For
all the advances in materials and manufacturing methods made over the years, a
fair number of parts used in the modern car still closely resemble those introduced
at the dawn of the motoring age over a century ago, writes just-auto.com deputy
editor Graeme Roberts.
The wheel, of course, pre-dates the car by aeons. Ever since someone probably
called Og, idly experimenting outside his cave one Sunday afternoon with a rock
and tools resembling a hammer and chisel, found that a flat rounded thing with
a hole in the middle, appropriately attached to a tree branch axle and frame,
made hauling mastodon steaks home from the hunt that much easier, no one’s
been able to improve much on the basic principle. Though it’s hard to see
why early cars were steered by a tiller when the soon-adopted steering wheel
made so much more sense.
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BMW
Valvetronic – maximum valve lift |
Squeezing blocks of abrasive material onto rotating surfaces to stop, or at
least slow, a vehicle also pre-dated the car and no doubt made cart horses everywhere
eternally grateful to the inventor of brakes.
Then there’s the piston with rings. The Otto four-cycle and Herr Diesel’s combustion
principles. Valves. Spark plugs. Fuel pump. Fan. Water pump. Thermostat. Radiator.
Fan belt. Camshaft. Glazed windows. Windscreen wipers. Gearbox. Gear lever.
Clutch. Muffler. Headlight.
Think about the basic operating principle of most items on the modern car and
you can generally trace it back all the way to the original examples. Or pretty
soon after in the case of the electric self-starter and on-board generator.
One item that looked like being on the car forever is, however, now in danger:
the humble throttle butterfly. This oh-so-simple idea – take a round piece of
thin flat brass, pivot it about a shaft in the intake tube leading to the carburettor,
and run a connecting mechanism back to the driver’s foot or hand – has survived
various attempts to ursurp it. But even switching from a carburettor that used
jets to vaporise petrol to electronic injection didn’t do the trick. That’s
because something was still needed to regulate the flow of air ‘twixt filter
and combustion chamber via hot wire or vane airflow sensor and vaporised fuel
injector.
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By GlobalDataImprovements
However, no matter how good an automotive idea might be at birth, beady engineers’
eyes are always fixed on it, thinking of a way to improve it, make it lighter
and cheaper or get rid of it. Think of how something as inconsequential but
useful as the humble automotive fuse has changed over the years.
It is BMW that has finally succeeded in eliminating the throttle butterfly,
due to advances in its variable valve timing and lift technology, first introduced
as the Vanos system about a decade ago.
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Compact
is first 3-series to get new 1.8-litre Valvetronic engine; two-litre follows next month across full range |
Company boffins make comparisons with a human’s breathing to illustrate how
their new Valvetronic system works. Humans breathe deeply when required to exert
themselves. Yet we do not close our nose or mouth when we need less air, but
simply breathe in shorter, more gentle rhythms. A conventional engine with a
throttle butterfly is comparable to a human closing his or her mouth to strangle
the air intake, the white coated ones say. With its infinitely variable valve
lift, a Valvetronic engine is able to take deep or shallow breaths according
to the demands of the driver.
The Valvetronic system is based around BMW’s proven double-Vanos system
which provides infinite camshaft adjustment and, therefore, valve lift. The
variable valve lift adjusts the cam action and, therefore, the duration of the
valve opening. A lever, positioned between camshaft and the intake valves, is
operated by an electric motor via an eccentric shaft and has infinite adjustment
capacity. Depending on the position of the Valvetronic control system, the lever
converts the cam contour to produce greater or smaller valve lift.
Unique
For the moment, the Valvetronic system is unique to BMW and the new 1795cc
four cylinder engine fitted in the confusingly-named 316ti version of the Compact
(the upcoming two-litre petrol model will be called 318ti though its two-litre
diesel equivalent is the 320d) but will spread rapidly across BMW’s four,
six and eight cylinder engine line-up. Next month, the entire 3-series range
including the Compact will receive a new two litre Valvetronic engine followed
later this year by Valvetronic V8s in the new 7-series. You can bet others will
copy – how long before Honda introduces a variation on the theme?
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‘Four
headlight’ nose unique to Compact in 3-series line-up |
BMW says that the major benefit of nixing the 316ti Compact’s throttle butterfly
is a saving of around 10% on fuel consumption with a corresponding reduction
in exhaust emissions, regardless of fuel quality.
