Speedster drag coefficient

Does anyone know , with any certainty if there are any measurements of the early speedsters air efficiency. Drag is such a selling point with the modern cars these days. The shape of the early speedster would be of interest

The 350Z reportedly has a drag coefficient of .034, and has comparable lines. I read a writeup in forsalebyowner.com with a walkaround on the Z. Here's a link -- including a by-name reference to the Speedster:

http://cars.forsalebyowner.com/review.php?iReviewID=3714

Its not really applicable. Really different cars. I read a thread acouple of years ago on the 356 registry that the speedster posted an incredible .28-29. Considering it 50's design I found it hard to believe.

The coupe had a lot lower drag than the open cars so I think the low number is for a coupe. Think that was pretty accurate.

I'm not surprised by those findings; the car's shape is so smooth.

Especially since it was designed without the benefit of a windtunnel.
Designer Erwin Komenda?? Also did the 550. Eventually they did put it in a wind tunnel and proved what he had predicted all along;)

The first 911 had a .032, and the 904 a .034. I doubt if the 356 coupe was close to those numbers.

I would think it had the drag of a brick.

This site has a coupe at .034
http://www.carfolio.com/specifications/models/car/?car=35277&Porsche

I can believe the 0.34. I've read several places that one reason the 356 was such a good performer was that it was so aerodynamic. You can look at it now and see that the non-flush trip and such would generate some turbulence, but the overall shape is very good for low drag. I would imagine that he tapered rear does result in some high speed lift, however.

It does resemble the cross-section of a wing. I imagine it is possible for the footprint of the tires to shrink at speed ...

The question was about a speedster not the coupe. I don't think our convertibles are efficient
at all. Good looking=yes. Cory, this design would lift at high speeds due to the shape.
Saab was the first (if memory serves) to use the wind tunnel during design. Their 9000
series had a drag co. of 30 and thats what they named the car 30cd. I doubt a speedster
comes close.

The question was about a speedster not the coupe. I don't think our convertibles are efficient
at all. Good looking=yes. Cory, this design would lift at high speeds due to the shape.
Saab was the first (if memory serves) to use the wind tunnel during design. Their 9000
series had a drag co. of 30 and thats what they named the car 30cd. I doubt a speedster
comes close.

Carfolio site is very cool, shows a coefficient of 0.31 on the 1953 356 pre A coupe;) They (E. Komenda et.al)actually afixed wool strings all over the body and " drove fast" to visualize the aero fx-- poor mans wind tunnel!

For the record, tires do "shrink" at speed - depending on how you look at it. Especially tall profile tires. Tires are acted upon by centrifical force the faster they are turned. The weight of the tread slightly stretches the sidewall out making the width of the tire slightly narrower and the height slightly greater.

Don't believe me? Watch a top fuel dragster. On launch the tires squat down short and wide (fairly low pressure) and when turned fast during the burnoff, the tires sidewall GROWS much taller and the width is visibly more narrow. This is a dramatic visual of what happens to a lesser degree in other tires.

Sounds crazy, but it is absolutely true.
angela

Someone once posted a drag number of .44 for the Cabriolet Convertible, but I can't remember where it was posted. I just remember it as being someone that I felt was reputable.

At 110mph in my Cabriolet, which isn't exactly aerodynamically the same as the original, if you don't have the tonneau on the convertible top is literally sucked upward into the air almost 12". I only realized I had a problem when I looked in my rear view mirror and saw nothing but black....I wasn't sure what was going on at first, but as I slowed down I realized it was the top trying to put itself up.

Three years ago, I had a Raby Type IV powered CMC with many suspension upgrades, all was well until 110 mph instantly there was a dramatic change in down force, too much air would get under the car causing it to sway 1" - 2" from side to side.....not good.

That's what a wing shaped car does. Air dams and some sort of spoiler on the rear to set up some turbulance (Some roll bar configurations work to some extant) are necessary if you're gonna go that fast.
ed

...OMG! Going 110mph+ in a tiny open-top fiberglass car riding on 40 year-old suspension technology! That would be like sledding Mt. Everest in a snow-saucer! COOL!!

