Aero advantage of early S bumper over standard?

[Shaun 69 E]

I'm not 100% in love with the S front bumper on my 73 and am considering replacing it with a standard bumper. Back when I had my 84, putting on a front rubber lip made a big difference, and even a duck after that added a little more stability at higher speeds.

the standard 69-73 bumper looks like it scoops air under the car. The S has at least a cursory attempt at a spoiler.

Is there a measurable difference (by feel, stability at speed) using an S bumper over a standard one at higher speeds?

[Tom F.]

Shaun, take a look at Frere's book. He has the numbers from when Porsche originally developed the S bumper.

[robmog]

It's an "S" bumper. That automatically makes it better.

[Flieger]

From the C to E series, when the 911S was first produced with the front S air dam, front end lift decreased by 40%:

C series (1970 2.2 liter): Cd=0.408 CLf=+0.190 CLr=+0.264
E series (1972 2.4 liter): Cd=0.408 CLf=+0.107 CLr=+0.261

At 143 mph,front lift was reduced from 83 kg to 46.5 kg (183 pounds to 102.5 pounds)....

This is a fully-equipped road car (number plates, mirrors, windscreen wipers) in the Stuttgart University Wind Tunnel with a standard flat rear lid. Tests which led to the air dam also inspired the duck tail, and IROC tail for the racecars....

[Dezzmo]

The next thing ya gonna wanna do is install a red interior and mount some kick-ass driving lights

Just kidding Shaun, I know robmog really likes the "S" bumper and I did too when I first acquired my car (which had the "S") but the standard bumpers simply have a much "cleaner" look to the early cars.

I know other folks here will disagree but it's simply just a matter of personal taste. As far as a difference in handling, I couldn't help you there.

[Shaun 69 E]

This is a fully-equipped road car (number plates, mirrors, windscreen wipers) in the Stuttgart University Wind Tunnel with a standard flat rear lid. Tests which led to the air dam also inspired the duck tail, and IROC tail for the racecars....

Thank you for posting. I'm going to keep the bumper. Also going to SC quarters and RS rear bumper quarters, probably no duck.

[Flieger]

Sounds like a cool project. Please keep us updated with photos as work progresses.

[gulf908]

Shaun,
Keep the S spoiler on.
The difference you will find is driving on the freeways on a windy day.
I bought my '71 six years ago and drove without a front spoiler for a year or so and found that the S spoiler was a great help on windy days.
It is not the rock solid feel of my previous '75 Carrera with front lip and whale tail,but it is much better than the standard front panel shape that just lifts the front of the car at freeway speeds.
The freeway speeds here are 110 kph(70 mph) and I can feel the difference on a windy day.
Unfortunately this is a characteristic of our rear engined cars and we have to adapt to this by using these spoilers.All to do with the centre of gravity versus the centre of pressure,I believe.

HTH,
Dennis.

[John Fusco]

My '67 Normal with the original lumps had some very nasty front end lift when I first got her. Like a small boat on a choppy sea.
After a full suspension rebuild, slight lowering, and corner balancing ( stock 13 front sway and rubber bushings and leaving the lead in) she is stable on the highway, even in crosswinds, and able to do an admirable job keeping up with the Big Dogs and their fancy spoilers and ducktails both on the track and on a recent, un named "stroll through the mts."

Probably cheaper to just put on the S spoiler and Frere and the #'s are what they are but my guess you aren't going to be driving too much anywhere near 150 - maybe, on the Duc.
There is no substitute for a well set up suspension - no matter what kind of lights you stick on the car.

[Boulder Bob]

I had a '69 E coupe - totally stock - was scary over 90 mph

later got a '73 S (it's a Targa) - much more stable at that speed and above

I think it's the front spoiler...