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      10-27-2007, 11:06 PM   #19
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Drives: E92 M3
Join Date: Sep 2006
Location: San Diego, CA USA

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Totally disagree

Originally Posted by enigma View Post
Until we can control for tires charts like this are of limited value. On an 8 min track tires alone can cause a 16s or so swing in results. Its why the CSL does much better than its projected time while the base car is worse than its projection.

The general rule with tires is going from a street tire like the Pilot Sport 2 to a DOT-R like the Pilot Sport Cup or Hoosier R6 is worth about 2s per min of track.

If you go to a full slick those are worth another 1s or more. In the video the noise you hear from the tires makes it unlikely that they are running a tire like a full slick or an R6. However, they could still be running a moderate dot-r.

Basically we don't have enough information to make a good comparison.

One thing that is possible. Nissan may have pulled a elise/z06/s2000 like move and put a good suspension in a stock car. The reason BMWs don't usually put up good times stock is the horrid front camber curve combined with the limited room for alignments adjustments and narrow tires for the weight of the car.

The reason the Z06/Nissan/Elise put up very, very good times for a stock car is the run an aggressive double wishbone suspension, a lot of tire for the weights of the car, and often have good alignment possiblites without needing to replace struts.

I have an E46 M3 and an Elise. Both make about the same HP/LB. Yet the elise is much faster at a track stock than the M was stock. The difference is almost 5s/min. 2 of those are from the fact the elise comes with tires similar to the CSL, still that leaves 3s thats mostly due to the suspension.
What happened to my ally in science? Well that is not so fair of me... If folks always agreed on everything life would be boring. Perhaps lucid has already properly defended the use of simple statistics to understand the performance cars obtain. But I will continue.

Like he said the chart covers tons of random variables the idea is the see what parts are random and what parts are due to the physics. I certainly agree that having two complete regressions, one with street tires and one with race tires would be more valuable, but for the most part that data are unavailable. Hence my comment about cars below the line and those above the line. Those like the Elise should (didn't check it myself) be below the line due to their inherent design strengths specifically to make them perform better than other cars of a similar power to weight ratio. For example their suspension (as you mentioned) low moments of inertia, low cg, etc., etc. All such factors engineered into the car will simply push it below the line. Tires are the same, they just happen to give a "big push".

This leads back to the GT-R. I do not doubt that Nissan has put some real high speed "trickery" into this car. By "trickery" I don't mean magic, I simply mean engineering and design effort focused on making it a real track monster. The trick AWD system, traction control system and DCT as well will push it below the line (or at least in that direction). This is then THE question: how far below the curve is reasonable/possible with a totally stock vehicle? lucid could translate this to a percentage/# of std. deviations out etc. or other more concrete numbers, but my gut tells me it is simply too far out to be running street tires and have the power and weight it claims to. My first observation of this was simply the fact that almost all cars <7:40 have >500 hp and <1500kg. Now that immediate observation is even more strongly shown as how far of an outlier it is - the furthest - even given cars known to be running (street legal) race tires. Heck we even now have the direct admission from the Nissan fellow about "shaved" tires or whatever. Even if I did not now know this extra piece of informaton I would still stick to my guns - the car is simply too far below the curve.

Give it just a bit more thought .

My conclusion and standing bet (if anyone is interested) is that at least one of my previous points 1-4 are the case for the GT-R and this 7:38 lap.