[California98Civic]

For the last 2 or 3 tanks I have been experimenting with a technique and I am getting interesting results, though I don't know for sure if there is any fuel economy benefit. I would welcome your thoughts. First some preliminaries:

1) Alternator cut-off switch: I installed one a couple years ago. I can turn the alt on when I want it and shut it off fairly easily from the dash.

2) DFCO or Deceleration Fuel Cut Off: when the engine control computer shuts off the fuel injectors to if the car is in gear, foot is off the throttle, and the RPMs are at maybe 1800 or more (I usually use 2000 as the llwer limit to be safe).

3) Hilly route: My commute features several very long and steep hills that end in stoplights that are usually red, or at which I must turn. I always have to break at these locations.

THE TECHNIQUE I AM TESTING: going down these hills I bump start the car, turn on the alt, and use the engine for breaking instead of the friction breaks. The result is a sort of DFCO-exclusive use of my alternator, exclusively under conditions where I would normally coast with the engine off and use the friction breaks. If you look at my fuel log, you'll see that the power I use from the grid to charge the battery at night has gone way down, but my fuel economy has been flat.

QUESTIONS: Do you think DFCO is really working? My FE numbers could be flat because I have been driving a lot on the freeway, more than in past spring seasons, because of my super tall transmission. Do you think the couple seconds it takes to get into DFCO after bump starting and the couple seconds after DFCO to cut the injectors could mean significantly more fuel use when repeated scores of times during a tank?

Thanks for any and all replies.

james