Convertible v Coupe - which is faster
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TechTranscript
00:00G'day, I'm Paul. So that is a Porsche 911 Turbo, and that is a Porsche 911 Turbo,
00:05except it's the convertible version, the cabriolet. Today we're doing something that's
00:08always intrigued me. I've always wanted to know how much slower, if at all, is the convertible
00:14version of the same car? Because, I don't know, in my mind, in theory, you should have turbulence
00:19and drag and all that kind of stuff when air is just collecting inside the cabin as you drive.
00:24So today we want to put that to the test in another Car Expert Drag Harrison. So how's
00:29today going to work? Well, we're going to run through the science of why this should, in theory,
00:33be slower than this. Then what we'll do is set some baseline acceleration times over a quarter
00:38mile to see exactly how fast the cars are with the roof on and then with the roof off. Then what
00:43we'll do, because I know some of you are thinking about this, the cabriolet is heavier, we will add
00:47some extra weight to the coupe so they weigh the exact same, and then we'll do those acceleration
00:52runs again where I suspect we will find an answer. Now, if you do want to skip ahead to
00:56other parts of this video, you can use the time codes up on the screen, or if you're on YouTube,
01:00just scroll down and use the chapters below. And if you haven't done so already, I'd love it if you
01:04could subscribe to our channel and press the bell icon. That's going to tell you every single time
01:07we publish one of these fun drag Harrisons, but let's get started. So let's talk about the science.
01:14Prior to shooting this video, I did some research on drag coefficients, and I'm not an expert on
01:19drag coefficients, but one of the studies that I found that compared a convertible against the
01:24equivalent coupe was that the drag coefficient was around 30% higher when you took the roof off
01:30compared to the coupe. And it all comes down to turbulent airflow, and I really love this graphic
01:36just here. It really sums up exactly what we mean by turbulent airflow. So you can see in this image
01:42here, the air is just smoothly flowing over the car, and then it just collects at the rear of the car.
01:47The second you take the roof off though, which is number four, it comes across the top of the car,
01:52gets mixed in with the interior, leaves the back of the car, and just becomes incredibly turbulent.
01:58Now in theory, when you do have a higher coefficient of drag, it means then that the
02:03car has to work harder to overcome the drag. It means you're then able to achieve a lower,
02:08higher speed and less acceleration. Well, that's the theory anyway. Now let's talk about some
02:13caveats really quickly. So Murphy's Law, it did rain the morning that we filmed this. It did dry
02:17out throughout the day, but we did notice there were some traction issues off the line. Both of
02:21the cars were independently timed, so when you see them cross the finish line, it's kind of irrelevant
02:26because they're independently timed and the finish line won't be determining which one was actually
02:31quickest. The spoiler also plays a big part in that turbulent airflow. You can see here in these
02:36diagrams with the spoiler, you get a whole lot less turbulent airflow behind the car, which is
02:41number one and number three there. It means that when the spoiler is deployed, the cars can overcome
02:45drag coefficient much quicker. Both of these cars have a spoiler. They deploy in the same way, so
02:50we left that all in its standard form. And finally, the weight of the cars. To make sure that
02:55we knew exactly how much weight to add to the coupe, we took them both to a calibrated weigh
03:00bridge to figure out exactly how much needed to be added in. And finally, the cars. They were both
03:05produced at the same factory, but at different times. And that means that, I don't know, perhaps
03:10there was a German who wanted to go home a little early and didn't do one car as good as the other,
03:14so that may play a part in how quickly they accelerate and their top speeds as well.
03:20But enough of this boring stuff. Let's get into the testing.
03:22Okay, here we go. So we are on the drag strip. So what's going to happen here is we are running
03:28these as baseline. So that's coupe and then the cabrio with its roof on. What we want to see is
03:34how quick are they in their standard form with varying weights. So we know that the cab is 60
03:39kilos heavier, and there's a slight weight difference between us drivers, but it'll be the
03:42same throughout the whole test. So that will be our baseline. It is incredibly wet here at the
03:47moment, so it's going to be a little bit sketchy to launch this, but we'll give it a shot. Steve,
03:51my colleague, is going to do the countdown from the other car. We're going to use maximum attack
03:56mode, so that's sport plus. You can see that because the wing is up. And then we will also
04:01use the launch control as well. So let's give this a shot and see how we go. Okay, in three...
