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      12-15-2007, 03:50 AM   #43
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Drives: E92 M3
Join Date: Sep 2006
Location: San Diego, CA USA

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Originally Posted by bruce.augenstein@comcast. View Post
OK Swamp, deep breath time.

To me, the jury is pretty much still out on this one. I read that Edmunds thing and thought that the 911 Turbo's superior acceleration at high speed seemed about right, given similar power and lighter weight (although aerodynamics gets more important than HP/weight as speeds rise).

Then I thought about slightly better GT-R performance against the six-speed 911 turbo in the quarter and thought OK, that trans has got to be worth something against an old-fashioned six-speed, right? Even the Tiptronic kicks the six-speed's butt, right?

So what the hell, here comes that dumbed down Quarter, Jr. program again.

I find some specs out on the net (4.05 first gear etc., 3.70 final drive, 480 HP etc.), plug in the best traction number (Quarter, Jr. don't know nuthin 'bout no all wheel drive stuff), and at 3970 pounds with a launch at 2800 rpm (who knows?), the thing runs an 11.69 at 120 flat.

That suggests (to me) that it may be making around 492 HP (or about 2.5% higher than rated) given a 121 MPH quoted pass by Nissan - assuming they ran it with full tank and a 170 pound hot-shoe aboard. With a 120 pound anorexic hot-shoe or 50 pounds less than a full tank, we get an 11.64 @ 120.5, so hell, we're down in the weeds here as far as Nissan being cute on power ratings goes.

Yeah, I know, there's that sterling 'Ring time, but hey, that 7.38 is only two seconds up on Rorhl's best pass in the 911, right? Plus pretty much everybody (including Edmunds) says that the GT-R is simply mahvelous (dahling!) in the twisties compared to the Porsche. We know Rorhl is an effing genius behind the wheel, but Nissan probably isn't going to put Ghosn's wife behind the wheel for a time this important, either.

I think the jury is still deliberating, and we'll see after the car is in general hands, but I'm beginning to think we have the genuine article here - no cheating, or if cheating, at least only a smidge.

Bruce, true or false, AWD systems exhibit significantly larger drivetrain losses than RWD vehicles of a similar component quality? Also true or false, a transmission located at the rear of a vehicle with an extra drive shaft to get power back up front also creates more losses than not having those components? Last but not least, true or false. Running a simulation assuming the GT-R is a RWD vehicle (which is what Quarter Jr. is doing) will fairly drastically underestimate the drivetrain losses of the vehicle?

Conclusion: Quarter Jr. software is not a very reliable judge of a AWD + rear tranmissioned vehicle since it misses out on a significant amount of loss the car will have.

Underestimating the drivetrain loss by only 5% (using the rough but reasonable estimate that RWD total drivetrain loss is approx. 15% and AWD is approx. 20%) could make Quarter Jr. underestimate the under-rating of the car by that same 5% of the vehicles total power or about 25 hp.