TECHNOFILE WEBER'S DCO CAR BURETTOR

Author

admin

Browse pages
Current page

1

Current page

2

Current page

3

Current page

4

Current page

5

Current page

6

Current page

7

Current page

8

Current page

9

Current page

10

Current page

11

Current page

12

Current page

13

Current page

14

Current page

15

Current page

16

Current page

17

Current page

18

Current page

19

Current page

20

Current page

21

Current page

22

Current page

23

Current page

24

Current page

25

Current page

26

Current page

27

Current page

28

Current page

29

Current page

30

Current page

31

Current page

32

Current page

33

Current page

34

Current page

35

Current page

36

Current page

37

Current page

38

Current page

39

Current page

40

Current page

41

Current page

42

Current page

43

Current page

44

Current page

45

Current page

46

Current page

47

Current page

48

Current page

49

Current page

50

Current page

51

Current page

52

Current page

53

Current page

54

Current page

55

Current page

56

Current page

57

Current page

58

Current page

59

Current page

60

Current page

61

Current page

62

Current page

63

Current page

64

Current page

65

Current page

66

Current page

67

Current page

68

Current page

69

Current page

70

Current page

71

Current page

72

Current page

73

Current page

74

Current page

75

Current page

76

Current page

77

Current page

78

Current page

79

Current page

80

Current page

81

Current page

82

Current page

83

Current page

84

Current page

85

Current page

86

Current page

87

Current page

88

Current page

89

Current page

90

Current page

91

Current page

92

Current page

93

Current page

94

Current page

95

Current page

96

Current page

97

Current page

98

Current page

99

Current page

100

Current page

101

Current page

102

Current page

103

Current page

104

Current page

105

Current page

106

Current page

107

Current page

108

Current page

109

Current page

110

Current page

111

Current page

112

Current page

113

Current page

114

Current page

115

Current page

116

Current page

117

Current page

118

Current page

119

Current page

120

Current page

121

Current page

122

Current page

123

Current page

124

Current page

125

Current page

126

Current page

127

Current page

128

Current page

129

Current page

130

Current page

131

Current page

132

Current page

133

Current page

134

Current page

135

Current page

136

Current page

137

Current page

138

Current page

139

Current page

140

TECHNOFILE WEBERS DCO CARBURETTOR

BEFORE THE ADVENT OF FUEL INJECTION, RACE TEAMS LOOKED HIGH AND LOW FOR THE PERFECT CARBURETTOR. AS KEITH HOWARD REPORTS, THE SOLUTION CAME FROM ITALY photography by Charles Best

here are few components boasting a thoroughbred racing pedigree which you could, or would want to, employ on a road car. But one item with just such a background encompassing five Fl championships as well as countless successes in other arenas has proved itself uniquely egalitarian, for decades being synonymous with readily available and adaptable bolt-on power: the Weber DCO twin-choke sidedraught carburettor. Introduced at the dawn of the 1950s, the DCO doppio corpo orizontale, meaning double-bodied horizontal wasted little time proving itself a winner in the most exalted company. In 1952 and ’53 it racked up its -first Fl world championships in the Ferrari Tipo 500, repeating the success in 1957 in the Maserati 250F and in 1959 and ’60 in the T51 and T53 Cooper-Climaxes. Although other carburettor makers Solex, SU, even Amal competed alongside it in the premier racing formula, Solex claiming a championship in the Lancia-Ferrari in 1956, Weber dominated thmugh both the DCO and various downdraught models like the DC’N L, which substituted far it in vet-engined applications. Founder Edoardo Weber’s long-standing relationship with Enzo Ferrari, with whom he had already worked prior to farming Weber Carburatori in 1924, meant that racing featured high on Weber’s list of priorii’s, great care being expended on making the throats