04:18Holy ****!
04:28Man!
04:32This thing was absolutely all over the place. So leaving the line, it basically snapped a little
04:38sideways and it was just, even as all-wheel drive, this was just scary. Okay, what were our times?
04:44We ended up doing 11.4 seconds at 206.3 kilometres an hour, and then our 0 to 100 time was 3.7
04:53seconds. So it's a pretty insane time, given it is wet. There was a slight difference off the line
04:59there, but given these were both timing sort of independently, we'll be able to see what those
05:04figures are. Steve, what were your times? Quarter mile was 11.5, 0 to 100 in 3.7.
05:13So there you go. My quarter mile time was slightly quicker, and I think that kind of
05:17makes sense. This is the lighter car, so even off the line it looked like it wasn't as quick.
05:23I think that weight difference really does make a difference over 400 metres.
05:27Okay, it's time for run two. This time, Steve has the roof down in the Cabriolet. Actually,
05:33it looks pretty good as a convertible. So my theory here is that that should be slower again
05:38because, you know, wind resistance and all that kind of stuff. So let's see what happens. So last
05:42time I took off a little slower, but like I said, we're independently timing these,
05:46so it doesn't actually make any difference outside and visually. So
05:50let's give this another shot. Launch control again, and let's see who wins.
06:04All right, it's close.
06:09This thing is insane. Absolutely insane.
06:14Oh, man.
06:19I feel sick to the stomach. That's how quick this is. That is ridiculous. So
06:230 to 100 in 3.3 seconds. Remember, it is wet. 3.3 seconds. Quarter mile was 11.1 seconds at 209.3
06:33kilometres an hour. Okay, Steve, what was your quarter mile time and speed and also 0 to 100?
06:39Quarter mile was 11.1 at 201.2, and 0 to 100 was 3.2 seconds.
06:49There you go. So he was quicker. That doesn't make any sense to me. So we were quicker over
06:55the quarter mile in terms of speed, but not in terms of time. Okay. Maths whizzers. You'll have
07:01to figure that one out because that's got me confused. Now what we're going to do is go back
07:04to the pits, make them weigh the same, so that then in theory, the only difference is going to
07:08be the roof off, and then we'll see what happens. Okay, we know that when these cars were on the
07:13weigh bridge, there was a 60 kilo weight difference between them. So I've done some sums here, and
07:18James, my colleague, come on in. James is going to be riding with me in the coupe. We've then got
07:2420 kilos worth of weight over here that we're going to load into the front of the car, and
07:29colleague Steve will still be in the cabrio. Now that will mean that these two cars weigh the exact
07:35same, and then the only difference is going to be whether the roof being off actually affects
07:40our speed. So apologies again for the rain. It's not something we really wanted today,
07:44but the track is kind of drying out, so it should mean that they launch the exact same,
07:47and a wet road is less of a factor as we get to the equal weight parts.
07:51Okay, so we're going to do two runs here. One run with the roof on,
07:55and then one run with the roof off. At the moment, we have all of our weights up the front
07:59there. James in this car, Steve over there. I think we're ready to rumble. Here we go. James
08:04is going to do the countdown, and we're good to go. Three, two, one, go. Go, go, go!
08:15Oh, come on. Oh, man. James, what did you eat? He bit it.
08:34Okay, so our times were 0 to 100 in 3.1 seconds and quarter mile, 10.9 seconds at 207.7
08:44kilometres an hour. That was a quick one. Steve, how did you go with that run?
08:47Quarter mile was 10.8 seconds at 211.3 kilometres an hour. 0 to 100 was 3.0 exactly.
08:58Wow. Okay, so the cab was actually quicker than us. So we added weight to this so that it matches
09:03the cab. That's interesting. That has me absolutely stunned. Maybe that car just
09:07out of the factory has a bit more oomph because the track is pretty much dry now.
09:10So let's see what the difference is now with the roof off. In theory, that should be slower,
09:16but I don't know. Let's see what happens. Okay, here we go. Roof is off on the cab now.
