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of the function is determined by the tapered profile of the needle. With appropriate selection of the needle, the fuel delivery can be matched much more closely to the demands of the engine than is possible with the more common fixed-venturi carburettor, an inherently inaccurate device whose design must incorporate many complex fudges to obtain usable accuracy of fuelling. The well-controlled conditions under which the jet is operating also make it possible to obtain good and consistent atomisation of the fuel under all operating conditions.
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force is the weight of the piston and the force of a compression spring that is compressed by the piston rising; because the spring is operating over a very small part of its possible range of extension, the spring force approximates to a constant force. Under steady state conditions, the upward and downward forces on the piston are equal and opposite, and the piston does not move.
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its nominal level. Similarly, if the airflow into the engine is reduced, the piston will fall. The result is that the pressure drop in the venturi remains the same regardless of the speed of the airflow – hence the name "constant depression" for carburettors operating on this principle – but the piston rises and falls according to the speed of the airflow.
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Since the position of the piston controls the position of the needle in the jet, and thus the open area of the jet, while the depression in the venturi sucking fuel out of the jet remains constant, the rate of fuel delivery is always a definite function of the rate of air delivery. The precise nature
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plate, or by allowing the engine revolutions to rise with the throttle plate at a constant setting – the pressure drop in the venturi increases, the pressure above the piston falls, and the piston is sucked upward, increasing the size of the venturi, until the pressure drop in the venturi returns to
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within it. This pressure drop is communicated to the upper side of the piston via an air passage. The underside of the piston is in communication with atmospheric pressure. The difference in pressure between the two sides of the piston creates a force tending to lift the piston. Counteracting this
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A major drawback of the constant-depression carburettor is its unsuitability in high-performance applications. Since it relies on restricting air flow to produce enrichment during acceleration, the throttle response lacks punch. By contrast, the fixed choke design adds extra fuel under these
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This self-adjusting nature makes the selection of the maximum venturi diameter (colloquially, but inaccurately, referred to as "choke size") much less critical than with a fixed-venturi carburettor.
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carburettors in the North
American market. In Australia, the CD-150 and CDS-175 models were fitted to the high-performance, triple-carburettored Holden Torana GTR-XU1.
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Carburettors, and over time, the Zenith brand name fell into disuse. The rights to the Zenith designs were owned by Solex UK (a daughter company of Solex in France).
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While better known for its much later products, Zenith produced carburettors that were standard equipment on some very early,
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British made Zenith/Stromberg carburettors as installed on a 1969 Jaguar E-type 6cyl 4.2l engine
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To prevent erratic and sudden movements of the piston, it is damped by light oil in a
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390:(under the white plastic cover in the picture), which requires periodic topping-up.
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metering rod (usually referred to as a "needle") that fits inside an orifice ("
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A very comprehensive SU and
Stromberg Carb Needle Selection and Analysis Tool
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If the airflow into the engine is increased – by opening the
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Hillman/Chrysler/Talbot/Sunbeam
Avenger/Plymouth Cricket
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Non-UK German
Pierburg (Stromberg) carburettor dashpot
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Defunct manufacturing companies of the United
Kingdom
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The flow of air through the venturi creates reduced
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Non-UK German
Pierburg (Stromberg) carburettor in a
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193:, founded in 1912 as a subsidiary of the French
487:Listing of application of Zenith carburettors
227:Zenith's best-known products were the Zenith-
174:Brass Zenith semi-updraught carburetter, 1925
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456:, Monday, 26 April 1965; pg. 16; Issue 56305
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527:Manufacturing companies established in 1910
32:For American company of the same name, see
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340:) and Harry Cartwright (Zenith) to break
336:Designed and developed by Dennis Barbet (
89:Learn how and when to remove this message
52:This article includes a list of general
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394:conditions using its accelerator pump.
522:British companies established in 1910
442:. Clerke & Cockeran. p. 146.
182:Limited was a British company making
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352:. This piston has a long, tapered,
102:Zenith Carburetter Company Limited
58:it lacks sufficient corresponding
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507:Constant-depression carburettors
418:for other companies named Zenith
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412:, works with the same principle
291:, MGs and some 1960s and 1970s
233:Humber Super Snipe Series Va/Vb
517:1910 establishments in England
452:Zenith Carburettor Prospects.
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436:Harold George Castle (1950).
197:Société du carburateur Zénith
152:Société du carburateur Zénith
467:"zenith stromberg tech tips"
123:; 112 years ago
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180:Zenith Carburetter Company
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406:for the Solex carburettor
34:Zenith Carburetor Company
532:Carburetor manufacturers
439:Britain's Motor Industry
27:British carburetor maker
416:Zenith (disambiguation)
285:Rapier Fastback (Arrow)
73:more precise citations.
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18:Zenith carburettor
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16:(Redirected from
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287:, 1970–1981
279:, 1967–1975
271:, 1966–1970
265:Hillman Minx
263:, 1966–1979
255:, 1969–1972
239:, 1967–1975
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184:carburettors
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136:Headquarters
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213:automobiles
71:introducing
501:Categories
423:References
257:Volvo 140s
251:and early
111:Automotive
54:references
454:The Times
331:Zenith IV
210:brass era
191:Middlesex
79:July 2009
398:See also
373:throttle
293:Triumphs
245:Saab 99s
223:Products
188:Stanmore
107:Industry
388:dashpot
354:conical
346:venturi
304:Saab 90
126: (
118:Founded
67:improve
350:piston
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147:Parent
56:, but
470:(PDF)
404:Solex
329:used
203:Solex
325:The
261:164s
259:and
253:900s
178:The
128:1912
121:1912
358:jet
249:90s
186:in
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