Older Article : Why Don't Pint-Sized Cars Get Better Gas Mileage?

[Cd]

Why Don't Pint-Sized Cars Get Better Gas Mileage? - Popular Mechanics

QUOTE : "The Spark's windshield angle is about 33 degrees. While that design yields more interior space, it also increases aerodynamic drag and reduces highway fuel economy."
"The Spark's short length impacts the drag in two main ways," explains GM's small-car development manager, Dan Molnar. "First, the grille and windshield are more upright to allow greater passenger space, and second, there's simply not enough length to smoothly guide air around the car."

The drag occurs at both ends: the air hitting the front of the car, and the vacuum created as the turbulent airflow spills off the car's rear. Longer cars may weigh more, but they can better approximate a teardrop shape, resulting in slightly less resistance as they travel, which helps highway mpg. Engineers attempt to reduce drag on shorter cars with various body features, such as smaller wheel openings and sometimes a rear lip spoiler, but there's only so much that can be done. The Spark's drag coefficient is a few percentage points higher than the Sonic's. "


The first thing that comes to mind when i see these comments is the Mercedes Benz A-Class, with it's excellent .27 Cd

Just look at the length . Look at the windshield angle .



Also the Mercedes Benz Bionic car with its excellent .19 Cd - just look at that steep windshield !



And the Sonic : Correction - Spark

[niky]

To be fair, the A-Class is bigger and longer. Too bad designers are constrained in these smaller cars by the need for rear headroom and cargo space... but likely more constrained by the need to have them look like cars.

[kamesama980]

That and how in my experience they rev the snot out of the engines so people can pass without it downshifting. general public is retarded, afraid to floor it, and thinks if the engine revs too high (like flooring it, downshifting to pass) it'll immediately explode. I've heard the general public make the arguement and I've heard industry people make the arguement.

[jamesqf]

This would be such an easy problem to solve, too. Just make the car longer and lower, so that people wouldn't have to sit in uncomfortable bolt-upright positions, and so high that it feels like you're balancing on a barstool with wheels. Compare e.g. the Honda CRX...

[Arragonis]

Originally Posted by Cd

...And the Sonic :

Thats a Spark

Originally Posted by jamesqf

This would be such an easy problem to solve, too. Just make the car longer and lower, so that people wouldn't have to sit in uncomfortable bolt-upright positions, and so high that it feels like you're balancing on a barstool with wheels. Compare e.g. the Honda CRX...

Agreed. A Hatchback is essentially a box, and it has to be to accomodate passengers and luggage, and also provide access to the rear. There isn't much you can do to a box to make it more aero friendly - without getting into major mods like a boat tail.

The CR-Z seems a waste IMHO (although I still want one ) - the engine is just too large. The 1.3 from the Insight would have been good enough but it is sold as a "sports" coupe.

[aerohead]

The good news is that all the cars depicted have very good body geometry as a starting point for enhancement.
It's merely a matter of rear elongation to add drag reduction.
An ultra-light,gap-less, integrated boat tail trailer or inflatable tail for out of town excursions,and the short,'practical' length for urban warfare.
I like 'em all.
If capitalism ever catches on in the U.S.A.,consumers may find themselves investing in automotive technology which actually has an R.O.I.,breakeven point,net gain compared to what they're driving now.
I pay only half-price for gasoline compared with some other 1/2-ton pickups on the road.
And that's from a Cd 0.44 starting point.Imagine starting from 0.30 or a bit less.

[Sven7]

Originally Posted by jamesqf

This would be such an easy problem to solve, too. Just make the car longer and lower, so that people wouldn't have to sit in uncomfortable bolt-upright positions, and so high that it feels like you're balancing on a barstool with wheels. Compare e.g. the Honda CRX...

Compact cars are generally compact for a reason- to fit in tight places where space is at a premium. You start lengthening a compact car and it becomes a midsize. In most of America it doesn't matter at all, but in Europe and Asia you sometimes need to build to a certain size.

[Cd]

Originally Posted by niky

To be fair, the A-Class is bigger and longer. Too bad designers are constrained in these smaller cars by the need for rear headroom and cargo space... but likely more constrained by the need to have them look like cars.

The Spark is a full TEN inches taller than a CRX, yet headroom is less than 2 1/2 " more.( 37 versus 39.4 in headroom )( 50.1 "versus 61.1 " height )
Even a new Camry is shorter at 57.9 " tall

A 5th generation Civic has a mere inch less headroom, but again the Spark is right at 10" taller.

Also the car is actually 4" skinnier than the 5th generation Civic.

( 66.9 Civic 62.90 Spark. )

[Sven7]

I wonder if you could toy with the rear seat H-point to get that roof down lower. It would probably feel awkward to ride back there...

[niky]

Originally Posted by Cd

The Spark is a full TEN inches taller than a CRX, yet headroom is less than 2 1/2 " more.( 37 versus 39.4 in headroom )( 50.1 "versus 61.1 " height )
Even a new Camry is shorter at 57.9 " tall

A 5th generation Civic has a mere inch less headroom, but again the Spark is right at 10" taller.

Also the car is actually 4" skinnier than the 5th generation Civic.

( 66.9 Civic 62.90 Spark. )

As said... bolt upright seating position. The extra height all goes towards legroom actually. Older microcars and subcompacts... the previous Spark and the older Fit, for example, had the seat squab low, so your knees would either be all scrunched up or you'd have to move the seat way back to be comfortable. The way they build the Spark gives it a lot of headroom and legroom combined.

They could make the cars longer and lower, but these size constraints are driven by very specific market needs and (stupid) tax regulations based arbitrarily on footprint size rather than overall weight.

Plus, given these are marketed for European urban drivers and third world markets, where they'll typically be driven at just 40-50 mph, the extra drag doesn't matter as much.

Perhaps something like the Merc concept would work if they didn't have to be built for four... Limit them to one rear passenger so you can pinch the body sideways instead of vertically.