It seems like to get a 10% improvement, you’d have to be going really, really fast. Air resistant force goes up disproportionately with speed, so maybe if the measurements were made at 85 mph a 10% might be possible. The OP refers to “highway speeds”, but that’s a little ambiguous. Some highways in Texas I think sport 80 mph speed limits, don’t they? And some highways have no speed limit in parts of the world.
He says in the article he drives a steady 100kph (62 mph) on a flat highway in Australia.
Any car manufacturer would kill for something that simple that would cause that kind of improvement in mileage. There are many millions of dollars at stake in how such an improvement would improve market position, sales, and the overall aggregate of mileage figures across the model range that comprise the CAFE figures. It would free Toyota to make power greater in their performance cars, for example.
It’s possible that this individual THINKS he got a 10% improvement. It’s even possible that this person MEASURED a 10% improvement… or at least believes he measured a 10% improvement. But I have to believe that Toyota aerodynamics engineers have already tested various underbody panels under controlled conditions far superior to what the individual in this thread has available. If you could see the technology, analysis, and testing that goes into design work you’d be skeptical too.
@mountainbike, Car manufacturers already know how to make cars more aerodynamic with much improved efficiency. The problem is consumers don’t like how they look and won’t buy them in large numbers.
"Teardrop-shaped bodies, fender skirts and other typical aero gimmicks may work miracles in the wind tunnel, but when they hit the street, consumers reject them. GM’s EV1 and first-generation Honda Insight HEV were the most aerodynamic vehicles of their day, sporting Cds of 0.19 and 0.25, respectively, more than 10 years ago. Despite innovative design and breathtaking efficiency, both flopped."“Customers don’t want to buy the most aerodynamic car. They want the prettiest car with the best performance at the best price point,” says Stefan Young, manager of the thermal systems and aerodynamics groups at Toyota Motor Engineering and Manufacturing North America."
And relating to underbody panels, Toyota says underbody drag is 30% of total aero drag and they are planning to use more underbody panels in future.
The vehicle underbody is responsible for about 30% of overall aerodynamic drag and the engine compartment cooling system another 10%, says Toyota’s Young. More underbody sheathing will continue to yield benefits in the future, plus under floor panels offer the additional benefits of reducing road noise and increasing high-speed driving stability.
I’m not buying into that claimed 10% increase in fuel mileage. At all or ever.
Think of all the other things claimed to provide a 10% increase (or more…) in fuel mileage. Cheap eBay “chips”, acetone in the gas, etc, etc. All bunk.
Jesmed, you’re contradicting yourself. You’ve implied that Toyota hasn’t implemented the underbody panel in the photos because consumers wouldn’t like the looks and then said that manufacturers plan to implement more underbody panels. Frankly, consumers can’t even see the underbody panels. The argument is moot.
The truth is that manufacturers have been adding underbody panels for decades when aerodynamic studies show any significant improvement. 10% would be an extremely significant improvement. Yes, manufacturers will likely be using more underbody panels, but they’re looking for fractions of a percent improvement, trying to meet a forthcoming CAFE requirement that’s insane.
The claimant is full of bulldroppings.
I would hope that law enforcement would get that heap off the road. I cringe when I see people hauling a mattress, or worse a sheet of plywood on the roof of their car but that car’s back yard scrap facelift looks like an accident looking for a place to happen. Can anyone imagine what would be left if that car ever reached 80 mph? And what about the traffic behind him?
Recently I saw a Grand Cherokee with a mattress securely(?) strapped to the roof rack travelling on a rural road at +/- 50 mph and when meeting a vehicle the road draft would lift the bed away from the roof. Sure enough, in a few miles the repeated lifting had loosened the straps and the mattress went airborne. luckily a bob tailed Peterbuilt was behind him no damage seemed to have resulted.
Some may remember a poster on this forum some years ago who inquired about strapping a large sofa to the top of a mini-van and lugging it from Houston to San Antonio.
So not only do you have the aerodynamics and wind gusts involved but also a lot of top heavy weight.
Needless to say, not doing this was the unanimous answer.
@ok4450 I would never advise anyone to carry a large sofa on the roof of a car, but have actually done that when first married. My father in law gave us a very nice large sofa but we lived 150 miles away, so I put my trusty roof rack on our 1965 Dodge Dart 2 door hardtop and strapped the sofa on it.
As might be expected, there was a lot of wind noise and luckily no cross winds. We arrived intact at our apartment and used the sofa for several years.
P.S. always unscrew the short legs from the sofa if you want to avoid dents in your car roof!
We used to put the duck boat on the car top carrier all the time with no problems. Of course it was heavy and pointed at both ends as well as roped down from the front too. Then we got a station wagon.
^^^ Man, are all the loons moving to Texas???
It should have a sign on the back that says “WARNING: makes wide turns”. Imagine how far that rear end swings out going around tight corners? It does, after all, pivot on the rear axle.
That’s a crappy looking way to increase bed space.
Does this aero package make my @ss look big?
It’s a great way to carry a 28-foot extension ladder, though. Maybe even up to a 40-footer! ; )
I too have carried sofas, mattresses, and numerous other large items on vehicle roofs - all securely tied down. You need to be cognizant of the impact on handling, but otherwise it was never a problem.
When I see a mattress on the roof of a car or SUV with the foundation on top and tied side to side and front to rear I wonder if the driver was an eagle scout or had a lot of experience on a sail boat. It’s possible to haul a mattress safely that way but so few seem to know how to do it or care to try.