I remember on the news seeing ways to increase fuel economy, and one of the best they said was to have a computer that would shut down your engine at red lights.

Well i'm thinking is there a system out there that will let you shut down your engine, maybe by a button or something temporarily while you're costing to a light and during the light, then another button that starts it back up... Yet during the whole time, maintaining power to the steering and brakes (airbags?) through the battery? (could this be as simple as wiring the power to these items to the accessory key position instead of the "on" position?)<--- although I think a seperate manual switch would make that better

Maybe would get rid of the dangerous inherend side effects of normal DFCO.

And is there a way to make it start up faster after a light, and not to have to make it crank a lot? I heard that it takes being off for 30 seconds before you can recoup savings from fuel because starting the engine uses a lot of fuel. But today with computerized fuel injectors and stuff, is that still true?

I guess this would be as close as a hybrid as you can get with out having an electric assist engine , there are plenty of times going through town where i can literally coast over a mile and it would be cool to be able to do this with the engine not sucking up fuel. Might need to get a bigger battery though aye?

 

Sounds like a neat concept, but you would need to address the problem of restarting the car. It would be really hard on the starter and also cause a delay from starting.

You could probably get away with reducing the idle RPM's a bit to save fuel.

 

yea i was kinda researching it and apparently hybrids have some type high voltage efficient starters that also keep the engine from running rich during start. Adjusting the idle RPM sounds like a good idea though

 

Fuel injectors are shut off when you're coasting. Besides you'll shorten the life of your starter which I think would outweigh the costs of the fuel you'll save at idle.

 

I've been wondering what the effects on MPG would be of manually shutting down a injector or two.

Sure 0-60 would be about 20 seconds, but....

I might pull an injector harness (or two) off this weekend and see what happens.

 

what are the inhererant problems with normal defco? i figure it you could control when you go in to defco without droping to a lower gear i think that would be the easiest way to save. so on shorter hills you can defco more often.

 

Then how does the engine stay running? You mean coasting in gear?
no power steering / brakes? If there was a way to keep those systems running it would be a lot safer

 

Power steering runs off an ele motor in the Fit Key to II and it works fine with engine off

Also brake booster holds enough vac for many stops.

 

Yes coasting in gear.

 

By contrast, a manual transmission, with the clutch engaged, can use the car's momentum to keep the engine turning, in principle, all the way down to zero RPM. This means that there are better opportunities, in a manual car, for the electronic control unit (ECU) to impose deceleration fuel cut-off (DFCO), a fuel-saving mode whereby the fuel injectors are turned off if the throttle is closed (foot off the accelerator pedal) and the engine is being driven by the momentum of the vehicle.

from wiki

so if you can wire a switch to shut off the injectors when coasting, i think that you can dfco more often i guess a push button would be better. wiring a light for when the injectors are off(dfco) you can find out when the ecu goes into dfco. if it happens when coasting in 5th gear then cool, but if not and it only goes into dfco when in a lower gear like engine braking. something like that.

 

1/2 right
You have to be coasting "foot off gas" at speed and in gear ..ie eng braking.. also above 1300rpm's or so. Fuel flow goes to zero

Idling will result in .18 to .3gph depending