Poor Man's Aero Package, Version 2

[oldE]

Jack,
Your vision of the long-hood always impresses me. The combination of early grace and later muscle and technology blows most of us away.
Black Beauty, I think is entering a new stage, in reflection of race cars of the sixties and seventies. At the beginning of that period, they were lithe, almost sensual creations of aluminum. By the end, the cars had become aerodynamic devices, their design dominated by the imperative of moving the car through the molecules of the atmosphere as efficiently as possible. So much was gained in that short time. So much was lost.
As BB enters this new phase in your vision, she will no doubt be a faster, better racing tool. I fear she will lose some of the stunningly beautiful grace she possessed, rather in the way a beautiful woman's aspect changes when she developes her muscles to the extent she can be a world-class weightlifter. Is such a goal to be spurned? No. But many who once thought her beautiful will remember how she looked.
Thank you for sharing Black Beauty with us in all her aspects.
Les

[Jack Olsen]

Thanks. The picture of my car next to Tyson Schmidt's 1969 does show the change from the original 911 design. In a perfect world, I'd have my RSR-bodied car and also a narrow one like Tyson's, preferably with steel wheels.

My car's not going to change in any significant ways in the forseeable future. It'll continue to get sandblasted by track use until I get another coat of paint put on it. But it'll always be more of a 'work dog' than a 'show dog.' If I can get a decent data-acquisition setup on it, I'd like to continue to tune and refine it as a fast, dual-purpose, street-tired car.

And even with the blasted paint, the right photographer can still make it look good. Here's a pair of pictures by Zachary Mayne that I really like:

[911S Targa]

I love this pic. Love how that front tire is off the track.

[Rob Channell]

How about that stuff the rally guys use that is kind of a rubber or plastic with a teflon coating to make it more likely to slide over an obstacle than to hook it? Let it bend down from the bottom and skid across the ground during your nose down braking. It will wear itself down to the appropriate level.

[Jack Olsen]

I had some left-over aluminum, so I'm doing a thrown-together diffuser for the rear. Next step is to fabricate mounts, which will tuck it up a little more on the ends. Then paint.

Any suggestions?

The bottoms of the vertical fins will be parallel with the ground. Being up on the rear ramps kind of makes it look otherwise.

[randywebb]

"Any suggestions?"

Yes. Don't paint yet. Instead buy some wool tufts and tape... You want to try and trace out the air flow first.

It could be that some of the areas want to be channels and others want to be bluff.

And... it's not clear that vortices from the wheels want to be kept away from the center...

Also, what does the leading edge look like? Is any air going to be scooped up above this piece?... where it can't exit?

[Tspringer]

You sure thats not going to impede the flow of air coming out from around the cylinders?

Do you have any hard data, or even WAG data that supports that all this really cool looking stuff is actually lowering your lap times at all?

I am assuming that next your going to install a full length sheet aluminum under tray. Then cut some venturi tunnels into it, channel the air up through the floor of the car, install some large blower fans to suck the air up and exit it out the rear window?

I would suggest you convert the car to a single central seat for the driver. Better weight distribution, and then you will have more room for large venturi tunnels on either side of the driver and the big fans you will need to create the vacuum effect.

I can see it now.... Jack driving BBII upside down on the ceiling of various tunnels.

[Craig 930 RS]

Jack -

Can we see a pic of the rear while on the ground?

[ted]

I don't know a thing about ground effects. Thanks for sharing, looks interesting. Looking forward to your test results.

[350HP930]

LOL, jack has been bitten by the aero and metalworking bug at the same time.

[tommy5305]

Won't that effect cooling ?

[Oldporsche]

The pit crew for the Whittington Brothers (Mid 80's) simply fiberglassed a vertical layer to the lower front of the spoiler. Next they took it out to the track and ran it. The track shaved off the excess material.

To get it back into the trailer, they would remove the nose.

David Duffield

[Craig 930 RS]

Drove at the track with a Ford GT. Was interesting to see the debris jostled up & about by the rear diffuser -

[TRE Cup]

well. that diffuser is plain wicked looking- BUT as others have posted "what about the cooling?" indeed. Look at the lower shield on the 964 and 993 for guidance. i would recommend a small lip on each cylinder head rectangular opening exit so you aid the air to escape the cylinders rather than create a positive pressure pocket. You will need to do some back to back testing- coast down tests, max rpm to see if that set up is effective.

[Jack Olsen]

Okay, progress update: I went out for more aluminum. I bridged the new metal pieces to the plastic sheet on the underside of the car that stops at the rear swaybar. I also cut out exits for the cylinder cooling, using a 964 undertray as a guide, and making the holes slightly larger. I tried to mimic the way the exit edge of the cooling holes on the 964 tray has a ridge -- which I presume prevents the "positive pressure pocker" TRE Cup is talking about.

But I'm nervous about cylinder head temps. Is there a quick and dirty way to wire up a cylinder head temp gauge to see if using this would result in cooking my motor?

Down on the ground, it definitely looks aggressive (and un-street-worthy). I'll take some pictures tomorrow.

[Bill Verburg]

It looks neat but if these guys aren't worried why should you?

[350HP930]

Originally posted by Jack Olsen
But I'm nervous about cylinder head temps. Is there a quick and dirty way to wire up a cylinder head temp gauge to see if using this would result in cooking my motor?

The least intrusive temporary head temp monifor would be an under plug thermocouple, but I am not sure if one can be squeezed into a 911 spark plug hole along with a plug socket.



Isn't that transplant of your's a modern engine with a mounting area on one of the heads for the motronic head temp sensor?

[Jack Olsen]

Originally posted by Bill Verburg
It looks neat but if these guys aren't worried why should you?

Sure, but those guys have much more aerodynamic bodies on their cars, and a lot more horsepower.

[Tspringer]

Jack....

I have to tell you, you have made the list with this latest diffuser thing.

Here is a link to the NASA boards thread about "You might be a road racer if...." thread. Lots of funny stuff there.

I'll have to post this one:

You have actually constructed, installed and driven around with advanced F1 style aerodynamics on your street/track car including a full rear diffuser. Then you evaluated your improved commute times to work and planned wind tunnel time to fine tune your aero package.

True story, you saw it right here on pelican parts!

[kaisen]

Originally posted by Bill Verburg
It looks neat but if these guys aren't worried why should you?

Umm.....well those cars are water cooled.....!?