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What is your city and highway mpg?

 
  #31  
Old 04-14-2014, 01:43 PM
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My first three Aston Martins were Lagonda's (1984 series II, 1985 Series III and a 1988 Series IV). I was luck to get 8MPG - on the highway! From that benchmark, the Vantages are OK by me.
 
  #32  
Old 04-18-2014, 09:57 AM
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Originally Posted by XWCGT View Post
...What determines MPG quality, is the rolling friction, and engine efficiency. this engine is not very efficient. Also the RPM range for cruise is way too high. 3000rpm at 80mph is just RPM just used up for no reason. 5th gear can accelerate you to some phenomenal speeds, and 6th should be an overdrive. However, its really about the entire gear ratio set. the rear end is WAY too high, as shown by the way too low, first gear. (no way it needs to be that short of a gear..... something like 10:1) most supercars have an 8.5:1 first gear, and that alone , by changing the rear end by 20%, you would get 80rpm RPM down to 2500rpm or so
I agree, but you'll need to go even farther. If 1st gear is really something like 10/1 (as you say, way too "short") then that suggests that simply installing a "taller" final drive ratio would correct the whole gearing situation. It would have to be tall enough to drop the engine down to around 2000 at 80mph, though. You want enough load on the engine at cruise to require a significantly larger throttle opening, which will reduce manifold vacuum/pumping losses. Right now, with the engine spinning at 3000 at 80mph, it's wasting a whole bunch of energy on needless friction and just trying to suck air past that comparatively small throttle opening. In fact, the taller the gearing, the better for fuel economy...short of actually lugging the engine, that is.

Are there other applications that utilize this differential...perhaps offering other final drive ratio choices? I know it seems counter-intuitive to put taller gears into a performance car, but Aston appears to have significantly over-done the gearing in this case...at least for American roads. In Europe, extended cruising may be relatively uncommon, but here? They should've realized...
 
 
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