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Re: well...
Posted by Stephen Goldberger [Email] (more from Stephen Goldberger) on Tue, 18 Dec 2007 10:29:30
In Reply to: well..., Jonathan Scupin [Profile/Gallery]
, Tue, 18 Dec 2007 07:33:58
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I need to agree with dmz. You will use less fuel coasting in neutral than with the foot off the gas and the car in gear. In one case, you are burning only enough fuel to keep the engine turning, while the energy lost is rolling and air friction. In the other, you must be burning more fuel, b/c the engine is turning faster and whatever air does get sucked into the engine is mixed with fuel at the stochiometric (15:1) ratio. But more important, you are using up energy sucking air past the closed throttle plate. That is where engine braking comes from. If you completely blocked the intake, engine braking would be minimal. This is how "variable displacement" engines work - the intake valves on the diabled cylinders are shut, so no air gets drawn into the engine on their account. (I'm not sure about exhaust valves, whether they are also kept shut).
As for accelerating, shifting to neutral to coast, then re-accelerating in gear - uhm, yes, that *IS* the driving regimine to optimize fuel economy - and you accelerate in as high a gear as possible and at full throttle (or as wide a throttle as possible without triggering WOT enrichment functions if they exist). Not a smooth way to drive, not traffic friendly, and possibly not even legal (I think coasting in neutral, aka "West Virginia Overdrive" is outlawed at least in some places), but it is thermally efficient.
posted by 70.126.233...
Posts in this Thread:
- Average clutch life........., Tim, Mon, 17 Dec 2007 16:39:35
- Mine has 148k on original clutch..., mdj, Thu, 20 Dec 2007 22:02:17
- 53K on original and going strong, normal driving nm/, Ells, Tue, 18 Dec 2007 17:24:21
- Re: Average clutch life........., Tim, Tue, 18 Dec 2007 13:14:46
- Re: Average clutch life........., John M, Tue, 18 Dec 2007 06:47:47
- Coasting in neutral...., Jonathan Scupin , Mon, 17 Dec 2007 21:15:14
- I hope you are joking... nm, dmz789abc, Mon, 17 Dec 2007 22:12:06
- uh, nope!, Jonathan Scupin , Mon, 17 Dec 2007 22:21:36
- Re: uh, nope!, dmz789abc, Mon, 17 Dec 2007 22:41:43
- well..., Jonathan Scupin , Tue, 18 Dec 2007 07:33:58
- Re: well..., Stephen Goldberger, Tue, 18 Dec 2007 10:29:30 <-- Viewing This Message
- Until it won't go...., Mike Lynch , Mon, 17 Dec 2007 18:10:17
- Re: Average clutch life........., Herb Hirsch , Mon, 17 Dec 2007 16:57:54
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