Optimum nose shape

[Otto]

I may facelift my Porsche 944 Turbo, which to my eye has less than optimum aesthetics and aerodynamics.

Suppose we start with a clean sheet of paper and re-do the nose forward of the hood. This would mean a new single-piece bumper cover, fixed and covered headlights instead of pop-up headlights, and perhaps a splitter or spoiler.

Question: Can anybody here post pics or graphic from tested designs of optimum car nose shapes?

In other words, just are diffusers at the rear have been studied, surely nose shapes, radiuses, contours, cooling inlet and light placements, etc.must have been optimized, so any suggestions or insights would be much appreciated.

[aerohead]

Hucho has a chapter section devoted to the 'ideal' nose.
It's basically what R.G.S.White displayed in his 'Method of Estimating Drag Coefficients,' 1968,which is just like Walter Korff's ideal nose of 1963,which is much like Paul Jaray's nose of 1922,which goes back to the half-teardrop form Hucho uses as his benchmark.
For what it's worth,and I've mentioned this elsewhere,the 'ideal' nose on my CRX meant virtually nothing at 100-mph,which meant it's contribution to drag reduction was very little and so it's value for mpg,also very little,whereas most of the speed record and 60+ mpg came from the boat tail.
The 944 has a pretty nice nose.And Porsche has probably already optimized it for the unibody chassis underneath.To significantly modify it would require structural modifications which could jeopardize other aspects of the cars makeup,especially progressive deformation and crumpling during impact should that ever happen.
If she were mine,I'd be looking at that Lange-type roofline and a way to push it out like the Porsche 917 Lange Hecht.

[Otto]

Originally Posted by aerohead

Hucho has a chapter section devoted to the 'ideal' nose.
It's basically what R.G.S.White displayed in his 'Method of Estimating Drag Coefficients,' 1968,which is just like Walter Korff's ideal nose of 1963,which is much like Paul Jaray's nose of 1922,which goes back to the half-teardrop form Hucho uses as his benchmark.
For what it's worth,and I've mentioned this elsewhere,the 'ideal' nose on my CRX meant virtually nothing at 100-mph,which meant it's contribution to drag reduction was very little and so it's value for mpg,also very little,whereas most of the speed record and 60+ mpg came from the boat tail.
The 944 has a pretty nice nose.And Porsche has probably already optimized it for the unibody chassis underneath.To significantly modify it would require structural modifications which could jeopardize other aspects of the cars makeup,especially progressive deformation and crumpling during impact should that ever happen.
If she were mine,I'd be looking at that Lange-type roofline and a way to push it out like the Porsche 917 Lange Hecht.

Thanks Aerohead.

I'd use all the same attach points, but where the 944 Turbo nose now breaks the natural sloping line of the hood and upper section of the panel between headlights, I'd just continue that line on down to the stagnation point. No more pop-up headlights, which are uber-draggy. Instead of long rectilinear slots for the cooling air intake, I'd consolidate that draggy design into on probably elliptical inlet at the stagnation point. Instead of a bumper cover, 2 headlight covers, and a panel between headlights, make all that one piece.

The front bumper is secured by shock absorbers, and that part would stay intact for safety reasons, as would all attach points.

Instead of separate light fixtures on each side for a headlight, 2 turn signal lights, a fog light, and a driving light down where they get sandblasted and rock chipped/broken, I'd consolidate all that into one covered fixture with the headlight, up out of the rock chip zone. Sorta a combination of Jag XKE and latest version Corvette.

This would weigh considerably less than what's on there now.

I'll check Hucho. Thanks for the suggestion.

Got any other sources of nose optimization ideas?

[cujet]

Way back when (30 years ago), my aerodynamics instructor in college gave the brick analogy. I probably don't remember the exact numbers correctly, but I am certain of the overall outcome.

Put the brick in the school wind tunnel, longways. Round the nose, drag drops by 8% (or something like that). Take a new brick and simply taper the tail (boat tail design) and drag drops by something like 70%. Combine the two and overall drag is greatly reduced.

Fast forward many years. The nose of piston powered Cessna/Piper single engine aircraft are often really ugly looking. Yet, they fly without excessive drag. Cowling mods produce nothing. However, reducing the cooling air inlet size does result in substantial drag reduction.

You might think about the drag increasing aspects of the hood to windshield angle and the cooling drag issues first.

