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When one hybrid is more equal than another

Consumers understand some basic calculus when shopping for cars. Used to be that Japanese > domestic, but these days it is more like Japanese ~ domestic.

But doesn’t hybrid = hybrid?  And surely BMW > Chevrolet, right?

Well no, actually. 

There are different kinds of hybrids, but one broadly safe generalization is that there are strong hybrids that have big batteries and strong electric motors and there are mild hybrids which offer little more than automatic engine stop/start for improved fuel economy in urban driving.

Chevrolet made the mistake a few years back of branding the Malibu mild hybrid as a hybrid, leading to disappointed customers who thought it would be a Prius-like system.  It wasn’t and to prevent such confusion Chevy now calls its mild hybrid model the Malibu Eco.

This is likely to be the way of most conventional internal combustion-powered cars in the not-too-distant future; the gas engines will stop and start automatically and there may be a bit of electric regeneration under braking and some mild assist during acceleration, but they will effectively be conventional gas cars.

BMW is following this road map, and as part of its increasing efficiency, the company has substituted a turbocharged 2.0-liter four-cylinder for its trademark inline-six cylinder engines in the new 528 and 328 models.  The Bavarians figure that drivers of the Ultimate Driving Machine will willingly swap some of the six’s signature smoothness and sound for more power and better gas milage.

They may be right, but that straight-six sound was one of the reasons to select BMW over its increasingly good alternatives.

Additionally, BMW has bolstered the four-cylinder’s frugality with an automatic stop/start system that avoids gas wasted idling at lights.  It is a sound concept embraced by more new models every year and the idea has been around long enough now that customers are familiar with it and comfortable with the notion.

Except that BMW hasn’t executed this basic technology with any finesse.   I first drove a stop/start-equipped car more than a decade ago at the proving ground of one of the electrical supplier companies that make starters and alternators for the car companies.

Telling people about the technology afterward, they were always skeptical: Isn’t it intrusive, having the engine stop and then having the starter crank it back up again all the time?  Won’t that wear out the starter?

No, silly, they wouldn’t be foolish enough to do stop/start with a regular starter: They do it with a special starter that doesn’t clank into engagement with the flywheel.  The strong hybrids have an electric motor starter built into the flywheel.  Mild ones like the Chevy use a souped up alternator that is connected to the engine with a belt.

But now comes BMW, with the nerve to do exactly what customers feared all along. They actually expect drivers to tolerate a conventional starter clanking into engagement and then cranking the engine up.

Unlike the seamless Chevy, which starts and stops unnoticeably, the BMW’s engine shudders to a stop, just like the one in your regular car.   You don’t really notice or care that your car does that because it only does it when you are finished driving, not at every red light.  When stopped, the Malibu Eco’s tachometer drops to 0 rpm, but that’s the only indication the engine has stopped.

On startup, the Malibu’s engine almost magically starts running like it never stopped in the time that it takes the driver’s foot to get from the brake to the gas.  The BMW makes the strained sounds of the starter churning the engine back to life, and it shudders as it regains the fire.

And get this: BMW uses conventional engine-driven hydraulic power steering.  That means the steering wheel goes heavy and dead in your hands at a stop.  Trying to turn the wheel a bit to prepare for a turn after the stop brings the surprise that the steering doesn’t seem to work.

Force it and the engine groans back to life annoyingly. The Chevy has electric power steering, which is much maligned for its typical lack of steering feel on cars whose software hasn’t been sufficiently tuned.  But it is a godsend in the Malibu in comparison to BMW’s ham-handed application of hydraulic steering to a car whose engine periodically stops running.

It is no accident that the Malibu’s stop/start procedure is seamless, explained Stephen Poulos, global chief engineer for General Motor’s stop/start technology.  The belt-driven electric motor brings the engine to life in less than one full rotation so it just springs to life.  When stopping, the same motor works to dampen any vibrations from the stopping engine.  It also halts its spinning in one rotation, while the BMW in contrast chugs on for a couple dying spins before its melodramatic silent-film death.

Chevy’s engine management computer also uses the throttle to assist a smooth stop, and stops the engine so precisely that it is in the best position for a quick, smooth restart.  BMW’s, umm, doesn’t.

So its worth noting that some carmakers are doing their homework, while others are counting on the idea that the teacher won’t check theirs based on their reputations as model students.  I checked and BMW gets an F for this one.  Time for them to head to study hall for some remedial work to make BMW = Chevy.