out their tendency to be abducted by UFOs!

No kiddin'!
Next time I do a set,it will be the ones which use the 3-Dzeus fasteners to hold them to the rim.