The strings to the body are called a flutter test. They show different airflow over the surface of the car. i.e., behind the pacakge tray the air is actually moving forward into the cockpit to fill the vacuum created by the windscreen. Thus the draft on the back of our neck. A hood scoop on the shark (68-82) vette actually opened at the back of the hood in from to the windscreen to collect that excess air pressure.

Alan, what was the fix? I'm about to have that problem!
I'd ultimately like to make a worm-gear for my decklid, ala the Crossfire or the Carerra. A manual crank to put on my tunnel would be nice.
No, Jim ... a manual crank.
:

Cory wrote:

"Alan, what was the fix?"

I slowed down, seriously.....

I don't notice any change in the way my car drives at hi speeds. I suspect the mid-engine design is keeping the front end from getting light, like it would in a rear engine design.

I would guess that I have had my car going as fast as any 356 has ever gone and while the handling doesn't seem to be effected, you can practically vacuum out the car with just the negative air pressure created above the car.

I plan to take it to the new local track this spring or maybe even yet this fall and see what it will really do, but I'm working everyday right now and just don't have the time.

Hmmm, just what I need is the Emory 356 coupe....as follows....


Year: 1955 Mileage: 2000 summer miles
Body Style: 356B Coupe ('60-'63) Engine: 1.5 litre 160 HP
Drive Train: rea wheel drive Transmission: 901 4 speed gear box
Exterior Color: silver metallic
Interior Color: tan leather sport seats
Price: $275,000.00
Contact Info:
For more information, contact
Richard Sloan at 1.203.675.3235
or richard@sloancars.com ...


Options and Notes:
This incredible Porsche is a 1955 356 Pre A Coupe finished in Laplatasiber Porsche Glasurit silver metallic paint fitted on a coupe built by the legendary Emory Motorsports and Parts Obsolete Vintage Racing Team of Oregon. This 356 Special was featured in a article in the November 2003 issue of Excellence 911 Porsche magazine. It was one of two (2) cars made with the other 356 Special shown at Porsches 50th Anniversary at Pebble Beach. This car was shown at Rennsport 2004 in Daytona,Florida, This " one off " 356 is fitted a Porsche 4 cylinder 911 1.5 liter engine boasting 160 HP mated to a five speed gear box, lexan windows and a sunroof. The chassis and body was executed by Emory Motorsports including Brembo mono black alloy brakes and spindles by Wright Drop of San Diego,CA .The front and rear suspensions are totally adjustable up and down and side to side.The rear suspension is a brand new Porsche NOS early 911 rear chassis integrated into the tubular frame. The engine is by Advanced Performance who makes 4 cylinder 911 Porsche engine ( stamped as POLO). It is overhead cam twin plug dry sump engine with a 15 quart Carrera style system. The engine is mated to a 901 5 speed gear box with a hydraulic clutch and an aluminum GT flywheel, 904 main shaft with special cut gears (one off ), and a new vintage twenty (20) gallon GT fuel cell. This car weights only 1770 lbs. dry weight .This remarkable engine has 100 HP per liter and is totally streetable.The instruments are Porsche 904 VDO ( first Porsche racing gauges) with a 8000 rpm tach. The car has a three (3) zone haylon fire suppression system with a thru - hood racing filler, racing harnesses and a Borsch external racing cut off system. The pedal cluster and hand brake are aluminum Porsche 550 Spyder pieces. The seats are RSK Spyder customs buckets honey wheat in color. The wheels are custom built Harvey Weidman 16 x 7 inch alloy rims which were used as RS America spare wheels before Weidman. Before transformation this car was a rust free one (1) owner never hit original 1955 356 pre A coupe with extensive modifications. The exhaust which exits the left of the body is a one (1) off by the founder of Bursh Racing Exhaust. This car was purpose built for road racing events and take on the World Land speed record for a 1500 CC GT engine.

by the way the record is "245.64 mph for the 1500cc class" don't think this coupe will do that.....

Well, thats a goal, but not one I'm willng to shoot for, heck my tires aren't rated for even close to that, and the driver is not rated brave enought for that.

The drag data is available in the book "Porsche 356, Driving in its Purest Form" by Dirk-Michael Conradt.

The engineers at Porsche put a bunch of their 356s into the wind tunnell in the 1980s to see what they came out at. Depending on the configuration (coupe, speedster, etc.), the drag coefficient ranges from 0.296 to 0.46.

The book has a whole table of data.