EDITOR’S NOTE: This is a good one. I was interviewing 23-year-old Jesse Srpan for an American Iron/Bikernet biker feature article and I mentioned the SU carb on his dad’s Panhead. “Do you know what SU stands for? Jesse said.
I didn’t. “It stands for Skinners Union, meat packers made these carbs.” That’s a good story, so I decided to investigate. And I’m still not convinced, but here’s the story from two different web sites. The first is a site that deals with SU carbs in England. The next is a site devoted to Austin car manufacturing history. At one time Austin cars ran SU carburetors.
There’s still a question here. Was Skinner Union a name the inventors came up with, and did it have anything to do with Unions or manufacturing this carb? Check the stories below:
Probably because they are not electrical in any way (and therefore exempt from the Lucas curse), the SU carbs of a vintage Volvo are, in my opinion, one of the few things the British car industry got really right, bless them…(contrary to what you might hear in the automotive world)!
History. SU carbs were allegedly developed working with plumbers (air and fuel “flow” through them, so that makes sense, sort of). It is well known that SU stands for Skinner’s Union, my careful research has uncovered however, the less well known fact, that they were actually developed by British pork butchers, and that SU was actually shortened from SSU, standing for the Sausage Skinners Union. Below, an earlier development of the Sausage Skinners Union. The SSU, SG5, featuring “Spiral Venturi Design” (SVD). It was said to be the inspiration for the first SU side draft carburetter…ca. 1902…the family resemblance is apparent.
In a wonderfully simple SU carburetter., the varying exposure of a tapered “metering needle” is the mechanical equivalent of the electronic engine management system’s lookup table or “engine map”. Naturally, in the modern electronic engine management system, there is a lot more optimization going on, but the SU had the really important issue – correct metering and dispensing of fuel for the volume of air drawn through – very well under control.
The SU carburetter is of a constant Velocity, variable choke design…that is, by varying the position of the dashpot (12) as a function of the volume of air the engine draws, the cross-sectional area of the throat of the carb is varied, which keeps the velocity at the venturi point constant…and by keeping the velocity constant, it is fairly simple to meter the fuel for a given volume of air induced, although this leads to somewhat of an oversimplification in fuel metering, since the fuel should be metered as a function of mass of the air being ingested and not just volume (as density of the air, which can vary due to things like weather, season and altitude, is not compensated for).
That is why I like to adjust the mixture for summer and winter. Other than that, they seem to thrive on neglect, I honestly don’t understand why some owners seem to continuously need to fiddle with them!
An exception to the constant velocity occurs during changes in the throttle position…like Acceleration.
“Tuning S.U. Carburettors,“ published by Speedsport Motorbooks 1975, ISBN85113-072-0
http://www.sw-em.com/su_carbs.htm
The variable-choke carburettor had always been recognized as being technically superior to that of the mechanically simpler fixed-choke instrument. But its commercial realization depended upon the resolution of numerous difficult production problems. Despite many setbacks, faith in the basic principle sustained the determination of early members of the company to over come these difficulties, with the goal of bringing the product to the market place.
These principles were devised early this century when the motor car was a new mechanical wonder, when a small engineering company was set up in London to manufacture a carburettor invented and patented by Mr G H Skinner in 1905. The company was registered on the 22 August 1910 by Mr Skinner and his two brothers, Mr T C Skinner and Mr J H Skinner and was known as ‘The SU Co Ltd’, with the SU standing for Skinner Union.
The carburettor consisted of a leather bellows which held a tapered needle, when the throttle was opened the engine then required more fuel, because the flow of air through the carburettor increased the bellows would rise, thus taking the tapered needle further out of the jet, allowing more fuel into the engine. Because the bellows were a crucial component, it was important that the finest leather having a smooth and polished surface was used. To this end Herbert’s wife Mabel actual made all the bellows needed, by hand.
Mr J H Skinner left the company to go and work in the Shoe making side of the family business, so Mr G H Skinner along with Mr T C Skinner carried on looking after the business. The company grew and as can be seen from the above picture of the London factory in 1912 they were producing carburettors in large numbers. In WWI the company was involved in munitions production, along with production of carburettors for Aero engines with a workforce of around 250.
One of the deficiency of the original design was that it did not have a cold start position (rich mixture). Wolseley Motors Ltd came up with a solution that was patented by them in 1918, which added another jet (choke) that could physically be operated by the driver. This modification was adopted by SU who paid Wolseley a royalty.
