Manifold

Manifold (pronounced man-uh-fohld)

(1) Of many kinds; numerous and varied:

(2) Having numerous different parts, elements, features, forms, etc.

(3) A copy or facsimile, as of something written, such as is made by manifolding (obsolete except in historic reference).

(4) Any thin, inexpensive paper for making carbon copies on a typewriter (archaic).

(5) In internal combustion engines, the part (1) of the exhaust system attached directly to the exhaust ports and (2) of the induction system attached directly to the inlet ports.

(6) In mathematics, a topological space that locally looks like the ordinary Euclidean space.

(7) The third stomach of a ruminant animal (an omasum) (US (mostly south of the Mason-Dixon Line)), usually in the plural.

(8) In computer graphics, a polygon-mesh representing the continuous closed surface of a solid object.

Pre 1000: From the Middle English adjective manifold (many times, in multiplied number or quantity), from the West Saxon & Old English manigfeald & manigfealde (monigfald was the Anglian variant) (various, varied in appearance, complicated; numerous, abundant), the construct being manig (many) + feald (fold).  From the Proto-Germanic managafalþaz came the common Germanic compound (the Middle High German manecvalt (manifold), the Icelandic margfaldr (multiple), the Old Frisian manichfald, the Middle Dutch menichvout & menigvoudig (various), the Danish mangefold (multiple), the German mannigfalt, the Swedish mångfalt (diversity) and the Gothic managfalþs), it’s thought perhaps a loan-translation of the Latin multiplex (multiply; having many forms) and the Old English also had a verbal form, manigfealdian (to multiply, abound, increase, extend), the meaning later extended to (the now obsolete) “make multiple copies of by a single operation”.  The adverb manigfealdlice (in various ways, manifoldly), was derived from the adjective.

The noun manifold was applied to the mechanical device (“a pipe or chamber, usually of cast metal, with several outlets”) from the mid-1850s and was a short-form (from engineer’s slang) of “manifold pipe” which had been in use since 1845 which originally was applied to the types of musical instruments mentioned in the Old Testament.  The familiar use to describe the components which are part of an internal combustion engine’s intake & exhaust systems dates from 1904 and applied initially to the pipe between a carburetor and the combustion chambers; the existence of exhaust manifolds was noted the following year.

Of manifold sins and wickedness: Lindsay Lohan smoking and smoldering.

 Among those first translating the Bible into English, manifold was a popular word and few phrases more concisely encapsulate the Church’s view of us than “manifold sins and wickedness”.  In the Book of Common Prayer (1549). the Church of England helpfully provided a general confession for those who knew they were wicked sinners (and of presumably greater significance knew that God knew) but had neither the time nor desire to list them all.  Once uttered, it invited God’s forgiveness.  The Book of Common Prayer became controversial within the more liberal factions of the Anglican communion because its more exacting demands were thought to be uninviting to a society which was changing while the Church was not.  However, despite many revisions (including some regionally exclusive to parts of the old colonial empire), sins and wickedness remain manifold in most editions. 

The General Confession from the Book of Common Prayer (1662 edition)

Almighty God, Father of our Lord Jesus Christ, maker of all things, judge of all men: We acknowledge and bewail our manifold sins and wickedness, which we, from time to time, most grievously have committed, by thought, word and deed, against thy Divine Majesty, provoking most justly thy wrath and indignation against us.

We do earnestly repent, and are heartily sorry for these our misdoings; the remembrance of them is grievous unto us; the burden of them is intolerable.

Have mercy upon us, have mercy upon us, most merciful Father; for thy Son our Lord Jesus Christ's sake, forgive us all that is past; and grant that we may ever hereafter serve and please thee in newness of life, to the honour and glory of thy name; through Jesus Christ our Lord.  Amen.

The Duesenberg manifolds

1935 Duesenberg Supercharged J (SJ) dual cowl phaeton with coachwork by LaGrande, the lines made more rakish still by the use of a Rollston V-shaped windshield.

The Duesenberg Model J was admired for it power, exclusivity, speed and coachwork but one aspect which always draws the eye of nerds is the exhaust manifold.  The look most associated with the marquee is that with four flexible pipes emerging from the right side of the bodywork, a motif used not only by Duesenberg’s corporate stablemates Cord and Auburn but also, if less extravagantly, by Mercedes-Benz where it was a feature of many of the supercharged cars of the 1920s and 1930s.

