Regression analysis for kg/hp vs. Ring laptimes

[jaiman]

can someone post up a table with the raw data that could be cut and pasted into excel? i'm interested in playing around with this a bit with a couple of additional variables.

[swamp2]

Originally Posted by sdiver68

...
Ok so we have the times, but what was there any special set up for the car and will others be able to validate Nissan's times? Well we did ask that in a long video taped interview of Mizuno-san (I am the fat old geek asking most of the questions). I specifically asked if there were any special tires, brake pads and engine tuning for the Ring laps. He clearly states that the car is stock. Yes, I did see the other comments about cut slicks, but I speculate that that has to do more with a misunderstanding or communication issue.
...

Thanks for a good post.

My comments about this are farily simple.

1. I don't care if they plotted the combustion pressure in each cylinder as a function of time through the lap, more data does not make quality data nor complete data. Despite Nissan's thoroughness with regards to data logging and documentation you can not deny the level of marketing involved here either. At this point in time a clear and full picture of the specs of the car is not known, period.

2. AFAIK we do not yet have complete descriptions of the specs of each trim level of the car. So what does "stock" mean exactly. Stock may mean race pads and the highest performing level of DOT legal tires. Both would come some way in explaining the time relative to the regression analysis.

[swamp2]

Originally Posted by 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.

The GT-R is 2.25*(std devation) better than the mean. This should happen )or be bested) by about 1.4% of all cars, which equates to almost exactly 1 car out of 74 (which was this sample size). The 1.4% comes from a numerical integration of the pdf. So again we are not quite to the level of magic, just something very very special.

[jaiman]

Originally Posted by swamp2

Thanks for a good post.



2. AFAIK we do not yet have complete descriptions of the specs of each trim level of the car. So what does "stock" mean exactly. Stock may mean race pads and the highest performing level of DOT legal tires. Both would come some way in explaining the time relative to the regression analysis.

There are no diferences in performance among the 3 trim packages offered. The difference are in accessories, ie Nav, and interior color (two tone seats).

AFAIK all of the specs for the japanese car have been released and it is those specs that this car conforms to.

[sdiver68]

Originally Posted by jaiman

There are no diferences in performance among the 3 trim packages offered. The difference are in accessories, ie Nav, and interior color (two tone seats).

AFAIK all of the specs for the japanese car have been released and it is those specs that this car conforms to.

Unless the forged wheels offered at trim level 2 and up are much lighter in weight than the cast wheels of the base car. On my 335i, my BBS forged wheels in stock sport package 18" sizing shave 46 total unsprung pounds from my car.

[sdiver68]

Originally Posted by swamp2

Thanks for a good post.

My comments about this are farily simple.

1. I don't care if they plotted the combustion pressure in each cylinder as a function of time through the lap, more data does not make quality data nor complete data. Despite Nissan's thoroughness with regards to data logging and documentation you can not deny the level of marketing involved here either. At this point in time a clear and full picture of the specs of the car is not known, period.

2. AFAIK we do not yet have complete descriptions of the specs of each trim level of the car. So what does "stock" mean exactly. Stock may mean race pads and the highest performing level of DOT legal tires. Both would come some way in explaining the time relative to the regression analysis.

Welcome

True, but at some point a leap in faith must be made for ANY of the N'ring times. Even Car and Driver's VIR one-lap same day all stock testing ran into criticism for different drivers and tires and condition for the different cars.

My own semi-pro racing experience is that racing is about who cheats the best without being caught. It was one of the things I disliked about a sport I otherwise love, well that and my shattered arm/broken neck/assorted other injuries career limiting wreck

[footie]

According to CAR magazine there is no V-spec style model officially, only the stock 480hp model, no performance packs, no handling packs and presently only stardard trim and a luxury pack.

Unofficially there will be a V-spec version which will not only provide more power but also been lighter as well.

[sdiver68]

Originally Posted by swamp2

Thanks for a good post.

My comments about this are farily simple.

1. I don't care if they plotted the combustion pressure in each cylinder as a function of time through the lap, more data does not make quality data nor complete data. Despite Nissan's thoroughness with regards to data logging and documentation you can not deny the level of marketing involved here either. At this point in time a clear and full picture of the specs of the car is not known, period.

2. AFAIK we do not yet have complete descriptions of the specs of each trim level of the car. So what does "stock" mean exactly. Stock may mean race pads and the highest performing level of DOT legal tires. Both would come some way in explaining the time relative to the regression analysis.

FYI, Here is what stock means in the US:

http://www.gtrnissan.com/specs.en.us.html

So now we do know exactly what the claim is, and exactly what the data logging proves. It really does not matter if it comes with race tires and race brake pads, as long as it comes from them by the factory, it is stock.

[sdiver68]

OK a couple more considerations.

Add motorcycles lap times to your regression analysis. You might even add a variable for type of vehicle (I forget what these are called, it's been 20 years since my Stats coursework and thesis paper, is it dummy variable?)

Also, add drag. The GT-R is reported at .27 cD. e92 M3 = .31 Although drag = cd x frontal area, I guess we can assume that similar sized cars have similar total frontal areas (~21sf?), unless you can find a source for this information.

