[fedinand]

I just read an article in one of the car mags where the X3 posted 5.3 0-60 and 13.8 in the quarter...I can't see how 300hp can do that in a two ton vehicle with the aerodynamics of a brick

[Insider]

Which car mag was that?

[fedinand]

MotorTrend page 64.

[ayio]

I think it can do.. twin turbo power

E.g. F11 35i with 2,4 tons has almost the same acceleration: 0-100 km/h in 6.1 sec

[fedinand]

Originally Posted by ayio

I think it can do.. twin turbo power

E.g. F11 35i with 2,4 tons has almost the same acceleration: 0-100 km/h in 6.1 sec

Twin power - not twin turbo (twin scroll single turbo instead of the twin turbos in the N54 engine).

[ayio]

right, right! but the power is there.. ))

[Lotus7]

Originally Posted by fedinand

I just read an article in one of the car mags where the X3 posted 5.3 0-60 and 13.8 in the quarter...I can't see how 300hp can do that in a two ton vehicle with the aerodynamics of a brick

As someone who's been a diehard manual transmission ONLY driver for the last 30plus years, I really hate to admit it, but the wide range 8-speed auto gets some of the credit. With the 35i gearing the overall starting ratio is a "stump-pulling 15.98:1 which makes for very quick launches from a standing start and the close spacing, and quick shifting of the rest of the ratios (not to mention the N55's extremely wide torque band) means the engine is always able to deliver maximum power at any speed.

[Insider]

Pretty fast stock, but should be quite the rocket with a tune...

[fedinand]

Originally Posted by Insider

Pretty fast stock, but should be quite the rocket with a tune...

No doubt…what a sleeper

[XB101]

Bit of and old thread but figure I will add to this one instead of starting another.

The 35i weights 4200 lbs. @~300 hp and 295 ft/lbs of torque. I was looking at the stats for a G37 and that car is about 500 lbs lighter. At 328 hp and ~270 ft/lbs of torque the 0-60 and 1/4 mi times are not far from the 35i. Depending on which magazine you look at it's about 5.3 sec 0-60, and 14.1 sec 1/4 mile. It's hard to believe a SAV can almost hang with a car like that in the straights!

[turbotoy4me]

Very interesting data. These are the reasons we are choosing to drive or soon to be driving the X3 35i. We get SUV versitility and sports car performance. Thanks for posting the informaion.

[clarence]

Autozeitung timed it at 5.7s for 0-100km/h.
4wd means all that torque won't be wasted on burnt rubber.

[LEDZEP]

Originally Posted by fedinand

I just read an article in one of the car mags where the X3 posted 5.3 0-60 and 13.8 in the quarter...I can't see how 300hp can do that in a two ton vehicle with the aerodynamics of a brick

What brick? The X3 is very aerodynamic as SUVs go.

[fedinand]

Originally Posted by LEDZEP

What brick? The X3 is very aerodynamic as SUVs go.

Its an aerodynamic brick or aerodynamic for a brick, but a brick nontheless!

[Vintage]

it is a sports car in handling and performance with the convenience of an SUV - pretty cool

[Lotus7]

Originally Posted by fedinand

I just read an article in one of the car mags where the X3 posted 5.3 0-60 and 13.8 in the quarter...I can't see how 300hp can do that in a two ton vehicle with the aerodynamics of a brick

Without getting into a dry, boring technical analysis (I hope), some of the reasons that the X3 35i is posting such seemingly amazing 0 to 60 mph or 0-100 kph times are:

1. Published horsepower and torque ratings for modern engines are much more accurate and less "optimistic" than those published in previous years. Manufacturers are required to prove that engines can develop their rated power by tests done on random samples in both US and European spec vehicles. Engines are tested with all accessories in place and operating, and with the engine connected to the vehicles actual production exhaust system. Before 2000, engines were tested without accessories and with open exhausts so rated hp and torque figures were higher than what could ever be achieved in the car. "300hp" in 2011 really means 300hp. "300hp" in 1999 typically meant something like 230 to 240 hp at the flywheel when the engine was actually installed in a car.

2. The X3 35i (N55) twin scroll turbo engine has an extremely flat and very extended torque curve. The engine can produce 83% of maximum torque at any RPM between 1750 and 5750*, unlike older, normally aspirated, high-performance engines that have a significant loss of torque at speeds below the (relatively high) peak torque RPM. More torque integrated under the curve = quicker acceleration.

4. The X3 35i has a wide ratio 8-speed transmission that, in combination with the wide, flat torque curve, means that the X3 can develop the absolute maximum possible wheel torque (which is what accelerates the vehicle) at ANY vehicle speed. The available torque does not peak and decay as it would with a "peaky" normally aspirated engine and with a 4 or 5 speed transmission.

5. The X3's ZF 8-speed transmission http://www.zf.com/corporate/en/produ...nsmission.html is designed to allow exceptionally fast shifts while maintaining full throttle, full torque transmission to the drive wheels. No acceleration is lost during shifts.

6. The X3's all wheel drive system is designed for optimum torque distribution to all wheels and allows up to 100% of the torque to be diverted to the rear wheels if necessary. Little or no wheelspin = quicker.

Regarding the X3's aerodynamics:

The 2011 X3 (F25) has a specified frontal area of 2.57 m2 and a drag coefficient (Cd) of 0.350.

(Lower Cd = less drag.)

A brick wall with the same frontal area of a X3 would have 2.86 X more drag than a X3.

As a comparison of the relative "aerodynamics” of different vehicles, here is a selected list of vehicles:

2010 Toyota Prius Cd = 0.25
2001 Audi A2 Cd = 0.25
2007 Nissan GTR Cd = 0.27
2007 Honda Accord Cd = 0.29
1947 Saab 92 Cd = 0.30
1995 Peugeot 406 Cd = 0.32
2008 Chevrolet Tahoe Cd = 0.34
2011 BMW X3 Cd = 0.35
2009 Lexus RX Cd = 0.35
2010 VW Tiguan Cd = 0.37
1998 Honda Odyssey Cd = 0.39
1938 VW Beetle Cd = 0.48
2010 Ferrari F1 car Cd = 0.7 to 1.1 depending on wing down-force settings

So, the X3 is actually more streamlined than a typical brick and is more aerodynamic than a Formula 1 racer. But of course, every current production car is also.

* N55 engine torque curve

[XB101]

Sweet post! Thumbs up.
You just sold me a X3 :-)

The Prius is aerodynamic!

[Beyu]

I'm surprised that a Chevy Tahoe is more aerodynamic than the X3. I had one riding my ass for like a mile after work today, now that car's a brick wall.

[Lotus7]

Originally Posted by XB101

..
You just sold me a X3 :-)

Please don't forget to mail the sales commission.

[Lotus7]

Originally Posted by Beyu

I'm surprised that a Chevy Tahoe is more aerodynamic than the X3. I had one riding my ass for like a mile after work today, now that car's a brick wall.

Those were manufacturer's published specs. Chevy probably does their testing on Pikes Peak (thinner air).

[fedinand]

Originally Posted by Beyu

I'm surprised that a Chevy Tahoe is more aerodynamic than the X3. I had one riding my ass for like a mile after work today, now that car's a brick wall.

That is a big brick..OK a big aerodynamic brick. Great info as always Lotus

[LEDZEP]

Good stuff, as aways Lotus!