It’s not often that a blogger has the opportunity to meet with GM engineers and test drive a one-of-a-kind prototype, but that’s exactly the opportunity I was given the other day. GM first presented a run-down of the interesting tech (which we've written up here) and then handed over the keys so I could see what I thought first hand. The HCCI-equipped Saturn Aura I drove was hot off the proving grounds and the only one of its kind in the United States (there are two HCCI Opels in Europe, like the Opel pictured), and evolved out of an idea hatched way back in the 70s.
My first impression (and the first negative) came before even stepping into the car, and that was when I learned I would be driving an automatic. Evidently, Americans don’t drive stick anymore, but I was still jealous when I learned the two HCCI Opels in Europe were stick shift. I’ll try to put that aside since I’m supposed to be considering the engine, not the whole car.
The Saturn Aura is a fairly large, family-size sedan, and is not uncomfortable by any means. I was given the impression by Paul Najt that this was the type of car currently targeted for HCCI, so I would wager it was a fairly representative of what we as consumers might actually be seeing. GM did hint at the possibility of a V6 HCCI in such a vehicle, but that is just speculation right now, as to the best of my knowledge, there is no such engine in existence.
Those disclaimers made, my first driving impression was “wow, this thing really is like a diesel.” It sounded and drove the part when in HCCI mode, and then in switching back to standard ignition (SI) mode showed its side as a typical gasoline-powered car. The transitions were definitely a little rough around the edges, but I was assured (and believe) that these things will be cleared up long before the car is sent to consumers.
Given the size of the car, the 2.2-liter 4-cylinder had a little less oomph than you would expect from your typical Detroit-built family sedan, but it definitely wasn’t unbearable and I didn’t find myself digging into the gas to keep up with traffic. Monitoring the HCCI display screen while cruising you could see (and feel) the engine performing its unique compression ignition. Such a screen won’t be available in production cars, but even in the unusually aggressive driving cycle that I put the car through in the downtown, live-traffic course, I was in fuel-saving HCCI mode over 50% of the time.
That was, in fact, the most impressive part of the test drive. While I understand that an HCCI mode monitor is unlikely to come with a production model (due to marketing reasons), even without being particularly conscious of my driving, this new technology was in use over half the time. Even though HCCI mode cannot carry the car to highway speeds (it only reaches up to 55 mph right now), the fact that is in operation the majority of the time bodes well for GM’s quoted 15% increase in fuel economy.
It was a pleasure to drive, and it will be interesting to see how (and if and when) it is introduced to the public. If the car does maintain a slight transition between HCCI and SI modes or the sound difference is profound (which really gives the impression of driving a diesel while in HCCI mode), driving an equipped engine will definitely take a shift in the mind of the consumer. However, I won’t fault GM for that now, as it seems that consumers are finally ready to make that switch.
Let’s just hope that those fears don’t keep GM from putting the kibosh on this technology. It gets a definite thumbs up from me.
written by EcoModder, May 13, 2008
written by Andy, May 13, 2008
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