319:. The slide carburettor has the same piston and main needle as an SU carburettor, however the piston/needle position is directly actuated by a physical connection to the throttle cable rather than indirectly by venturi airflow as with an SU carburettor. This piston actuation difference is the significant distinction between a slide and an SU carburettor. The piston in a slide carburettor is controlled by the operator's demands rather than the demands of the engine. This means that the metering of the fuel can be inaccurate unless the vehicle is travelling at a constant speed at a constant throttle setting - conditions rarely encountered except on motorways. This inaccuracy results in fuel waste, particularly as the carburettor must be set slightly rich to avoid a lean condition (which can cause engine damage). For this reason
244:
236:
290:
of the function is determined by the 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.
28:
286:
upwards, increasing the size of the venturi, until the pressure drop in the venturi returns to 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 rate of air delivery.
410:
179:
353:
345:
36:
308:
operation - increasing the supply of fuel so that the carburettor will deliver an enriched mixture at all engine speeds and throttle positions. The 'choke' mechanism on an SU carburettor usually also incorporates a system for holding the throttle plate slightly open to raise the engine's idling speed and prevent stalling at low speeds due to a rich mixture.
304:, which requires periodic replenishment. The damping is asymmetrical: it heavily resists upwards movement of the piston. This serves as the equivalent of an "accelerator pump" on traditional carburettors by temporarily increasing the speed of air through the venturi when the throttle is suddenly opened, thus increasing the richness of the mixture.
285:
If the airflow into the engine is increased - by opening the throttle plate (also known as the "butterfly"), or by allowing the engine revs 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 pushed
281:
in the venturi. This pressure drop is communicated to the upper side of the piston via an air passage. The underside of the piston is open to atmospheric pressure. The difference in pressure between the two sides lifts the piston. Opposing this are the weight of the piston and the force of a spring
289:
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
282:
that is compressed by the piston rising. Because the spring is operating over a very small part of its possible range of extension, its force is approximately constant. Under steady state conditions the upwards and downwards forces on the piston are equal and opposite, and the piston does not move.
482:
Standard S.U. carburetors (American spelling) were also a popular upfit for Harley-Davidson motorcycles, given their space saving "side draft" design and superior ability to self-compensate for changes in air density/altitude. Many owners replaced the stock
Linkert, Bendix or Keihin carbs with SU's
307:
SU carburettors do not have a conventional choke flap, which in a fixed-jet carburettor enriches the mixture for starting the engine from cold by restricting the air supply upstream of the venturi. Instead a mechanism lowers the jet assembly, which has the same effect as the needle rising in normal
335:
One of the downsides of the constant depression carburettor is in high performance applications. Since it relies on restricting air flow in order to produce enrichment during acceleration, the throttle response lacks punch. By contrast, the fixed choke design adds extra fuel under these conditions
115:
Following the outbreak of war in 1914, carburettor production nearly stopped, with the factory making machine gun parts and some aircraft carburettors. With peace in 1918, production resumed, but sales remained slow and the company was not profitable, so Carl
Skinner approached his customer,
367:"H": introduced in 1937 in which the float bowl has an arm cast into its base, which mounts to the bottom of the carburetor with a hollow bolt or banjo fitting. Fuel passes through the arm into the carburetor body. The bolt attaches to the carburetor body just behind the main jet assembly.
397:
To determine the throat size from the type number: If the final number (after one, two or three letters, beginning with H) has 1 digit, multiply this number by 1/8", then add 1". For example, if the type number is HS6, the final number is 6: 6/8 = 3/4", add 1, total is 1-3/4", etc.
100:, London, manufacturers of their carburettor. Herbert continued to develop and patent improvements through to the 1920s, including the replacement of the leather bellows by a brass piston, even though he was a full-time director and divisional manager of Lilley & Skinner.
372:"HD": introduced in 1954 with the float bowl mounted with its arm fastening directly below, and concentric with, the main jet. The arm has a flange that fastens with 4 screws to the bottom of the carburetor, and sealed with a rubber diaphragm integral with the main jet.
