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 was 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. Sonoramic is a noun; the noun plural is Sonoramics. There are no standard derived forms but there are owners who might have coined the informal adverb sonoramically to describe the way their machine does its stuff.
Fluid
dynamics and resonant conditions
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). One way to increase the throughput is to use an external device such as a supercharger or turbocharger but it can be achieved also by creating resonance in the induction
system, this done 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 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
their elongated tubular "ram-runners" was make a dramatic fashion statement in designer
colors.
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, being under pressure, this stuff 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".
Most of the Sonoramics produced were "long-tubes" with a tuned internal-length of 30 inches (760mm), generating prodigious quantities of mid-range torque, optimized 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 both shared the same external dimensions. The critical difference was the short-tube units had only a 15 inch (380mm) length of the internal passages 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.
The first four generations of Chrysler's 300 letter series had used increasingly larger versions of the Hemi V8 and the 1958 300D with a 392 cubic inch (6.4 litre) version even was (briefly and abortively) offered the novelty of a very expensive fuel-injection system. The Hemi, heavy and expensive to produce, was in 1959’s 300E replaced by the larger capacity, wedge-head 413 (6.7) 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 and opinion is divided about which look is the coolest but, impressionistically, red ones seem to be the most photographed. That is likely a function of the red having been produced in the greatest volume (followed by the silver) while the gold (used on the expensive Chrysler 300s) was comparatively rare. The blue units seem never to have been fitted to standard production cars and because the look can be re-created with high-temperature paint, collectors suspect there are now more blue tubes than were ever produced by the factory.
Engineers and other real nerds tend to use terms like “short ram” & “long ram” for the induction system but because of the attraction of the word, most today seem to prefer “Sonoramic”. Within the corporation, Dodge used “D-500 Ram Induction” and Plymouth called it “SonoRamic Commando” but when installed on the letter-series Chrysler 300s, both “Ram Induction” & “Ram Injection” appeared, the latter apparently exclusive to print advertising (which at the time tended to be more in magazines (not necessarily specialist automotive publications), the agency’s tactic to engage in a bit of what would later be called “ambush marketing” by piggy-backing on the image created by General Motors’ successful promotion of the mechanical “fuel-injection” system their Rochester division was producing for Chevrolet and Pontiac. These days, such an approach might be labelled “deceptive and misleading conduct” but if folk in the early 1960s weren’t more forgiving, they were less litigious.
The Sonoramic's plumbing couldn’t match what fuel-injection achieved but as the acceleration tests and high-speed runs confirmed, it did what it said on the tin and was considerably cheaper than the intricate mechanical mechanism. However, there were drawbacks to the simplicity because unlike most of Detroit’s other implementations of dual four-barrel carburettor (“dual-quad” to the nerds) the Sonoramics ran permanently with all eight throats feeding the engine, each unit attached to the opposite bank of cylinders. On systems where the carburettors were more closely placed (in-line or side-by-side), the usual practice was to use just one except when needed, the same principle as the “demand superchargers” used during the inter-war years by Mercedes-Benz in which the blower was engaged only when the upper gears were in use and the throttle was pushed wide open, high in the rev-range. What that meant was the dual quad cars delivered fuel economy which was “poor” rather than “atrocious” but they appealed to a demographic which accepted that for everything one does there’s a price to be paid and gas (petrol) then was cheap although not quite as cheap and its expression in pre-inflation dollars & cents make it appear to twenty-first century eyes.
Anyway, when filling up, owners of Sonoramics had the consolation of being able to open the hood and gaze lovingly at their sensuous tubes, a construction visually more accomplished than Rochester’s business-like hardware. Unfortunately the affection didn’t always extend to the behaviour when starting a Sonoramic on a winter morning, the combined 120 inches (3 metres) of cold aluminum far from ideal at maintaining the fuel-air mix in the required aerosol. Until the metal was warm, fuel was prone to condensing, creating what was soon known as the dreaded “puddling effect” and in colder places some owners improvised “heated inlet manifolds”, the most simple approach being a pair of incandescent light bulbs rigged above the tubes for 30 minutes prior to starting, one instance where the inherent inefficiency of the old technology (where much energy was lost as heat rather than light) proved useful. Others gave up and had the system exchanged for a prosaic single four-barrel carburetor, an echo of Chrysler’s miserable experience in 1958 when 35 cars were built with Bendix “Electrojector” fuel injection. Unfortunately, the on-board analogue computer (which which had performed reliably in testing) proved fragile in real-world conditions and all but one of the cars was returned to dealerships in response to a corporate recall to be converted to the standard dual-quad apparatus. It would be decades before advances in solid-state technology made electronic fuel-injection a viable mass-market product.
One of the Sonoramic’s relations: 1993 Mercedes-Benz 600 SEC (C140).
Despite the impression probably gained by the few souls who now trouble themselves to see what lies under a hood (bonnet), long-tube induction is common but now usually concealed beneath enveloping plastic moldings (sometimes fashioned from real or fake carbon fibre as the price tag rises). The manufacturers have sound reasons for doing that but the expanse of flat, black plastic is an uninspiring sight compared with things like the 6.0 litre (365 cubic inch) Mercedes-Benz V12 (M120). The C140 was unusual in that it was the last of the “SECs” and the first of the “CLs”, its mid-life spent as an “S”. the alpha-numeric trajectory of the 600:
1992 600 SEC
(Not sold in North America)
1993 600 SEC
(Global)
1994-1995 S
600 (Global)
1996-1997 S
600 (North America) & CL 600 (Rest of the world
1998 CL 600
(Global)
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 HP, was tested in a Republic P-47 Thunderbolt (1947-1945), an appropriate platform given the P-47 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 HP was achievable (at least for short durations under the EWR (emergency war rating protocol), with the advent of the jet engine the days of the big piston-engined fighters were nearly done so the V16 project was cancelled, a fate suffered also by the other outstanding big aero-engine of that last generation: the Napier-Sabre H24.
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 fighter aircraft, a few generations of some a bit smaller were
about to start roaming American roads.
The cars and their engines would be like nothing before seen in mass-produced, affordable cars, 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 it’s used still,
even if things inside are now a bit less hemispherical.
The new Hemi V8 had obvious performance potential and
the engineers experimented with the tuned-length induction system used on the
V16 before the aero-engine's final supercharger/turbocharger combination was adopted. So successful was the ram-tuned V8 (named
A-311) 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 so declared it didn’t comply with the rules (even tweaking them a bit to ensure it never would).
The research however continued and, although it’s not clear to what extent their efforts received factory-support, in the late 1950s some of Chysler's 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 a less obtrusive version of the system was made available on certain Plymouths, Dodges and Chryslers, the highest evolution of Sonoramic offered on the 300 letter series cars until 1964.
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 subsequently were banned.
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. Success isn't always rewarded.
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 (7.0 litre) 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.
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