Fuel cutoff switch for P&G with an automatic

[abogart]

Now equipped with a functioning TC lockup switch I have been toying with the idea of installing a switch or button to cut power to the fuel injectors. My idea here is to kill the fuel with the TC locked for deceleration and engine braking which should (in theory) keep the engine and all accessories turning so that when I flip the switch back on or release the button, the I should have power immediately restored.

Because the engine won't actually shut off, the ECU shouldn't even realize that I have cut the fuel. The only exception being that the O2 sensors might read off the scale, causing the ECU to max out fuel trim for the time that it is cut.

Having my own controllable DFCO could make for a significant improvement in my city driving. I live in a small town and make many short trips, and it's hard to even break 20mpg around town. I wouldn't doubt if half the fuel I use is just to keep the engine turning during decel and idling.

Another thought... I have been thinking that this would enable me to do a modified P&G on the highway by cutting fuel with the TC locked and "gliding" in OD with the throttle open as far as I can get it (without causing a downshift) to reduce pumping losses, then restoring fuel and pulsing at max load. I am unsure, however, if drivetrain, friction, and the remaining pumping losses would even out the efficiency gained from the high-load pulse.

Suggestions, comments, concerns?