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10-28-2008, 01:05 AM | #67 |
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10-28-2008, 01:13 AM | #68 | |
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Cheers. |
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10-28-2008, 03:11 AM | #69 | |
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10-28-2008, 09:07 AM | #70 | |
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Huh. I guess we're all ignorant in different areas. Shut my trap? Wow! Swamp the Sanctimonious turns nasty! Bruce |
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10-28-2008, 03:24 PM | #72 |
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Bruce, perhaps I misunderstood the reference, my apologies if so.
Regardless of a compliment or not asking to keep relevant on on topic (even if harshly) isn't as bad as your ad hominem name calling. |
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10-28-2008, 04:03 PM | #73 |
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Well you see, when you are continually ignorant to someone over and over again it gets to a point when enough is enough, that point was a short while ago but calm has returned.
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10-28-2008, 05:48 PM | #74 |
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Herein I have always graciously admitted errors, typos, mistakes, etc. each and every time I've made them. I've even done so simply from being too harsh on folks. You can't point out cases to the contrary. As well I offer apologies quickly and without stipulations when I owe them.
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10-28-2008, 08:31 PM | #75 |
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Hey fellas, everyone is over at the ZR1 thread, this is old now.
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MY22 X5 M-Sport 45e White, 22"rims, Red Calipers, Ceramic Pads. Better off saying what it does not have and that's a B&O Audio System, otherwise all option boxes are ticked. |
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10-29-2008, 08:55 PM | #76 |
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OK, I finally found the time to read through all this. Great discussion IMO! Thanks for taking the time to post this Swamp.
Swamp has done a great job in presenting a case for his estimate, and Footie has done an equally solid job critiquing it. (I think Swamp should give Footie more credit considering Footie does not have a technical background despite the fact that Footie does seem to wonder off topic at times.) A few questions/observations for Swamp: 1. Where is the spreadsheet??? I wanted to see the numbers, but can't find the file anywhere on this thread. Am I just overlooking it somewhere? 2. Wind is modeled as static force, which is probably not the case. I am not an expert on weather dynamics, but I bet surface winds change direction often, and there is the possibility of short gusts, and even direction reversals depending on topography, etc. 3. You are agreeing that a static 15mph tail wind would validate the observed performance of a 530hp GTR, and saying there is no reason to believe that is the case since Nissan would not have ran the test under windy conditions. I don't think that is sufficient rationale. It might be possible that the track layout and the geography, in conjunction with a specific wind direction on a specific day, might actually result in positive net tailwind on the faster straights on a windy day. In order words, roughly speaking, one might trade off headwind on slower parts of the course for tailwind on the faster parts. 4. You are using a WOT assumption for all cars throughout the section you observed. I don't drive on tracks at those speeds, but when you are on such long straight at such high speeds, there might be reason/hesitation not to go absolutely WOT all the time. Since I can't see the spreadsheet, I can't comment on this in more detail. 5. As Bruce mentioned, atmospheric conditions on the different days might lead to output differences. 6. Does your CarTest speed vs. time output match the speed vs. time data on the ZR1 run precisely over time during the duration? Again, I can't see the data for myself. You have only reported time to complete the track section on this thread.
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10-29-2008, 11:16 PM | #77 | |||||||
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One additional point is worth bringing up. Whenever possible I chose very conservative values/assumptions which favor a LOW estimate of the under rating. Such examples include very conservative transmission losses (equivalent to the other two RWD vehicles) and very quick transmission shift times for the GT-R. It is clear evidence of a distinct pro GT-R/anti under rating point of view when ONLY assumptions which provide a larger under rating are questioned in all of the replies. Like many other situations with a tremendous number of contributing variables you have to focus first on the most dominant factors and count on some of the other minor unknowns affecting results in one direction and others pushing in the opposite direction. No this can't be "proved" but it is most likely. I am looking forward to your thoughts on the additional regression work as well. It is fairly clear/strong evidence to me that those particular cars were not as under rated as the 7:29 car. |
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10-30-2008, 02:51 AM | #78 | |
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swamp,
Look back to the original posts and I don't see an attack on you or your methods, only that I felt you were wrong and gave a very valid reason. Quote:
Is it a case that when someone else points out possible errors in your methods it OK and you listen but when it's me, because of my continued hole picking you've build up a wall to reason. |
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10-30-2008, 11:52 AM | #79 | |||||||
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Yes, what you mentioned about the deviation decreasing as the track gets "tighter" is interesting. You are attributing that to the actual power/weight of the GTR, but if the "GTR can put down power earlier" argument has merit, that can also contribute to decreasing deviation since the car will carry whatever speed it can build earlier along the straight even if it does not necessarily accelerate any faster on the straight itself, so there might be a combination of those two issues.
