How does it work?
More
than any other new vehicle, the BMW i8 requires this explanation up
front — not just for the dull process of turning energy to motion, but
for the whole enterprise of a $135,700 supercar designed for maximum eco
appeal with styling from the 23rd century.
In BMW engineer speak, the 2015 i8 is properly called a “plug-in
electric hybrid sports car” — one with a 129-hp electric motor driving
the front wheels and a turbocharged,1.5-liter three-cylinder engine with
228 hp driving the rear axle. Since the prototype of the i8 came
in August, some fine-tuning of the all-important software and electrical
power unit has been done by the Munich madhatters, but the i8 remains
the giddy thrill and conversation piece it was then.
I
can already sense the comments that 357 hp and 420 lb-ft of torque for a
$137,000 car is, like, a complete rip-off, man. That someone can buy
two Ford Mustang Shelby GT500s for the price, blow an i8 away when the
light turns green, and put the rest in a bank account. I wish them peace
and happiness with this, but pure speed isn’t the point of the i8,
although it can hustle to 60 mph in 4.2 seconds or less when set up in
Sport mode.
The i8 looks like no other car,
and its complex drivetrain (with two transmissions, a lithium-ion
battery pack and more software than the starship Enterprise) leaves you
grasping for comparisons. Up in the hills and pushing it hard, the i8
did pretty damned well in upholding BMW’s ancient mantra of “ultimate
driving machine.”
While
the front e-motor gets a two-speed transmission – first gear good up to
75 miles per hour, second on up to the 155-mph maximum – the rear gas
engine gets a six-speed automatic you can leave to shift by itself or
which you can shift manually via the console lever (only in Sport) or by
using the steering wheel paddles.
Once you get all the various new drive
rhythms of the i8 imbedded in your subconscious and inner ear, the play
time up and down the gears was entertaining. Both the electro-mechanical
steering and adaptive dampers of the suspension are outstanding.
But
there were a couple of refinement issues for testers
on these launch cars that caused healthy conversation. The first one
was the less than seamless transitions when going from the 129-hp
front-wheel-drive eDrive to the all-wheel-drive 357-hp parallel hybrid
mode in either Comfort or Sport. There is a slight feel of driveline
shunt every so often, and I mean slight, but enough of it to make your wrinkle your nose whenever it happens. Between the software, the central
electric brain, and a secondary 15-hp e-motor attached to the rear
engine to in part help with these transitions, every so often an order
or two gets missed
Then,
when a wheel happens to leave the pavement over a bump while in motion
in the all-wheel-drive parallel hybrid state, the brakes blip on the
axle with the momentarily lifted wheel. The subsequent resumption of
normal all-wheel motion after all rubber re-meets the road can be less
than smooth.
In
straightforward momentum and handling, the i8 takes your sports car
thrills to a different level. One of the more serious bits to decide was
what tires to use, since the i8 needs to be a thrilling driving machine
and not an extremely suped-up Honda Insight. BMW i has elected to give
journalists the wider and less tall optional set of 20-inch tires to
test – 215/45 front and 235/40 rear. These Bridgestone Potenzas do a
good job overall, even while promising less rolling resistance and, in
theory, less lateral grip.
The
logic in these skinny 20s is: what one loses in width of footprint, one
gains in footprint length. Added assistance comes in no small part from
a micro-managing stability control that is smooth in these conditions
over good pavement. Any lateral slip movement is relatively neutral and
what little controlled tail wag happens gets wrangled well without
killing the fun. Weight distribution is 47 percent front and 53 percent
rear, which also helps in keeping things handled even if grip limits are
exceeded.
Another
big helper dynamically is the low stance of the i8. The central
rotational point of the is just 17.8 inches from the ground, the lowest
of any BMW by a good bit. This and the natural ultra-stiffness of the
underlying aluminum and carbon-composite body and chassis make for an
extremely satisfying sports car in any pilot’s hands
No comments:
Post a Comment