Writers across the automotive blogosphere are guilty of using the words “direct injected” as an adjective meant to give some punch to the description of a new engine. I am no exception:
Buick will offer a no-extra-cost 3.6-liter direct-injected V6…
But what does “direct injected” really mean? Many readers of this blog are enthusiasts and know exactly what the term describes, but for others, it’s just more techie jargon that sounds cool in front of the term “V6.”
I’ll briefly describe what it means, but more importantly, ask if direct injection is the savior some automakers believe. Some evidence is beginning to crop up that could translate to future maintenance disasters.
First, for the uninitiated:
A direct-injected engine injects pressurized fuel directly into the combustion chamber, rather than into an intake manifold where it gets mixed with air and then enters the combustion chamber.
The results of direct injection are improved fuel economy and cleaner emissions due to a leaner fuel burn, which Ford, GM, Volkswagen, Hyundai and others love to tout in advertisements and press releases.
The problem, though, is pretty dirty.
Auto Observer reports that the issue lies in the tendency of direct-injected engines to build up a layer of carbon around the intake valves that can significantly affect the performance and economy of the engines over time. The dirty grime builds up in a DI engine because, unlike a port-injected engine, there is no constant spray of fuel to keep the deposits washed off the valves.
The repair can be quite expensive, though some guys at a BMW forum swear that “giving the car a good flogging” once in a while burns the deposits off. Maybe… but that’s probably not a substitute for dropping the bucks and having the valves cleaned.
Volkswagen has known about the DI problem for quite some time, saying in a patent application that the carbon deposits can have extremely negative effects on performance.
Owners of Cadillac’s direct-injected V6 have also reportedly started to complain, though GM remains adamant that it has engineered around the problem.
Whether the problem exists only in the Caddy owners’ heads or not, it’s becoming quite clear that direct injection still has some hurdles to clear before automakers roll out the technology across the board.
Would you buy a vehicle with a direct-injected engine knowing about the potential carbon layering problem?