[ChrstphrR]

Air compression wouldn't be an issue except at high mach numbers; thus the whole concept of that is irrelevant, off-topic scatter being raised up.

I think RobertSmalls' made a much more photogenic backing of what I mentioned about how a pointy nose doesn't matter for well below Mach one. That's just part and parcel of the reason why it hasn't been widely persued.

I've two more drawbacks to dredge up, one's aerodynamically related, one isn't.

A long supersonic nose for a car would cause more separation, turbulence, and thus, more drag with anything but a headwind or tailwind. Yes, that means boattails also have this drawback.

However, we shouldn't just consider pure aerodynamics for the sake of meagre gains versus... vehicle dynamics and stability.

A Boattail does have the same drawback as a huge nosecone I just mentioned; the boattail with a side wind will increase the tendency to understeer, handling/dynamics wise, which is generally easier for drivers to counteract and anticipate.

A large pointy schnoz, that makes your car look like a MiG 29 or a Tomcat from the front, will contribute to oversteer with sidewinds, which is generally NOT stable, and harder for most drivers to anticipate, or correct for.

The other angle on vehicle dynamics: Corvette Stingrays were infamous for the uplift their high, pointy noses caused.

The "ideal" pointy nose would be almost a wedge that veers to the ground, but that isn't practical, since most people have to have at least ONE end of the car, if not two, that can clear the transitions* from steet to driveway.

Thus, a practical pointy nose, would have it's furthest point foward up from the ground. The generally rounded shapes that have been cited as ideal push air overtop the car, and to the sides, mostly -- with a small amount going underneath, comparatively.

Too high a pointy nose, too much air is directed underneath, and you get lift on the front axle, which gives the driver a lightened steering response at highway speeds, or above. This is simply not conducive to SAFE driving.

Walter H. Korff detailed that effect in his tome, Designing Tomrrow's Cars.

And from Julian Edgar's practical test on just little tiny front tire deflectors, from an oft-cited set of aero articles from Autospeed:

Firstly, fuel economy slightly improved, indicative of the drag again being decreased. The gain wasn’t nearly as great as achieved by the new undertray but the best-ever 100 km/h freeway 5-minute fuel consumption was achieved – 24 km/l (4.2 litres/100 km)... and that was with the air con on! Secondly, 5-minute fuel consumptions of 22 km/litre were also more frequently achieved with the deflectors in place.

However, the aero stability of the car was poorer than standard. While I stated above that the new undertray may have resulted in a stability improvement, with the deflectors in place, stability was without a doubt inferior to standard. The reason that stability had declined can be sheeted home to an aerodynamic pressure build-up on the undertray ahead of the new deflectors. With the deflectors in place, steering corrections were more frequently needed and the car was more susceptible to the bow waves and wakes of cars in adjoining lanes.

I’d already bought the high density foam rubber with which I’d intended to make the final versions of the deflectors but after testing the quickie foam-and-duct-tape prototypes, I decided to not go ahead. Here was a clear case of deciding to either further reduce drag while trading-off stability – or to have lower drag and lower stability.

I chose to maintain the stability!

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...darn! where's the MythBusters when you really need them? A drop of falling water is round, not teardrop shaped.

Teardrops slinking down a cheek do have something closed to a bobbed "teardrop" shape.

Until my commute approximates free-falling for miles on end, I'd rather approximate a teardrop which hugs an approximately flat** roadway instead.

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* I live in Canada, and some civil engineers and city planners think that an 8" curb at 45 degrees is a reasonable transition from road to driveway. I think these people just hate mufflers, tailpipes, and oilpans.

** I live in Canada, we have these collections of potholes and patches they call "roads" up here; so, yes I did mean approximately.