Carburetor (pronounced kahr-buh-rey-ter
or kahr-byuh-yey-tor)
(1) A device for mixing vaporized fuel with
air to produce a combustible or explosive mixture for use in the cylinder(s) or
chambers of an internal-combustion engine.
(2) In the slang of drug users, a water
pipe or bong; a device for mixing air with burning cannabis or cocaine (rare since
the 1970s and then usually in the form “carb” or “carby”).
1866: From the verb carburate, from the Italian carburate
(to mix (air) with hydrocarbons”), an inflection of carburare & the feminine plural of carburato. As a transitive
verb carburet was used mean “to react with carbon”. Strangely, the exact origin of the word is
uncertain but it was likely a portmanteau of carbon (in the sensor of a clipping
of hydrocarbon) + burette (a device for dispensing accurately measured
quantities of liquid). The construct was
carb (a combined form of carbon) + -uret (an archaic suffix from Modern
Latin) (uretum to parallel French
words using ure). The earlier compound
carburet (compound of carbon and another substance; now displaced by carbide)
was from 1795 and it was used as a verb (to combine with carbon) after 1802. The use with reference to the fuel systems used
in the internal combustion engines of vehicles dates from 1896. Carburator,
carbureter and carburetter were
the now obsolete earlier forms and the standard spelling in the UK, Australia
& New Zealand is carburettor. Carb &
carby (carbs & carbies the plural) are the the universally used informal
terms (gasifer was rare) and although most sources note the shortened forms
weren’t recorded until 1942 it’s assumed by most they’d long been in oral use. Outside of a few (declining) circles, “carb”
is probably now more generally recognized as the clipping of carbohydrate. Carburetor & carburetion are nouns; the
noun plural is carburetors.
One carburetor: 1931 Supercharged Duesenberg
SJ with 1 x updraft Stromberg (left; the exhaust manifold the rare 8-into-1 monel "sewer-pipe") (left), 1966 Ford GT40 (Mark II, 427) with 1 x
downdraft Holly (centre; the exhaust headers were referred to as the
"bundle of snakes") and 1960 Austin Seven (later re-named Mini 850) with 1 x
sidedraft SU.
Except for some niches in aviation, small
engines (lawnmowers, garden equipment etc) and for machines where originality
is required (historic competition and restorations), carburetors are now
obsolete and have been replaced by fuel-injection. There is the odd soul who misses the
challenge of tinkering with a carburetor, especially those with the rare skill to
hand-tune multiple systems like the six downdraft Webers found on some pre-modern
Ferraris, but modern fuel injection systems are more precise, more reliable and
unaffected by the G-forces which could lead to fuel starvation. Fuel injection also made possible the tuning
of induction systems to produce lower emissions and reduced fuel consumption, the
latter something which also extended engine life because all the excess petrol which
used to end up contaminating the lubrication system stayed instead in the fuel
tank.
Two carburetors: 1970 Triumph Stag with 2 x
sidedraft Strombergs (left), 1960 Chrysler 300F with 2 x Carter downdrafts on
Sonoramic cross-ram (long) manifold (centre) and 1969 Ford Boss 429
with 2 x Holly downdrafts on hi-riser manifold.
Until the 1920s, all but a handful of
specialized devices were simple, gravity-fed units and that was because the
engines they supplied were a far cry from the high-speed, high compression things
which would follow. In the 1920s,
influenced by improvements in military aviation pioneered during World War I
(1914-1918), the first recognizably “modern” carburetors began to appear, the
conjunction of adjustable jet metering and vacuum controls replacing the
primitive air valves and pressurized fuel supply mechanisms allowed engineers
to use a more efficient “downdraft” design, replacing the “updraft” principle
necessitated by the use of the gravity-feed.
