Right, but this assumes that there is no compression braking in the engine. You can't do the same coast in gear because you have to turn the motor/pump air through it.
Now, if you're braking during that coast to keep your speed down, you'll get better fuel economy staying in gear and using the engine for most of that braking. -Z On Jun 16, 2008, at 10:06 AM, Ken Bogart wrote: > Not exactly sure how to calculate it, but if I use some *rough* > estimates, this is what I come up with: > > Assuming 24mpg to maintain 60MPH and 1/2 gal per hour to maintain > idle. > > Drive for 1 hour and you would use 2.5 gallons (no coasting). If you > can coast for 25% of that in neutral (15 minutes), you would consume 2 > gallons (1.875 + .125 for idle) (30mpg). If you can do the same coast > in gear, you would consume 1.875 gallons. (32mpg) > > 30MPG is about right for steady 60mph, which is about 2 gallons per > hour at 60mph. Of course, this "math" all depends on the underlying > assumptions which are a SWAG. > > Ideally, if I could communte downhill both ways, I suspect I could > attain 50MPG or more... > > > KEN > > > On Mon, Jun 16, 2008 at 12:48 PM, Aleksandr Milewski <[EMAIL PROTECTED] > > wrote: >> Bill Cardell wrote: >>> Does the slowing from the wheels >>> driving the car (which then has to re-accelerate more than if the >>> car >>> coasted) outweigh shutting off the fuel? >> >> I have to believe that the losses from running that big air pump from >> the wheels far outweigh the fuel burned idling. I have a 5 or so mile >> run on my commute that I can dead-stick. I'll have to play with the >> trip >> computer in the Audi. :) >> >>> As far as safety aspect, I had >>> an audi that did this from the factory. 5000TD, if your foot was >>> completely off the gas it free-wheeled. >> >> Automatic or manual? Lots of automatic transmissions have an overrun >> clutch such that there's no engine braking in top gear. I know the >> 727 >> Torqueflite in my old Jeep was that way. And yes, it's very strange. >> >> I still get caught out occasionally by the asymmetry of the turbo >> motor >> in the A6. Not nearly as much compression braking as there is power >> under boost. ;) >> >> >> _______________________________________________ >> Miatapower mailing list >> [email protected] >> http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower >> > _______________________________________________ > Miatapower mailing list > [email protected] > http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower _______________________________________________ Miatapower mailing list [email protected] http://list.miatapower.net/cgi-bin/mailman/listinfo/miatapower
