downforce v weigt/drag

[BReyes]

downforce v weigt/drag

What do you think the outcome on adding a carrera tail to 87 targa narrow body 3.2. The top is always done when i drive it. Oh yeah it rains, quick pull over.

Thank you.

[Geronimo '74]

You'll get more downforce, most likely + some additional kilos

[Bill Verburg]

The only aero packages that develop dowb force are the ones developed for the 993RS and later models, they include the basic design along w/ front, rear and side appendages to manage aero characteristics.

the best you can expect is reduction of lift, there is little or no increase in drag from the factory aero packages as they are appendages and not true wings, the appendages are able to manage air in such a way so as to not increase drag.

[Wil Ferch]

Bill:

....my highly-respected internet friend......

(biting tongue).... you say " The only aero packages that develop down force are the ones developed for the 993RS and... "

Please...insert the word "net" between "develop" and "down".... otherwise we'll be back to the old semantics chestnut of using words "downforce" vs. "decreasing lift".....


Like "going into debt"...vs. "making negative profit"...

- Wil


EDIT - absolutely correct..the tail appendages that contribute to downforce may not necessarily increase drag. Porsche specs of the day show a higher top speed by about 1-3 mph when there was a factory tail installed.

[Bill Verburg]

Will, we all know you have a fetish about this, I feel no need to modify my post.

If you wish to quibble, be my guest

if this makes you happy so be it
'net' force up is lft

'net' force down in downforce

there are numerous components to all of them, if you feel that adding the word 'net' makes a significant difference to the meaning you have done so and may continue to post about it to your hearts content.

[Wil Ferch]

Point being all tails "create" downforce....some simply more than others such that some are felt as a "net" downforce result on the car....

Not a fetish...but an irritation whenever we hear..."it doesn't create downforce, it only lessens lift"....

The only way around this is the concept of "net"...simple. I know you and I have been through this, and for some reason you seem to think it is nonsense....but it should help clarify the issue to others.

OK...done....standing down ....

Wil

[island911]

hmmm, it seems that this arguement is cycling more often, than years ago.

. .. so I want in.


Spoilers spoil (ie ruin/ kill / destroy/ eclipse ..) LIFT.

AND since LIFT produces DRAG, a spoiler (reducing lift) can also reduce drag. (unless you are into wearing womens clothes . . )

[Wil Ferch]

Not taking ther bait...I'm polite ( I think) and DONE ......

Wil

[island911]

Originally posted by Wil Ferch
Not taking the bait...

was it the " wearing womens clothes" remark?

[randywebb]

It would be useful if we all used the same words to mean the same things...

[island911]

Hey, don't blame me. . .. Bill V used "fetish" and "drag" first.


. ..or do you mean "less-lift and downforce" ?

[Rex Walter]

I really don't think I want to get into this thread, with all the fetishes and womens clothes and all, but.....

AND since LIFT produces DRAG, a spoiler (reducing lift) can also reduce drag.

Lift is created when the airflow follows the surface, or the top of the car in this case. Spoilers get in the way of the airflow, and cause it to separate off the surface, so it cannot produce as much lift, and they cause relatively large amounts of drag, due to the separated flow. If Porsche did their homework, and created a spoiler that both reduces lift, and reduces drag, they did very well. Better than most manufactures.

Rex

[Wil Ferch]

They did..... see earlier post on higher top speed with tail-equipped cars. I believe it's also in Frere's book as well as Excellence by Ludwigsen.

Wil

[jluetjen]

Originally posted by Wil Ferch

EDIT - absolutely correct..the tail appendages that contribute to downforce may not necessarily increase drag. Porsche specs of the day show a higher top speed by about 1-3 mph when there was a factory tail installed.

Actually Wil's onto a good point. You can't get something for nothing. If you have lift (or conversely downforce), you'll generally have in drag. In so much as a spoiler (like a duck-tail) decreases lift, it also decreases drag. But as soon as you start to generate downforce, the drag will start to go back up again. If you're good, you'll be able to increase downforce more then your increasing drag. But where there's lift/downforce -- there's drag. It's a fact of life (and I believe physics).

[Rex Walter]

Porsche specs of the day show a higher top speed by about 1-3 mph when there was a factory tail installed.

What type of tail are they talking about in the above quote? To me, the duck-tail is a classic spoiler, causing the airflow to separate early, and resulting in a relatively large amount of drag. I imagine that Porsche went away from this type of tail because of the drag, and developed better solutions that both reduced lift, and reduced drag.

Rex

[masraum]

Oh Rex. We have numbers, the classic front lip/rear spoiler on a 911 of duck or whale variety reduce lift to nearly 0 and also reduce Cd. We have numbers, hang on, I'll find them.

[masraum]

here's the first thing that I found

Originally posted by oldE

It has been demonstrated you can reduce the effects of drag by acheiving separation of the air flow by using a device such as a duck tail a spoiler or a Kamm tail. As mentioned above, Paul Frere quotes research figures gained from testing. The duck tail added to a Carrera RS with a standard air dam reduced the drag co-efficient from .409 to .397 (a small amount to be sure) but had the more noteworthy effect of reducing lift from320 lbs to 93 lbs at 152mph. (Quoted from Porsche 911 story, p 227)
Les

[masraum]

and you may want to check out these threads

Downforce
911 rake front/rear
major effect of the Ducktail is to reduce drag!.

[mikequig]

Many of us who are club racing are running big GT racing style front spoilers in combination with some version of tail. We then mount our oil coolers in these front spoilers which in my mind then creates a system that is vulnerable to damage from even trailer loading much less some unintended excursion. Addtionally, I think we have created a great deal of drag.

I am considering installing a cooler inside each fender, losing the big front spoiler and going back to the front lip spoiler that so many SC's came with.

What does the collective consciousness think. Will it reduce drag, increase top speed and still keep the motor cool?

Mike Quigley
911 Euro SC "F"

[masraum]

The best way to keep the motor cool is with the cooler in the front spoiler. Most people who try multiple coolers and fender setups end up spending money on those setups and eventually end up with a front cooler.