02-06-2012, 05:23 PM
|
#1 (permalink)
|
|
The Saudi Terminator
Join Date: Jan 2012
Location: Buckhead,Ga
Posts: 61
Thanks: 5
Thanked 3 Times in 2 Posts
|
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?
__________________
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.
|
|
|
|
|
02-06-2012, 05:31 PM
|
#2 (permalink)
|
|
Pishtaco
Join Date: Jun 2009
Location: Bay Area, California
Posts: 1,278
Thanks: 39
Thanked 193 Times in 127 Posts
|
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.
__________________
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
49.4 mpg avg over 30,375 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
Clean Green Toaster Machine
45.8 mpg over 2235 miles, 164% of '08 EPA
|
|
|
|
|
02-11-2012, 12:24 AM
|
#3 (permalink)
|
|
Schwinning!
Join Date: Aug 2011
Location: Stillwater, MN
Posts: 990
Thanks: 310
Thanked 237 Times in 133 Posts
|
If you bump start does it change the mixture? (Specifically Mazda F2 engine)
__________________
Quote:
Originally Posted by Weather Spotter
Nothing fell off so that is good.
|
|
|
|
|
|
02-11-2012, 02:18 PM
|
#4 (permalink)
|
|
The Saudi Terminator
Join Date: Jan 2012
Location: Buckhead,Ga
Posts: 61
Thanks: 5
Thanked 3 Times in 2 Posts
|
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.
|
|
|
|
|
02-11-2012, 06:04 PM
|
#5 (permalink)
|
|
Pishtaco
Join Date: Jun 2009
Location: Bay Area, California
Posts: 1,278
Thanks: 39
Thanked 193 Times in 127 Posts
|
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..
|
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.
__________________
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
49.4 mpg avg over 30,375 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
Clean Green Toaster Machine
45.8 mpg over 2235 miles, 164% of '08 EPA
|
|
|
|
|
02-11-2012, 06:27 PM
|
#6 (permalink)
|
|
EcoModding Apprentice
Join Date: Oct 2011
Location: Windsor ON Canada
Posts: 166
Thanks: 8
Thanked 13 Times in 13 Posts
|
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
__________________
|
|
|
|
|
02-11-2012, 09:35 PM
|
#7 (permalink)
|
|
EcoModding Lurker
Join Date: Dec 2011
Location: Ann Arbor, MI 48104
Posts: 14
Thanks: 3
Thanked 0 Times in 0 Posts
|
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?
|
|
|
|
|
02-11-2012, 09:49 PM
|
#8 (permalink)
|
|
Pishtaco
Join Date: Jun 2009
Location: Bay Area, California
Posts: 1,278
Thanks: 39
Thanked 193 Times in 127 Posts
|
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.
__________________
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
49.4 mpg avg over 30,375 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
Clean Green Toaster Machine
45.8 mpg over 2235 miles, 164% of '08 EPA
|
|
|
|
|
02-11-2012, 09:52 PM
|
#9 (permalink)
|
|
EcoModding Lurker
Join Date: Dec 2011
Location: Ann Arbor, MI 48104
Posts: 14
Thanks: 3
Thanked 0 Times in 0 Posts
|
Thank you. Now does that figure change with kick-starting?
|
|
|
|
|
02-11-2012, 10:06 PM
|
#10 (permalink)
|
|
Pishtaco
Join Date: Jun 2009
Location: Bay Area, California
Posts: 1,278
Thanks: 39
Thanked 193 Times in 127 Posts
|
Quote:
Originally Posted by wanderling
Thank you. Now does that figure change with kick-starting?
|
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
49.4 mpg avg over 30,375 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
Clean Green Toaster Machine
45.8 mpg over 2235 miles, 164% of '08 EPA
|
|
|
|
|
