Regression analysis for kg/hp vs. Ring laptimes

[lucid]

Thanks for the post and the reference sdiver.

Nissan should clarify what they mean by stock in this case since everybody kind of knows that there will be different versions of this car (people on that Nissan board are saying the same thing). Why don't they simply release the specs of the car that made the run? Or did they do that already and have I missed it?

[lucid]

Here are the descriptive stats on the residuals from the second analysis. I think Swamp and Coaster asked for these. The distribution is pretty even. Not exactly a normal distribution, but pretty close.

[jaiman]

Originally Posted by lucid

Thanks for the post and the reference sdiver.

Nissan should clarify what they mean by stock in this case since everybody kind of knows that there will be different versions of this car (people on that Nissan board are saying the same thing). Why don't they simply release the specs of the car that made the run? Or did they do that already and have I missed it?

its pretty simple, the version of the GTR that debuted at the TMS (the base model) is the one that Nissan says did the ring in 7:38. When asked whether the car had higher boost, special tires or any other mods, Nissan said no.

[Garrett]

Originally Posted by swamp2

Nice work lucid, you have quantified nicely exactly the basic physics that we all (many of us at least...) understand quite well.

Those asking about the CSL the answer is indeed obvious - tires make a huge difference and that car comes basically with street legal race tires. That being said the CSL may be below the curve fit without those tires. Cars below the line are in a way the best designed and engineered cars for going fast, those above less so.

This also makes my point perfectly about the Nissan GT-R. I have sloppily added the car to you graph (man that was harder than Excel - I should have just asked you to do it...). The GT-R is an massive outlier in the data. This means one (or more) of a couple things to me.

1. They have really reinvented the sports car and bested everyone by a significant margin. Maybe it could be their AWD system.
2. The car is under rated in term of power
3. The car is under rated in terms of weight (claimed>actual)
4. The car had street legal race tires

What is the most likely scenario. I'd vote in order 4,3,2,1.

Lastly, bringing it back OT... I have added the new M3 at 7:57 and 8:03 (with US hp figure - 414). Again 8:03 is a provisional time and 7:57 is a good rumor directly from Richter and both times are still up in the air as to which tires are invlolved.

Nissan, BMW, whom ever, you simply can't beat physics.

Swamp, just curious... where does the 135i fall into that chart @ 198lbs lighter than a 335i..? Near the Cayman S..?

[footie]

Is there not to be more than just one model. I thought there was 3 versions coming with the top producing over 520hp.

[footie]

When on earth is the M3's time going to be made official?

Anyone.

[lucid]

Originally Posted by footie

When on earth is the M3's time going to be made official?

Anyone.

I think the sportauto time will be published soon in the next issue.

[lucid]

Originally Posted by jaiman

its pretty simple, the version of the GTR that debuted at the TMS (the base model) is the one that Nissan says did the ring in 7:38. When asked whether the car had higher boost, special tires or any other mods, Nissan said no.

So, we are talking about the 3800lb 480hp version?

[Garrett]

Originally Posted by lucid

Not sure what your point here is. As I've said from the very beginning, this analysis simply establishes the 480hp GTR time of 7:38 as the most extreme outlier in the bunch after the GT2 number. With time, as Nissan discloses more info on that run, and as the test is repeated by others, we will find out why that is. Nothing more, nothing less. Nobody is insulting the Nissan engineers here. Relax. Also, you are still missing the whole point of doing the regression analysis, and it seems, statistics, in general as despite the strong regression outcome, you still insist that weight/power does not have much to do with lap times around a complex circuit. I am sure handling is a major factor as well, but so are driver, weather, tires, transmission and many other things that this analysis does not account for. They all cause variance, but not to the extent that they overwhelm the linear relationship between weight/power and lap time. Why argue against this in light of the evidence?

It is possible that Nissan has a superb driver, state of the art transmission, AWD system, and suspension all in one car, and therefore manages to escape the trend. If the GT2 can do it, and since the GTR can be expected to be more advanced than the GT2, it is possible that it raises the bar slightly further. That doesn't invalidate the outcome of the analysis--that there is a strong linear relationship between weight/power and lap time on the Ring.

Bravo!

[Garrett]

Originally Posted by coaster

That's exactly the problem. What's great about you (and swamp as well -let's not leave him out cause he'll be pi$$ed) is that you take issue with what I said even when you don't see my point. That's raw genious at work!

