Aero comparison of electric charge doors vs. manual

rs38

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I think it was alread discussed in this forum:

how much are the closed air vents beneath the A pillar degrading the good aerodynamics of the Taycan?

We will never get quite (precise) answers unless we measure and test ourselves :)

He are some results of tests done with a 2020 Taycan 4S on custom, quite open, 21" wheels, manual charging doors and small battery done on the autobahn.
The tests were done at night, warm conditions, dry and constant cruise controlled.

It's not perfectly scientific but pretty much what you can do as an enthusiast with car scanner app and a smart phone.

there are two tests, each covered constant speed at 200kph (effectively 196,x) and each coasting down to 100kph.

One test was done with open air vents and one with closed (taped).
Can you figure out, which was which?

The abstract of the tests is shown in the red markers and shows the differences in percent between test 1 and 2 of the relevant measurements. It shows more or less nothing than a deviation +/- of the expected observational error.

Edit: improved text and PDF
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Jayyvr890

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Can you maybe explain a little more for us regular people? I understand next to nothing in that document lol
 

Fish Fingers

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I am also a bit lost looking at that document*.

What were the end results (in layman's terms?).

Keen to know the answer as it does crop up fairly regularly on this forum and nobody has any idea what the open/closed vent difference amounts to.

* I believe NASA are having a few issues with that rocket. You should offer to help them out.
😁
 

bsclywilly

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It looks like he did two tests with each configuration. The first is constant speed consumption where lower Wh/100km the better (less drag). The raw number difference looks negligible but should be normalized for velocity which would take a bit of math to post process.

The second test are coast down runs where a higher Wh/100km is better but it’s hard to compare because the elevation profiles are so different and the results have a significant amount of spread. It looks like on test 1 he did 7 coast down attempts but 2 of them were aborted so the road profile was not as comparable between the two configs.

Anyways from the raw numbers looks like test 1 was the lower drag so you might assume this was with the vents open? The fact that he’s running with aftermarket wheels may also bring into question their interaction with the airflow past the wheel well.

Also, not drag related, but the side vents presumably would lower the wheel well pressure which may improve airflow past the radiators for improved cooling. @rs38, could your next test involve pressure and a thermocouple array up and downstream of the radiators?:idea:
 


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rs38

rs38

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it was kind of intended to omit the result, because there is no result other than: you cannot measure it, because it's too small.

it took quite some time to analyze the car scanner data and I mix a lot of german / english words (even car scanner does with csv export columns to localize it). But now the Jupyter stuff is more or less reusable and I see some lacking of context :)


I will improve the doc and add some explanations during the day!
 

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I've always "felt"/assumed that because the Turbo S comes with the electric charge port as standard and therefore has blocked vents – it can't be making too much of a difference.

I wouldn't think Porsche would purposefully cripple their highest-performance model by a meaningful amount.
 

f1eng

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IME, which is all with racing cars, mainly Formula 1 but a bit of Indy car and a couple of Le Mans sports cars small changes can only be reliably measured in a wind tunnel.

Back in the late 1970s where a week in the wind tunnel testing my ideas (me and a technician) would sometimes yield 30% performance gain the driver almost always noticed the difference but only felt the extra downforce, drag was visible on speed traces if the gain was big enough and all gain was obvious from better lap time.

Latterly even though they have 130 guys working full time on aero rather than one part time :) the gains are too small to feel or, sometimes, to see consistently on the stopwatch. One just has to keep making incremental gains and trusting the data with gains evident only over a long period.

Bravo for doing this test as well as you could @rs38 it is by far the best test I have seen on an internet forum and way better than any of the YouTube reviewers I have seen manage.

Having written that I still wouldn't choose the electric ones, even if the detriment is small, since it is also added weight and 2 more things to go wrong and completely un-needed since one has to be next to the hatch to plug in anyway.

Even as a gadget fan it is too negative in principle for me.
 


f1eng

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I've always "felt"/assumed that because the Turbo S comes with the electric charge port as standard and therefore has blocked vents – it can't be making too much of a difference.

I wouldn't think Porsche would purposefully cripple their highest-performance model by a meaningful amount.
A bit of extra drag on the least efficient model wouldn't be high on the designer's agenda :) .
 
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rs38

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I've always "felt"/assumed that because the Turbo S comes with the electric charge port as standard and therefore has blocked vents – it can't be making too much of a difference.
Porsche's officially says the Turbo S has a cw of 0,25 whereas the Turbo has 0,22 which is quite a big relative difference. But the Turbo S also has the Mission E as stock wheels which look nice but are very open and therefore produce negative drag and ventilation(!) forces, whereas the smaller 20" Turbo stock wheel is quite optimised.

The test drive procedure wasn't done by myself but Mr. X promised to conduct another wheel comparison run in the near future :)

The same is true for finding consumptions optimizations with pre and post WNJ8 with a similar procedure but slower test layout (more fitting for slow WLTP)
 
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rs38

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IME, which is all with racing cars, mainly Formula 1 but a bit of Indy car and a couple of Le Mans sports cars small changes can only be reliably measured in a wind tunnel.
or much easier with CFD nowadays and only finally check the results within an expensive wind tunnel.

improving the aero are many, many tiny steps that may eventually result in a noticeable result, but my idea was to answer the question of omitting the electric charge doors can have an effect you really would notice somehow in the decimals of you long term consumption, and I doubt it very much, although Porsche's Nardo test cars had manual doors.


BTW: I edited the first introducing text and the PDF to make it a bit clearer I hope.
 

f1eng

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r much easier with CFD nowadays and only finally check the results within an expensive wind tunnel.
Indeed, but there is still a big question of correlation, particularly with open wheeled cars where 50% of the effort goes into minimising the detrimental effect of the (unsteady) wheel wake which CFD models poorly IME.
It is a lot of work and “fudge factors” to make the CFD model match the actual surface flow and the forces are not that accurately predicted by CFD either.

It is excellent for duct flow and front wing on a F1 car, from there back less so and the number of elements needed near the ground to accurately model the flow when the car is low - very important - is so great many teams don’t do it properly because of the computing limit in the rules.
It is a false economy IMO as shown by their surprise at the return of aero instability with the new rules this year 🤦‍♂️
 

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Have to say i can‘t believe it would have much impact.

Personally, i love the electric charging ports and the way it can be opened as soon as i arrive. It just means that i can plug in straight away and i think it looks great opening and closing with a touch.

Also, i have seen some vandalism on EVs and the flap is the thing to break off!

My cousin has the manual version and he has optioned the electric charge ports on the GTS he has ordered.

The push button flaps look cheap Imo but it’s personal choice and cost.
 

gnop1950

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Have to say i can‘t believe it would have much impact.

Personally, i love the electric charging ports and the way it can be opened as soon as i arrive. It just means that i can plug in straight away and i think it looks great opening and closing with a touch.

Also, i have seen some vandalism on EVs and the flap is the thing to break off!

My cousin has the manual version and he has optioned the electric charge ports on the GTS he has ordered.

The push button flaps look cheap Imo but it’s personal choice and cost.
I have to agree, I too really like the Power Port Charge Cover. The test was well done but it would need to be a pretty big difference for me personally to forego the power port covers. I just like the way they look and operate.
 
 




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