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 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 it’d been used in racing engines for years, the mathematical equations determining acoustics & resonance having been published by German physicist and physician Hermann Ludwig Ferdinand von Helmholtz (1821–1894) in an 1863 scientific paper.  Indeed, the concept had before been used on road cars but always in a discrete manner but 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 and short-tube 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 with a particularly extravagant implementation of the technology, the surrealistically tall intake manifold, a device built for dynamometer testing and never intended for a moving vehicle.  The 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 Hyper-Pak performance option for the 170 cubic inch (2.8 litre, 1959-1969) version 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’s life was limited because it was a victim of its own success.  Although less suitable for street use because it turned the mild-mannered straight-six into something happiest at close to 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 cubic inch (3.7 litre, 1960-2000) version which gained the Slant Six its stellar reputation for durability and the ease with with 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, it was a famously 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 carburettor (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.  Only when tighter US emission regulations forced its adoption did a two-barrel 225 appear in the home market but it was installed to minimize power losses rather than seek gains.

Dual & Duel

Dual (pronunced doo-uhl or dyoo-uhl)

(1) Of, relating to, or denoting two.

(2) Composed or consisting of two people, items, parts, etc., together; twofold; double; having a twofold, or double, character or nature.

(3) In the formal grammar of Old English, Old Russian, Arabic and Ancient Greek, denoting a form of a word indicating that exactly two referents are being referred to (a form in the dual, as the Old English git (you two), as opposed to ge (you) referring to three or more.

(4) In mathematics and formal s logic (of structures or expressions) having the property that the interchange of certain pairs of terms, and usually the distribution of negation, yields equivalent structures or expressions

1535–1545: From the Latin duālis (containing two, relating to a pair), the construct being du(o) (two) + -ālis (-al) The Latin duo was from the primitive Indo-European root dwo (two).  The General sense of "relating to two, expressing two, composed or consisting of two parts" is from 1650s.  Dually is the adverb.  The general sense of "division into two" has been in use since 1831.  The noun duality (two-fold nature, state of being two or divided in two) is a late fourteenth century form from the Late Latin dualitas.

The noun dualism dates from 1755 as a term in philosophy, the sense being "a way of thinking which explains phenomena by the assumption of two independent and absolute elements," from the French dualisme (1754).  The theological adoption to describe the doctrine of “two independent divine beings or eternal principles” was first noted in 1847.

Duel Pronounced doo-uhl or dyoo-uhl)

(1) A prearranged combat between two persons, fought with deadly weapons according to an accepted code of procedure, especially to settle a private quarrel.

(2) Any contest between two persons or entities.

1585–1595: From the earlier English form duell (a single combat (also "a judicial single combat”), from the late thirteenth century Medieval Latin duellum (combat between two persons), a poetical variant of the old Latin form of bellum (war) (related to bellicose), probably maintained and given the sense “duel” by folk etymology with the Latin duo (two).  The Old Latin word was retained in poetic and archaic language, the fancied Medieval connection with duo organically creating the linguistic semi-coincidence.  In pre-Modern English, the Italian form duello was also used.  By the 1610s, the English word had taken on the specialized sense of "premeditated and pre-arranged single combat involving deadly weapons in the presence of at least two witnesses", the general sense of "any contest between two parties" dating from the 1590s.  The related verbs are duels, dueling & dueled , dueler & duelist are nouns and duelistic an adjective.  The US spelling favors the double “l”.

Dualism in Philosophy

In Metaphysics, dualism holds there are two kinds of reality: the physical world (material) and the spiritual world (immaterial).  In the philosophy of mind, Dualism is the position that mind and body are in some categorical way separate and that mental processes and phenomena are, at least in some respects, non-physical.  Both positions are radically different from even nuanced flavors of monism (which, at its most pure, maintains there is but the universe and that any form of division of the whole is artificial and arbitrary) and pluralism suggests there are many kinds of substance and not just dualism’s two.  In the pre-enlightenment age, dualism had some appeal but it’s now of only historic interest except as a device to train the mind to explore speculative paths.