To my point. Nobody disputes that horsepower is an important determinant of laptime. Certainly not me and certainly not anyone I know. To see this clearly consider a car with an engine that produces zero horsepower. The car will not move at all and its laptime will be infinite. I think we also agree that there are other variables that contribute strongly to laptimes. But the regression line you fit to the "normalized" power data doesn't contain any of these other variables. That's OK you say, as long as the regression error bands from all OTHER cars I have already charted contain or "bound" any new cars, I am not going to question their laptimes. But when one new point of data arrives that is slightly outside the current error bands your world is shattered. Something is amiss you say, my single parameter regression model doesn't fit as well so something is wrong with this picture and I am going to question it (that's what swamp says at least). This is exactly my point. YOU CANNOT INFER ANYTHING from this model about your new data point. Nothing, nada. Neither can swamp (even if he thinks otherwise ) To do so you require additional information which YOU DO NOT HAVE!

Oh, by the way, I am completely relaxed ...

No, because that scenario you just described (say better tyres) only alters that regression table in a single vector. Which is clearly stated by Swamp & Co.

Tyres don't add HP or weight. So you'd see that VARIANCE plotted as TIME!

[lucid]

Kind off topic yet not: how do they handle liability issues on the Ring? I don't know much about what one needs to do to drive, but it seems like you pay the fee and you're on. Is that right?

[jaiman]

Originally Posted by lucid

So, we are talking about the 3800lb 480hp version?

according to Nissan, yes.

[Garrett]

Originally Posted by lucid

Kind off topic yet not: how do they handle liability issues on the Ring? I don't know much about what one needs to do to drive, but it seems like you pay the fee and you're on. Is that right?

Buy a ticket, sign a waiver!

[lucid]

Originally Posted by Garrett

Buy a ticket, sign a waiver!

Thanks. Are there many fatal accidents? Are the accident stats public?

[lucid]

Originally Posted by jaiman

according to Nissan, yes.

In that case, it would be interesting to see a "stock" M3 time with DCT and a stellar driver. I bet that would be around 7:50 or maybe even better--assuming the 6MT Sportauto time indeed comes in around 8:03 or so.

[paulyd]

Does the 480hp version weight the same as the 530hp GTR?

3836lbs?

[footie]

If you are interested the video of the lap is on Youtube.

Here's the link

[paulyd]

Originally Posted by lucid

In that case, it would be interesting to see a "stock" M3 time with DCT and a stellar driver. I bet that would be around 7:50 or maybe even better--assuming the 6MT Sportauto time indeed comes in around 8:03 or so.

Yeah that will be interesting. The regression suggests the M3 should only be about 6 seconds slower than the 480hp GTR simply given the kg/hp (assuming all else equal).

So if we can eventually compare an M3 DCT to the GTR DCT, on the same tires, then we could see how much better the GTR's awd, suspension, etc is compared to the M3...

So if we guess the M3 DCT time is 7:50
GTR is 7:38

Then there is a 12 sec difference
6 seconds are gained because the GTR has superior kg/hp ratio ('known' via regression)
Other 6 seconds are gained because? suspension, awd, balance, driver, etc

[southlight]

Originally Posted by footie

When on earth is the M3's time going to be made official?

Anyone.

Nov 23rd.

Best regards, south

[footie]

Originally Posted by chitown08

Yeah that will be interesting. The regression suggests the M3 should only be about 6 seconds slower than the 480hp GTR simply given the kg/hp (assuming all else equal).

So if we can eventually compare an M3 DCT to the GTR DCT, on the same tires, then we could see how much better the GTR's awd, suspension, etc is compared to the M3...

So if we guess the M3 DCT time is 7:50
GTR is 7:38

Then there is a 12 sec difference
6 seconds are gained because the GTR has superior kg/hp ratio ('known' via regression)
Other 6 seconds are gained because? suspension, awd, balance, driver, etc

If the M3 is lapping the ring in 8:03 then I very much doubt DCT will drop this by anything approaching 13 seconds, maybe 4~5 seconds is possible but no more.

I agree with the 6 seconds being gained by the superior kg/hp ratio but the rest (13~14 seconds if the DCT M3 does as I believe a 7:58 lap) will be made up by this amazing transmission/suspension/steering set-up that Nissan has blessed the GTR with.

The M3 is good but it's not in the same class as the GTR is in terms of handling and balance. I think swamp2 described it best saying Nissan has re-written the book on how a sportscar should perform.

[lucid]

Originally Posted by chitown08

Does the 480hp version weight the same as the 530hp GTR?

3836lbs?

Don't know, but it would be safe to assume whatever weight data that has been released is for the base version since the other version(s) are not officially announced yet.

[lucid]

Originally Posted by footie

If the M3 is lapping the ring in 8:03 then I very much doubt DCT will drop this by anything approaching 13 seconds, maybe 4~5 seconds is possible but no more.

It's not just DCT. I also said stellar driver (Nissan seems to have one). Driver can make a significant difference. If I remember correctly, the #2 Nissan test driver was said to be running 10-15 sec slower than the #1 guy.