Rennteam 2.0 - EN - Forum - Re: Wings and tails - Page1

Jun 14, 2002 8:10:33 PM

RC: Rennteam Administrator; Loc: Rennteam HQ , Germany; Posts: 59581, Gallery; Registered on: Mar 26, 2002

When RC and CR meet, this is the result ...

... 334 kph (209 mph), public street, absolutely legal ... at least over here in Germany.

Sorry for the shaken image but it is pretty difficult to drive that fast with one hand only.

Before anybody is shocked: we know what we're doing, trust us. And yes, don't do it at home ... at least not if you don't know what you're doing.

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Jun 14, 2002 9:10:56 PM

VS+: Junior; Loc: Long Island, NY; Posts: 59, Gallery; Registered on: Apr 7, 2002; Reply to: RC

Hmm...

Is this a stock car? You don't need to reply

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Jun 14, 2002 9:33:04 PM

RC: Rennteam Administrator; Loc: Rennteam HQ , Germany; Posts: 59581, Gallery; Registered on: Mar 26, 2002; Reply to: VS+

Re: Hmm...

Please define "stock" car.

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Jun 15, 2002 6:48:23 AM

william: Senior; Loc: New York/Hong Kong , Hong Kong; Posts: 670, Gallery; Registered on: Apr 9, 2002; Reply to: RC

Re: When RC and CR meet, this is the result ...

You and CR....

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Jun 15, 2002 1:31:14 PM

VS+: Junior; Loc: Long Island, NY; Posts: 59, Gallery; Registered on: Apr 7, 2002; Reply to: RC

"Stock car" as described in Service Information

Technical Introduction publication PNA 488 120 - the p/n may be different in Germany but I guess you know what I mean - that overview booklet thing.

According to the boost pressure vs RPM plot on page 2-7, the boost at 6,500 should be 0.65 !

Purely hypothetically

if the boost were 1.1 you'd expect to pick up around 45 to 50 hp just from that. Of course this boost level would indicate some kind of ECU "malfunction"

If there were another "malfunction" affecting timing and fuel mixture there could be another 50 something hp on top of that.

All just pure speculations of course

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Jun 15, 2002 9:59:28 PM

pierre: Veteran; Loc: there , Switzerland; Posts: 1192, Gallery; Registered on: Apr 7, 2002; Reply to: RC

Re: When RC and CR meet, this is the result ...

...and here's my version.
Car is 996TT with H&R suspension, and that's about it. Two persons onboard (didn't take the pics by myself!) and some luggage.
:-)

Greetings,
--Pierre

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Jun 15, 2002 10:20:07 PM

RC: Rennteam Administrator; Loc: Rennteam HQ , Germany; Posts: 59581, Gallery; Registered on: Mar 26, 2002; Reply to: VS+

Re: "Stock car" as described in Service Information

Well, then I guess there must have been some sort of malfunction, right?

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Jun 16, 2002 9:35:20 PM

RC: Rennteam Administrator; Loc: Rennteam HQ , Germany; Posts: 59581, Gallery; Registered on: Mar 26, 2002; Reply to: RC

Forgot to mention ...

I forgot to mention something:
during our testdrives, we drove almost for one hour (!) speeds over 300 kph (188 mph). Sometimes we drove over 300 kph for at least one or two minutes. It was very sunny and temperature has been around 33*C. NO PROBLEMS at all with coolant temperature, oil temperature, tires or anything else. Check the coolant temperature on the picture. Unbelievable. Weissach did a marvelous job on the 996 Turbo.

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Jun 17, 2002 10:35:49 AM

MKSGR: Rennteam Moderator; Loc: Germany , Germany; Posts: 8098, Gallery; Registered on: Jun 17, 2002; Reply to: RC

Kit 3?

P.S.: Can anybody confirm the following statement: down force of the GT2 rear wing is approximately equal to the down force of the standard turbo wing - which is why the GT2 front can easily be installed without damaging the aerodynamic balance of the car.

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Jun 17, 2002 1:59:41 PM

VS+: Junior; Loc: Long Island, NY; Posts: 59, Gallery; Registered on: Apr 7, 2002; Reply to: MKSGR

Wings and tails

I have been told by several people that GT2 wing creates MORE downforce at high speeds so it is NOT safe to replace just the front or just the tail. However, all this stuff is relevant if you drive fast. For speeds even around 125 mph I would doubt that really matters?

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Jun 17, 2002 2:03:26 PM

MKSGR: Rennteam Moderator; Loc: Germany , Germany; Posts: 8098, Gallery; Registered on: Jun 17, 2002; Reply to: VS+

Re: Wings and tails

Just checked the SportAuto Nürburgring tests of turbo and GT2 again. Down force (rear wing) is 7.5kg for GT2 and 6kg for turbo. This would support the statement contained in my previous post.

