" Aerodynamics doesn't begin to have an effect until 60 MPH "

[MeteorGray]

I can't remember seeing a chart that features MPG at various speeds that was conducted with some semblance of scientific controls that don't show the best speed for any given vehicle is the lowest speed after getting into the final gear. IE, the lowest RPM = the lowest speed = the highest fuel economy.

[skyking]

Originally Posted by Autobahnschleicher

Surprisingly I tested a Mercedes Benz E220 D and it genuinly had its best fuel economy at 110 km/h (just under 70 mph).
That was 4,7L/100 km (50 mpg)
However it is a rather aerodynamic car with a 2,5L turbodiesel and very tall 6-speed manual.

how did it do @50 MPH?

[pwillikers]

235/mpg=l/100km
235/(l/100km)=mpg

[Autobahnschleicher]

Originally Posted by skyking

how did it do @50 MPH?

It's been a while, but going slower increased the fuel consumption slightly.
Sadly I don't remember by how much.
110 km/h was its most efficient speed, surprised me as well.

[Piwoslaw]

Originally Posted by Cd

Can someone suggest a direct link to some info on this ?
It gets frustrating.

Every time you need to prove this, either to someone or to yourself, find a bicycle and see how long you can keep your speed around 30 km/h (~20 MPH), and how that compares to 15 km/h (~10 MPH).
It doesn't look like much but the difference is noticeable.

[Isaac Zachary]

Originally Posted by kach22i

This is a source of angst for me, looking at my beautiful 4-seat coupe the other day all I could think of was the waste.

I've only had a passenger in the car for maybe 5% of the miles I've put on it, and the rear seat may never see use.

This is the tragedy of most vehicles in the USA, at least as daily work commuters consisting only the driver.

Especially when those daily commuters are large SUV's under the excuse that they get "good" fuel mileage just because they get more than 15mpg.

There are plenty of vehicle configurations that get hundreds of miles per gallon per passenger. Why can't people see the waste?

[aerohead]

Clearly, the road load horsepower requirement of any vehicle, at any velocity, will track along with velocity.
How efficiently any particular vehicle behaved at any given velocity would have to do with the specifics of its powertrain and BSFC map, or BCFC-e map, if an EV.
* AeroStealth's 2014 F-150 will return 22- mpg at a constant 62- mph.
* 32-mpg at a constant 35-mph.
* The F-150 Lightning will be approx. 77-mpg at 62-mph.
* 112- mpg at 35 mph.
* The 'sweet-spot' would always be a on 'case-specific' basis.

[vadimr4]

When I hear people say that aero doesn't come into play until 30 or 40 mph haven't ridden a bicycle recently. On a bike, even 10 to 15 mph you can feel a difference if you are tucked in or sitting straight up.

[racprops]

First on areo:

About the not being blown off the roads:

I bought my 93 Star Craft Custom Van after having stock Chevy vans for decades (1978 till around 2005 when I bought the 93) I was concerned that with the raised roof and side ground effects would make winds worst for driving.

I drove a 74 Chevy van full time during the 80s and crossed the US on many times, in the 90s and into the 2000s it was then a 78 van. Again we did a lot of road trips all over.

I was VERY used to fighting for control with cross winds and when passing or being passed by BIG RIGS. The bow wake of air would buffer and push my vans all over the road; I am sure near every Van owner knows what I am talking about.

My first road trip showed me that was NOT a problem. Cruising at 75 MPH I was over taking a Big Rig and I braced for the fight as I over took the cab…and..and WTH no fight, I breezed by this big truck….

Must have been a trick cross wind that stopped the bow wake of the big rig, BUT it happened again and again, almost no effects of passing trucks, and even when I was over took by even faster big rigs.

OMG The stream lining ground effects of the Star Craft panels which I loved for their LOOKS really works. I have had the van for 15 years now and LOVE this effect.

I believe these ground effects keep air from under the van and I believe this nearly stops the effects of bow wakes and losers the effects of cross wind on my G20 van.

But there seems to be a catch, as far as I have been able to learn this ONLY works with the old Star Craft costume vans, the newer look alike vans are not close enough to the ground for this to work.

As these only came on these old van and may people really are not interested in completely rebuilding an old van my best suggestion is to either lower the newer vans or add to the front air dam and side skirting to get this effect.

[racprops]

Back when I was testing a 2000 Mercury Grans Marques and tiring MPG Improvement devices I found the following:


At 65MPH and at 1750 RPMs this car was able to get 27 to 30MPG.

This was a stock 2000 200HP 4.6 Non- IP intake running stock wheels and tires and a 3.27 Rear end.

I was able to get 35MPG at 65MPH and at 1750RPMs by Leaning it out to its best reading at 16.4 A/F ratios.

Later on a road trip to Riverside CA from Phoenix AZ I drove at 85MPG to the CA border (just short of Blythe CA) where I filled up. Apox 145Miles and I was getting 24 MPG. Once in CA with its speed limit of 70 MPH rather than the AZ limit of 75MPH I drove slower and ran 75/80 from Blythe to Riverside which is about 163 miles when I again filled up and recorded 25/26 MPG.

Last year I made a to Lake Havasu to buy a pair of transmissions in my 02 Vic P71/Mercury clone. She drove and rode great and her passing power on the old two lane rood was great.

MPG were not bad was running 80/85 on I 10, then 65/75 on the old two lane highway. Got gas at Quartzite to check and read around 21/22MPG then refilled at Quartzite on return and read 22/23.

This was a stock 03 P71 250HP IP intake 4.6 running stock wheels and tires and a 3.27 Rear end.

Even with a 4L80e and a US Gear overdrive in the trunk. I could hardly feel the extra weight.

These two transmissions are for my 93 G20 Van. I am making the Van into a 5 speed double overdrive system.

It is my theory that with a V8s like the 4.6 and a 383 I can drop the RPMs down to 1600 to 1800RPMs and get very good MPG.