I've always wondered - when you take the roof off a car, how much slower is it compared to the coupe version of the same car? To find out, we lined up a 2022 Porsche 911 Turbo (992) next to a 2022 Porsche 911 Turbo Cabriolet (992) to see exactly what the story is. The end result is me being very, very confused!
Convertible CFD study by Serkan Solmaz: http://sersol.weebly.com/workshop/convertible-aerodynamics
Let me know how you explain the science in the comments section.
More Porsche content: https://www.carexpert.com.au/porsche
More Porsche 911 content: https://www.carexpert.com.au/porsche/911
Skip Ahead:
Intro: 00:00
The Science: 01:12
Cab v Coupe baseline drag race: 03:22
Cab v Coupe same weight drag race: 07:11
Verdict: 12:44
We review every new car on the market, bust car myths, cover the latest car tech and answer your burning questions.
Whether you need new car advice, purchase validation or simply love learning more about new cars and technology, we are your car experts.
Subscribe to Car Expert: https://www.youtube.com/channel/UC7DvMhvy3H7ntEgn9n3xQcQ?sub_confirmation=1
You'll find us dropping new video content three times a week. If you'd like to ask a question about one of our videos, simply leave us a comment. If you'd like to give us any feedback on our content, feel free to email us, or alternatively, hit us up on social media.
Finally, we want this channel to grow with your support and feedback. If there's anything you don't like or would like to see us change, we'd love to hear from you!
Follow us on social media to see what we're up to and to ask any questions!
CarExpert:
Facebook: https://www.facebook.com/CarExpertAus
Twitter: https://www.twitter.com/CarExpertAus
Instagram: https://www.instagram.com/carexpert.com.au
Paul Maric:
Facebook: https://www.facebook.com/PaulMaric
Twitter: https://www.twitter.com/PaulMaric
Instagram: https://www.instagram.com/PaulMaric
#porsche #911 #dragparison
Convertible CFD study by Serkan Solmaz: http://sersol.weebly.com/workshop/convertible-aerodynamics
Let me know how you explain the science in the comments section.
More Porsche content: https://www.carexpert.com.au/porsche
More Porsche 911 content: https://www.carexpert.com.au/porsche/911
Skip Ahead:
Intro: 00:00
The Science: 01:12
Cab v Coupe baseline drag race: 03:22
Cab v Coupe same weight drag race: 07:11
Verdict: 12:44
We review every new car on the market, bust car myths, cover the latest car tech and answer your burning questions.
Whether you need new car advice, purchase validation or simply love learning more about new cars and technology, we are your car experts.
Subscribe to Car Expert: https://www.youtube.com/channel/UC7DvMhvy3H7ntEgn9n3xQcQ?sub_confirmation=1
You'll find us dropping new video content three times a week. If you'd like to ask a question about one of our videos, simply leave us a comment. If you'd like to give us any feedback on our content, feel free to email us, or alternatively, hit us up on social media.
Finally, we want this channel to grow with your support and feedback. If there's anything you don't like or would like to see us change, we'd love to hear from you!
Follow us on social media to see what we're up to and to ask any questions!
CarExpert:
Facebook: https://www.facebook.com/CarExpertAus
Twitter: https://www.twitter.com/CarExpertAus
Instagram: https://www.instagram.com/carexpert.com.au
Paul Maric:
Facebook: https://www.facebook.com/PaulMaric
Twitter: https://www.twitter.com/PaulMaric
Instagram: https://www.instagram.com/PaulMaric
#porsche #911 #dragparison
Category
🚗
MotorTranscript
00:00 I'm Paul. So that is a Porsche 911 Turbo, and that is a Porsche 911 Turbo, except it's the convertible version, the cabriolet.
00:07 Today we're doing something that's always intrigued me.
00:09 I've always wanted to know how much slower, if at all, is the convertible version of the same car?
00:15 Because, I don't know, in my mind, in theory,
00:17 you should have turbulence and drag and all that kind of stuff when air is just collecting inside the cabin as you drive.
00:23 So today we want to put that to the test in another Car Expert Drag Harrison.
00:28 So how's today going to work?
00:30 Well, we're going to run through the science of why this should, in theory, be slower than this.
00:34 Then what we'll do is set some baseline acceleration times over a quarter mile to see exactly how fast the cars are with the roof on,
00:41 and then with the roof off.