120:, and managed to sell him the business. Carl Skinner (T. C. Skinner) became a director of Morris's privately held empire, and remained managing director of S.U. until he retired in 1948 aged 65. Production was moved to the W. R. Morris-owned Wolseley factory at
80:(1872–1931), pioneer motorist and an active participant in the development of the petrol engine, invented his Union carburettor in 1904. His much younger brother, Carl (Thomas Carlisle) Skinner (1882–1958), also a motoring enthusiast, had joined the
377:"HS": introduced in 1958 the float bowl can be rigidly or rubber mounted to the main body, fuel is transferred by an external flexible pipe to the jet. The jet moves down to enrich the mixture for cold starting,when the 'choke' linkage is pulled.
323:
motorcycle manufacturers ceased to fit slide carburettors and substituted constant-depression carburettors, which are essentially miniature SUs. It is also possible - indeed, easy - to retrofit an SU carburettor to a
528:
In 1929 SU introduced the
Petrolift electric fuel pump, which could be fitted as a substitute for the vacuum type pumps common at the time. This was superseded in 1932 by the L type fuel pump, which used a
108:
S. U. Company
Limited — Skinner-Union — was incorporated in August 1910 to acquire Herbert's carburettor inventions, and it began manufacture of the carburettors in a factory at Prince of Wales Road,
311:
The beauty of the SU lies in its simplicity and lack of multiple jets and ease of adjustment. Adjustment is accomplished by altering the starting position of the jet relative to the needle on a fine
929:
SU Carburetors Owners
Workshop Manual by Don Peers: Part 1 Chapter 2 and Part 2 Type H, Haynes Publishing Group, Spsrkford YEOVIL Somerset England. Copyright JH Haynes and Company Limited 1976
566:
S. U. Company
Limited, 386—388 Euston Road, N.W. Capital £5,000 in £1 shares. Formed to acquire from G. H. Skinner certain inventions relating to carburettors for motorcars &c
158:, which incorporated an entirely new company with the name The S.U. Carburetter Company Limited, which continues to manufacture carburettors, pumps and components, mainly for the
593:
which was imported into
Knowledge before November 2008 and is therefore validly licensed for use on Knowledge. All relevant terms must be followed. The original article was at
274:, so the movement of the piston controls the amount of fuel delivered, depending on engine demand. The exact dimensions of the taper are tailored during engine development.
270:
into the airstream passing through the carburettor. Since the needle is tapered, as it rises and falls it opens and closes the opening in the jet, regulating the passage of
684:
H. Jones: Herbert
Wakefield Banks Skinner. 1900-1960. Biographical Memoirs of Fellows of the Royal Society, Vol.6, (Nov. 1960), pp.259-268, publisher: The Royal Society
140:
Manufacture continued, then by The S. U. Carburetter
Company Limited, which was incorporated 15 September 1936, as part of the Morris Organisation, later known as the
315:(26TPI for most pre-HIF versions). At first sight, the principle appears to bear a similarity to that of the slide carburettor, which was previously used on many
590:
401:
If the final number has 2 digits, it is the throat size in mm. For example, if the type number is HIF38, the final number is 38, size is 38 mm etc.
92:, South Kensington in 1934. In 1905, Herbert applied for a patent, which was granted in early 1906. Later, Carl sold his interest in footwear business
391:
The
Imperial sizes include 1-1/8", 1-1/4", 1-1/2", 1-3/4", 1-7/8", and 2", although not every type (H, HD, HS, HIF) was offered in every size.
394:
There were also H models made in 2-1/4" and 2-1/2", now obsolete. Special purpose-built carburetors (Norman) were made as large as 3".
997:
977:
892:
693:
293:
This self-adjusting nature makes the selection of the maximum venturi diameter (colloquially, but inaccurately, referred to as "
117:
382:"HIF": (1972) the float bowl is horizontal and integral (hence the name) Horizontal Integral Float. Example: 1972-1974 MGB.
54:
made by a British manufacturer of that name or its licensees in various designs spanning most of the twentieth century.
31:
Original design incorporating a leather bellows which was replaced by a piston. This image was published 1908 and 1909
1002:
849:
808:
788:
222:
204:
360:
SU carburettors were supplied in several throat sizes in both Imperial (inch) and metric (millimetre) measurement.