Dualism in Carburetion

1967 Shelby C7zx dual quad-aluminum intake manifold for Ford 427 FE.

From the late 1950s, Detroit’s V8s, with a sudden and increasing rapidity, grew bigger and more thirsty, the most rapacious of the engines out-pacing the capacity of the carburetors brought from outside suppliers, with the result the only solution was to use two or even three carburettors.  The manufacturer did eventually produce units with sufficient throughput but it took a while for supply to meet demand.  For street use, triple induction was for some time quite a good solution because the three-in-a-row layout lent itself to a good compromise, the engine most of the time being fed only by the central two-barrel carburetor, the outer two used only when the throttle was pushed wide open.  It meant engines with great available power were actually surprisingly economical most of the time although the delicate business of tuning could be a challenge, especially in conditions where there were notable variations in temperature or humidity.  For the high performance engines however, the best cost-performance equation (ignoring the fuel consumption which was the customer's problem) was dual induction, two four barrel carburettors, mounted either in-line or side-by side, the air-flow dynamics of the latter delivering the optimal top-end-power.

Short & Long-Ram Sonoramic dual quad intake manifolds.  The difference was that the short versions had 15 inch (380 mm) tuned intake runners while the long rams had their entire 30 inch (760 mm) length tuned.  

Most dramatic in appearance of all the dual quad setups were the Sonoramics, offered by Chrysler on a handful of models between 1959-1963.  Sonoramic was a linguistic novelty but the engineering principles of tuned resonance in thermal dynamics had been known for decades, the trick being to create a shape which essentially caused the fuel-air mixture to “bounce around”, emulating a low-boost “ram-air” effect.  There were two different versions which looked externally similar but differed internally, the rare so-called “short-ram” tuned for top-end power, the “long-ram” for the mid-range torque which was ideal for street use because the additional performance was delivered in the speed-ranges at which highway passing manoeuvres typically were undertaken.

Jaguar E-Type 4.2 with triple SUs (top) & with dual Strombergs (bottom).

From its introduction in 1961, the Jaguar E-Type (XK-E for the cars delivered in North America) used triple SU HD.8 carburetors but in 1967, to conform to US emission control rules, the switch for the units delivered there was made to dual Stromberg 175 CD2SEs.  Unlike some manufacturers which arranged a separate specification for the US and other markets with more rigorous regulations, Jaguar applied the change to the entire range.  Power and torque dropped a bit, especially higher in the rev range, a prelude to the malaise which would affect so many in the 1970s.  The changes made by Jaguar to comply with the US regulations were marked by the change in designation from Series I to Series II and the most obvious modifications were (1) the carburetors, (2) the slight truncation of the cigar-shaped tail & the substitution of the elegant tail-lamps with rather more agricultural-looking units, (3) the use of safer, softer rocker switches on the dash instead of the stylish but sharp toggle switches and (4) the deletion of the lovely, fared-in head-lamp covers, the slightly elevated  replacements lending the car a slight bug-eyed look.  There were a host of other changes, most of which made the Series II a better car but it was just a bit slower and didn't look as good.

The lovely, pure lines of the Jaguar E-Type Series 1 (1961-1968, left).  It's not certain Enzo Ferrari (1898-1988) really did say it was "the most beautiful car ever made" but he never denied it and he was a fair judge of such things.  The Series 2 cars (1968-1971, right) were a little more cluttered.

