RE: Direct Injection

["Storhok, Eric (E.M.)" <estorhok@domain.elided>]

Now that we are getting to the technical side of the DI article (who cares who is the best, I've seen documentation that the "real" alfa will be less than we can all imagine...).

Anyway, as james pointed out direct injection (di, since I'm a lazy engineer) has been around for a long time, first in diesels (no kidding...), and in spark ignition engines in the 30's (can't say gasoline, as Germany experimented with some rather interesting fuels...).

But for modern DI motors, some of the hype isn't quite up to snuff.  First the gas mileage.  There is an increase, but in my opinion, its debatable whether the owner will save enough on gas bills to pay for the DI, even at $4 a gallon.

Next, important for me, the emissions.  The fuel atomization isn't as good as one might think, its amazing what a little turbulence and mixing will do for port injected fuel.  But the hard part is the cold start (which to me is a 70 F ambient start).  The system can't generate enough pressure quickly to get a good combustible mixture, so it will be very difficult to achieve the really low emissions.

Then there is the long term durability- when I worked at Chevron, a friend of mine worked on an diesel injector clogging problem, which I would think will be a problem with gas, also.  While "gas" is a much simpler average molecule than diesel, it will still deposit in the cylinder and might clog the injector.

I don't know where it will go, and I hope I'm wrong on some of these problems, but there are still issues...

Eric Storhok
Core Emissions and Fuel Economy Team
Advanced Powertrain Engineering
(313)33x75011
MD 35, FPC-B
Ford Motor Company

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