Sunday, June 12, 2011


The deal is, get the most output from the least input.
Yes, this is the philosophy of the lazy man. But engineers also use this as the definition of efficiency.
The overall efficiency of fossil-fuelled automobiles — how much of the latent energy of the fuel is converted into motion — is somewhere around 20 to 25 per cent. Much of the rest is lost to heat.
If we can recoup and re-use some of that energy — well, it's free. Sort of.
That's the principle behind every hybrid car: capture the heat lost to braking, and use it to help power the car. The engineers can decide to use this power to move the car farther, or to move it faster, or some combination of the two.
Most hybrids are distance-oriented—go farther on the same amount of fuel.
Infiniti is exploring the other side of the equation with the M35h, what the company is calling the first “true performance luxury hybrid sedan.” It's on sale now, priced at $67,300.
(I wonder what the marketing manager for the Lexus GS450h hybrid, which goes pretty quick itself, thinks of that claim.)
The M35h begins with the all-new-a-year-ago M sedan, Consumers Reports' highest-rated luxury sedan. It recently received a Ward's Automotive “interior'' award. And in the only opinion poll that really matters, sales are up 158 per cent over the previous model.
Into this, Infiniti has baked a hybrid powertrain that in overall concept is similar to what GM (Yukon), Chrysler (Aspen) and Mercedes-Benz (S-Class) have done. It's even (although to a less-similar-looking extent) similar to Honda's Integrated Motor Assist system.
In other words, replace the torque converter with an electric motor, which can add that regenerated energy to the drive wheels, and also act as a starter motor as needed.
The engine is Nissan's corporate 3.5 litre V6, modified to run on the “Atkinson” cycle, as do most hybrids.
Without getting into too much technical detail, this cycle delays the closing of the intake valves on the compression stroke, which allows some of the intake charge to escape back into the intake manifold.
This reduces the pumping losses inside the cylinder, resulting in an engine that is (a), about 10 per cent more fuel-efficient, but (b), considerably down on low-end torque production.
This torque deficiency is more than made up for by the introduction of the electric motor, which quite conveniently generates its maximum torque at zero r.p.m.
The car can scoot from rest to 100 km/h in the low-five second range, which is pretty quick.
More than outright performance, Infiniti is aiming for a direct performance “feel,” with a fast-reacting if conventional seven-speed automatic transmission, instead of a rather more leisurely CVT used in many hybrids.
The system can run on battery alone — up to about 100 km/h if you're below 20 per cent throttle application and there's enough juice in the battery, but only for a maximum of just under 2 km.
More of a party trick then.
The engine will also shut off at idle or during deceleration, when the kinetic energy is being converted back into electrical energy.
The engine will switch back on if the battery gets too low, or when full acceleration is called for.
The packaging is pretty good; the electric motor is only 50 mm longer than the torque converter it replaces, and the lithium-ion traction battery pack still leaves 11.3 cubic feet of trunk space.
Enough, Infiniti says, for four bags of golf clubs, which seems to be the critical criterion in this class of car.
The added components tack about 125 kg onto the car. To compensate, the M35h uses the stiffer springs from the Sport package of the regular M37. Recommended tire pressures are 3 psi higher, to the same intent.
Only rear-wheel drive is offered.
So, how does this all work?
For the most part, pretty well because it drives like an M37 with a bit more power — which is essentially what it is. With a bit of fiddling, you can dial up an energy flow graphic on the instrument panel (whether staring at this constitutes “distracted driving” has yet to be determined).
While smooth transitions from gasoline to electric power are a major objective with this car, you won't ever be in the dark about which system is operating. You can hear and feel the engine kick in when it does.
As it does in the sister cars, this automatic transmission offers four driving modes: ECO (you won't want that); Standard (that's better); Sport, with quicker shifts at higher rev thresholds (more fun, and perhaps consistent with this hybrid, if not most of the others); and Snow, which modulates throttle response to minimize wheelspin. The 'ECO-pedal' which resists depressing to minimize fuel consumption is standard on the M35h.
You're really gonna hate this, but it only works in ECO mode which is why you won't want that ...
One aspect that Infiniti has nailed: the regenerative brakes, which have a grabby feel on most hybrids, are as seamless in operation as I have ever encountered.
The big question: is it all worth it?
The hybrid comes in just one trim level — pretty much loaded for that $67,300, which is about six grand more than a comparably-equipped rear-wheel drive M37, or close to fifteen grand more than a base M37.
Using the Transport Canada protocol, Infiniti quotes an “annual fuel cost” of $1,587, versus $2,254 for the M37 RWD. So it'll take you about nine years to break even. Then again, you'll have performance closer to the M56, which costs about the same to buy, and even more to fuel.
Infiniti expects about 20 per cent of M-buyers to opt for the hybrid version, based on their understanding of how the car's closest competition (Lexus GS 450h) sells.
Not all of these customers will be pure “conquests,” some would surely have chosen another M variant if the hybrid were not offered.
But Infiniti presumably figures there'll be enough newbies that offering the hybrid is worth the considerable development cost this car must have incurred.
Travel was provided freelance auto reviewer Jim Kenzie by the car maker. Reach him at:
Infiniti M-35 Hybrid
ENGINE: Gasoline - 3.5 litre V6, Electric - AC permanent magnet synchronous motor.
POWER/TORQUE: Gasoline - 302 hp / 258 lbs.-ft.; Electric - 67 hp/ 199 lbs.-ft.. Net hybrid system output: 360 horsepower.
FUEL CONSUMPTION: (L/100km) City / Highway, 7.5 / 6.1. claimed
WHAT'S BEST: All the virtues of the existing M37/M56 (the handling, safety technology, the classy interior, all of the luxury equipment) plus an industry-leading combination of performance and economy; the best regenerative brakes of any tested.
WHAT'S WORST: Transitions from gasoline to electric power are not as seamless as they should be. It's still difficult to justify a hybrid on purely economic terms.
WHAT'S INTERESTING: The car actually makes a speed-dependent sound to warn pedestrians of its approach when running in “otherwise silent” electric mode.

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