The 1.8 litre, 115 bhp, 175 Nm, four cylinder engine is built in the new Hams
Hall engine plant in England and gives the 316ti with five-speed manual transmission
a top speed of 125 mph and 0-100km/h (62 mph) acceleration in 10.9 seconds.
Using the Valvetronic system along with many other changes has increased the
1.8-litre engine’s power by 10% and reduced fuel consumption and emissions
by 10%, compared to the previous model (power up from 105 to 115 bhp and fuel
consumption improved from 37.2 to 40.9 mpg). As a result the entry level Compact
achieves 40.9 mpg in the European test cycle – a 3.8 mpg saving and close
to what you’d have got from a diesel a decade ago – despite having
an engine delivering 10 bhp more and up to 15% better than its competitors.
Next month’s two litre version, also made at Ham’s Hall, will deliver
143 bhp and 200 Nn of torque while reducing fuel consumption and CO2 emissions
by 16% and increasing power by 21% compared to the previous engine. The 318i
saloon manages 45.3 mpg in the combined EU cycle. The upcoming 7-series V8s
get a 14% boost in power and 14% cut in fuel economy thanks to Valvetronic and
an innovative new variable intake manifold.
The four cylinder Valvetronic engine’s ‘open deck’ crankcase
features a new crossflow cooling concept which reduces coolant flow resistance
and allows a smaller water pump which uses only 60% of the normal power drain.
The aluminium engine block ends on the centre line of the crankshaft bearings.
A ladder frame between the crankcase and sump connects the lower halves of the
bearing bridges to form one unit and also accommodates the balance shaft housing
and the two-stage oil pump. This makes the entire unit stiff and robust minimising
vibration. All ancillaries are bolted directly to the crankcase – without
elaborate supports – which also contributes to running smoothness with
reduced vibration.
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Valvetronic
fours are built at new highly automated Ham’s Hall plant in England |
All mod cons
BMW’s latest four cylinder engine also comes with all modern technologies
such as anti-knock control for running on all fuel grades between the U.S.’s
87 and Japan’s 99 octane; maintenance-free ignition with individual coils;
maintenance-free valve drive with automatic hydraulic adjustment; service interval
indicator (a well-established BMW feature since emulated by others); double-mass
flywheel for maximum running smoothness; roller bearing valve drive for minimum
friction and fuel consumption; and advanced catalysts mounted near the engine
in special manifolds for minimum emissions.
Apart from the decreased fuel consumption and exhaust emissions, BMW reckons
the engine’s dynamic performance and spontaneous response is much improved
when compared to its predecessor. Added to this, they cite a higher standard
of running smoothness since the valves move less in the precisely-controlled
Valvetronic process. Instantaneous throttle response is also improved because
load control, the technical term for pressing the accelerator, now takes place
where the action is, directly in the combustion chamber. This eliminates the
time lag between the process of touching the throttle and the actual acceleration
of the car due to the need to fill the intake manifold between the throttle
butterfly and the combustion chamber.
Feels just right
Imagine explaining all that to most non-industry, non-technical people. Eye
glaze-over time, huh? In most cases few owners will know or care and there is
absolutely nothing to indicate to the driver that this quite momentous change
has been made to the engine. Start up and blip the throttle and the engine,
well, blips. Call for more neddies when overtaking and they respond instantly
to the command. And, reflecting the experience of earlier ‘drive-by-wire’
throttle control systems, pedal feel is just right.
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Stiffened
Compact suspension and quicker steering rack spread to rest of 3-series range in September |
The engine itself is the usual fine BMW four – smooth, refined, willing – though
perhaps lacking a little in low range punch on the tight, low mileage examples
we sampled recently on a fast Highlands dash from the Scottish town of Inverness
to the Isle of Skye via that controversial toll bridge. The rest of the driveline
displays the usual BMW tautness with no hint of slop in sudden power on-off
situations and a lovely crisp, short-throw gear shift and smoothly progressive
clutch.
