[Delta Flyer]

I have heard a number of ideas to improve either the Insight's fuel economy, performance, or both. I doubt most of them would improve the Insight. I will add a dubious suggestion of my own.

Install an airfoil over the passenger compartment of the Insight so the rear would be partially airborne at highway speeds. This would not be an ordinary airfoil. A brilliant engineer would need to interface this mini-wing to a computer. At under 30 mph, it would be resting on the roof. If the driver is on the freeway, he activates the airfoil. The computer calculates the proper angle of attack. The front wheels shoulder nearly all the weight at cruising speed. It would be as if the Insight weighed just a few hundred pounds. If a sudden stop is made, the airfoil becomes an airbrake.

I doubt the Department of Transportation would allow this, but think of the possibilities on open highways. No, I don't think this would be suitable in urban traffic.

If this ever happened, tailfins would make a comeback.

 

[cakley]

The new expensive benz has an electric air brake of some sort...

 

[james]

That wouldn't get you anything. The increased drag due to the airfoil (well, not really drag per se, but the energy taken from the airstream to produce the upward force that lifts the rear end) would take more energy than you'd save by reducing road friction.

What might work, though, is a telescoping "sail" airfoil. (Don't know if you've ever seen serious competitive landsailers, but they can hit speeds over 100 mph just from the wind on a similar airfoil.) You have computer controls to adjust it, so that when there's any crosswind, it extends to the proper angle to grab maximum wind assist.

 

[MikeF]

"That wouldn't get you anything. The increased drag due to the airfoil (well, not really drag per se, but the energy taken from the airstream to produce the upward force that lifts the rear end) would take more energy than you'd save by reducing road friction. "

Actually, it is drag. The forces that create lift also create drag. When an airplane wants to turn to the left, the ailerons create more lift on the right wing, which puts the aircraft into a bank to the left, thereby turning it to the left. But it also creates "adverse yaw" -- the extra drag on the right wing which comes with the extra lift -- which pulls the nose of the aircraft to the right. That's why airplanes have rudders -- the rudder is used to swing the nose back into the turn and overcome adverse yaw, making the turn "coordinated" and much more efficient.

MF

 

[james]

True - What I meant was to emphasize the difference between drag from something just hanging out in the wind, and drag that's energy of motion turned into lift.

 

[Tim Maddux]

Right; the wings generate lift but also generate the drag y'all are mentioned which is often referred to as "induced drag." Additional drag induced by the generation of lift. I agree that this would outweigh the drag reduction from reduced rolling resistance.

Better to keep the wheels down and engineer some sort of tail cone to further reduce the vehicle Cd. Make it crumple-able for rear-end protection since some of us tend to get rammed

 

[PlaneJob]

like those guys said, you can't get lift in exchange for nothing - that would be some amazing drag. And besides that - raising the rear wheels, or taking the load off of them, would make the car highly unstable, directionally. To counteract this you could add a stabilizer, but that is more drag and would have to be almost as tall as the car to be effective. nevermind trying to tur the car, exit off the highway or do evasive manuevers to avoid an accident.

Another thing to consider is how well the front wheels would contact the ground - by lifting the rear you are taking an amount of weight off of the front wheels.

Probably the best thing you could do for this car is lower it another inch or two - or add airdams all around.

To improve my fuel mileage I am going to go on a diet, lol. I figure if i add a stereo @ around 15lbs, and lose 40lbs, I am 25lbs for the better, and I might save a little on the kibble i didn't eat to help pay for the tunes.

 

[flunkysama]

Why don't you just go halfway. Since most of the weights on the front wheels, you can probably get rid of 1 of the rear wheels. Stiffen up the srping on the side that keeps the wheel, put a aero cover over the side that looses a wheel and you are set. Saves weight too. :wink:

Actually, one place you can "go to town" is to make the underside more aero.

 

[Sparky5501]

For those of us in the know, when you get the Insight past 100 mph the body squats down due to the down force created by the body itself.

So, something as simple as removing the small spoiler on the Kamm tail would decrease the rear downforce. Or, adding an extension that curves down to the Kamm tail would also ruin the rear spoiler effect to a degree.

Personaly I don't think the drag benefit is worth the safety hazard created by reducing the rear downforce of the vehicle. I would just fit skinny 145/75 R14's to reduce rolling friction.

 

[b1shmu63]

The Insight has a "Kam" back like the CRX before it. This cut off style grew out of the discovery that extending the rear further did not benefit drag significantly. The EV1 and the Dihatsu UFE2 prototype have drag coefficients of .19. :shock: The Insight's .25 Cd could likely be improved. The body of the Insight is aluminum which is an excellent conductor of heat. Some of the cooling of the engine could be done by the body or under panels, which would allow for a smaller radiator and a more streamlined shape.