1935 Duesenberg Model J Special Speedster (SSJ)

The official factory designation was always “Model J” and their documents referred to the supercharged cars as the “Supercharged J” but the latter is known universally as the SJ.  The public imagination was further stimulated in 1935 when a short wheelbase version of the SJ was announced.  The factory referred to it as the “Special Speedster” but people preferred SSJ although it was a rare sight as only two were produced before Duesenberg finally succumbed to the effects of the Great Depression.

Of manifold shapes and weaknesses

The original manifolds used with the Model J were a variety of eight-port (8-into-1 in motorcycle parlance) units made from monel (a high-strength alloy of nickel, and copper, blended with carbon, iron & manganese) which engineers called “sewer pipes” (in modern parlance they’re known also as “dump pipes”).  In terms of fluid dynamics they were efficient but, cast in one piece they were prone to cracking as the torsional forces to which they were subject tended to find the weakest points so they were redesigned as two-piece units (4-into-1) which better distributed the loadings.  This improved durability though the propensity for the cast monel to crack wasn’t wholly eliminated and the the eight-pipe design made difficult the installation of the vertically installed supercharger hardware, added to which the heat-soak from the manifold was undesirable so the system was redesigned to used siamesed ports which fed the distinctive four external exhausts.

Memel 8-into-1 "sewer-pipe" manifold on 1934 Duesenberg SJ with the centrally-mounted supercharger fitted between cylinders 4 & 5 (left), the two piece (2 x 4-into-2) monel sewer-pipe manifolds in 1934 Duesenberg J (centre) and 8-into-1 sewer-pipe emerging through the engine-compartment right-side panel (right).  The use of the apple-green color for engine components was a signature feature of the brand.

The externally-routed pipe-work is regarded as one of the most charismatic features of the big Duesenbergs and still it’s associated by many with the presence of a supercharger but some of the SJs used the monel manifolds and, for the most flamboyant, the factory anyway offered the look as a retro-fit option for US$1000 (at a time when a new Ford V8 could be purchased for US$505).  Because of the fragility of the monel pipes and the fashion for the external ducting, only a handful of supercharged cars with the original manifolds are thought to survive.  To those who make a fetish of intricacy, the monel sewer-pipe manifolds are thought the most photogenic of all.

Manifold porn: Chrysler's Slant Six was an engine of modest specification and expectations but typical of the corporation in those days, the basic engineering was fundamentally sound and in a variety of displacements (170 cubic inch (2.8 litre, 1959-1969), 198 (3.2, 1970-1974) & 225 (3.7 1960-2000), it was produced between 1959-2000 making it one of the US industry's longest-serving powerplants.  One unusual aspect of the Slant Six's design was the block was canted to the right at a 30^o which meant there was much space available to the left and a range of intake manifolds followed, some of which remain available to this day.  Using variations of the Sonoramic tuning, manifolds were produced for single, two & four barrel carburetors and between 1965-1968, Chrysler's Argentine operation produced the Slant Six in a version with twin single barrel carburetors.  The use of the properties of fluid dynamics to gain power or torque as desired quickly was adopted by the industry as an engineering orthodoxy.

Carburetor

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 “180^o 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).

Polysphere

Polysphere (pronounced pol-ee-sfeer)

(1) In mathematics, a product of spheres.

(2) In mechanical engineering, a design of combustion chamber formed by the two shallow concave domes under the intake and exhaust valve seats.

1955: A compound word, the construct being poly + sphere.  Poly is from the Ancient Greek πολύς (polús or polys) (many, much), from the primitive Indo-European polhiús (much, many) from the root pele (to fill), akin to the Old English fela (many).  Sphere is from the Middle English spere, from the Old French spere, from the Late Latin sphēra, from the Classical Latin sphaera (ball, globe, celestial sphere), from the Ancient Greek σφαῖρα (sphaîra) (ball, globe), of unknown origin.  Despite spread of the myth by some medieval writes, sphere is not related to superficially similar Persian سپهر‎ (sepehr) (sky).  Poly, in modern English (especially in industrial and scientific application) use became a word-forming element meaning "many, much, multi-, one or more" with derivatives referring to multitudinousness or abundance.  It was equivalent to the Latin multi- and should properly be used in compounds only with words of Greek origin but this, etymologically slutty English ignores.  Polysphere is a noun and polyspheric is an adjective; the noun plural is polyspheres.

