Why is S car fuel mileage so poor?

[Huw Powell]

> Why would they make more power?  Remember, this is in a highway cruise 
> test.

engines capable of more power waste more when it's not being used.

>  From the EPA web site: "The highway is a 10 mile trip with an average 
> speed of 48 mph. The vehicle is started "hot" and there is very little 
> idling and no stops."

>> Why are the S cars mileage numbers so low?  I figured consumption 
>> would be
>> a matter of engine load and efficiency.  As both engines are pulling the
>> same weight (and shape in the case of the S8), the load should be roughly
>> similar.  So does that make the S cars 15% engines less efficient?
>>
>> Take the S8 for example.  Two naturally aspirated V8's of the same
>> displacement and hauling the same weight.  Looking at highway numbers (as
>> it's fairly steady state):
>> S8 vs A8 (both 2001)
>> 21 vs 24 mpg
>> 4024 vs 4068 lbs
>> 360 vs 310 HP
>> 317 vs 302 ft/lbs
>> 11.0 vs 10.8 comp ratio
>> 13.9 vs 14.2 ¼ mile
>> 6.3 vs 6.7 0-60 mph
>> An aside: 345x30mm vs 312x25mm (323x30mm for the A8L)
>>
>>
>> As for the S6:
>> S6 vs A6 4.2 (both 2002)
>> 21 vs 25 mpg
>> 4024 vs 4024 lbs (surprised by this)
>> 340 vs 300 HP
>> 310 vs 295 ft/lbs
>> 11.0 vs 11.0 comp ratio
>> 14.5 vs 15.0 ¼ mile (14.7 for the 2.7tt w/6-speed)
>> 6.5 vs 6.7 0-60 mph (6.0 for the 2.7tt w/6-speed)
>> Curiously, both have 321x30mm front rotors.  I expected the S6's to be
>> bigger.
>>
>> Numbers taken from the AudiWorld site.

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/