Pump air from the engine using electric computer controlled linear actuating valves into a high pressure air tank to slow the vehicle; release the pressurized air back into the engine (at the right time for each piston of course) to start the engine back up and start the vehicle moving. The fuel injectors and spark plugs would also be computer controlled to shut off while engine braking, and turn back on when its time to go again.
I’m assuming that the engine would have an extra valve for each cylinder (a third valve instead of just two for example) dedicated to the air tank.
And the valves don’t have to be circular in shape, they could be circular sectors.
I imagine there would also be a pressure sensor inside of the air tank, and a small air pressure gauge on the instrument panel.
Maybe the alternator could be replaced with a smaller one. And a small air pump could possibly be attached to the air tank, to slowly pressurize it. And there could be a small photovoltaic cell on the roof to “trickle charge” the battery.
I believe this system would save a lot of fuel, and recover some otherwise wasted energy.-- BJS, Aug 18 2006 This works well on Diesels with their extreme compression ratios, but not so well on cars with thier low pressure gasoline engines.-- jhomrighaus, Aug 18 2006 There are diesel cars...
It would probably also need to have a manual transmission (or some other type of transmission that allows for engine braking), like most large diesel trucks have, but most cars have automatics (at least in the U.S.).-- BJS, Aug 18 2006 I've had a similar idea to this for a while now. I think it would work well, but I'm sure I've seen it described somewhere else. Now I can't find any reference to it. If it's not already baked then it gets my vote.-- Srimech, Aug 19 2006 I think somebody in France has developed an air pressure operating car.-- s1n4m1n, Aug 21 2006 you could have a tubine on the front of the crankshaft that fills the air tank up and then you use the air pressure to push against the turbine for slow the engine down thanks Nick-- randylandy666, Jul 25 2007 random, halfbakery