Between them, the “downdraft” and “sidedraft” (a favorite of European
manufacturers) would constitute the bulk of carburetor production. The next major advance was the “duplexing” of
the carburetor’s internals, doubling the number of barrels (known now variously
as chokes, throats or venturi). Although
such designs could (and sometimes were) implemented to double the capacity (analogous
with the dual-core CPUs (central processing units) introduced in 2005), the greatest
benefit was that they worked in conjunction with what was known as the “180o
intake manifold”, essentially a bifurcation of the internals which allowed each
barrel to operate independently through the segregated passages, making the
delivery more efficient to the most distant cylinders, something of real significance
with straight-eight engines. Few
relatively simple advances have delivered such immediate and dramatic increases
in performance: When the system was in 1934 applied to the them relatively new
Ford V8 (the “Flathead”), power increased by over 25%.
Three carburetors: 1967 Jaguar E-Type (XKE)
4.2 with 3 x sidedraft SUs (left), 1967 Ferrari 275 GTB/C with 3 x downdraft
Webers (centre) and 1965 Pontiac GTO with 3 x downdraft Rochesters.
Advances however meant the demand for more
fuel continued and the first solution was the most obvious: new manifolds which
could accommodate two or even three carburetors depending on the configuration
of the engine. Sometimes, the multiple
devices would function always in unison and sometimes a secondary unit would
cut-in only on demand as engine speed rose and more fuel was needed, an idea
manufacturers would perfect during the 1960s.
World War II (1939-1945) of course saw enormous advances in just about
every aspect of the design of internal combustion engines (ICE) and carburetors
too were improved but in a sense, the concept had plateaued and it was
fuel-injection to which most attention was directed, that being something which
offered real advantages in flight given it was unaffected by G-forces,
atmospheric pressure or acrobatics, working as well in inverted as level flight,
something no carburetor could match.
Four carburetors: 1973 Jaguar XJ12 (S1)
with 4 x sidedraft Zenith-Strombergs (left; the Jaguar V12 was unusual in that
the carburetors sat outside the Vee), 1976 Aston Martin V8 with 4 x downdraft
Webers (centre; Aston Martin-Lagonda originally fitted the V8 with fuel
injection but it proved troublesome) and 1965 Ford GT40 (X1 Roadster 1, 289)
with 4 x downdraft Webers (right, again with the "bundle of snakes"
exhaust headers).
After the war, like the chip manufacturers
with their multi-core CPUs in the early 2000s, the carburetor makers developed
four-barrel devices. In Europe, the
preference for multiple single or two barrel (though they tended to call them “chokes”)
induction but in the US, by the early-1950s just beginning the power race which
would rage for almost two decades, for the Americans the four-barrel was ideal
for their increasingly large V8s although sometimes even the largest available wasn’t
enough and the most powerful engines demanded with two four-barrels and three
two-barrels. It was in the 1950s too
that fuel-injection reached road cars, appearing first in a marvelously
intricate mechanical guise on the 1954 Mercedes-Benz 300 SL (W198)
Gullwing. Others understood the
advantages and developed their own fuel-injection systems, both mechanical and
electronic but while both worked well, the early electronics were too fragile
to be used in such a harsh environment and these attempts were quickly abandoned
and not revisited until the revolution in integrated circuits (IC) later in the
century. Mechanical fuel-injection,
while it worked well, was expensive and never suitable for the mass-market and
even Mercedes-Benz reserved it for their more expensive models, most of the
range relying on one or two carburetors.
In the US, Chevrolet persisted with mechanical fuel injection but
availability dwindled until only the Corvette offered the option and in 1965
when it was made available with big-block engines which offered more power at
half the cost, demand collapsed and the system was discontinued, the big
engines fed either by three two barrels or one very large four barrel.
Other four barrel devices
Reggie
(Reggie Bannister (b 1945) with Regman Quad-Barrel Dwarfcutter in Phantasm
(1979).