85:
939:
768:
189:
17:
128:. In 1936, W. R. Morris sold many of his privately held businesses, including S. U., to his listed company,
612:
329:
243:
235:
860:
300:
To prevent erratic and sudden movements of the piston it is damped by light oil (20W Grade) in a
200:
77:
972:
457:
141:
582:
449:
151:
The S. U. Carburetter Company Limited of 1936 was voluntarily liquidated in December 1994.
8:
429:
93:
88:
could remember his mother sewing the first leather bellows. It would be given on loan to
66:
58:
363:
The carburettor identification is made by letter prefix which indicates the float type:
196:
982:
940:"HIF4 Carburetor - Carburetors - Fuel, Intake & Emissions - MGB | Moss Motors"
547:
542:
476:
472:
445:
89:
62:
845:
804:
784:
764:
650:
Handbook of the Collections illustrating Land Transport, II. Mechanical Road Vehicles
594:
568:
New Companies Registered. Private Companies. The Automotor Journal, 24 September 1910
266:(usually referred to as a "needle") that fits inside an orifice ("jet") which admits
917:
879:
468:
278:
260:
145:
27:
983:
Classic Motorsports magazine's guide to understanding, tuning and rebuilding SUs
437:
328:
that was originally manufactured with a slide carburettor, and obtain improved
81:
991:
973:
A very comprehensive SU and Stromberg Carb Needle Selection and Analysis Tool
501:
491:
421:
387:"HV" (1929), "OM" and "KIF" types also exist but were less commonly employed.
154:
In 1996, the name and rights were acquired by Burlen Fuel Systems Limited of
129:
121:
517:
252:
109:
84:
in London in 1899. He helped Herbert to develop the carburettor. Herbert's
509:
505:
495:
453:
441:
316:
294:
159:
97:
51:
461:
325:
125:
504:
also built carburettors based on the SU design which were used on the
414:
409:
155:
952:
486:
S.U. carburetors remained on production cars through to 1994 in the
207:. Statements consisting only of original research should be removed.
530:
425:
271:
479:
type rather than the firm's patented constant-depression design.
57:
The S.U. Carburetter Company Limited also manufactured dual-choke
433:
356:
Three 2-inch SU HD8 carburettors as installed on an E-type Jaguar
301:
297:
size") much less critical than with a fixed-venturi carburettor.
704:
3257 G H Skinner, Carburetting apparatus. reported in page 152,
344:
513:
352:
256:
40:
483:
until the Keihin Constant Velocity carb became stock in 1990.
968:
Burlen Fuel Systems - manufacturer of genuine SU carburetters
348:
An SU fitted to an MZ in place of the original BVF slide carb
320:
312:
967:
487:
267:
35:
420:
S.U. carburettors were widely used not only in Morris's
135:
801:
Malloch's Spitfire: The Story and Restoration of PK350
277:
The flow of air through the venturi creates a reduced
865:
Biographical Memoirs of Fellows of the Royal Society
494:, by which time the company had become part of the
694:The Science Museum's (1965) carburettor, sectioned
989:
475:, but these were of the conventional fixed-jet
978:Guide to setting up and tuning SU carburettors
634:, Wednesday, Jan 06, 1932; pg. 12; Issue 46023
516:Cars. While these appear the same, only their
148:, and traded under the name SU Carburetters.
96:and became a partner in G Wailes & Co of
721:, Tuesday, Jun 02, 1896; pg. 14; Issue 34906
672:, Saturday, Nov 15, 1958, Issue 54309, p.10.
72:
818:
816:
589:, a source licensed under the terms of the
861:Herbert Wakefield Banks Skinner. 1900-1960
893:"SU Carburettor Halted By Protest Strike"
664:
662:
660:
658:
626:
624:
223:Learn how and when to remove this message
836:
834:
813:
413:An HV type carburettor fitted to a 1930
408:
351:
343:
332:and more tractable low-speed behaviour.
242:
234:
103:
34:
26:
822:
730:Skinner-Union Carburettor Improvement.
652:, Science Museum South Kensington, 1936
339:
14:
990:
875:
873:
655:
621:
464:, for much of the twentieth century.
168:
831:
755:
753:
136:The S. U. Carburetter Company Limited
737:
680:
678:
644:
642:
640:
471:including the early versions of the
467:S.U. also produced carburettors for
172:
144:. The companybecame a subsidiary of
112:, in North London. Sales were slow.
