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      08-20-2008, 02:43 PM   #80
T Bone
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Drives: 2008 335xi Coupe
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Originally Posted by bruce.augenstein@comcast. View Post
Not at all. The M3 tends to beat the RS4 because it weighs less. More on that in a moment, but can we now agree that your 335 vs A6 4.2 comparison is nonsense?
No. By your calculations, what is the impact of weight as speed increases? Drag / Drivetrain losses become a higher percentage of the "resisting" force. Additionally, if weight was the key issue, why is the RS4 quicker to 60 (assuming good traction on the M3)?

Hey, I'm not complaining that the 335 is underrated, but the fact remains that the drive wheel power output of these engines is in the 275 - 285 HP arena, which means in turn that the 300 HP "at the flywheel" number is nonsense. In addition, boost against preload (or popping the clutch at high rpm) gives the 335 a huge advantage off the line. That, plus the several hundred pound weight disparity, gives your current car a major advantage over your old car - but it ain't because Quattro is some power-robbing "horrible" powertrain.
Modern turbo cars can adjust for ambient conditions much more effectively than N/A cars. Dyno runs can be adjusted or even manipulated as you know. If you know better than BMW / SAE than please share with us.

I've never seen a chassis dyno result on a 335 xi, but you can bet the results will be down compared to a rwd 335 - so you can also expect chassis dyno results to be down on the RS4 compared to the M3. After, all, you're transmitting power through three differentials instead of one, plus the attendant u-joints, cv joints, etc. Then you've got to add in the rolling resistance of the two additional tires on the dyno wheels.

Look, guy, because of awd and the weight differential, you'd expect the RS4's quarter mile trap speeds to be down by between three and four percent, with the ET disparity closer due to the awd launch capabilities. Near as we can tell from the lists, that's where the cars fall.

Bottom line, I'm not trying to say anything about which car is better, just that based on what I see in this string plus my own experience, Quattro is far from "horrible", and it certainly isn't particularly power hungry.


PS - Since third gear in our A6 4.2 was good for about 110 mph, it certainly felt very strong to me at 150 kph, and in fact it was at 150 kph and above where our car began to pull on both of the 540s I happened to meet.

Sure I would expect the XI to be down on from the regular I. But what is not being addressed is the observed performance gaps of the RS4 and other old school Quattro systems.

It is not weight as the significance of the other forces are much higher after say 70 mph.

Also personally, I remember the A6 4.2 as being slow off the line, a happy 60 - 140 kph type of car and after a few high speed runs, the car was slow.

"Aerodynamics are for people who cannot build engines"......Enzo Ferrari