However, unlike the US manufacturers (and most of the Germans), even by 1967 there were cottage-industry aspects to some of Jaguar's production facilities and the E-Type changed from Series I to Series II in increments rather than one distinct movements and even then there were inconsistencies and these detail differences intrigue the E-Type cognoscenti, concerned as many are with originality.  For this reason, although the factory never used the designations, informally, what are thought “transitional cars” are often referred to as Series 1.25 or 1.5, base on the mix of earlier & later features present, the identification of which is sometime challenging because many later models were modified to make them appear partially or in whole “classic” Series 1 E-Types.  The first of the 1.25s are regarded as the models built for US delivery after January 1967 and fitted with the open head-lamps, this change not applied universally until phased in over June-July the same year.  The 1.5 designation is used of those built after August-October which in addition to certain detail changes received the dual Stromberg carburetors (if built for delivery to North America) and the rocker switches (the open head-lamps at this point slightly raised by the use of a different assembly) but the “teardrop” tail-lamps above the rear bumpers were retained.  Once the revisions were made to the tail and the tail-light, the transition to Series 2 was complete (the Series 2 cars also receiving slightly larger head-lamps).  However, in recent years the factory records have been reviewed and it’s clear some of the cars built in 1967 for delivery to North America had the covered head-lamps so these, combined with the Series 1.25 & 1.5 cars modified retrospectively, mean the task of verifying the originality of the later Series 1.X cars can be challenging.

Apparently, at the premiere of Disney’s The Parent Trap (1998), then CEO Michael Eisner (b 1942; chairman and chief executive officer (CEO) of The Walt Disney Company, 1984-2005), believing the central parts in the film had been played by identical twins asked her “Where's your twin?”.  She told him she didn’t have one and that she should have been paid double.

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.

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 1959 Daimler V8, designed along the lines of a motorcycle power-plant, was originally designed to be air-cooled and run 8 carburetors.  The production version was water-cooled and used 2 x sidedraft SUs.

Lindsay Lohan admiring Herbie’s carburetors (Herbie: Fully Loaded (2005)).

Desmodromic

Desmodromic (pronounced des-moh-drom-ick)

(1) In internal combustion engines, a valve drive-train in which poppet valves are positively closed by a cam and leverage system, rather than a conventional spring.

(2) By extension, in various mechanical devices, a component having different controls for its actuation in different directions.

1953:  A construct from the Ancient Greek δεσμός (desmós) (band, connection; fibrous connection, ligament; bond or knot) + δρόμος (drómos) (a course; travel; road).  The etymology is likely oblique to all but mechanical engineers but denotes the characteristic of valves continuously being "bound" to the camshaft.  The idea of desmo + dromic is thus often deconstructed as something like “running in unison” or “connected racing” but that’s because of the historic association with engines and speed and the desmo- prefix is also used in medicine and other biological sciences in the sense of “being or maintaining a connection”, a desmosome a filament-like substance with which cells adhere to each-other and desmoplakin" is the protein associated with this intercellular junction.  In zoology, the term most closely analogous to desmodromic valve trains is desmopelmous, a type of foot in birds in which the hind toe cannot be bent independently because planter tendons are united (ie they are connected and work in unison).

Conventional valve activation (left) versus desmodromic (right).

Probably as soon as there were poppet valves engineers began to ponder way of perfecting their opening and closing, the use of a spring for the latter effective but inexact and embryonic ideas would have been discussed but it was the German Daimler company which was first granted a patent for a desmodromic like valve-train system for a V-twin engine in 1889.  After that, designs, prototypes and even the odd racing car appeared so equipped and while there was some success on the track, no manufacturer attempted mass-production because of the high costs inherent in the intricate design and, more practically, the formidably frequency with which the system demanded adjustment to maintain perfect operation.  However, as the trophies won in competition had celebrated, the desmodromic arrangement uniquely permitted very high engine speeds and thus more power without the need to increase displacement and therefore bulk and weight.

A desmodromic valve schematic.

During World War II, there were great advances in metallurgy and the design of internal combustion engines and one manufacturer which had learned much was Daimler-Benz which had perfected the pressurized fuel-injection system which early in the conflict had given Luftwaffe pilots some real advantages over the allied opposition which continued to rely on primitive carburettors for fuel delivery, these adversely affected by gravity while the German aircraft were not.  However, the valve-train relied still on a spring to effect closing and this was a limitation which prevented the advantages of fuel-injection being fully explored.  The big aero-engines in the wartime Messerschmitts has been low-revving so the valve-springs weren’t challenged by physics but the company’s interest has returned to the race tracks and there, the systems limitations were exposed, “valve-float” intruding at high engine speeds.  The dreaded valve float is a phenomenon which occurs at high engine speeds when valve springs can’t return the valves to their seat with the cam follower still in contact with the cam.  This means the valves can be launched too high, even to the point where it can be still wide open when the piston arrives at the top dead centre (TDC), something which in the worst case can result in impact between the two, bending or even snapping the valve.  That will often be catastrophic, the debris perforating and possibly collapsing the hot aluminium piston head.  From that point on, the damage caused will be a matter only of extent, ranging from severe to complete destruction.