Chrysler, the poly, the hemi and the hemi which is really a poly

Chrysler didn’t invent hemispherical combustion chambers but they certainly made a cult of them.  In internal combustion engines of the mid-late twentieth century, the hemispherical combustion chamber was one of the best designs with with to provide an efficient burn-space while minimizing thermal loss and permitting the use of large diameter canted-valves to optimize intake and exhaust flow.  The early Chrysler Hemi V8s (1951-1958) were the most powerful of their generation but there were drawbacks.  To take advantage of the large valves at diverging angles, the valve train assembly was both bulky and heavy, needing two rocker shafts rather than the single units used with in-line arrangements.  Adding to the cost and complication were the inherently more expensive casting and machining processes required to produce the hemispherical shape of the combustion chambers in the cylinder heads.  To enable the mass-production of a less expensive V8 to use in their lower-priced lines, Chrysler created new cylinder heads with polyspheric (two shallow concave domes under the valves and named the “Poly”) combustion chambers and a less elaborate system of valve activation which needed only a single rocker shaft.  Although less powerful than the Hemis, the Polys were cheaper and lighter although it wouldn’t be until the 1960s that Chrysler standardized engines across their divisions; an early adoption of such economies of scale might have saved the corporation more money than retaining an exclusively Hemi-headed line would have cost.

The Hemi, 1951-1958 & 1964-1971 (left), the polyspheric, 1955-1967 (centre) and the new "Hemi" which is really a swirl Chamber, 2003- (right).

However, the Poly proved a cul-de-sac.  In an era of cheap petrol, larger capacity engines proved a more attractive route to horsepower than sophisticated combustion chamber design and the Hemis were retired in 1958, replaced by larger engines with wedge-shaped chambers, used by other manufacturers and much more suited to mass-production.  Consigned to the grave with the Hemis were almost all the Polys, only the 318 V8 (5.2 litre) retained as a rare oddity until 1967.  The Hemi would return, available between 1964-1971 as a 426 cubic inch (7.0 litre) race engine (there were also some reduced displacement versions to satisfy local rules) which, for homologation purposes would in 1966 be released in slightly detuned form detuned for street use.  The name however held such an allure that it was revived in 2003 for Chrysler's new (and perhaps final) generation of V8s although in the narrow technical sense, Hemi is now more a marketing than an engineering term because the twenty-first century combustion chambers are something of a hybrid of hemispheric and polyspheric, the general term describing them for the last fifty-odd years being swirl chambers, a design which makes possible a high out-output of power, low emissions and an economy in operation which would have been thought impossible to achieve as recently as the 1980s.

Lindsay Lohan with polyspheric hair.  Polyspheric hair styles are possible, the classic example of which is the symmetrical “twin dome” look which is difficult exactly to achieve and harder still to maintain for more than a brief time.  They’re thus seen usually only at photo-shoots or for one-off events but the design element is popular with asymmetric styles.