[gone-ot]

...there's an old SAE article about the "design & testing" of the MoPar Daytona NASCAR vehicle that had some decent 'summary' information about the "optimization" of size, shape, and spoiler shape and position.

....see SAE paper #700036: "The Aerodynamic Development of the Charger Daytona for Stock Car Competition," by R. P. Marcell and G. F. Romberg, both of Chrysler Corp.

[Frank Lee]

944s are beautiful! Don't geek it out!

[Otto]

Originally Posted by Frank Lee

944s are beautiful! Don't geek it out!

Not gonna geek it out. Clipped a guard rail, dinged rt front fender, header panel between pop up headlights, headlight cover, and bumper cover. No frame damage. Got eBay replacement parts, ready to paint and bolt on. No frame damage.

I may make duplicate parts of fiberglass or high impact plastic, and with those do a pop-up delete and nose job, which would give it a face more like a Carrera GT, latest Corvette, Ferrari Maranello, etc.. This one-piece fascia would use the same attach points, but better internal cooling ducting and include a Calibra-like splitter. It would include proper exit vent for the intercooler, which stock just feeds into the engine bay to find its way out somehow. Porsche did a good job with cooling inlets, but sorta forgot about efficient cooling outlets.

Undertray would be pretty easy on this car, as well as rear diffuser by simply unbolting the rear valence and using its attach points.

Wheel fairings oriented to the relative wind would streamline the wide tires, and if done right feet the brake cooling inlets.

The car could be restored to stock easily.

[aerohead]

Originally Posted by Otto

Thanks Aerohead.

I'd use all the same attach points, but where the 944 Turbo nose now breaks the natural sloping line of the hood and upper section of the panel between headlights, I'd just continue that line on down to the stagnation point. No more pop-up headlights, which are uber-draggy. Instead of long rectilinear slots for the cooling air intake, I'd consolidate that draggy design into on probably elliptical inlet at the stagnation point. Instead of a bumper cover, 2 headlight covers, and a panel between headlights, make all that one piece.

The front bumper is secured by shock absorbers, and that part would stay intact for safety reasons, as would all attach points.

Instead of separate light fixtures on each side for a headlight, 2 turn signal lights, a fog light, and a driving light down where they get sandblasted and rock chipped/broken, I'd consolidate all that into one covered fixture with the headlight, up out of the rock chip zone. Sorta a combination of Jag XKE and latest version Corvette.

This would weigh considerably less than what's on there now.

I'll check Hucho. Thanks for the suggestion.

Got any other sources of nose optimization ideas?

Everything I have basically says ignore the nose,work on the rear of the car.
Hucho refers to 'saturation',which infers that beyond a certain degree of leading edge radius,increasing the radius will return basically zero benefit.
It's my opinion that a nose should be 'idealized' as White showed in his Cd 0.24 recipe car.A full semi-circular nose ( in plan view ) with Morelli's dropped fenders,highly rounded,everything faired in under Lexan.
This would give the best sectional density,most gentle pressure gradients,average flow accelerations,minimum pressure spikes,and best quality flow aft,to allow best performance of aft-body streamlining which is TOTALLY DEPENDENT on fore-body flow.But that's just MHO.
Much of what is printed is within the context of maintaining the 'flavor' of a stylist's 'design'.
The Record Vehicles use the good stuff.
You might re-visit Solaraycer,MG EX 181,Mickey Thompson's "Pumkinseed," the Viking series of vehicles from Western Washington State Univ.
basjoos AERO CIVIC' nose wouldn't hurt.
The 'experts' will whine.Follow your inner voice.

[jamesqf]

Originally Posted by cujet

The nose of piston powered Cessna/Piper single engine aircraft are often really ugly looking. Yet, they fly without excessive drag.

That depends on your definition of "excessive". Ever try to glide one, and compare the performance to even an old Schweitzer trainer?

Seriously, though, do you suppose the lack of effect of nose aerodynamics on single-engine performance might have something to do with the propellor hanging out in front, and shielding the nose from the actual airflow?

[Otto]

The Porsche Carrerra GT, the Boxster, and the Cayman S all have virtually semi-circular nose planforms.

In profile, the Carrera GT and Boxster noses both have upper edges with a ~4-6" radius curve, the Cayman somewhat less.

Such shapes should not be too difficult to duplicate. Well-rounded and with gentle curvature, presumably they are efficient aerodynamic shapes.