09:21We have all the extra weight in this car, so they weigh the exact same. The only difference
09:25between them is going to be the roof being off on that car and the roof obviously being on here.
09:29Let's give this one final crack. I think in theory, this should be quicker across the
09:33quarter mile and also 0 to 100, given the theory that the roof being off on that should
09:38slow it down a little bit. So let's see what happens. All right, three, two, one, go.
09:50All right, we had a good start.
09:58Oh no, I think he's going to win again.
10:01Oh man, that's so annoying.
10:06Ah, okay. All right, so here are the results. 0 to 100 in 3.1 seconds, and quarter mile,
10:1411 seconds flat, 206.6 kilometres an hour. So Steve won there. Let's see how Steve went.
10:22I don't like Steve anymore. Steve, how did you go? What were your times?
10:26And it's ridiculous. That thing is faster than this, even though it has no roof.
10:30All right, the final thing we're going to do here is swap sides of the track one last time,
10:35just to be 100,000% sure it's not the side of the track, and then we will have a look at the results.
10:41Okay, so I'm going to try and get this car to go through the quarter mile.
10:46I'm going to try and get this car to go through the quarter mile, and then I'm going to try and
10:50it's not the side of the track, and then we will have a look at the results.
10:54Okay, so I don't know. It's looking like it's either this side of the track that is better,
10:59or potentially these cars at the factory just had a slight difference in terms of their
11:04tune, and that one's just a little faster than this is. This one has about 5,300 k's on the
11:09clock. That one is about 1,100 or so. So there is a slight difference. That one is newer,
11:12but they're running the same tyres, they're on the same track, they now weigh the same.
11:16In theory, the car without the roof should be slower. So we'll give this one final shot.
11:19I should also mention as well that Steve over there is a professional race driver,
11:23but given we're using launch control and I'm just holding my foot flat to the board,
11:26there really shouldn't be an advantage when it comes to him being a race driver or not. So
11:31we'll give this one final shot. We'll see what the side says.
11:34Three, two, one, go.
11:41Oh, that felt good. That felt good.
11:50Oh, all right.
11:55Oh, man, I still just cannot believe how fast this is every time we do this.
12:01I don't even have time to think. Okay, there we go. We've got some new results here. So 0 to 100
12:06that time was 2.9 seconds, and our quarter mile, 10.8 seconds at 206.5. Okay, Steve,
12:14how did you go that time?
12:15Quarter mile was 11.1 seconds at 208.1 kilometers an hour, and 0 to 100 was 3.2 seconds.
12:27This doesn't make any sense to me. So he was doing a faster time at the end of the quarter mile,
12:33but his quarter mile elapsed time was slower, and so was his 0 to 100 time.
12:39So as he got towards the end of the track, that thing became quicker despite not having a roof.
12:45Okay, so we've spent the whole day testing this and all the different variations,
12:48and I am officially confused because, I don't know, according to the numbers that we just got,
12:53the convertible car, when it weighs the same as the coupe, is faster in terms of its terminal
12:59velocity at the end of the quarter mile than the coupe is. I would have thought it'd be the other
13:04way around. So I don't know if Porsche's just defied the laws of physics with this car, which
13:08they kind of have because it is a missile of a thing, or if perhaps the engine in this has some
13:13extra goodies in it, or maybe they forgot to put an S on the back of the turbo badge, I don't know.
13:17That one was quicker over the quarter mile in terms of seconds, and also to 100 kilometres an
13:22hour, but it seems the more runway this had, the faster it went regardless of whether the
13:26roof was there or not. So yeah, I'm officially confused, but as with all of these things,
13:30I always want your feedback. So do you have a theory on what's happened here? I think we
13:35kind of ruled out the track conditions as much as we could by swapping sides, but at the end of the
13:39day with just a launch control system where you just launch it and walk away from it, literally
13:43anybody can do it, I think it just came down to the car itself. So sorry I didn't have a logical
13:49conclusion here. Let me know what you reckon in the comments section below. Which other videos do
13:53you want to see? What else do you want to see us testing? I always look for your feedback before
13:57we lock in the next one of these sort of random drag parison car explainer type videos. If you
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14:15take it easy.