00:42 Then what we'll do, because I know some of you are thinking about this, the cabriolet is heavier,
00:46 we will add some extra weight to the coupe, so they weigh the exact same, and then we'll do those
00:51 acceleration runs again where I suspect we will find an answer.
00:54 Now, if you do want to skip ahead to other parts of this video,
00:57 you can use the time codes up on the screen, or if you're on YouTube, just scroll down and use the chapters below.
01:02 And if you haven't done so already, I'd love it if you could subscribe to our channel and press the bell icon.
01:06 That's going to tell you every single time we publish one of these fun drag Parisons, but let's get started.
01:11 So let's talk about the science.
01:13 Prior to shooting this video, I did some research on drag coefficients, and I'm not an expert on drag coefficients,
01:20 but one of the studies that I found that compared a convertible against the equivalent coupe was that
01:26 the drag coefficient was around 30% higher when you took the roof off compared to the coupe.
01:31 And it all comes down to turbulent airflow, and I really love this graphic just here.
01:37 It really sums up exactly what we mean by turbulent airflow.
01:41 So you can see in this image here, the air is just smoothly flowing over the car,
01:45 and then it just collects at the rear of the car.
01:47 The second you take the roof off though, which is number four, it comes across the top of the car,
01:52 gets mixed in with the interior, leaves the back of the car and just becomes incredibly turbulent.
01:57 Now in theory, when you do have a higher coefficient of drag,
02:01 it means then that the car has to work harder to overcome the drag,
02:05 means you're then able to achieve a lower higher speed and less acceleration.
02:09 Well, that's the theory anyway.
02:11 Now let's talk about some caveats really quickly.
02:13 So Murphy's Law, it did rain the morning that we filmed this.
02:16 It did dry out throughout the day, but we did notice there were some traction issues off the line.
02:21 Both of the cars were independently timed.
02:23 So when you see them cross the finish line, it's kind of irrelevant because they're independently
02:27 timed and the finish line won't be determining which one was actually quickest.
02:31 The spoiler also plays a big part in that turbulent airflow.
02:35 You can see here in these diagrams with the spoiler,
02:38 you get a whole lot less turbulent airflow behind the car, which is number one and number three there.
02:42 It means that when the spoiler is deployed, the cars can overcome drag coefficient much quicker.
02:47 Both of these cars have a spoiler.
02:48 They deploy in the same way, so we left that all in its standard form.
02:52 And finally, the weight of the cars.
02:54 To make sure that we knew exactly how much weight to add to the coupe,
02:58 we took them both to a calibrated weigh bridge to figure out exactly how much needed to be added in.
03:03 And finally, the cars.
03:05 They were both produced at the same factory, but at different times.
03:08 And that means that, I don't know, perhaps there was a German who wanted to go home a little early
03:12 and didn't do one car as good as the other.
03:14 So that may play a part in how quickly they accelerate and their top speeds as well.
03:19 But enough of this boring stuff, let's get into the testing.
03:22 Okay, here we go.
03:23 So we are on the drag strip.
03:25 So what's going to happen here is we are running these as baseline.
03:29 So that's coupe and then the cabrio with its roof on.
03:32 What we want to see is how quick are they in their standard form with varying weight.
03:37 So we know that the cab is 60 kilos heavier,
03:40 and there's a slight weight difference between us drivers,
03:42 but it'll be the same throughout the whole test.
03:43 So that will be our baseline.
03:45 It is incredibly wet here at the moment,
03:47 so it's going to be a little bit sketchy to launch this, but we'll give it a shot.
03:51 Steve, my colleague, is going to do the countdown from the other car.
03:54 We're going to use maximum attack mode, so that's sport plus.
03:57 You can see that because the wing is up, and then we will also use launch control as well.
04:02 So let's give this a shot and see how we go.
04:05 Okay, in three, two, one.
04:11 Holy ****!
04:18 Holy ****!
04:22 Man!
04:28 This thing was absolutely all over the place.
04:35 So leaving the line, it basically snapped a little sideways,
04:38 and it was just, even as all-wheel drive, this...
04:41 It's just scary.
04:43 Okay, what were our times?
04:44 We ended up doing 11.4 seconds at 206.3 kilometers an hour,
04:51 and then our 0-100 time was 3.7 seconds.
04:54 So it's a pretty insane time, given it is wet.
04:57 There was a slight difference off the line there,
04:59 but given these were both timing sort of independently,
05:02 we'll be able to see what those figures are.
05:04 Steve, what were your times?
