View Single Post
Old 08-19-2009, 12:02 PM   #20 (permalink)
EcoModding Lurker
Join Date: Aug 2009
Location: Southeast Michigan
Posts: 1
Thanks: 0
Thanked 1 Time in 1 Post
For those who have a stumbling engine when trying to cut fuel, I would guess that the reason is that not all of the injectors are being cut off. You're essentially running on 3 cylinders (if you have a 4 cyl engine).
On my Focus, there is a single +12v power wire coming from the power distribution box that then splices into 4 separate power wires... one to each injector. The 4 wires that come out of the 4 injectors are then the ground wires that go to the engine control module. The control module "switches" the ground wire in order to control each individual injector. So if your car is like my car, you cannot cut just one ground wire, or you will be cutting only one injector. In my case, I cut the single power wire before it splices into 4 separate wires. I have a normally closed momentary switch attached to the shift lever, and it works beautifully (except that the switch broke today, almost leaving me stranded in traffic). No relays necessary. I found this thread while searching for a source for a more robust NC momentary switch, to replace my broken one.

So my technique is to simultaneously lift the throttle, press the clutch, and press the fuel cutoff switch. I watch the tachometer drop to zero, and then let go of the switch. It does take some time for the engine to spin down to zero, especially if you are traveling at higher speeds. Around 45mph in 5th gear at about 2000rpm requires around one second to kill the engine. 65-70mph at 3000rpm can take around 2 full seconds to spin down, before you can release the switch.
I can tell you that pulse & gliding with the engine off (versus letting it idle while gliding) is definately worth it. Idling at stop lights also destroys your trip average fuel economy. Glide to a stop light with the engine off, leave it off, and when the light turns green then key up and go. I'm getting 55-57mpg in my Focus, and before I wired in the fuel kill switch I was getting 40-45mpg.
  Reply With Quote
The Following User Says Thank You to Brent72 For This Useful Post:
TEiN (09-01-2009)