When Chrysler in 1964 introduced the 273 cubic inch (4.5 litre) V8 as the first of its LA-Series (that would begat the later 318, 340 & 360 (the V10 Magnum used in the Dodge Viper is also as descendent)), the most obvious visual difference from the earlier A-Series V8s was the noticeably smaller cylinder heads.  The A engines used as skew-type valve arrangement in which the exhaust valve was parallel to the bore with the intake valve tipped toward the intake manifold (the classic polyspherical chamber).  For the LA, Chrysler rendered all the valves tipped to the intake manifold and in-line (as viewed from the front), the industry’s standard approach to a wedge combustion chamber.  The reason for the change was that the decision had been taken to offer the compact Valiant with a V8 but it was a car which had been designed to accommodate only a straight-six and the wide-shouldered polyspheric head A-Series V8s simply wouldn’t fit.  So, essentially, wedge-heads were bolted atop the old A-Series block but the “L” in LA stood for light and the engineers wanted something genuinely lighter for the compact (in contemporary US terms) Valiant.  Accordingly, in addition to the reduced size of the heads and intake manifold, a new casting process was developed for the block (the biggest, heaviest part of an engine) which made possible thinner walls.  With the exception of the Hemis, the new big-block engines used wedge-heads and the small block polyspheres (the A-Series) were replaced by the LA except for an export version of the 313 (5.1 litre) which in small numbers was manufactured until 1965 and the 318, the last of which was fitted in 1967.  Confusingly, the replacement LA engine was also a 318, a product of carrying over certain components, both the 318-A & 318-LA sharing the same bore & stroke.  In an example of production-line rationalization, when Chrysler Australia bored out their 245 cubic inch (4.0 litre) Hemi-6 to create the 265 (4.3), the bore chosen was the same as the 318s so pistons could have been shared with the V8 although for technical reasons this wasn't actually done.  The Australian "Hemi" straight sixes used another variation of the combustion chamber in that chambers sat in upper third of the globe, hence the "low hemispherical" slang which wasn't wholly accurate but Ford's Boss 429 V8 had already been dubbed the "semi-hemi" and linguistic novelty was becoming hard to find.

Sonoramic

Sonoramic (pronounced sonn-o-ram-ick)

A form of enhanced induction for internal combustion engines; sometimes called cross-ram or long-ram induction.

1959:  A compound word constructed by engineers (apparently with no contribution from the marketing department), the construct being the Latin sonō (make a noise, sound) + the English ram + -ic.  Sonō was from the primitive Indo-European swenhe (to sound, resound) which was cognate with the Sanskrit स्वनति (svanati) (to sound, resound).  The more productive Latin derivative was Latin sonus (sound, a noise) from the primitive Indo-European swon-o, again from the root swenhe.  Ram was from the Old English ramm (in the sense of "battering ram", from the Old High German ram, thought probably related to the Old Norse rammr (strong) and the Old Church Slavonic ramenu (impetuous, violent).  The suffix -ic is from the Middle English -ik, from the Old French -ique, from the Latin -icus, from the primitive Indo-European -kos & -ḱos, formed with the i-stem suffix -i- and the adjectival suffix -kos & -ḱos.  The form existed also in the Ancient Greek as -ικός (-ikós), in Sanskrit as -इक (-ika) and the Old Church Slavonic as -ъкъ (-ŭkŭ); A doublet of -y.  In European languages, adding -kos to noun stems carried the meaning "characteristic of, like, typical, pertaining to" while on adjectival stems it acted emphatically; in English it's always been used to form adjectives from nouns with the meaning “of or pertaining to”.  A precise technical use exists in physical chemistry where it's used to denote certain chemical compounds in which a specified chemical element has a higher oxidation number than in the equivalent compound whose name ends in the suffix -ous; (eg sulphuric acid (H₂SO₄) has more oxygen atoms per molecule than sulphurous acid (H₂SO₃).  The engineers were influenced in their coining of sonoramic by the debut three years earlier of the sonogram (thereby creating sonogramic), a form of diagnostic imaging used in medicine.

Fluid dynamics and resonant conditions

1960 Chrysler 300F with long-ram Sonoramic 413 cid (6.8 litre) wedge V8.

All else being equal, increasing the volume of the fuel-air mixture (energy input) flowing through an internal combustion engine (ICE) increases power and torque (energy output).  This can be done with an external device such as a supercharger, or resonance can be created in the induction system by designing a passage which uses the physics of fluid dynamics to increase pressure in specific spaces.  Obviously uninvolved in the engineering, Chrysler’s marketing people claimed in 1960 that the Sonoramic was new technology but for many years the principle had been used in racing engines, the mathematical equations determining acoustics & resonance having been published by German physicist and physician Hermann Ludwig Ferdinand von Helmholtz (1821–1894) in a scientific paper published in 1863.  Indeed, the concept had before been used on road cars but always in a discrete manner; what Chrysler did in 1959 with the long-tube ram-runners was make a dramatic fashion statement in designer colors.

Representation of fluid dynamics under specific resonant conditions.