870:
743:Profile Professor Herbert Skinner,
428:products but such British makes as
251:SU carburettors feature a variable
24:
750:
39:A pair of SU carburettors from an
25:
1014:
961:
827:. Salisbury: Burlen Fuel Systems.
675:
637:
585:, this article uses content from
998:Constant-depression carburettors
825:SU Carburettor Company catalogue
668:Obituary. Mr. Thomas C. Skinner
523:
177:
946:
932:
923:
911:
885:
854:
793:
773:
560:
404:
724:
711:
698:
687:
606:
591:GNU Free Documentation License
13:
1:
630:Obituary. Mr. G. H. Skinner.
575:
533:to operate a diaphragm pump.
259:. This piston has a tapered,
61:for aero-engines such as the
336:using its accelerator pump.
7:
618:magazine, p 577, 7 May 1954
536:
203:the claims made and adding
10:
1019:
844:, Stratus, Cornwall, 2001
50:was a constant-depression
763:, Stratus, Cornwall 2001
73:Invention and development
1003:Carburetor manufacturers
553:
920:company number 03285338
882:company number 00318520
734:, 24 August 1920, p.28.
717:'Lilley & Skinner,
595:"PowerPedia:Carburetor"
823:Burnett, John (2012).
417:
357:
349:
248:
240:
43:
32:
520:are interchangeable.
412:
355:
347:
246:
238:
142:Nuffield Organisation
104:S. U. Company Limited
38:
30:
897:Honest John Classics
732:The Commercial Motor
340:SU carburettor types
94:Lilley & Skinner
82:Farman Automobile Co
59:updraft carburettors
247:HS6 without dashpot
169:Operating principle
67:Rolls-Royce Griffon
953:SU technical pages
781:Tuning for Economy
548:Zenith carburettor
543:Amal (carburettor)
473:Rolls-Royce Merlin
418:
358:
350:
249:
241:
188:possibly contains
90:The Science Museum
63:Rolls-Royce Merlin
44:
33:
842:Wheels to Fortune
761:Wheels to Fortune
745:The New Scientist
706:AutoMotor Journal
233:
232:
225:
190:original research
16:(Redirected from
1010:
955:
950:
944:
943:
936:
930:
927:
921:
915:
909:
908:
906:
904:
899:. 5 January 1973
889:
883:
877:
868:
858:
852:
838:
829:
828:
820:
811:
803:, Casemate 2014
797:
791:
783:, Springer 1981
779:Colin Campbell,
777:
771:
757:
748:
747:14 November 1957
741:
735:
728:
722:
715:
709:
702:
696:
691:
685:
682:
673:
666:
653:
646:
635:
628:
619:
610:
569:
564:
469:aircraft engines
255:controlled by a
228:
221:
217:
214:
208:
205:inline citations
181:
180:
173:
21:
1018:
1017:
1013:
1012:
1011:
1009:
1008:
1007:
988:
987:
964:
959:
958:
951:
947:
938:
937:
933:
928:
924:
918:Companies House
916:
912:
902:
900:
891:
890:
886:
880:Companies House
878:
871:
859:
855:
839:
832:
821:
814:
798:
794:
778:
774:
758:
751:
742:
738:
729:
725:
716:
712:
708:3 February 1906
703:
699:
692:
688:
683:
676:
667:
656:
647:
638:
629:
622:
611:
607:
601:
578:
573:
572:
567:
565:
561:
556:
539:
526:
407:
342:
279:static pressure
229:
218:
212:
209:
194:
182:
178:
171:
146:British Leyland
138:
106:
78:Herbert Skinner
75:
23:
22:
15:
12:
11:
5:
1016:
1006:
1005:
1000:
986:
985:
980:
975:
970:
963:
962:External links
960:
957:
956:
945:
931:
922:
910:
884:
869:
853:
840:James Leasor,
830:
812:
792:
772:
759:James Leasor,
749:
736:
723:
710:
697:
686:
674:
654:
636:
620:
604:
603:
577:
574:
571:
570:
558:
557:
555:
552:
551:
550:
545:
538:
535:
525:
522:
460:, and Swedish
406:
403:
389:
388:
384:
383:
379:
378:
374:
373:
369:
368:
341:
338:
231:
230:
185:
183:
176:
170:
167:
137:
134:
105:
102:
74:
71:
48:SU carburettor
18:SU carburetter
9:
6:
4:
3:
2:
1015:
1004:
1001:
999:
996:
995:
993:
984:
981:
979:
976:
974:
971:
969:
966:
965:
954:
949:
941:
935:
926:
919:
914:
898:
894:
888:
881:
876:
874:
866:
862:
857:
851:
850:0-7551-0047-6
847:
843:
837:
835:
826:
819:
817:
810:
809:9781612002521
806:
802:
799:Nick Meikle,
796:
790:
789:9780412234903
786:
782:
776:
770:
766:
762:
756:
754:
746:
740:
733:
727:
720:
714:
707:
701:
695:
690:
681:
679:
671:
665:
663:
661:
659:
651:
648:E A Forward,
645:
643:
641:
633:
627:
625:
617:
614:
609:
605:
602:
599:
598:
596:
592:
586:
584:
563:
559:
549:
546:
544:
541:
540:
534:
532:
524:SU fuel pumps
521:
519:
515:
511:
507:
503:
499:
497:
493:
489:
484:
480:
478:
474:
470:
465:
463:
459:
455:
451:
447:
443:
439:
435:
431:
427:
423:
416:
411:
402:
399:
395:
392:
386:
385:
381:
380:
376:
375:
371:
370:
366:
365:
364:
361:
354:
346:
337:
333:
331:
327:
322:
318:
314:
309:
305:
303:
298:
296:
291:
287:
283:
280:
275:
273:
269:
265:
262:
258:
254:
245:
237:
227:
224:
216:
206:
202:
198:
192:
191:
186:This section
184:
175:
174:
166:
163:
161:
157:
152:
149:
147:
143:
133:
131:
130:Morris Motors
127:
123:
122:Adderley Park
119:
113:
111:
101:
99:
95:
91:
87:
83:
79:
70:
68:
64:
60:
55:
53:
49:
42:
37:
29:
19:
948:
934:
925:
913:
901:. Retrieved
896:
887:
864:
856:
841:
824:
800:
795:
780:
775:
760:
744:
739:
731:
726:
718:
713:
705:
700:
689:
669:
649:
631:
615:
608:
600:
588:
580:
579:
562:
527:
500:
485:
481:
466:
419:
405:Applications
400:
396:
393:
390:
362:
359:
334:
330:fuel economy
310:
306:
299:
292:
288:
284:
276:
264:metering rod
263:
250:
219:
213:January 2015
210:
187:
164:
153:
150:
139:
118:W. R. Morris
114:
110:Kentish Town
107:
76:
56:
47:
45:
510:Datsun 260Z
506:Datsun 240Z
496:Rover Group
430:Rolls-Royce
317:motorcycles
165:Relocating
160:classic car
98:Euston Road
52:carburettor
992:Categories
903:7 February
769:0755100476
613:The Two Rs
576:References
512:and other
239:HS6 damper
197:improve it
126:Birmingham
863:H Jones,
719:The Times
670:The Times
632:The Times
583:this edit
477:updraught
415:MG M-type
201:verifying
156:Salisbury
537:See also
531:solenoid
490:and the
321:Japanese
162:market.
587:PESWiki
518:needles
502:Hitachi
492:Maestro
458:Triumph
434:Bentley
302:dashpot
261:conical
253:venturi
195:Please
848:
807:
787:
767:
616:Flight
581:As of
514:Datsun
456:, and
454:Jaguar
450:Austin
446:Turner
422:Morris
257:piston
554:Notes
462:Volvo
442:Riley
438:Rover
313:screw
295:choke
905:2021
867:1960
846:ISBN
805:ISBN
785:ISBN
765:ISBN
488:Mini
424:and
326:bike
272:fuel
268:fuel
65:and
46:The
199:by
86:son
41:MGB
994::
895:.
872:^
833:^
815:^
752:^
677:^
657:^
639:^
623:^
508:,
498:.
452:,
448:,
444:,
440:,
436:,
432:,
426:MG
132:.
124:,
69:.
942:.
907:.
597:.
226:)
220:(
215:)
211:(
193:.
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
.jpg)
.jpg)