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Last edited by lucid; 10-30-2008 at 01:30 PM.. |
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10-30-2008, 01:32 PM | #80 | |
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Last edited by swamp2; 10-30-2008 at 01:54 PM.. |
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10-30-2008, 01:54 PM | #81 | |
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All pretty reasonable criticisms^, but also the only thing left to do would indeed be a ton of bounding/sensitivity studies. Would be interesting but the tail wind example was probably the most important one. Again many small effects which can vary in terms of benefit/detriment and they will tend to average out. As well I think all such studies would do at this point would be to increase the confusion and take things even further off topic. The methodology for getting the differences between the ACR times and predictions was to assume a faster corner exit speed for the ACR (totally justified IMO) and to then match the ZR1s acceleration. Not rigorous nor particularly strong assumption but it does make everything loosely consistent. Really we can leave the ACR out as a weaker part of the argument. There was no speed data so is is much harder to compare. The primary argument here is ZR1 vs. GT-R. |
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10-30-2008, 02:30 PM | #82 | |
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When did you send me email? I didn't get it. My email has been acting up recently. The attachment doesn't work for me, but maybe the it's the unpacking software. I'll try another one.
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10-30-2008, 02:39 PM | #83 | ||
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1/ Audi Banner over head early on the straight. ZR1 reaches it 0.3s ahead of the GTR at a speed of 144mph. At that point using my eyes as a gauge the ZR1 would be about 3 lengths ahead of the GTR. 2/ Taller sign at the right hand side (second in the line) ZR1 reaches this 0.6s ahead of the GTR at a speed of 163mph. Again using my eyes as a gauge on this the ZR1 looks to be about 8~9 car lengths ahead of the GTR. 3/ The Bridge just before the kink. ZR1 reaches this 0.9s ahead of the GTR at a speed of 176mph. At this speed it's harder to gauge but I reckon it looks close to 12 car lengths ahead. Doing the maths (60mph = 1 mile per minute) and there is 1609m in a mile. At point 1 the ZR1 was 19.3m ahead of the GTR At point 2 the ZR1 was 46.9m ahead of the GTR At point 3 the ZR1 was 76.1m ahead of the GTR. So within the time it took the ZR1 to accelerate from about 100mph to 144mph it had pulled out about 4 car lengths on the GTR. By the time it had increased this by 19mph it was almost 10 car lengths ahead and finally by the bridge it was almost 16 car lengths ahead. Now go back to your simulation and figure in these gaps based on these speed points and see if you come back with a GTR with 550hp. |
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10-30-2008, 02:43 PM | #84 | |
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Use good old time pointers to see how much faster or slower the ACR is than the ZR1 or GTR. I remember doing it a while ago and the Viper was in between the Vette and the Nissan, though it was riding the limiter for most of the time and would have been clearly quicker than both if this hadn't been the case. |
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10-30-2008, 05:56 PM | #85 | ||||
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I am not saying the GT-R is faster in this straight section, the ZR1 is ahead from 0.4 - 1.1 seconds at identical points along the track (and just FYI I used many many more points than you consider here above). The ZR1 is always ahead! Please see my spreadsheet. It seem abundantly clear you still have not looked at it and that you can not read the videos properly. When a car is accelerating you can not estimate distances in the lead based on speeds at single data points. This is physics 101. Talk about ridiculously incorrect analysis. This takes simulation or calculus to determine! Sharpen up your pencil, have another think about it. So even though the ZR1 was faster and most likely exited faster what I am saying is that the observed (lesser) performance of the GT-R is still consistent with 550 hp. |
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10-30-2008, 06:41 PM | #86 |
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swamp,
Like Lucid, I tried to open the file but no go. Don't know for why. I believe my observations of the times are roughly correct, as I chose to use the Nissan's timer as it was in hundredth unlike the Vette timer. I also believe my observations of the distance the Vette was gaining to be correct, based on experience and good judgement. Motortrend tested the ZR1, GTR, 599 and GT2 And the times for the 1/4mile runs showed the ZR1 to be 0.1s ahead of the 599, 0.2s ahead of the GT2 and 0.4s ahead of the GTR. Now if you were to look at the acceleration times by speed the ZR1 totally destroys the GTR, posting a time 1.1s ahead of the GTR to 100mph, but only 0.4s ahead by the 1/4mile. Call me stubborn but these figures don't sound unlike what is seen happening in the comparison video on the ring. I know we are talking about higher speeds but I think everyone else knows the point I am trying to make. Edmunds also tested both the ZR1 and GTR and posted dyno results, with the ZR1 (505hpwhp) and the GTR (406whp), is it possible that the GTR has a 24% drivetrain lose, personally I doubt it. I even doubt 20%. As I can't open the file, can to provide some split times with speed and distance points for both cars so as I can get a feel for your data and see how it looks. P.S. I still disagree with the ZR1 exiting the corner quicker, based on watching the entire two videos and matching the two cars from corner to corner, if anything the GTR should be the one leaving that corner the sooner. |
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10-30-2008, 09:21 PM | #88 | |
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I tried again with both my Mac and Windows machines and the zip file opens perfectly to reveal two spreadsheets with multiple pages each. I used the zip program built in to Windows as opposed to WinZip but it shouldn't matter. |
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