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Jun 17, 2002 3:29:59 PM

VS+: Junior; Loc: Long Island, NY; Posts: 59, Gallery; Registered on: Apr 7, 2002; Reply to: MKSGR

Re: Wings and tails

Just to clarify: what speed did they measure the downforce at? As you know, this is (roughly) proportional to the square of the speed. Also, HOW did they measure the downforce? The only reliable method I know of is to use the wind tunnel and the four-corner scales.

Personaly, I would only trust the factory numbers on that. But unfortunately I don't have these numbers

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Jun 17, 2002 7:47:54 PM

RC: Rennteam Administrator; Loc: Rennteam HQ , Germany; Posts: 59581, Gallery; Registered on: Mar 26, 2002; Reply to: MKSGR

Re: Kit 3?

I could confirm this but I'm not allowed to do so.

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Jun 17, 2002 7:49:58 PM

RC: Rennteam Administrator; Loc: Rennteam HQ , Germany; Posts: 59581, Gallery; Registered on: Mar 26, 2002; Reply to: VS+

Re: Wings and tails

The GT2 wing delivers almost the same downforce as the Turbo wing as long as the GT2 wing is left alone in the factory adjusted position. And I won't say more now, already burned my tongue ...

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Jun 17, 2002 8:15:55 PM

FixedWing: Veteran; Loc:; Posts: 870, Gallery; Registered on: May 25, 2002; Reply to: RC

RC plays with fire.

Oh go on RC ... take another little taste. Hot and spicy food can be very entertaining.

Seriously, I didn't think that the GT2 wing was adjustable. Just the GT3. Am I wrong?

If so, what is the range of downforce that is possible? What is the offsetting drag?

For those considering this tread, keep in mind that these numbers are almost inconsequential. The goal is to spoil lift and not create downforce. Putting a golf bag on the back shelf will make more of a difference.

By comparison, the downforce on a modern prototype car or F1 car is more than the weight of the car even at slower speeds. In theory at least, these cars could drive inverted on the ceiling at 160 km/h.

That funny thing on the back of the Turbo is mostly for show.

S.

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Jun 17, 2002 8:30:32 PM

RC: Rennteam Administrator; Loc: Rennteam HQ , Germany; Posts: 59581, Gallery; Registered on: Mar 26, 2002; Reply to: FixedWing

Re: RC plays with fire.

The rear wing on the GT2 is adjustable. But the factory warns owners to keep their hands off as long as they don't need a different setup for the track.
In case you didn't know: the GT2 is a turbo charged GT3.

Do you really mean that the wing on the Turbo is mostly for show? Nope, it isn't for show only. You have to look at the 6 kg downforce at 200 kph in conjunction with the downforce of the front spoiler. At 300 kph, the created downforce is even much bigger. So big, that even Arnold Schwarzenegger couldn't lift the rear lid of the engine compartment at that speed.

The whole thing is actually called "aerodynamical balance".

Even the Turbo Aerokit doesn't improve aerodynamics too much and I really enjoy reading all that GT2 bodykit/Turbo aerokit myth I find on different boards.

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Jun 18, 2002 1:01:10 PM

FixedWing: Veteran; Loc:; Posts: 870, Gallery; Registered on: May 25, 2002; Reply to: RC

Re: RC plays with fire.

"In case you didn't know: the GT2 is a turbo charged GT3."

Well let's not get into this debate. There are some that would say that the GT2 is less of a Turbo rather than more of a GT3.

Personally, I like the GT3 very much but I'm not so fond of the GT2.

I find the whole downforce issue confusing. Firstly, the downforce numbers are in reference to what? Certainly the body of the 996 has natural lift to it and some sort of spoiler is necessary to counter this lift. That's why it needs spoilers at the back. But are these contraptions ("wings" might not be the right term) actually creating downforce?

I remember Porsche claiming that the spoiler on the Turbo countered, but did not eliminate, all of the lift on the Turbo but that the GT2 actually produced a very small amount of downforce. I still say that this downforce is basically inconsequential (though spoiling the lift is not).

That's my take on all of this. RC, can you add anything?

S.

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Jun 18, 2002 1:25:37 PM

RC: Rennteam Administrator; Loc: Rennteam HQ , Germany; Posts: 59581, Gallery; Registered on: Mar 26, 2002; Reply to: FixedWing

Re: RC plays with fire.

I'll try ...

The GT2 is a turbo charged GT3. Why? Because the suspension/drivetrain is pretty much GT3 with a few exceptions. The only "problem" with the GT2 is ... weight.
The only thing the GT2 has pretty much in common with the 996 Turbo is mainly the engine and the body. Compare to the 996 Turbo, the GT2 is way to expensive in my opinion.