At an ultra-high speed track like the N'ring, I think you are going to find a significant missing variable is drag.

[footie]

Originally Posted by sdiver68

At an ultra-high speed track like the N'ring, I think you are going to find a significant missing variable is drag.

That could explain why the Audi R8 doesn't perform as well on the ring as it does on other slower track, based on these other track times the R8 should have been up there with the 997tt but it's miles away. I believe it's drag co. is 0.35.

[jaiman]

Originally Posted by sdiver68

OK a couple more considerations.

Add motorcycles lap times to your regression analysis. You might even add a variable for type of vehicle (I forget what these are called, it's been 20 years since my Stats coursework and thesis paper, is it dummy variable?)

Also, add drag. The GT-R is reported at .27 cD. e92 M3 = .31 Although drag = cd x frontal area, I guess we can assume that similar sized cars have similar total frontal areas (~21sf?), unless you can find a source for this information.

At an ultra-high speed track like the N'ring, I think you are going to find a significant missing variable is drag.

if i have a chance i want to run one with dummies for suspension type and awd as well as variables for weight distribution and cd. might have a chance on the weekend.

[swamp2]

Originally Posted by sdiver68

FYI, Here is what stock means in the US:

http://www.gtrnissan.com/specs.en.us.html

So now we do know exactly what the claim is, and exactly what the data logging proves. It really does not matter if it comes with race tires and race brake pads, as long as it comes from them by the factory, it is stock.

My lack of keeping up to date on this car is showing. Thanks for the correction. I do agree with your point that stock it stock and that is all that counts. I am quite curious to know if these tires are basically DOT legal race tires. That will explain pretty much everything wrt the lap time. 10-15 seconds for tires removes this as an outlier.

[swamp2]

Originally Posted by sdiver68

OK a couple more considerations.

Add motorcycles lap times to your regression analysis. You might even add a variable for type of vehicle (I forget what these are called, it's been 20 years since my Stats coursework and thesis paper, is it dummy variable?)

Also, add drag. The GT-R is reported at .27 cD. e92 M3 = .31 Although drag = cd x frontal area, I guess we can assume that similar sized cars have similar total frontal areas (~21sf?), unless you can find a source for this information.

At an ultra-high speed track like the N'ring, I think you are going to find a significant missing variable is drag.

I would expect a similar trend across a very wide range of bikes, but if you narrowed your list to ultra high performance bikes I believe the trend and R^2 values would not be nearly as good. Too many tire, chassis, state of tune variables when the bikes themselves are very close.

Drag would be an interesting effect especially on a high speed track. However, I'd be willing to bet that the slope and R^2 for a drag regression do not show as strong of an effect. This will be in part to drag not varying as much as power to weight ratio. Sporty cars are simply all pretty darn similar in regards to fronal area as well as Cd.

[sdiver68]

Originally Posted by swamp2

I would expect a similar trend across a very wide range of bikes, but if you narrowed your list to ultra high performance bikes I believe the trend and R^2 values would not be nearly as good. Too many tire, chassis, state of tune variables when the bikes themselves are very close.

Drag would be an interesting effect especially on a high speed track. However, I'd be willing to bet that the slope and R^2 for a drag regression do not show as strong of an effect. This will be in part to drag not varying as much as power to weight ratio. Sporty cars are simply all pretty darn similar in regards to fronal area as well as Cd.

My only real point with the cycles was to point out the effect of drag at high speeds. In my own experience, on a 600cc cycle I could out ccelerate almost any car on the road by a large margin up (1/4ths in the low 11's) to about 125mph...after that ultra high performance cars started catching up or even passed me if given long enough as the cycle would top out around 155. Thus, though I raced a 600, for the street I ran 1000's that were good for 186.

I am theorizing that some of the outliers may be partially explained by drag, and that by adding drag to the existing model it might become even more predictive. And by adding drag I bet the model might even account for both "Super-performance" cars and Superbikes without the need for a dummy variable.

[swamp2]

Originally Posted by sdiver68

My only real point with the cycles was to point out the effect of drag at high speeds. In my own experience, on a 600cc cycle I could out ccelerate almost any car on the road by a large margin up (1/4ths in the low 11's) to about 125mph...after that ultra high performance cars started catching up or even passed me if given long enough as the cycle would top out around 155. Thus, though I raced a 600, for the street I ran 1000's that were good for 186.

I am theorizing that some of the outliers may be partially explained by drag, and that by adding drag to the existing model it might become even more predictive. And by adding drag I bet the model might even account for both "Super-performance" cars and Superbikes without the need for a dummy variable.

Bikes are such different beasts than cars. It is def. nothing more than power to weight that lets bike kill cars in acceleration. Modern sport bikes can get to 1:1 kg/hp a really quick car is "only" 4:1. The other major differences are the down force that cars can and do generate as well as the massive total wheel contact patches that cars have compared to bikes!

