Direct Injection Gas Engines
With the trend to direct injection gas engines what happens going down a hill on compression. Diesel engines without intake butterflies have little hold back on compression, so I assume that gassers w...
Forum Discussion
Yes, it has gotten much more complicated to figure out stuff
Some direct gasoline injection has throttles, some do not
When decelerating, it depends on the direct gasoline injection computer's software
whether it squirts gasoline or not and how much
With throttle plates, the pumping losses are higher is my guess. With no throttle
plate, the net is what it takes to compress vs push from that compressed is a
net zero, minus the pumping losses. Assuming not fueled to maybe a tiny amount
to keep it fired/warmed/etc
Never looked closely into exhaust braking and admit to not really knowing how
they work.
From listening to them on the road, guessing that they block and release the
exhaust so that the pumping losses are increased. Therefore engine braking, but
that is just a guess till find time to read up on them (not motivated just yet
but if the direct injection systems do not have throttle's, then this might also
work on gasoline ICE's)
With the speed of the newer solid state injectors, think the computer systems can
multiplex the squirts to go from ultra lean burn to stoichiometric to zero fuel
during one combustion cycle, or am I wrong on that line of thinking?
There is much more to direct gaoline injection, as the OEMs want very high MPG
when used as a 'car' and lots of grunt for truck/SUV towing usage
That means small displacement for MPG and meat in everything (block, crank, rods,
journals, piston, head, valves, etc, etc) for high torque.
Along with that will be the need for good thermal characteristics (rejection and
the sensors to manage that). Meaning stuffing in big block V8 levels
of air/fuel into an econo sized engine will have higher stresses and
less surface area to reject the heat
Some direct gasoline injection has throttles, some do not
When decelerating, it depends on the direct gasoline injection computer's software
whether it squirts gasoline or not and how much
With throttle plates, the pumping losses are higher is my guess. With no throttle
plate, the net is what it takes to compress vs push from that compressed is a
net zero, minus the pumping losses. Assuming not fueled to maybe a tiny amount
to keep it fired/warmed/etc
Never looked closely into exhaust braking and admit to not really knowing how
they work.
From listening to them on the road, guessing that they block and release the
exhaust so that the pumping losses are increased. Therefore engine braking, but
that is just a guess till find time to read up on them (not motivated just yet
but if the direct injection systems do not have throttle's, then this might also
work on gasoline ICE's)
With the speed of the newer solid state injectors, think the computer systems can
multiplex the squirts to go from ultra lean burn to stoichiometric to zero fuel
during one combustion cycle, or am I wrong on that line of thinking?
There is much more to direct gaoline injection, as the OEMs want very high MPG
when used as a 'car' and lots of grunt for truck/SUV towing usage
That means small displacement for MPG and meat in everything (block, crank, rods,
journals, piston, head, valves, etc, etc) for high torque.
Along with that will be the need for good thermal characteristics (rejection and
the sensors to manage that). Meaning stuffing in big block V8 levels
of air/fuel into an econo sized engine will have higher stresses and
less surface area to reject the heat
