Quote:
Originally Posted by racprops
"Port fuel injected engines generally spray fuel early on the back of the hot intake valves before they open, which fully vaporizes the gasoline before it enters the cylinder."
Sorry that is incorrect, this hot intake valve at around 500 degrees helps vaporize some of the fuel, but cannot get it all. In theory it helps with a part vaporize which help start the burn sooner and faster that help vaporize more of the fuel within the chamber.
"Direct injection engines do not, of course, which I think (?) is why they produce soot. However, DI engines typically also get better fuel economy."
I know that does not really compute…all I can guess it they inject less fuel as part of the system.
"Gasoline vapor claims are unicorn material."
YET cars truly can only burn vapor.
Rich
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DI engines generally run at the same air fuel ratios, so less fuel isn't being injected.
Something to keep in mind, even if fuel isn't vaporized at all before entering the combustion chamber, as a piston compresses the contents... let's say 10:1. If the intake charge starts at 100F, and is compressed to 1/10 the volume, the temperature inside the combustion chamber will be just under 1,000° F before the spark plug even fires. Once some of the fuel starts burning, the contents of the cylinder can reach 5,000° F.
Without digging any further, I would imagine this would vaporize any gasoline that hasn't already. Anything that failed to burn simply didn't find the oxygen it needed.
I'm all about taller gearing, however. Friction goes down exponentially as RPM decreases. Load goes up, which also helps.
EDIT: Also, a large part of a catalyst's job is to convert CO into CO2, and NOx into N2. Even if there were zero HCs in the exhaust we'd probably still have catalysts.