Reference? What do you mean? You put a car in the wind tunnel and check aerodynamics. That simple. At 200 kph, the GT2 front part creates a downforce of x kg in front and the rear wing a downforce of y kg in the rear. I don't know why you're asking for a reference or speak about natural lift?! Yes, the front part and rear wing actually create this downforce. Drive a GT2 without front nose and rear wing at 250 kph or even more and you can start a career as a pilot at Lufthansa.

SPORT AUTO tested aerodynamics on the GT2 and 996 Turbo. This is why we were talking about specific kg numbers regarding the downforce or to address some of your doubts: yes, both aerodynamical packages on the GT2 AND 996 Turbo create downforce.

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Jun 18, 2002 2:59:32 PM

FixedWing: Veteran; Loc:; Posts: 870, Gallery; Registered on: May 25, 2002; Reply to: RC

Re: RC explains fire

I have to agree with your comments on the GT3 vs. GT2 vs. Turbo and especially your comments on the weight issue. I would add that even the GT3 is too heavy and that I think that another problem with the GT2 is that the power application of the Turbos makes the car more difficult to drive on the track. The turbocharger is more useful on the street.

On the lift issue ... only thing to add is a link to Porsche's web page on the topic:

http://www.porsche.com/english/911/gt2/aerodynamics/default.htm

Here they talk about cancelling lift and minimizing drag. That's one of the main reasons I think that the GT2 "wing" is a spoiler really (though the adjustability suggests otherwise). Ditto the Turbo. But I think that the GT3 wing is more of a wing (which explains the additional drag of this device). Wings add tremendously to the induced drag.

Oh, the front air dam will affect both the front and the back of the car. There is no defuser which would help a lot but normal graphs of the effect of a spoiler show improvements at the front and back.

I haven't seen the article you refer to. I would love to see more real figures on this stuff!!! (Go on RC, tell us what you know!!)

I thought about flying for the USAF once but Luftansa was never an option. Wouldn't want to reconsider my decision now.

S.

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Jun 18, 2002 9:01:24 PM

RC: Rennteam Administrator; Loc: Rennteam HQ , Germany; Posts: 59581, Gallery; Registered on: Mar 26, 2002; Reply to: FixedWing

Re: RC explains fire

Well, doesn't the link on Porsche's website say "it also generates optimum downforce on both the front and rear axles."?

The weight of the GT3 is not much of a problem. It is pretty easy to reduce weight on the GT3. But try this on the GT2 ... almost impossible.

SPORT AUTO tested the 996 Turbo and the GT2 in the wind tunnel, here are the results as far as I have them:
996 Turbo -> 6 kg downforce on the rear at 200 kph.
GT2 -> 8 kg downforce on the rear at 200 kph.
So there is no real advantage of the GT2 body kit on the street, not even at high speeds.
Now it is very understandable that the Porsche Marketing department wants to make the GT2 look better aerodynamically.

And actually they're right: you can adjust the rear wing from 1* to 6*.

What is very interesting: the GT3 street version has 0 kg lift/downforce at 200 kph, pretty neutral.
The GT3 Cup version has 19 kg downforce on the rear at 200 kph. There is no lift on 996 Turbo/GT2 on the front.

To give you an comparison: the Mercedes CLK 55 AMG produces 43 kg (!) lift on the rear at 200 kph. Ouch.

I know that aerodynamical balance is the most important thing but I can assure you that 996 Turbo and GT2 are perfectly balanced.

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Jun 19, 2002 12:35:58 AM

VS+: Junior; Loc: Long Island, NY; Posts: 59, Gallery; Registered on: Apr 7, 2002; Reply to: RC

And the conclusion is?

From the above discussion it seems pretty safe to conclude that ANY combination of GT2/Turbo nose/tail is acceptable!
The difference between 6kg and 8kg at 200 kph is pretty negligible.

BTW, RC: at 300 kph the downforce becomes 13.5kg and 17kg respectively for Turbo and GT2. Not bad but I guess Arnie could lift that with his pinkie

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Jun 19, 2002 2:04:41 AM

FixedWing: Veteran; Loc:; Posts: 870, Gallery; Registered on: May 25, 2002; Reply to: VS+

Arnie's pinkie

Humm .... even with these latest numbers for downforce at 300 km/h it is still possible that RC is right about poor Arnie.

The measurement is for the net downforce as measured at the wheels. But this downforce is a combination of 1) natural lift due to the wing-like shape of the 996 body, 2) downforce due to the front spoiler preventing airflow under the car (yes, this will create downforce at the back as well as the front) and 3) downforce due to the rear wing/spoiler. The first is positive and quite big. I'm not sure how much of a difference the second makes. So the third must be responsible for the remainder. Just to pick some numbers, it is quite possible that the natural lift of the car at 300 km/h is 200 kg. Let's guess that the front spoiler causes 50 kg of downforce at the back of the car. If the net is 8kg down then the rear spoiler/wing would be responsible for 158 kg of downforce -- more than Arnie's pinkie could handle. The numbers are guesses but the point is that the downforce is a combination of factors and it is not possible to just isolate the rear spoiler/wing and say that that is the cause.