05:06 Quarter mile was 11.5, 0-100 in 3.7.
05:12 So there you go.
05:13 My quarter mile time was slightly quicker, and I think that kind of makes sense.
05:18 This is the lighter car, so even off the line, it looked like it wasn't as quick.
05:22 I think that weight difference really does make a difference over 400 meters.
05:26 Okay, it's time for run two.
05:28 This time, Steve has the roof down in the Cabriolet.
05:32 Actually, it looks pretty good as a convertible.
05:35 So my theory here is that that should be slower again,
05:38 because, you know, wind resistance and all that kind of stuff.
05:41 So let's see what happens.
05:42 So last time, I took off a little slower, but like I said,
05:45 we're independently timing these, so it doesn't actually make any difference
05:48 outside visually.
05:50 So let's give this another shot.
05:51 Launch control again, and let's see who wins.
05:54 Okay, in three...
06:04 All right, it's close.
06:05 This thing is insane, absolutely insane.
06:11 Oh, man.
06:15 I feel sick to the stomach.
06:20 That's how quick this is.
06:21 That is ridiculous.
06:22 So 0-100 in 3.3 seconds.
06:26 Remember, it is wet.
06:27 3.3 seconds.
06:28 Quarter mile was 11.1 seconds at 209.3 kilometres an hour.
06:34 Okay, Steve, what was your quarter mile time and speed, and also 0-100?
06:38 Quarter mile was 11.1 at 201.2, and 0-100 was 3.2 seconds.
06:47 There you go.
06:49 So he was quicker...
06:51 It just doesn't make any sense to me.
06:53 So we were quicker over the quarter mile in terms of speed, but not in terms of time.
06:59 Okay, math's whizzers.
07:00 You'll have to figure that one out, because that's got me confused.
07:03 Now what we're going to do is go back to the pits, make them weigh the same,
07:06 so that then in theory the only difference is going to be the roof off.
07:09 And then we'll see what happens.
07:11 Okay, we know that when these cars were on the weigh bridge,
07:13 there was a 60 kilo weight difference between them.
07:16 So I've done some sums here, and James, my colleague, come on in.
07:20 James is going to be riding with me in the coupe.
07:23 We've then got 20 kilos worth of weight over here that we're going to load
07:27 into the front of the car, and colleague Steve will still be in the cabrio.
07:32 Now that will mean that these two cars weigh the exact same,
07:35 and then the only difference is going to be whether the roof being off actually affects our speed.
07:40 So apologies again for the rain.
07:42 It's not something we really wanted today, but the track is kind of drying out,
07:45 so it should mean that they launch the exact same,
07:47 and a wet road is less of a factor as we get to the equal weight parts.
07:51 Okay, so we're going to do two runs here.
07:53 One run with the roof on, and then one run with the roof off.
07:57 At the moment we have all of our weights up the front there.
07:59 James in this car, Steve over there.
08:01 I think we're ready to rumble.
08:02 Here we go.
08:03 James is going to do the countdown, and we're good to go.
08:07 Three, two, one, go.
08:10 Go, go, go!
08:15 Come on!
08:22 Oh man.
08:27 James, what did you eat?
08:29 He bit it.
08:30 Okay, so our times were 0 to 100 in 3.1 seconds,
08:36 and quarter mile, 10.9 seconds at 207.7 kilometres an hour.
08:41 That was a quick one.
08:42 Steve, how did you go with that run?
08:44 Quarter mile was 10.8 seconds at 211.3 kilometres an hour.
08:51 0 to 100 was 3.0 exactly.
08:55 Wow. Okay, so the cab was actually quicker than us.
08:58 So we added weight to this so that it matches the cab.
09:01 That's interesting.
09:02 That has me absolutely stunned.
09:03 Maybe that car just out of the factory has a bit more oomph,
09:06 because the track is pretty much dry now.
09:08 So let's see what the difference is now with the roof off.
09:11 In theory, that should be slower, but I don't know.
09:14 Let's see what happens.
09:15 Okay, here we go.
09:16 Roof is off on the cab now.
09:18 We have all the extra weight in this car, so they weigh the exact same.
09:21 The only difference between the two is the weight.
09:23 The only difference between them is going to be the roof being off on that car
09:27 and the roof obviously being on here.
09:29 Let's give this one final crack.
09:30 I think in theory, this should be quicker across the quarter mile and also 0 to 100,
09:35 given the theory that the roof being off on that should slow it down a little bit.