its carburettors as aerodynamically efficient as possible. Available with throat diameters from 35 to 58mm, the DCO was also unusually flexible. With hindsight, nevertheless, it might seem odd that the DCO was given the opportunity of winning Fl world championships right up to 1960. (Weber’s last championship success, appropriately with Ferrari, came in 1961 but with bespoke triplechoke downdraught 40IF3Cs provisioning the Sharknose’s V6.) In 1954 and ’55 Mercedes-Benz had proved the worth of fuel injection in the victorious W196s, and Vanwall had repeated the lesson in 1958. On the face of it, by the time the Coopers tarried the DCO to victory the carburettor was already outmoded. But this is an oversimplification: you have to bear in mind the relative crudity of fuel

injection systems of the time, and understand the significance of changing fuel regulations.

When Mercedes won in 1954 and ’55, potent alcohol blends were still legal. As these were a lot less sensitive to variations in fuel :air ratio than unadulterated petrol is, the relatively inexact metering of fuel by the Bosch injection system although it was a good deal more sophisticated in this respect than the American Hilbom-Travers continuous spray alternative, as Connaught discovered didn’t matter a great deal. What was important was that fuel injection removed the carburettor’s need for a venturi (choke) in the inlet manifold, thereby improving engine breathing. This situation didn’t last, though. The fuel rules changed for 1958, outlawing alcohol blends, with

the result that high.-octane Avgas (aviation gasoline) became the fuel of choice. Not only did engine powers fall as a result, mixture control also became much more critical. Vanwall succeeded using the Bosch injection system nonetheless, but it was a close run thing. Then the rules tightened still further, insisting on fuel more akin to what the ordinary motorist used as specified by the FIA.

None of this tinkering with fuel regs would have mattered much were full load, wide open throttle perfarmance the only issue: in this respect fuel injection continued to offer an advantage. But as Wally Hassan of Coventry Climax was to explain in a lecture to the Society of Automotive Engineers in 1966, “If the use of engine performance is studied… it is evident that the time during which the car operates at maximum rpm and power is extremely small.

The most successful engine is, therefore, the one which combines a good maximum power with exceptional torque spread.” For so long as the carburettor enjoyed an advantage in the latter respect due to its superior fuel metering or suffered no significant disadvantage it still had life in it.

Not that the carburettor itself was without quirks. As cornering forces increased as a result of improved tyre technology, lowered centres of gravity and more enlightened suspension design, teams began to report problems caused by fuel surge in the float chambers. For those who remembered the Battle of Britain it was a curious echo of what happened when the carburetted Spitfire met the fuel injected Messerschmitt Bf109. Pulling negative g in a Spit caused its Merlin engine to hesitate sufficiently for a diving Bf109 to make its escape. RAF pilots overcame this by performing a half-roll to convert negative into positive g unfortunately, not a manoeuvre with a race track equivalent.

Eventually, of course, the carburettor’s game was up. Lucas introduced its superior ‘shuttle type’ fuel injection metering unit with which BRM won the F1 title in 1962 and Lotus the fallowing year, and the DCO was history. Even Ferrari finally embraced fuel injection, albeit by Bosch, during the 1963 season.

Today we live in an era where arranging for precisely the tight amount of fuel to be introduced into the cylinder, whatever the engine speed or load, is no more complex than entering the appropriate figure into the engine management’s look-up table. The fiddly, inexact and, let’s not forget, costly business of juggling main, air-corrector, slow-running, pump and starter jets, emulsion tubes, choke sizes and accelerator pump strokes has been superseded by plugging numbers into digital memory. And by any measure that’s welcome progress.

Remarkably, though, Weber still exists (now as a division of engine management specialist Magneti Marelli) and the DCOE the best-known DCO variant, produced in by far the largest numbers remains in production. Not only to satisfy the replacement market, either. For significant numbers of hands-on car enthusiasts, particularly those tuning an engine with a reactionary original equipment fuel injection system, the DCOE remains one of the most cost-effective ways to bolt on performance. Our world isn’t all computer controlled yet. CI