EFI fuel pump and water; alt approach

[Stuart Hastings]

(/lurk; end lurk mode, open mouth, insert foot)

Just for reference, the two-stroke folks have been thinking about
atomization for a while now. Modern marine two-stroke engines use
pretty sophisticated direct injection techniques.

Outboard Marine (http://www.omc-online.com) uses a combination
solenoid/pump/atomizer that generates more than 250 PSI internally.
It's probably not applicable to the current discussion about water
injection. Very elegant-looking technology; looks like EFI, but the
injectors are bigger, and they squirt directly into the cylinders:

	http://www.omc-online.com/ficht/FichtRam.htm

Critics of OMC's system say the injectors are unduly complicated,
require huge amounts of electical energy and a hefty ECU to control,
and are probably RPM-limited.

Orbital Engine of Australia (http://www.orbeng.com.au) has an
air-assisted injection process that *might* be of interest, because
they claim it produces superior atomization. The injector they use for
four-stroke DI uses 6.5 bar air and 7.2 bar fuel (about 96 and 106
PSI). Here's a PDF of their injector:

	http://www.orbeng.com.au/pdf/oec_4s.pdf (PDF - 249Kb)

Here's a pretty picture of their DI atomization plume:

	http://www.orbeng.com.au/tech/cpt7.htm

Outboard engines fitted with Orbital's scheme
(e.g. http://www.mercurymarine.com) supposedly use a conventional EFI
fuel pump, and a belt-driven air pump that's a close relative of an
air-conditioning compressor. Alas, I wasn't able to find a nice online
picture of such an engine with the belt-driven compressor and all.

Critics of Orbital's scheme say the seperate belt and compressor are
potential failure points, it clutters the engine with lots of air
plumbing, and the equipment weighs more than OMC's Ficht scheme.

In practice, both schemes seem to work exceptionally well in outboard
engines, their weights, prices, performance, fuel economy, emissions,
and reliability are all comparable. Both systems have had embarrassing
early mortality problems, and both OMC and Mercury have made good on
those troubles.

My point is posting this is to show that high pressure (OMC's Ficht)
will atomize pretty well, and an air+liquid injector (Orbital/Mercury)
will atomize really well. However, for DIY-intermittent-WI, I guess
that 200 PSI distilled water is much cheaper and simpler.

Anyone interested in DIY Direct Injection? :-)

stuart hastings
(back to lurk mode)
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