Quote:
Originally Posted by JMAN311
17/29 mpg (city/hwy) – 3.6L DI VVT V6 with manual transmission
18/29 mpg (city/hwy) – 3.6L DI VVT V6 with automatic transmission
16/24 mpg (city/hwy) – 6.2L V8 with manual transmission
16/25 mpg (city/hwy) – 6.2L V8 with automatic transmission
So you have a 426hp 6-spd manual tranny car getting 16/24 mpg
and an active fuel management 6-spd auto car with 26 less hp can only get 1 mpg better?!?!?!?
What's up with that? Guess I didn't realise how much at automatic tranny can rob fuel mileage.... 
Now let me ask this....How many mpg do you think it would get as an LS3 w/ 6-spd auto tranny (no AFM, just a 426hp LS3 like the manual tranny car uses slapped to the auto tran)?
Also I think it's a testament to how well the LS3 manual can do....It's not much of a trade off over a V6 to only lose 1city and 5 highway mpg and have 122 more hp. |
You have to realize that even with AFM (which deactivates 4 cylinders in low-load situations), it only cuts fuel to those cylinders. Energy is still required to suck in a dry charge (no fuel, just air), compress it to 1/11th its original volume, let it expand, then blow it out the exhaust. It still takes quite a bit of energy to compress that dry charge. So some of the fuel that you save by not injecting it into the cylinders is used to compress the air in those dead cylinders. That's why you don't get much better mpg with it.
And the automatics have a taller (lower number) rear end than the manuals. 3.23 auto, 3.45 manual. This helps with mpg numbers.