02-06-2012, 06:23 PM
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#1 (permalink)
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The Saudi Terminator
Join Date: Jan 2012
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Engine off coasting?
How long do you need to coast before you actually gain increased mpg? Engine off for more than 6 seconds? At what point does it actually cost more to start (fuel enrichment) the engine back up vs just engine on coasting?
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1993 Geo Metro- 361k on original drivetrain minus head. Best mpg of 75.23. Grille block,mirror delete, kammback, fender skirts, and 135-80-15 tires..... Oh and alot of Hypermiling techniques.
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02-06-2012, 06:31 PM
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#2 (permalink)
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Pishtaco
Join Date: Jun 2009
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It depends on how long and how hard you used the gas pedal before you started the coast, and how long your trip is. Typically with a Scangauge or Ultra-gauge, you'll see immediate mpg gains when you start coasting, within a block or two. Get instrumentation like that, and eliminate the guesswork.
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Darrell
Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg
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02-11-2012, 01:24 AM
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#3 (permalink)
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Master EcoModder
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If you bump start does it change the mixture? (Specifically Mazda F2 engine)
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He gave me a dollar. A blood-soaked dollar.
I cannot get the spot out but it's okay; It still works in the store
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02-11-2012, 03:18 PM
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#4 (permalink)
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The Saudi Terminator
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I have heard that the engine if left off to long (eoc) then when fired back up the ECM goes into fuel enrichment ... I am not sure..just curious..
__________________
1993 Geo Metro- 361k on original drivetrain minus head. Best mpg of 75.23. Grille block,mirror delete, kammback, fender skirts, and 135-80-15 tires..... Oh and alot of Hypermiling techniques.
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02-11-2012, 07:04 PM
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#5 (permalink)
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Pishtaco
Join Date: Jun 2009
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Quote:
Originally Posted by Georgboy
I have heard that the engine if left off to long (eoc) then when fired back up the ECM goes into fuel enrichment ... I am not sure..just curious..
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Again, it depends on the ECU software. My 2002 Sentra went into open loop (enrichment) for a full 4 minutes following any EOC. My 2006 Scion stays in closed loop most of the time when restarted, even after a 5 mile EOC.
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Darrell
Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg
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02-11-2012, 07:27 PM
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#6 (permalink)
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Master EcoModder
Join Date: Oct 2011
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5 miles is a long coast, those are definelty worth turning the engine off, but for anything under 30 seconds i don't think it's worth turning the engine off
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02-11-2012, 10:35 PM
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#7 (permalink)
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EcoModding Lurker
Join Date: Dec 2011
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Similar question: What's the shortest time where turning off and re-starting your engine is a net gain over idling? Or, at what time is it the same or better to idle, if any?
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02-11-2012, 10:49 PM
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#8 (permalink)
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Pishtaco
Join Date: Jun 2009
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The automotive pundits say 7 seconds is the magic number with modern fuel-injected cars. Shut your engine down at any stoplight where you'll be idling >7 seconds. You'll use less gas to restart it than you'd waste idling. The EPA says $.17 of every gas dollar is wasted idling.
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Darrell
Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg
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02-11-2012, 10:52 PM
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#9 (permalink)
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EcoModding Lurker
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Thank you. Now does that figure change with kick-starting?
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02-11-2012, 11:06 PM
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#10 (permalink)
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Pishtaco
Join Date: Jun 2009
Location: Bay Area, California
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Quote:
Originally Posted by wanderling
Thank you. Now does that figure change with kick-starting?
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Probably not. The 7 second comparison is strictly fuel used. It doesn't consider electricity to crank the starter. Bump starting is more efficient than using the starter, but you may pay by replacing your clutch sooner.
__________________
Darrell
Boycotting Exxon since 1989, BP since 2010
Have you ever noticed that anybody driving slower than you is an idiot, and anyone going faster than you is a maniac? George Carlin
Mean Green Toaster Machine
49.5 mpg avg over 53,000 miles. 176% of '08 EPA
Best flat drive 94.5 mpg for 10.1 mi
Longest tank 1033 km (642 mi) on 10.56 gal = 60.8 mpg
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