I would be happy to run the regression in multi-variable form if you send me a list with the bikes, their power, weight, get the list from Lucid of the car data and add completed columns for both frontal area AND Cd. You have to have both! Cd is big for bikes but it is countered by their very small frontal area.

[footie]

Originally Posted by swamp2

My lack of keeping up to date on this car is showing. Thanks for the correction. I do agree with your point that stock it stock and that is all that counts. I am quite curious to know if these tires are basically DOT legal race tires. That will explain pretty much everything wrt the lap time. 10-15 seconds for tires removes this as an outlier.

swamp2,

Am I right in thinking that in your opinion street legal race tyres like the ones on the CSL and others can make as much as 10~15 seconds over a full lap of the ring.

If so could someone explain to me why the improvement aren't found with the M6 compared to the M5. I believe the M5 did it's lap (8:13) with normal street tyres while the M6 did it's lap (8:09) with street legal race tyres, when you consider that the M6 is not only lighter but because of it's CF roof has also a lower centre of gravity, all things which in theory should improve handling and acceleration you would have thought that in combination with these tyres the gap would have been bigger than just 4 seconds.

What's your opinion on this or is it as simple as some cars seem to perform better with these tyres than others.

[lucid]

Attached is the spreadsheet including the data and analysis I ran. People have been asking for this.

[swamp2]

Originally Posted by footie

swamp2,

Am I right in thinking that in your opinion street legal race tyres like the ones on the CSL and others can make as much as 10~15 seconds over a full lap of the ring.

If so could someone explain to me why the improvement aren't found with the M6 compared to the M5. I believe the M5 did it's lap (8:13) with normal street tyres while the M6 did it's lap (8:09) with street legal race tyres, when you consider that the M6 is not only lighter but because of it's CF roof has also a lower centre of gravity, all things which in theory should improve handling and acceleration you would have thought that in combination with these tyres the gap would have been bigger than just 4 seconds.

What's your opinion on this or is it as simple as some cars seem to perform better with these tyres than others.

Do keep in mind that the basic comparison M5 vs. M6 ,despite many similarities, is basically an apples to oranges comparison.

The estimates based on actual real world testing indicate about 2 seconds per minute saved by going from a top notch UHP tire to a DOT legal race tire. Sure the number depends on the car, driver, speed of track, other track details. temperature, etc., etc. But the savings is fairly dramatic and consistent.

I did find references on the net that the 8:09 was obtained with a "sport package" or "sport tires" for the M6. If those tires are similar to Michelin Pilot Sport Cup tires or equivalent I am not sure why the time difference would be so small. South or another German speaking board member can probably comment based on the exact Sport Auto test of the M6. Maybe the tires are not so close to a Pilot Cup.

Also, South: Can you let us know which entries in lucid data do have such "UHP+" tires? If you can I will highlight them in a color and post the graph. I expect that would explain many of the data points well below the regression prediction.

[footie]

By the way guys, while surfing the others sites for info on the GTR I found this on a site called RS6.com. According to this guy he says that the GTR was using cut slicks and it's true time will be much, much more than 7:38, in fact closer to 8:00. Sounds like , but there you go.

Here the link.

http://www.rs6.com/forum/showpost.ph...1&postcount=11

[jaiman]

Originally Posted by footie

By the way guys, while surfing the others sites for info on the GTR I found this on a site called RS6.com. According to this guy he says that the GTR was using cut slicks and it's true time will be much, much more than 7:38, in fact closer to 8:00. Sounds like , but there you go.

Here the link.

http://www.rs6.com/forum/showpost.ph...1&postcount=11

yeah that is BS. if you go to the link i posted in post #48, nissan specifically says that cuts slicks were not used as that would not be real world.

[jaiman]

So I added cd and skidpad numbers to the regression and now get an Adjusted R Square of .87 with good significance on the new variables. The GTR goes from a 21 second outlier to a 12 second outlier. if i can figure out how to post up the excel file, i'll do that this evening. I'd like to add some metric for brake performance and see if that helps.


I also tried a dummy variable for AWD but it didn't really add anyhitng at a level of significance that was worthwile.

[footie]

Originally Posted by jaiman

yeah that is BS. if you go to the link i posted in post #48, nissan specifically says that cuts slicks were not used as that would not be real world.

I think we all have to eat humble pie here.

http://www.pistonheads.com/news/defa...?storyId=17066

Here's what was written in the artictle.

Originally Posted by Pistonheads.com

HONED AT THE 'RING

GTR chief engineer Kazutoshi Mizuno told PistonHeads that his baby had covered over 3000 miles at the Nordschleife and avoided other circuits as they were deemed 'too easy'.

Nissan's original target was to beat the 911 Turbo at the 'ring but they ended up worrying the Porsche Carrera GT.

They didn't beat the GT's 7min 32sec lap time, but got a 7.38 in semi-wet conditions.

'We used cut slick tyres' said Mizuno.

'I was not interested in full slick times as this bears no resemblance to a road tyre. 1.2G of force was being pulled in wet and over 2 in dry'.

That's sounds like special tyres to me.

P.S.

This was posted by the same guy on RS6.com by the way. He might not have been the fool we all thought.