View Single Post
Old 06-15-2012, 05:03 PM   #8 (permalink)
EcoModding Lurker
Join Date: Apr 2009
Location: n/a
Posts: 60

TBA - '07 Honda Fit
Thanks: 11
Thanked 9 Times in 6 Posts
Originally Posted by lbeew View Post
In modern fuel-injected vehicles, as soon as you release the throttle, the engine management stops feeding fuel to the injectors, as long as the rpms are high enough (I am guessing higher than 800-1000 rpm). This means that when you release the gas and coast IN GEAR, the wheels turn your engine, without the engine management injecting ANY fuel. Thus effectively not using any fuel.
While this does sound logical in theory, here's what I've noticed ACTUALLY happens (using the scangauge to verify when the car is and is not in deceleration fuel cut off):

1) Leave in gear to decelerate
2) Crap I wasn't going fast enough


1) Leave in gear to decelerate
2) Count to 5
3) Deceleration fuel cut off FINALLY kicks in

DFCO is far more inconsistent than actually turning off the car. It also slows you down MORE, causing you to to have to accelerate more.

9 times out of 10, I use engine off coasting. The other times are when it's generally too short of a distance to justify EOC or when I actually need to slow down or a combination of the two.
  Reply With Quote