Piston Slap: Frontal Area, Our Friend?

Sajeev Mehta
by Sajeev Mehta

Bill writes:

After reading you post on modern interior design, I had to ask about another fad that seems to be all the rage with designers: big grilles (they really love the grille on the Lancer X) With modern cars being all about gas mileage (judging by their advertising), would they get better highway gas mileage if they were a bit more aerodynamic?

Take the original Honda Insight for example, it could get around 70mpg on the highway and it had a very aerodynamic design with no fins, slits, nor much of a grille.

Today’s compacts are just a little better and thus use bigger engines, but their grilles are big enough to eat full pie! If modern cars were a little more aerodynamic, and less style-driven how much of a boost in gas mileage would we see?

PS: I’ve come up for a term for the black-painted sections on some grilles like the new Alfa Dart, I call it a “Mustache”.

Sajeev answers:

Maybe my time studying Industrial Design can come in handy once again. No wait, my years studying Mechanical Engineering are actually better. Maybe it’s both. Well then, glad we got the self-congratulatory BS out of the way!

Your problem with grilles is valid, but not the underlying cause of the problem. Proof: the plankton filters on the Lincoln MKT. This whale of a beast has most of its cooling fins blocked off for better aerodynamics. The grille on the original Chrysler Sebring coupe technically didn’t even exist, it was only black paint!

See?

My point? Modern grilles are a part of a larger shape formed at the wind tunnel. All our technical advancements have made a low coefficient of drag a non-starter to this issue. Put it this way, your phone is far more powerful than the original technology used to make the slick, aero-cheating experiments from the 1970s. How can you not have a low-coefficient of drag with all of our processing power?

What concerns me is frontal area. Just like the restaurant biz, your real estate is how you hit automotive aerodynamic Gold. Or at least several positive foodie reviews on Yelp…

New cars are too tall and front overhang too short to be aerodyamic enough to justify the “buy me for fuel economy” marketing we hear these days. Overhang shaped like that of the 1980s Honda Accord is a nice place to start.

From there, we can narrow down the frontal area with a more aggressive rake to the nose. Which means less room for lights, bumpers and most importantly, grilles. Granted you can take this to an extreme, making a nose so small that the rest of the vehicle is unlivable, impossible to cool, etc. but that’s just being silly.

The biggest problem with reducing frontal area? Cars get generic. And while the Honda Insight, Aston Martin Lagonda, Ford Sierra, Chrysler Airflow, Mercury Sable, Tatra V570 and even the Ferrari Testarossa are icons of their respective classes and markets, being truly aerodynamic is more about the socio-economic conditions (progressiveness, gas prices) that demand a certain performance outcome, and styling trends (modern or retro?) of the people in and around the car business. The Chrysler 300, the rise of the HUMMER brand and the climate surrounding these two come to mind.

Keeping with a plan and sticking with it? Even Miami Vice’s addictive take on film noir couldn’t survive the end of the 1980s, son!

Send your queries to sajeev@thetruthaboutcars.com . Spare no details and ask for a speedy resolution if you’re in a hurry.

Sajeev Mehta
Sajeev Mehta

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  • ThatMustangGuy ThatMustangGuy on Feb 27, 2012

    I'm no expert on the subject either, but just a few things I'd like to add to the discussion: Many cars from the 80s and 90s where mouth breathers, where most of the air for the engine bay was picked up from low on the car. Usually an air dam would be used on the radiator support to create a low pressure, which causes air to travel through the radiator and cool the car. In the interest of underbody aerodynamics for fuel economy and high speed stability, many cars have some degree of belly panning the bottom of the car, which would not work well with said design. To make up for this, some amount of extra air must come through the front end of the car. Also, I would imagine that since most airflow must be provided from higher up the front of the car, the 2 tier openings many cars now have would be to possibly separate functions, with the upper opening for the radiator, and lower for power steering/intercooler/AC condenser/etc. Styling is probably part of it, but cars like the Volt or Leaf show that car companies are not afraid of no or nearly no grill front end styling if it would make the most sense... though they do try to emulate a grill somewhat I suppose... This doesn't answer all the concerns with the larger front ends, but might just be another line item in the list.

  • Ciddyguy Ciddyguy on Feb 27, 2012

    Also, notice how the front of most cars curve, that is, they are flat through the center, more or less, then slant back to the corner where the front fenders meet. This gives the often awkward appearance of a severe frontal overhang as found on some of the latest models of the past couple of years or so if viewed from the side. It seems to me, that on some larger cars (C and D segments and up), the wheels, both front AND back seem to be far from the corners than they once were, giving the appearance that the car has an overly short wheelbase for its length and that to me looks awkward. Small cars, such as the A/B segment models tend to have MUCH shorter overhangs overall, especially for the rear wheels which now almost meet up with the rear bumper in many cases, but the front still has a bit of an overhang. I totally get it that with FWD on most cars built these days, some overhang is unavoidable due to the machicals, such as the cooling system that fit up in front of the motor. As for grills, it was once fashionable I believe to have little to no grill above the front bumper, 86-89 Integra/Accord come to mind with the main functional grill discreetly mounted below the bumper. The Fiat 500 only has a slit just above the front bumper, but has a more discreet looking egg crate grill down below and yet it's still a rather blunt front end, but it IS mimicking the original 500 stylistically speaking. Yet, when you get it above 70mph, this shape becomes a disadvantage and one's mileage suffers more so than some other shapes (besides, it's short at 140" long and is tall for its size). But despite having taller hoods (actually, not a bad thing since now we have some way of seeing them when we drive), what I would like to see are frontal designs that are more wedge like in that the front can remain somewhat on the tall side, but slant the grill/headlight area back some, while pushing the front bumper area out some to let the air slip over the front a little easier - all the while meeting pedestrian regs. Also let's not have windshields that slope so far away that you see acres of dash before you even see the hood as that can be a bit disconcerting while driving. Plus, if we got rid of Ethanol, then our gas mileage would go up just by that one change alone.

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