Four (and more) barrel weapons have long been common in fixed or mobile
structures (warships, gun batteries etc) but are rare in anything hand-held because
of the increases imposed in size & weight as well as the heat generated. In fiction (notably video games and horror
films) they’re a popular prop and the four barrel shotgun in Don Coscarelli’s
cult classic Phantasm (1979) was among the more memorable. An ad-hoc creation born of the need for more
firepower (very much in the vein of the “…going to need a bigger boat” philosophy in the
Film Jaws (1975), a line apparently improvised during filming because it
appears neither in Peter Benchley’s (1940-2006) 1974 novel nor the original screenplay),
it was made by welding together two double barrel shotguns and named the “Regman
Quad-Barrel Dwarfcutter”. It
was that sort of film and freaks attracted to the design (which does seem hard
to resist) have created Nerf-guns in the style.
Although rare, hand-carried, multi-barrel firearms have a history dating
back centuries and provided the intended application is appropriate, they can
be both effective and convenient, a number of manufacturers offering three and
four barrel shotguns, all of which presumably include a section in the owner’s
manual covering “recoil management”. Very much in the spirit of those who took
advantage of the modular construct of the early (and anyway already sometimes lethal)
two-stroke Kawasaki triples (H1, H2, S1, S2 & S3; 1969-1975) to build a
48-cylinder version, nine-barrel(!) shotguns have been made... just in case.
Custom four
barrel Vierling longarm by Johann Fanzoj (1790) of Ferlach, Austria.
The
four-barrelled longarm was configured with a side-by-side double rifle (calibre:
9,3/9,3x74R), paired with an over-and-under shotgun (gauge 12/12/76). Built to a customer specification to shoot
four (plus two) times in sequence with “hot” barrels, the Vierling used
H&H-type sidelocks with automatic ejectors.
An impressive example of the gunsmith's art, this was not a Phantasmesque
welding job but an intricate design which had to regulate the rifle barrels
two-times-two so they would shoot together to the same point of impact, in
sequence. First, the 9,3 barrels
discharge, then by pushing the barrel selector forward, the shooter continues
with the 12-gauge barrels with automatic ejection of the shotgun cartridges facilitating
quick reloading… just in case.
English “Duck’s
foot” four-barrelled pistol with walnut slab-sided butt and silver-wire scroll
inlay, said to date from the early nineteenth century. Note the angle of the barrels and thus the
wide field of fire.
Collectors
also prize bizarre and ambitious designs such as the four-barreled “duck’s foot” pistol. Historians have questioned whether these
weapons really were manufactured in the Georgian or Regency eras and some
suggest they were a product of entrepreneurial Victorians creating “relics”
which played into prejudices about just how bad were what were then the “olden days”. The legend is these were early crowd-control
devices with which some worthy (squire, mill or mine owner etc) could deter the
mob (revolting peasants, disgruntled factory workers, whatever) which would
have been inclined to take a chance against someone armed only with a
single-shot pistol. There’s nothing in
the historic record to suggest riots and strikes were ever “controlled” with
such things but the Victorians of the late nineteenth century were well aware
they were the first generations to benefit from a standing, regulated
constabulary so the need for such things would have seemed at least
plausible. The legend is they were also carried
by naval captains in case of mutiny and while the Admiralty apparently never
issued them, it’s not impossible some officers bought their own… just in case.
Five carburetors: Le Monstre's 331 cubic inch (5.4 litre) Cadillac V8 (left) with its unusual (and possibly unique) five-carburetor induction system; the layout (one in each corner, one in the centre) is a "quincunx", from the Latin quīncunx. Le Monstre ahead of Petit Pataud, Le Mans, 1950 (right). At the fall of the checkered flag, the positions were reversed.