Essentially, the Sonoramic is an implementation of Sir Isaac Newton's (1642–1727) first law of motion, more commonly known as the law of inertia: “An object at rest tends to stay at rest and an object in motion tends to stay in motion” and it’s the second part which Sonoramic exploited.  During the intake cycle of an engine, the fuel-air mix flows through the intake manifold, past the intake valve, and into the cylinder, then the intake valve shuts.  At that point, the law of inertia comes into play: Because the air was in motion, it wants to stay in motion but can’t because the valve is shut so it piles up against the valve with something of a concertina effect.  With one piece of air piling up on the next, the air becomes compressed and this compressed air has to go somewhere so it turns around and flows back through the intake manifold in the form of a pressure wave.  This pressure wave bounces back and forth in the runner and if it arrives back at the intake valve when the valve opens, it’s drawn into the engine.  This bouncing pressure wave of air and the proper arrival time at the intake valve creates a low-pressure form of supercharging but for this to be achieved all variables have to be aligned so the pressure wave arrives at the intake valve at the right time.  This combination of synchronized events is known as the "resonant conditions".

Long (lower) and short-tube (upper) Sonoramic intake manifolds.

Most of the Sonoramics produced were long-tubes with a tuned internal-length of thirty inches (760mm), generating prodigious quantities of mid-range torque, ideal for overtaking under highway conditions.  These characteristics were ideal for road cars but also built were a small number of the so-called short-tube Sonoramics, a somewhat misleading term because they shared the external dimensions of the standard devices, the difference being that only a fifteen-inch (380mm) length of the internal passages were resonance-tuned and this, at the expense of mid-range torque, produced much more power high in the rev-range making them more suitable for competition.  Used by Chrysler to set a number of speed records, these were the most charismatic of the breed and a handful were built with manual gearboxes.  At auction, in November 2010, the sole 1960 Chrysler 300F short-tube Sonoramic convertible with the Pont-a-Mousson 4-speed gearbox, sold for US$437,250.

1960 Chrysler 300F long-ram Sonoramic 413 cid (6.8 litre) wedge V8.

The first four generations of the 300 letter series had used increasingly larger versions of the Hemi V8 and the 1958 300D (with a 392 V8) even offered the novelty of a very expensive fuel-injection option but, unlike the mechanical systems offered by Mercedes-Benz, Chevrolet and a handful of others, the Bendix "Electrojector" system used a rudimentary computer which proved unreliable and most were returned to the dealer to be retro-fitted with carburettors.  The Hemi, heavy and expensive to produce, was in 1959’s 300E replaced by the larger capacity, wedge-head 413 which matched it for power but lacked the mystique, something substantially restored in 1960 when the 300F debuted with the sexy Sonoramic.  Ram Induction today is common, although contemporary designs, integrated with fuel-injection systems, are not as photogenic as the original Sonoramics.  As well as raw aluminium, the tubes were available in the designer colors of the time, red, gold and blue; red ones are thought most cool.

Republic P-47 Thunderbolt test-bed with XI-2200 V16 (1945).

Chrysler’s interest in ram tuning was an outgrowth of the desire to exploit the findings of research undertaken during the war developing very high-performance piston engines for fighter aircraft.  This had culminated in the XI-2220, a 2,220 cubic inch (36.4 litre) V16 aero-engine which, rated at 2450 horsepower, was tested in a Republic P-47 Thunderbolt, an appropriate platform given that the P47 was then the biggest, heaviest single-engined fighter ever to enter service (among piston-engined aircraft it still is).  Although the indications were that close to 4000 horsepower was achievable (at least for short durations), with the advent of the jet engine the days of the big piston-engined fighters were nearly done.  The V16 project was cancelled, a fate suffered also by the other outstanding big aero-engine of that last generation: the Napier-Sabre H24.

XI-2220, V16 aircraft engine (1944-1945).

The lessons learned however would be applied on the ground instead of in the skies because although big capacity piston engines had mostly been rendered obsolete for aircraft, a few generations of some just a bit smaller were about to start roaming American roads.  The cars and their engines would be like nothing before seen, Chrysler adopting for their new 331 cubic inch (5.4 litre) V8 in 1951 the V16’s hemispherical combustion chambers, a feature it would use for most of that decade and the next and such was the aura of the name that it’s used still, even if things are now a bit less hemispherical than before.