The Mercedes-Benz W196 Formula One Grand Prix (1954-1955) car used the desmodromic straight-eight in 2.5 litre form.  A 3.0 litre version was created for the W196S (300 SLR) used in sports car racing.  

That was something desirable to avoid in any engine but especially so in a racing car because, as the saying goes, “to finish first, first one must finish”.  Thus was designed Daimler-Benz’s surprisingly simple desmodromic system for the Mercedes-Benz W196 Formula One car for the 1954 season, ruin under the new 2.5 litre (152 cubic inch) displacement rule.  An amusing mix of new (fuel-injection and the desmodromics) and old (archaic swing axles and a straight-eight configuration), it succeeded, dominating the World Championship in 1954-1955 and in 3.0 litre form as the 300 SLR (technically the W196S), sports car racing too.  One thing which proved vital in all this was that the engineers had removed from the desmodromic hardware the small, final closing spring which had previously been thought necessary.  What the Daimler-Benz engineers discovered was that if a residual clearance of a mere 0.03 mm (0.001181099 inch) was machined, by simply leaving the return “desmo valve” in the closed position, the inertia of the valve and the gas pressure in the cylinder was sufficient to maintain the closure, a variation of the exploitation of the long-documented behaviour of fluid dynamics Chrysler would soon market (somewhat opportunistically) as Sonoramic.  The innovation was made possible by the development of metals stimulated by the demands of war; in the pre-war years, the desmodromic design adopted for the W196 simply wouldn’t have been possible.

Schematic of the Mercedes-Benz W196 straight-eight.

The desmodromic valve control system used an opening cam which directly controlled a shoe at the upper end of the cylindrical tappet rod while another (closing) cam used a deliberately out-of-alignment rocker arm which engaged in a hole drilled in the same tappet.  It was simple, precise and effective and reliably delivered such power that even Enzo Ferrari (1898-1988) considered matters desmodromic, discussing the matter with Dr Fabio Taglioni (1920-2001) who was working on the idea, his design first used by Ducati in 1954 on their 125 cm³ (7.6 cubic inch) racer and later adopted for many of their production and competition machines, used even to this day. 

Lindsay Lohan with Ducati Monster 600 (Desmodromic) in Freaky Friday (2003).

Not needing return springs, the valves being positively opened and closed by a cam and leverage system, desmodromic offered higher engine speed, more power and a variety of improvements to specific efficiencies.  Despite that, except for Ducati, it never became a system used by volume manufacturers (or indeed low-volume operations) because of the disadvantages which included complexity, cost, noise (especially as the cylinder count grew) and, critically, more frequent maintenance.  It was advances in high-speed photography and later computer analysis which rendered desmodromic an engineering cul-de-sac.  With a frame-by-frame view of how valves and valve springs behaved, designers were able to engineer solutions to the problems previously though inherent to conventional valve-trains and, by the 1980s, vastly more powerful computers permitted the virtual testing of every design permutation.  Eventually, the advantages offered by desmodromics became so small that few attempted to justify to additional cost and maintenance penalty.

2002 Ducati MH900e (desmodromic).

What the photography revealed was that valve float was caused mostly by resonance in the springs which generated oscillating compression waves among the coils and that at specific resonant speeds, the springs were no longer making contact at one or both ends, leaving the valve “floating” before crashing into the cam on closure.  The solutions were varied and some, such as Norton's “mousetrap” or “hairpin” spring were soon discarded because, although they worked well, the engineering challenges in integrating them with existing combustion chamber designs created as many problems as were solved.  A less elegant but more manageable approach was to install as many as three concentric valve springs, sometimes nested inside one other; not for more force (the inner ones having no significant spring constant), but to act as dampers, both absorbing and reduce oscillations in the outer spring (engineers delighting in calling the additional springs “snubbers”).  Again, the advances in metallurgy made possible what was once though unattainable.  Complex valve springs were engineered which did not resonate, being progressively wound with a varying pitch varying diameter and dubbed “beehive springs” because of the shape.  The number of active coils in these springs would vary during the stroke, the more closely wound coils located at the static end, becoming inactive as the spring compressed or (as in the beehive) where the small diameter coils at the top were stiffer.  Thus valve float was conquered with springs.

