Experiment: smooth wheel discs tested A-B-A - 4.6% mpg improvement @ 65 mph

[rjstegbauer]

Cool.

This seems like a simple and effective way to improve FE.

However I've noticed one small gotcha. There is no access to the tire's valve cap, so the wonderful new hub cap will have to be removed just to check the tire pressure. That doesn't seem like a good idea, since they could break if repeatedly removed. Especially if you spend $100 on aftermarket hub caps.

Randy

[tasdrouille]

Denis, Isn't there a renowned aeronautical engineering faculty in Toulouse? I'm pretty sure they would have copies of yearly SAE transactions books at their library, in which case you can probably have free access, at least for on site consultation. Around here just about anyone can walk in a University library at have a look at all the books they have.

[Xringer]

Originally Posted by rjstegbauer

Cool.

This seems like a simple and effective way to improve FE.

However I've noticed one small gotcha. There is no access to the tire's valve cap, so the wonderful new hub cap will have to be removed just to check the tire pressure. That doesn't seem like a good idea, since they could break if repeatedly removed. Especially if you spend $100 on aftermarket hub caps.

Randy

I've seen a few guys leave off the valve holes with the bolt-on Moon Disc, but if I get some pizza pans, I'm going to try drilling some holes in them and use a valve extender when I top off the 44 PSI..

[Concrete]

Tasdrouille,
Awesome data - like the interesting low speed non-domed anomaly
glad I have my wonderful domed pizza pans

it would be good to understand how that Cd change impacted total drag
did they calculate it in any way a person could directly convert to FE for a similar car
it might help folks understand how significant wheel covers are or are not
.5 mpg improvement is terribly hard to tease out of real life - even with a scan gage
while I recommend smooth covers - I would hate to create too high of expectations

I do not think most modern cars will show a savings without a wind tunnel
wheel wells are tight and tires are flush (suvs and trucks maybe another story)
I attribute my results being more significant because of my large wheel wells & very recessed wheels
at least with the covers the air can re-establish which way it is supposed to be going
In fact I only tested and reported because I noticed a difference
I really did not expect to notice it when I installed them (thus my $20 budget for the design)

if I get some pizza pans, I'm going to try drilling some holes in them and use a valve extender when I top off the 44 PSI..

Xringer,
you are a man after my own heart (right down to the 44 psi )
attached a picture of my set up - just like you described

Also took the picture in it's natural state (dirty), for those considering clear covers
what does it take to get this splatter - dust, rust and a puddle
clear covers are best left for concept cars

[bluesfan]

Originally Posted by Concrete

+150 miles later heres the data (raw)

(sorry about the odd table format - got to be abetter way- but I don't know it )

A-B-A average 29.3 mpg with vs. 28.0 mpg without

* scan gage was reset 0.2 miles into course due to possible semi interference, so this run is .2 miles shorter
** I may have punched it too hard on acceleration - the ECU seems to stay in a higher performance/ lower FE mode for ~90 seconds or so after +50TPS - My bad - not very Hypermiler like. very noticable loses in real time at beginning of course - not too much difference in the averages over the course.

Variances noted, but all data is used in findings

Nice work, and sorry for the delay. VBulletin code tags are a better way:

                                 Outbound          Return                Average

With wheel covers                  28.5             29.2
                                   29.8             30.7
                                   29.2             29.7
                                   29.4             29.8
                                   29.7             30.1                 29.6 mpg

Wheel covers removed               28.0             28.2
                                   28.0             28.5*
                                   28.0             28.2
                                   27.7**           27.7**               28.0 mpg

With wheel covers                  29.0             29.5
                                   28.8             28.0 **
                                   28.7             29.5
                                   28.8	             29.4                 29.0 mpg

Hit the Quote button to see how easy it is.

[Big Dave]

Hey! I'd take a 1.3 MPG improvement.

[crexcrex]

Wheel disks is a topic warm to my heart as there is none that i can attach to a vehicle that will not remain in place. many of you have scan gauges and the one that works for me and is free is my brain gauge.

In all fairness one cannot determine whether the racing disks, moons are effective without first removing the splash shield from the rear of the disk brakes. You may have noted that they are shaped to deflect the rushing air to the brake disks to keep them cool.

The splash shields effectively minimize the aerodynamics of the racing disks and actually cause more drag as the rushing air is trapped behind the racing disk.

I removed my splah guards and the effects were immeadiate, smoother wheel response less road noise and better fuel economy.

there are times when i hear that someone is who is a tad afraid to make any mods for fear that they may ruin thier pretty car, that bieng the case why bother bieng on ecomodders. Might be better to go and polish the car and hope that the gas mileage will improve. Maybe a chrome dipstick will give you the extra miles that you dreamed of.

There are guys here who in the interest of better gas mileage go to extremes and like myself are laughed at. The one thing that they cannot laugh about is the gas mileage that we are getting compared to the squeamish who like things the way they are.

If i were to count all of the people who laughed at my mods i would need a calculator, laugh as they may i know what i am getting per tank or qurater tank that i run on and it is i who has the last laugh.
Best yet is that i have come up with a aerodynamic invention that will turn me a few bucks and that did not come about by bieng squeamish, you either mod or don't bother!

[crexcrex]

I cannot understand why everyone has to make holes for air stems, glue racing disks, screw them on with every conceivable attachment whereas on hole dead center with a small stainless torx screw does the job, 6,000 miles through rough and smooth roads, snow and mud and they have not moved nary an inch.
Remove the one screw and air the tire , reinstall..........less than four minutes per wheel

Why you guys drill through those cool racing disks for air stems is beyond me, the three point set up sucks as well.............pop on's pop off and easy to steal.
Think out of the box and you will understand what i am talking about..............not sure if the racing disk pix on the crx show up well enough to show how it is done.
CRX is now history, time to move onto something more challenging

[99metro]

With my low speeds, I doubt they would make much of a difference. If anything, they'd look better than what I have now (nothing). BUT, if they gave me one or two MPG - that would be something. I found some 13 inchers, if anyone was interested for $85:

Racing Disc Pop-On 13 inch

[Xringer]

"Why you guys drill through those cool racing disks for air stems is beyond me, "..

It must be just that guys who want to check their air pressure once a week,
without getting out the tool kit..