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Old 06-07-2020, 07:09 PM   #1 (permalink)
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Porsche Taycan

Dr Thomas Wolf (head of Porsche aero) just sent me the tech paper on the Taycan, as presented at the 2019 FKFS conference. Very nice of him - and very exciting!

They're obviously keeping a lot under cover as despite being 28 pages long, there is a fair bit that is just skated over. However, there's certainly enough for me to do multiple videos, which I will.

But one thing immediately stands out - that shape develops a fair amount of lift but in eco mode (no rear spoiler deployment) has the lowest drag.

With the rear spoiler deployed, Cd increases substantially (from 0.22 to 0.27!) but rear lift drops to near zero.

They don't give clear CLf and CLr figures but they can be worked out pretty well by interpreting front/rear lift balance graphs. (It's complicated by the 'active' aero components - front shutters x 4 and rear spoiler).




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Last edited by JulianEdgar; 06-07-2020 at 07:15 PM..
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Old 06-10-2020, 01:31 PM   #2 (permalink)
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rear spoiler

Quote:
Originally Posted by JulianEdgar View Post
Dr Thomas Wolf (head of Porsche aero) just sent me the tech paper on the Taycan, as presented at the 2019 FKFS conference. Very nice of him - and very exciting!

They're obviously keeping a lot under cover as despite being 28 pages long, there is a fair bit that is just skated over. However, there's certainly enough for me to do multiple videos, which I will.

But one thing immediately stands out - that shape develops a fair amount of lift but in eco mode (no rear spoiler deployment) has the lowest drag.

With the rear spoiler deployed, Cd increases substantially (from 0.22 to 0.27!) but rear lift drops to near zero.

They don't give clear CLf and CLr figures but they can be worked out pretty well by interpreting front/rear lift balance graphs. (It's complicated by the 'active' aero components - front shutters x 4 and rear spoiler).



* Two inches ( 50.8 mm ) would put it about right on 'template.' It's a heavy car. Nobody has complained about high speed stability.
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Old 06-10-2020, 06:31 PM   #3 (permalink)
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Quote:
Originally Posted by aerohead View Post
* Two inches ( 50.8 mm ) would put it about right on 'template.' It's a heavy car. Nobody has complained about high speed stability.
I am sorry but this is becoming quite ridiculous.

Let's look at the actual facts.

1. As you'd expect from that high camber shape and attached flow, the Taycan has - even with the flat underfloor that would be offsetting a lot of it - front and rear lift. eg Clr = 0.16.

2. As you'd expect, that is an unacceptable amount of rear lift, so Porsche fit a rear deployable spoiler. That starts to rise from 90 km/h (56 mph). The spoiler position passes through three stages, and at its most deployed, drops CLr to 0.01 - ie basically no rear lift.

3. Nobody has complained about high-speed stability because the spoiler is deployed, massively reducing rear lift.

This idea that you keep pushing, that 'the template' will have low/no lift, is simply completely wrong. My on-road pressure measurements have shown your theory of how lift occurs on modern cars is wrong, and (what a surprise!) the Porsche Taycan shows that as well.

I don't care what you believe, but when you start leading others astray, that's not right.
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Old 06-12-2020, 11:42 AM   #4 (permalink)
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deployable spoiler

Quote:
Originally Posted by JulianEdgar View Post
I am sorry but this is becoming quite ridiculous.

Let's look at the actual facts.

1. As you'd expect from that high camber shape and attached flow, the Taycan has - even with the flat underfloor that would be offsetting a lot of it - front and rear lift. eg Clr = 0.16.

2. As you'd expect, that is an unacceptable amount of rear lift, so Porsche fit a rear deployable spoiler. That starts to rise from 90 km/h (56 mph). The spoiler position passes through three stages, and at its most deployed, drops CLr to 0.01 - ie basically no rear lift.

3. Nobody has complained about high-speed stability because the spoiler is deployed, massively reducing rear lift.

This idea that you keep pushing, that 'the template' will have low/no lift, is simply completely wrong. My on-road pressure measurements have shown your theory of how lift occurs on modern cars is wrong, and (what a surprise!) the Porsche Taycan shows that as well.

I don't care what you believe, but when you start leading others astray, that's not right.
* Volkswagen AG had to pay millions in damages to survivors of the 5-dead Audi TT owners, killed by the mutilated roofline of that car. Later production cars received a pop-up spoiler as a palliative to kill the rear lift responsible for the fatalities. And a perspicacious observer would notice that that rear spoiler reaches up to the 'template.'
* Have you calculated the amount of rear lift for the Taycan at 85- MPH? You can estimate frontal area at around 85% of gross area.
* The weight distribution is published.
* Tell us the amount of lift as compared to the static wheel loading, with two passengers and luggage.
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* As Hucho says, you'd have less drag and lift, if Porsche had simply lofted the rear contour up to where the top of the spoiler is.( as high as the depth of the separation)
* The spoiler is there because Porsche got the roofline wrong in the first place.
- the Beetle was wrong
- the New Beetle was wrong
- the New New Beetle was wrong
- the E-Bugster was wrong
- the Audi TT was wrong
- the Audi R8 was wrong
- the Bugatti EB 110 is correct
- the Porsche 911 GT1 is correct
- the VW XL1 is correct
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* Your theory of vehicle lift fails on page-2 of Hucho's text. But he told you on page-1 of the Preface that his book was about fluid mechanics. And since you have an aversion to 'gobbledeygook' it's lost on you.
* He gave you Sir Issac Newton on page-50.
* He gave you Bernouuli on page-2 and page 50, 51.
* He gave you Hoerner on page-9.
* Koenig-Fachsenfeld on page-11
* Schlicting on page-54.
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* If you'd had a single molecule of perspicacity in your constitution you'd already know that your theory of lift is physically impossible and violates all ground rules of fluid mechanics as spelled out in Hucho's text, as you present it. We can't understand that for you.
--------------------------------------------------------------------------------------
Your color photograph of the Volkswagen XL1 undergoing smoke testing is the 'smoking gun', disproving your theory. See if you can figure it out.

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