2023 Ducati Multistrada V4, the first Ducati in decades to use conventional valve activation.

But Ducati persists to this day, their raucous machines, once a cult known to a few now enjoying a wider audience which seems prepared to accept both the frequency of with which valve-train adjustments are required and the inherent clatter (which is admittedly quite spine-tingling if sampled at speed when wearing a crash helmet).  Tellingly, Ducati’s motor-cycles are almost all V-twins because the noise level does become intrusive as the cylinder count increases and their recent Multistrada V4 was the first in decades to not use desmodromic valves, the owner rewarded, inter alia, with recommended maintenance intervals of 60,000 km (37,500 miles), a considerable advance on the traditional 12-18,000 km (7500-11,200 miles).  Still, among collectors of Ferraris, Jaguars and such there are those who can think of no more pleasurable way to spend a day than adjusting solid valve lifters or tinkering with an array of twin-choke carburettors, the synchronization of which defy all but the chosen priesthood of such things so Ducati seems likely to offer the devoted their desmodromics as long as such things remain somewhere lawful.

Cavitation

Cavitation (pronounced kav-i-tey-shuhn)

(1) The formation of pits on a surface.

(2) In fluid dynamics, the rapid formation and collapse of vapor pockets in a flowing liquid in regions of very low pressure (associated especially with devices such as rotating marine propellers or the impellers used in pumps.

(3) Such a pocket formed in a flowing liquid; the formation of cavities in a structure.

(4) In biology, the formation of cavities in an organ (used originally to describe those appearing in lung tissue as a result of consumption (tuberculosis)).

1868: The construct was cavit(y) + -ation.  Cavity was a mid-sixteenth century borrowing from Middle French cavité or the Late Latin cavitās, from the Classical Latin cavus (hollow, excavated, concave), the construct being cav +‎-ity (the nominal suffix).  The suffix -ation was from the Middle English -acioun & -acion, from the Old French acion & -ation, from the Latin -ātiō, an alternative form of -tiō (thus the eventual English form -tion).  It was appended to words to indicate (1) an action or process, (2) the result of an action or process or (3) a state or quality.  Cavitation is a noun, cavitate, cavitated & cavitating are verbs and cavitatory & cavitatory are adjectives; the noun plural is cavitations.

The original use of cavitation dates from 1868 and appeared in the literature of human pathology, describing “the formation of cavities in the body”, especially those appearing in lung tissue as a result of consumption (tuberculosis).  The use in fluid dynamics (particularly pumps and marine engineering) emerged in circa 1895 although oral use may have predated this: the verb cavitate (to form cavities or bubbles (in a fluid)) documented since 1892 so it was either a back-formation from cavitation or the construct was cavit(y) + -ate.  The related verbs were cavitated & cavitating.  The suffix -ate was a word-forming element used in forming nouns from Latin words ending in -ātus, -āta, & -ātum (such as estate, primate & senate).  Those that came to English via French often began with -at, but an -e was added in the fifteenth century or later to indicate the long vowel.  It can also mark adjectives formed from Latin perfect passive participle suffixes of first conjugation verbs -ātus, -āta, & -ātum (such as desolate, moderate & separate).  Again, often they were adopted in Middle English with an –at suffix, the -e appended after circa 1400; a doublet of –ee.  The noun supercavitation was a creation of plasma physics and described an extreme form of cavitation in which a single bubble of gas forms around an object moving through a liquid, significantly reducing drag.  As observational technology & techniques improved, the form ultracavitation also appeared to describe instances where instances of the phenomenon meant drag tended as close to zero as was possible.

