[ACEL]

Before to fabricate and install the "definitive" wheel covers, two mock-up were tested. First was a open perimeter wheel cover. Second was an almost full wheel cover with the wheel center open (pics). Tape mock-up was installed on all four wheels to get aerodynamics information.

The goals are :
1. Find the most appropriate wheel cover for this 1999 Acura EL car in terms of actual fuel economy and aerodynamics behavior.
2. Determine which wheel cover will allow brakes heat to escape.
3. Aesthetic constraint: the final wheel covers have to look good on the car and not disfigure the good looking wheels (wifey requirement)

To measure the parameters to satisfy goal 1, Torque Pro App was used to log : throttle opening (%), acceleration (x), mileage instant, RPM, Speed GPS. The data series were logged every half second.

To satisfy goal 2, simple observation and "touch feeling" were used

Goal 3 is satisfied when "wifey" says it looks good. She did. See pics.

Testing of the mock-ups were conducted "back-to-back" on the same morning and road segment. The previous day, on the same road and similar conditions a series of runs without any cover were done in order to obtain a baseline data for comparison.

The metrics for comparison were the top speed achieved at a constant throttle opening according to the "throttle stop" method proposed by Julian Edgar on Youtube. The instant mileage averages over the few seconds that the speed remained constant at the said throttle opening were also compared.

Tests were conducted in the following order:
0. Baseline test, no covers (32 Celsius)
1. Open perimeter mock-up (17 to 20 Celsius)
2. No perimeter mock-up (17 to 20 Celsius)
3. Final wheel cover installed

Results and observations:

1. Open perimeter mock-up : allowed a top speed increase of 1 to 3 % over the base line even though the air temperature was lower by more than 10 degrees Celsius.
2. No perimeter mock-up : did not allow an increase in top speed as the open perimeter did. On the contrary, it decreased the top speed obtained by the open perimeter mock-up by at least 13 %. Also, the tape on the wheel perimeter felt hot to the touch on one front (disc) and one rear (drum) wheels. For mileage, the open perimeter mock-up used at least 7 % less fuel than the full perimeter blocked wheels. The final wheel covers will be with an open perimeter like the Tesla "aero" wheel covers and the design will have to match the underlying wheel.

3. Final wheel covers (17 Celsius : same road): Projected wheel covers fabricated with aluminum pizza pans and decorated with back sticking lettering vinyl was okay’ed for aesthetic.

These final wheel covers did not allow for a significative increase in top speed for a given throttle opening over the mock-up open perimeter wheel covers. On the other hand, fuel economy was improved by 2 to 5 % over the said mock-up. No particular heat accumulation was felt on the perimeter of the aluminum pizza pans.

Conclusions

Cheap modification mock-up is a good way to test various alternatives to orient the search for the appropriate modification.

Definitive wheel covers design retained are appropriate to the 1999 Acura EL and are proved to be a worthy modification that saves fuel.

Addition

Final wheel covers had to be removed from wheels because the attachment method was wrong and the covers moved causing wheel balance problems.

First attachment method was simply with zipties attached to the “spokes”

Second method was with toggle bolts: removing and reinstalling the covers made the toggle part move between the spokes thus promoting cover movement and wheel imbalance.

Next wheel cover attachment method will be to use longer lug nuts, drill their center, stick a nut on hit with epoxy glue and use fine pitch machinery screws to secure the cover to the wheel. (this attachment method is proposed on ecomodder.com for a Tesla owner).

Happy and best success in EcoModding !

Acel