What I'm curious about is what happens if the rear wing is adjusted from 1 to 5 degrees. I would guess that it might increase the downforce but the induced drag would go up considerably. I bet the top speed will drop dramatically.

The wing on the back of the GT3-RS is a real wing and that wing will have a considerable impact on the potential top speed of the car. Wings carry a high cost.

One of the big problems for the 996 is that it is impossible to mount a defuser with a rear flat-6 engine. Good reason alone to consider some sort of V engine for the next generation (the same thing happened in F1 racing years ago with Ferrari's flat-12 engine being dominant until underbody aerodynamics appeared).

S.

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Jun 19, 2002 5:54:22 PM

VS+: Junior; Loc: Long Island, NY; Posts: 59, Gallery; Registered on: Apr 7, 2002; Reply to: FixedWing

Arnie may have a chance!

I have not read that article so it wasn't clear to me if they were talking about downforce from the spoiler OR about total lift at the rear axle. Thanks for clearing this up!

However, please observe that unlike with a wing, it is not true that when you add a spoiler the total lift is a sum of (basically unchanged) lift from the body plus downforce from the wing. Just as you said, the spoiler changes the airflow at the rear of the body. So the total lift in this case is NOT a sum of the "naked body" lift and the "downforce" from the spoiler. As a result, the decklid is not necessarily pushed down with a force of 100-150 kg as it is on a winged Cup car. Arnie may still have a chance

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Jun 19, 2002 6:16:01 PM

RC: Rennteam Administrator; Loc: Rennteam HQ , Germany; Posts: 59581, Gallery; Registered on: Mar 26, 2002; Reply to: VS+

My conclusion is ...

... that I have to work on my English and that I really have to apologize for some confusion I might have created.

Lift, downforce, drag ... sometimes it is pretty difficult for me to explain a few simple things in English. So please be gentle guys ... I do my best.

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Jun 19, 2002 8:35:41 PM

FixedWing: Veteran; Loc:; Posts: 870, Gallery; Registered on: May 25, 2002; Reply to: VS+

Arnie is my hero ...

VS: True. I was simplifying to make my point.

As I understand it, the job of a spoiler is to disturb the airflow over the car. If the car is a giant wing then the spoiler in effect stalls that wing so that it doesn't create lift anymore. And as you point out, a spoiler counters the lift wherever it is and doesn't add a counteracting downforce.

A wing on the other hand does create lift (downwards in the case of a car).

That's why a spoiler can be small and still do the job and why a spoiler doesn't create much additional drag. A real wing on the other hand creates massive amounts of drag. And that's why I think that Porsche is interested in adding a spoiler to these cars and not a wing (though marketing dictates that it be called otherwise).

S.

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Jun 19, 2002 8:47:00 PM

FixedWing: Veteran; Loc:; Posts: 870, Gallery; Registered on: May 25, 2002; Reply to: RC

Re: My conclusion is ...

RC:

Don't be so hard on yourself! Even in English these are difficult terms that a large percentage of the population doesn't understand.

In my own case, I've read a bit, I'm interested in this stuff and its application to automobiles and I start out as being a pilot (note my nickname!). So don't be surprised.

And as I think I've said before, I believe that the marketing people are intentionally confusing some of this stuff for their own purposes.

S.

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Jun 19, 2002 10:14:57 PM

RC: Rennteam Administrator; Loc: Rennteam HQ , Germany; Posts: 59581, Gallery; Registered on: Mar 26, 2002; Reply to: FixedWing

Re: My conclusion is ...

Marketing and confusion are brothers in arms.

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Crown

Forum - Thread

When RC and CR meet, this is the result ...

Hmm...

Re: Hmm...

Re: When RC and CR meet, this is the result ...

"Stock car" as described in Service Information

Re: When RC and CR meet, this is the result ...

Re: "Stock car" as described in Service Information

Forgot to mention ...

Kit 3?

Wings and tails

Re: Wings and tails

Re: Wings and tails

Re: Kit 3?

Re: Wings and tails

RC plays with fire.

Re: RC plays with fire.

Re: RC plays with fire.

Re: RC plays with fire.

Re: RC explains fire

Re: RC explains fire

And the conclusion is?

Arnie's pinkie

Arnie may have a chance!

My conclusion is ...

Arnie is my hero ...

Re: My conclusion is ...

Re: My conclusion is ...

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