2003 TDI Beetle TDI FE mods

[cems70]

In my travels this morning, I came across this retired engineer who increased FE in his 2003 VW Beetle TDI from the EPA highway 49 MPG to 65 MPG (including a record 78 mpg tankful) w/ slightly larger diameter and LRR tires plus a wing on the rear hatch. Is this guy a gassavers.org member?nnThere are comments further down the page from someone who claims acetone added to gas improved FE in his '93 Civic by 9%.

http://www.greencarcongress.com/2004..._wings_of.html

Here's the link to the Beetle owner's website:

http://www.max-mpg.com/

[LxMike]

not bad. thats about 50-60% over epa ratings.

(edit) epa combined is 45 so he's in mid 40's % wise, still a nice gain.


the 78 mpg tank was done driving at 55 mph.

[SVOboy]

His FE isn't that high, could prolly be done by driving technique alone, especially with that diesel, but I'm sure the wing would help with the crappy aero on that beetle.

In any case, I think he's registered here, but doesn't post.

[omgwtfbyobbq]

Yup yup. When he did go 55mph for prolonged periods, he supposedly pulled near 80mpg. Slowing down is always good for mileage, especially on cars that have such crappy aero.

Originally Posted by Ernie

THIS IS AN UPDATE ON THE BEETLE'S SUMMER MILEAGE

As expected, mileage during this last summer (2005) averaged about 65 miles per gallon, when traveling at a normal highway speed of 65 miles per hour. There is a rule of thumb that a car will get 10% better mileage by slowing down 5 mph on the highway. Or, if you slow down 10 miles per hour, your mileage should improve by a whopping 20%. So, you can calculate how well the car would do at a different driving speed. Remember, when figuring speed, you should include any headwind.

In early September, I traveled from Utah to Wisconsin to attend the annual meeting of the TDI Club, an on-line group of VW diesel car owners. I wanted to see just how good my mileage could be-- I drove all the way to the meeting at 55 miles per hour. Early on Wednesday morning, I topped off my tank (filled with 5% biodiesel blend) at Park City, Utah, waved goodby to the attendants, and headed out determined to see just how far I could get. I was blessed by perfect weather, almost no wind, all the way.

I finally stopped for fuel about noon the next day at Davenport, Iowa, a one-tank trip of 1,209 miles. (All at 55 mph, remember. I was honked at four times.) I filled the tank, taking 15.5 gallons. I had obtained a record --for me-- 78 miles per gallon.

Ernie Rogers

[skewbe]

Originally Posted by omgwtfbyobbq

Yup yup. When he did go 55mph for prolonged periods, he supposedly pulled near 80mpg. Slowing down is always good for mileage, especially on cars that have such crappy aero.

how is a coefficient of .37 possible on a car with such curves?!? Is the 30 degree angle of death rear hatch? The wheel flares? What is the deal?

[omgwtfbyobbq]

It's not about smoothness so much as angles, anything greater than 10-15 degrees is bad. The round back end looks to be near a 40 degree, if you cut straight from the roof line to the bumper, so I'd guess it's worse than the angle of death rear hatch. The wheel flares that stick out from the body are also pretty bad imo because they have that same steep angle that will result in a big pressure drop behind them, and lots of drag. Not to mention it has more reference area than more aerodynamic autos like Honda's passenger cars. Even the Corolla is way better, and if you look at it, from the roof to the top of the trunk is not very severe, while the trunk down is a big drop off... So the area of the angle of death has the most impact on aero imo.

[Mike T]

My smart car has a Cd of 0.38, which is pretty bad, and the surface area is high too. Nonetheless, 100+ US MPG is possible at 50 MPH. Imagine what it'd be with a slippery low-profile body.

[Lug_Nut]

I've known Ernie about three years now. He's a former aeronautical engineer and doesn't jump into these things arbitrarily. He has repeatedly tested single variable changes (including many different angles of attack) as the present design has developed. The only issue with his on the road testing methods may be that they are obviously not "double blind". His goal is to reduce the Cd of the N-B as far as is possible without going outside the projected area. He knows he'll never get the Beetle's Cd as low as a CRX or other, but he's made big advances so far.

[korax123]

That wing looks rediculos but it's very functional. Congrants to him on what he accomplished.