09:39 So let's see what happens.
09:41 All right.
09:41 Three, two, one, go.
09:45 All right, we had a good start.
09:50 Oh no, I think he's going to win again.
10:00 Oh man, that's so annoying.
10:06 Okay.
10:09 All right, so here are the results.
10:11 0 to 100 in 3.1 seconds and quarter mile, 11 seconds flat, 206.6 kilometers an hour.
10:20 So Steve won there.
10:22 Let's see how Steve went.
10:24 I don't like Steve anymore.
10:26 Steve, how did you go?
10:27 What were your times?
10:28 So quarter mile, 10.8 seconds at 208.2 kilometers an hour.
10:35 0 to 100 was 2.9 seconds.
10:38 And it's ridiculous.
10:40 That thing is faster than this, even though it has no roof.
10:43 All right, the final thing we're going to do here is swap sides of the track.
10:47 One last time, just to be 100,000% sure it's not the side of the track,
10:51 and then we will have a look at the results.
10:53 Okay, so I don't know, it's looking like it's either this side of the track that is better,
10:59 or potentially these cars at the factory just had a slight difference in terms of their
11:03 tune, and that one's just a little faster than this is.
11:06 This one has about 5,300 k's on the clock.
11:09 That one is about 1,100 or so.
11:10 So there is a slight difference.
11:11 That one is newer, but they're running the same tires, they're on the same track.
11:14 They now weigh the same.
11:15 In theory, the car without the roof should be slower.
11:17 So we'll give this one final shot.
11:19 I should also mention as well that Steve over there is a professional race driver,
11:22 but given we're using launch control and I'm just holding my foot flat to the board,
11:26 there really shouldn't be an advantage when it comes to him being a race driver or not.
11:30 So we'll give this one final shot.
11:32 We'll see what the side says.
11:34 Three, two, one, go.
11:37 Oh, that felt good.
11:42 That felt good.
11:42 Oh, man, I still just cannot believe how fast this is every time we do this.
12:00 I don't even have time to think.
12:02 Okay, there we go.
12:04 We've got some new results here.
12:05 So 0 to 100 that time was 2.9 seconds, and our quarter mile, 10.8 seconds at
12:12 206.5.
12:14 Okay, Steve, how did you go that time?
12:15 Quarter mile was 11.1 seconds at 208.1 kilometers an hour, and 0 to 100 was 3.2 seconds.
12:25 This doesn't make any sense to me.
12:28 So he was doing a faster time at the end of the quarter mile, but his quarter mile elapsed time
12:35 was slower, and so was his 0 to 100 time.
12:38 So as he got towards the end of the track, that thing became quicker despite not having a roof.
12:43 Okay, so we've spent the whole day testing this and all the different variations, and I am
12:48 officially confused because, I don't know, according to the numbers that we just got, the
12:53 convertible car, when it weighs the same as the coupe, is faster in terms of its terminal velocity
12:59 at the end of the quarter mile than the coupe is.
13:02 I would have thought it would be the other way around.
13:04 So I don't know if Porsche's just defied the laws of physics with this car, which they kind
13:08 of have because it is a missile of a thing, or if perhaps the engine in this has some extra
13:13 goodies in it, or maybe they forgot to put an S on the back of the turbo badge, I don't know.
13:17 That one was quicker over the quarter mile in terms of seconds and also to 100 kilometers an
13:22 hour, but it seems the more runway this had, the faster it went regardless of whether the roof was
13:26 there or not.
13:27 So yeah, I'm officially confused, but as with all of these things, I always want your feedback.
13:31 So do you have a theory on what's happened here?
13:34 I think we kind of ruled out the track conditions as much as we could by swapping sides, but at the
13:39 end of the day, with just a launch control system where you just launch it and walk away from it,
13:42 literally anybody can do it, I think it just came down to the car itself.
13:47 So sorry I didn't have a logical conclusion here.
13:50 Let me know what you reckon in the comments section below.
13:52 Which other videos do you want to see?
13:54 What else do you want to see us testing?
13:55 I always look for your feedback before we lock in the next one of these sort of random
13:59 drag parison car explainer type videos.
14:02 If you did enjoy this video, please make sure you share it with your mates and hit the like
14:05 button. And if you haven't done so already, subscribe to our channel and press the bell
14:09 icon so you can find out every single time we discover a vehicle that defies the laws of
14:14 physics.
14:14 But until next time, take it easy.