Le Monstre was a much-modified 1950 Cadillac which ran at that year's Le Mans 24 hour endurance classic. one half of a two car team the other being a close to stock 1950 Cadillac coupe. The idea behind the five carburettors was that by the use of progressive throttle-linkages, when ultimate performance wasn’t required the car would run on a single (central) carburettor, the other four summoned on demand and in endurance racing, improved fuel economy can be more valuable than additional power. That’s essentially how most four-barrel carburettors worked, two venturi usually providing the feed with all four opened only at full throttle and Detroit would later refine the model by applying “méthode Le Monstre” to the triple carburettor systems many used between 1957-1971. As far as is known, the only time a manufacturer flirted with the idea of a five carburetor engine was Rover which in the early 1960s was experimenting with a 2.5 (153 cubic inch) litre in-line five cylinder which was an enlargement of their 2.0 litre (122 cubic inch) four. Fuel-injection was the obvious solution but the systems then were prohibitively expensive (for the market segment Rover was targeting) so the prototypes ended up with two carburettors feeding three cylinders and one the other two, an arrangement as difficult to keep in tune as it sounds. Rover’s purchase of the aluminium 3.5 litre (214 cubic inch) V8 abandoned by General Motors (GM) meant the project was terminated and whatever the cylinder count, mass-produced fuel injection later made any configuration possible. Motor racing is an unpredictable business and, despite all the effort lavished on Le Monstre, in the 1950 Le Mans 24 hour, it was the less ambitious Petit Pataud which did better, finishing a creditable tenth, the much modified roadster coming eleventh having lost many laps while being dug from the sand after an unfortunate excursion from the track. Still, the results proved the power and reliability of Cadillac’s V8 and Europe took note: over the next quarter century a whole ecosystem would emerge, crafting high-priced trans-Atlantic hybrids which combined elegant European coachwork with cheap, powerful, reliable US V8s, the lucrative fun lasting until the first oil crisis began in 1973.
Six carburetors: 1979 Honda CBX with six
sidedraft Keihins (left), 1965 Lamborghini P400 Miura (prototype chassis) with
6 x downdraft Webers (centre) and 1970 Ferrari 365GTB/4 (Daytona) with 6 x
downdraft Webers (right).
It was the development of these big four
barrels which in the US reduced the place of the multiple systems to a niche
reserved for some specialist machines and even the engineers admitted that for
what most people did, most of the time, the multiple setups offered no
advantage. The research did however
indicate they were still a selling point and because people were still prepared
to pay, they stayed on the option list.
There were a handful of engines which actually needed the additional
equipment to deliver maximum power but they were rare, racing derived units and
constituted not even 1% of Detroit’s annual production. Paradoxically, the main advantage of the
multiple setups was economy, a six-barrel (ie 3 x two-barrel) engine running
only on its central carburetor unless the throttle was pushed open. As it was, the last of Detroit’s three-carb
setups was sold in 1971, the configuration unable easily to be engineered to
meet the increasingly onerous exhaust emission rules.
Eight carburetors: 1955 Moto Guzzi 500cm3 Ottocilindri V8 Grand Prix motorcycle with 8 x Dell'Ortos. One carburetor per cylinder was long common practice in motorcycle design and the two 1959 Daimler V8s (2.5 & 4.6 litre, 1959-1969), were designed along
the lines of a motorcycle power-plant, intended originally to be air-cooled
and run 8 carburetors; the production
versions were water-cooled and used 2 x sidedraft SUs. The very thought of keeping eight carburetors synchronized would alarm most but clearly such intricacy doesn't scare the Italians because, in 1967, the Cooper-Maserati Formula One team, seeking that elusive quality of increased power and sustained reliability did ponder bolting a dozen Webers to what was their by then antiquated (pre-historic in F1 terms) 3.0 litre V12. To the eternal regret of those who value mechanical complication for its own sake, that idea, like the notion of using three spark plugs per cylinder, never left the engineers' sketch pads and the more rational fuel injection was adopted.
Lindsay Lohan admiring Herbie’s carburetor in Herbie: Fully Loaded (2005).
Before
fuel-injection was late in the century used for some, most Volkswagen Type 1s (Beetles)
were fitted with a single Solex carburettor although there were exceptions, some
more expensive and higher performance (such things are relative) variants in
Europe, Mexico and Brazil using twin Solexes.
Additionally, because it wasn’t difficult to swap in the twin
carburettor units used in the Karmann Ghia (Types 14 & 34) and Type 3 cars,
many were upgraded and over the years there were literally dozens of kits to
create multi-carburetor induction systems using equipment from a variety of
manufacturers including Solex, Weber, Dell'Orto and Kadron (Solex-Brosol).