For many, though, a BMW is about straight-six power and the 325ti’s 2.5
litre, 192 bhp, 245 Nm engine with, we suspect, near-obsolete butterfly throttle
control is as smooth and silky as you expect while bragging about its 146 mph
top speed and 7.1 second 0-100km/h/62 mph sprint. We sampled it with the smooth
five-speed adaptive automatic which always seems to be in the right gear for
the occasion yet allows you to make clutchless ‘manual’ changes by
prodding the lever forward or back.
So much for the oily bits, what’s the rest of the new Compact like? Well,
for a start, it’s shed that slightly ‘low rent BMW’ feel of its
predecessor. The old car was nonetheless very good, and highly successful with
over 400,000 sold since its 1994 debut, but it always left a slight taste of
inferiority if you were also familiar with the regular 3-series saloons, coupes
and wagons. It was mostly to do with the retention of an earlier generation
of 3’s simple beam rear axle, rather than the complex Z-axle introduced
on other 3s around ’91, and the cheap-looking dashboard with ’60s-style
headlamp knob. So handling and ride, and interior ambience weren’t quite
the same as in a regular 3-series.
BMW listens
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For
this new generation, cabin is all but indistinguishable from 3-series cousins |
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With the new car, it’s clear BMW listened to grumbles about the older model
and upped the specification. So you get the full current 3-series suspension
layout and a cabin you can’t pick from the rest of the range. In fact, the Compact
leads its cousins with suspension that has stiffer settings all round and a
quicker steering rack which will find its way into other 3-series models next
month to answer criticisms the latest cars are ‘too soft’ compared with their
predecessors.
Existing Compact owners will marvel at the quality feel of the new interior
and owners of older saloon models will no longer curl their lips should you
dare suggest the Compact is now worthy of consideration alongside the rest of
the range rather than an entry-level sop to wannabe BMW owners. The outgoing
model, by the way, attracted two out of three buyers new to the marque, 65%
of whom went on to trade up within the brand.
This is not to suggest, however, that the new Compact is now blandly absorbed
too deeply into the mainstream range. It has even more of its own identity these
days with a delightful ‘four headlight’ nose and superb tail lights
designed in the same clear-cover-over-round-lens style as previously seen on
the Lexus IS series and since copied by Nissan’s U.S. Altima and Maxima.
Versions
Although Honda can seemingly wheel out 113 variations on the Civic simultaneously
world wide, BMW specialises in the, er, gradual introduction. Left hookers came
first a few months ago and it was Britain’s turn yesterday (other right
hand drive markets to follow) with 316ti, 316ti SE and 325ti SE models on offer
at launch while 318ti and 320d versions follow in a few months’ time. The
SE versions are BMW GB’s way of grouping a stack of popular options together
into a variant priced cheaper than if you ordered the bits individually but
there is still plenty of scope to add numerous items from one of the industry’s
longest list of ‘available’ goodies.
Despite being 21cm shorter that the 3 series saloon (on the same wheelbase),
the new Compact is larger than its predecessor, gaining 15mm in height, 53 mm
in width and 52mm in length.
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Round
lenses under clear cover follow latest tail light styling trend |
The rear hatch is 36 mm or 1.4 inches wider, allowing loading right up to the
lower sill of the rear hatch making the Compact suitable for transporting loads
up to the size of a Euro-style front-load washing machine with the hatch closed.
Boot capacity is up 70 litres to 1,100 litres. The latest Compact also has a
remote control function that opens the hatch to its widest point as either standard
or optional equipment. Another detail touch, available later this year, is an
adaptable parcel shelf storage system incorporated into the load cover which
can be used to carry smaller items in an expandable compartment or adapted to
hold shopping in carrier bags, suspended from hooks. It includes a special umbrella
storage compartment.
Reflecting a trend developing in the industry, buyers can now choose from 18
interior colours, 11 paint shades, two fabric upholstery colours, four fabric/leather
options and five full leather choices. They can also match the interior trim
to the exterior colour of the car with a new design option called Young Line.
Even on this entry-level range BMW’s key and car memory is now fitted as
standard. Key memory remembers personal settings including seat position and
air conditioning temperature for up to four separate keys to the same car. Car
memory activates non-personal preferences such as ‘follow me home’
lights where the headlights remain on for 30 seconds after the car has been
locked and owners can change these settings to suit.
All this is bundled together with the latest electronic stability aids, airbags
galore and a package that is vastly improved over its predecessor. Say hello,
then, to the BMW that banished the butterfly.
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