Cavitation is an interesting aspect of fluid dynamics but it’s studied because it’s something which can cause component failure in devices like the pumps used for liquid, fluid & gas which can have catastrophic consequences for both connected equipment and people in the vicinity and beyond.  Such components typically feature robust construction but cavitation is a function of sustained operation (often 24/7) at high speeds and some vulnerable parts may be heavy and the fragmentation at high velocity of a heavy, reciprocating mass is obviously a serious problem.  Technically, it’s the formation of vapour- or gas-filled cavities in a flowing liquid when tensile stress is superimposed on the ambient pressure and one novelty in the science of cavitation was in 2021 noted by researchers in an oncology laboratory.  Using a gassy, explosive bacteria to destroy cancer cells by bombardment, the strikes were observed to produce a brief sonoluminescence (in physics, the emission of short bursts of light from imploding bubbles in a liquid when excited by sound), the cavitation bubbles producing a brief flash of light as they collapsed.

In the specific case of “pump cavitation”, the problem typically occurs when a hydraulic pumps which pumps liquids suffers a partial pressure drop.  What the change in pressure can induce is the formation of air bubbles, leading to cavity creation.  Inside the pump, the pressure shift transforms the liquid into a vapor which is then converted back to liquid by the spinning impellers.  The air bubbles thus are constantly moving inside the housing and as they implode during pressure changes, the surfaces of the impeller are eroded and it’s the creation of these tiny cavities which can accumulate sufficiently to weaken the structure to the point of failure.  The issue particularly affects centrifugal pumps but can occur in submersible devices.

Lindsay Lohan enjoying the effects of fluid dynamics.

Although something identified by engineers in the nineteenth century, the exact nature of cavitation wasn’t fully understood until the application in the 1950s of high-speed photography and the mathematical models developed then were later confirmed as close to exactly correct by computer simulations later in the century.  What was found was two causes of cavitation : (1) Inertial Cavitation in which a shock wave is produced by the collapse of bubble or void present in a liquid and (2) Non-inertial Cavitation which is initiated when a bubble in a fluid undergoes shape alterations due to an acoustic field or some other form of energy input.  Also observed were two behaviors of cavitation: (1) Suction Cavitation induced by high vacuum or low-pressure conditions which reduce the flow of fluid, bubbles forming near the eye of an impeller eye; as these bubbles move towards the pump’s discharge end, they are compressed into liquid, and they will implode against the impeller’s edge and (2) Discharge Cavitation which occurs when the pump’s discharge pressure becomes abnormally high, altering the flow of fluid, leading to internal recirculation, the liquid becoming “stuck” in a pattern between the housing (and the impeller) thereby creating a vacuum which in turn creates the air bubbles which will collapse and cavitate the impeller.

Representation of fluid dynamics under specific resonant conditions.

In fluid dynamics, a flow becoming “stuck” is often something to avoid but an aspect of the behavior can be exploited and it was a specific instance of certain “resonant conditions” Chrysler’s engineers exploited in 1959 when designing their Sonoramic induction system.  The idea wasn’t new, the math explained as early as 1863 and in racing cars it had been used for years but what Chrysler did was make it a focal point.  Sonoramic was 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 was 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”.

Representation of cavitation in mechanical gears.

The behavior in pumps is now well understood and both design parameters and maintenance schedules are usually cognizant of cavitation and its potential consequences.  However, instances remain not infrequent, especially when pumps are fitted into systems by non-specialists, the most common causes being (1) low fluid pressure, (2) insufficient internal diameter of suction pipes, (3) excessive distances between a fluid source and a pump’s impeller(s), (4) pumps being run at too high a speed (which may be within a manufacturer’s recommendations but inappropriate for the system in which it’s installed), (5) too many fittings added to a suction pipe and (6) debris intrusion (often a consequence of inadequate filter cleaning & maintenance).  Cavitation is a function of speed and in devices such as slow-speed propellers (such as those in many marine applications), cavitation is not an issue, thus the frequent use of light, efficient, thin blades.