After the War normal work started back up, but there was not much work about, so in 1919/20 the company made a loss. The company continued supplying carburettors to Wolseley, Austin, Lagononda and Napier for many years. But in 1922 the company supplied it first carburettor to Morris Motors and in that year total production increased to 2,000 carburettors and mechanical pumps.
In 1926 the company was getting into financial difficulties yet again, and Mr G H Skinner decided to leave the company. So it was left to Carl Skinner to find away out of the difficulties. So he approached W. R. Morris (Lord Nuffield) and following negotiations the S.U company was purchased by Morris for £100,000.
The following year the London factory was closed down and relocated to a part of the old Wolseley Car Plant at Adderley Park Birmingham. Morris Motors Ltd required 1,000 units a week, so £17,000 was spent on plant and equipment. With now strong financial backing, the company could develop new products, the first of which was the Petrolift in 1929 followed by a Aero carburettor in 1932. One type was fitted to the Rolls-Royce aero engines that powered the Hurricane, Lancaster and Spitfire. Another type was used on the Napier engines which powered the Tempest and Typhoon planes.
With the out break of WWII it was important that production was secured, so a duplicate plant was set up at Riley Motors Coventry. In 1940 the factory in Birmingham was damaged twice, so they moved to Highlands Road, Shirley, South Birmingham. Around this time the Air Ministry had set up a shadow factory in the Wharfe Valley Yorkshire, and in 1941 the SU Company acquired it to produce components for aircraft engines, including a fuel injection pump that was developed for the Rolls Royce Merlin engine.
After the war car carburettors and petrol pumps resumed and the company moved to a new site in Wood Lane Erdington Birmingham in July 1947, seen below. With production approaching a total of 223,000 carburettors and pumps per year. In December that year the company’s founder Mr T C Skinner retired and the company decided to sell its fuel injection manufacturing to the Stirling Company of America.
With the merger of Morris Motors Ltd with the Austin Motor Co Ltd in 1952 to form the British Motor Corporation, production was again increased. A Service Department was set op on the Wood Lane site so that customers cars fitted with SU carburettors and fuel pumps could book in for an engine tune, and in the early 60s on average 150 cars per week would be serviced.
In the late 50s the company produced a new fuel pump, called the PD. This pump was cheaper to make than the current pump, but when it was fitted to the new Mini did not prove to be that reliable.
When Jaguar, Guy and Coventry Climax joined the group in 1965 to form the British Motor Holdings, orders increased and production was around 30,000 carburettors per week which now included the newer version like the ‘HD’ to ‘HS’ types. The next development was the HIF carburettor which stood for Horizontal Integral Float that incorporated a electronically controlled cold start system.
In 1976 the company name was changed to SU Fuel System, then in 1983 it became Austin Rover Fuel Systems. 1984 saw the Design and Development Departments transferred to Longbridge, with Wood Lane plant just be coming a manufacturing plant. With engine manufactures using less carburettor’s as the general trend was to fit fuel injection systems, SU moved some of their production over to Single Point and Multi Point Throttle Bodies. Additional work was transferred from Morris Engine plant in Coventry which was closing down, so SU started to make the ‘O’ series oil pumps. Around the same time 1984/5 the UK division of Solex went into liquidation and in conjunction with Burlen Fuel Systems, negotiated the manufacture and supply of Zenith -Solex components required for spares.
1988 was a another year of change when British Aerospace, sold off SU to the Hobourn Group and another change of name to Hobourn SU. But in 1989 the Hobourn Group was acquired by Echlin Inc of the USA. The Echlin Group’s UK companies included Quinton Hazell which supplied the after sales market with a range of products, thus giving SU another avenue for sales.
After much development the company produced a Plastic throttle body for the Rover ‘K’ series engines. which was a first. The company was not making much money with its market share diminishing and in 1999 the parent company Echlin Group was taken over by the US company Dana Inc, so another change of name to Dana-SU Automotive. It was at this point that SU contacted Burlen Fuel Systems Ltd to manufacture and supply all SU carburettor units, pumps and spares. So the closure of the Wood Lane plant took place and manufacture was transferred to Burlen Fuel Systems Ltd who have a factory in Salisbury Wiltshire.
If you are looking for parts or technical help then visit their Web site at www.sucarb.co.uk
http://www.austinmemories.com/index.html