Chrysler A-311 V8 experimental engine.

The new Hemi V8 had obvious performance potential and the engineers experimented with the tuned-length induction system used on the V16 before the final supercharger/turbocharger combination was adopted.  So successful was the ram-tuned engine (named A-311) that attempts were made to contest the 1952 Indianapolis 500 but the race’s sanctioning body understood the implications the remarkable new powerplant would have on their carefully-curated ecosystem of owners and sponsors and declared it didn’t comply with the rules, even tweaking them a bit to ensure it never would.

Ramcharger Club’s 1949 Plymouth with extreme ram-charging.

The research however continued and, although it’s not clear to what extent their efforts received factory-support, in the late 1950s some young engineers formed the drag racing-focused Ramchargers Club using, somewhat improbably, a 1949 Plymouth business coupe fitted with a particularly extravagant implementation of the technology, a surrealistically tall intake manifold, a device built for dynamometer testing and never intended for a moving vehicle.  They dubbed the Plymouth "High & Mighty".  Bizarre it may have looked but the cartoon-like Plymouth achieved results which vindicated the approach and the system was introduced on 1960 Plymouths, Dodges and Chryslers, the highest evolution of Sonoramic offered on the Chrysler 300 letter series cars until 1964.  Interestingly, while it was only Plymouth which used the Sonoramic name, Dodge labelling the system D-500 Ram Induction and Chrysler simply Ram Induction, all of them are commonly referred to as Sonoramics.

Lindsay Lohan enjoying the effects of fluid dynamics.

Not content with applying the science of fluid dynamics only to the induction system, the Ramchargers used it also for the exhaust headers.  Rather than additional power, the commendably juvenile quest was for noise, the exaggerated, trumpet-like tubes using the megaphone principle which increases volume by raising acoustic impedance.  The desired result was achieved and although there's no record of anyone with a decibel-meter taking a reading, the old Plymouth was said to be spectacularly loud.  Megaphone exhausts were subsequently banned.    

Chrysler Slant Six with Hyper Pak.

Chrysler didn’t restrict the ram induction idea to the big-block V8s, using it also on the short-lived (1960-1962) Hyper Pak performance option for the both 170 cubic inch (2.8 litre, 1959-1969) and 225 cubic inch (3.7 litre, 1987-2000) versions of their Slant Six, the engineers taking advantage of the space afforded by the angled block to permit the curvaceous intake runners nearly to fill the engine bay.  The Hyper Pak wasn't seen in showrooms but was available as an over-the-counter kit (literally a cardboard box containing all necessary parts) from Dodge & Plymouth spare parts departments and its life was limited because it became a victim of its own success.  Although less suitable for street use because it turned the mild-mannered straight-six into something at its best at full throttle, in the race events for which it was eligible it proved unbeatable, dominating the competition for two years, compelling the sanctioning body cancel the series.

Although it was the longer lived 225 version which gained the Slant Six its stellar reputation for durability and the ease with which additional power could be extracted, there's always been a following for the short-stroke 170 because of its European-like willingness to rev, the characteristics of the over-square engine (unique among the slant-six's three displacements (170-198-225)) unusually lively for a US straight-six.  Despite some aspects of the specification being modest (there were only four main bearings although they were the beefy units used in the 426 cubic inch Street Hemi V8), for much of its life it used a tough, forged steel crankshaft and high-speed tolerant solid valve lifters, features which made a robust engine.  Despite that, after the Hyper Pak affair, Chrysler showed little interest in any performance potential, knowing the US preference for V8s, something which doomed also Pontiac's short-lived single overhead camshaft (SOHC) straight-six (1966-1969).  A version of the 225 with a two-barrel carburetor (rated at 160 horsepower, an increase of 15 over the standard unit) was offered in some non-North American markets where V8 sales were not dominant and it proved very popular in South Africa, Australia, New Zealand and Central & South America but only when tighter US emission regulations forced its adoption did a 225 with a two barrel carburetor appear in the home market, installed to restore power losses rather than seek gains.