Stromberg carburetor

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A Stromberg carburetor is a flat-flow carburetor whose mixing chamber pressure above the main nozzle is approximately the same under all load conditions. Together with the products of the companies Bing and Skinner United (SU) it belongs to the constant pressure carburetors .

construction

A Stromberg carburetor is a round slide carburetor in which the round slide is not lifted mechanically by means of a throttle cable, but by negative pressure.

Open Stromberg carburetor ( Saab 90 )

The structure of the carburettor is a tube through which air flows and in the bottom of which there is a main nozzle that is closed by a needle with a conical cut. Under the main nozzle in the float chamber, there is an even gasoline level under external pressure, regulated by the float needle valve. The nozzle needle is suspended from an air piston which closes the tube almost completely (90 degrees). This air piston is controlled by a membrane (almost the size of a palm) that experiences external pressure from below.

The main nozzle is installed in this tube in a slightly raised manner (bridge), which creates a Venturi effect (negative pressure when the gases flow over), as the diameter is reduced at this point.

The vacuum space (bell) above the membrane is connected to the space between the main nozzle and the throttle valve via two holes through the air piston (round slide).

function

The element of the Stromberg gasifier that controls the air flow rate is the throttle valve behind the mixing chamber (viewed from the direction of air flow). If the throttle valve is closed (idling), the pressure differences in front of and behind the air piston are the same. When the accelerator is depressed, the throttle valve is opened and the pressure drops on the throttle valve side, which means that the air piston (round slide) is lifted from the diaphragm. The air piston releases more diameter in the pipe and at the same time pulls the needle of the main jet higher (more gasoline). The air piston has an oil-filled damper in its center, which prevents overshooting.

The membrane controlled by the control flap produces an approximately constant stoichiometric fuel ratio; Additional devices for mixture enrichment such as accelerator pumps are usually not necessary.

Designations

Stromberg 175 CDTU: installed in four-cylinder engines from the Mercedes-Benz W 201 , Mercedes-Benz W 123 and Mercedes-Benz W 115 model series

Stromberg 175 CDET: installed in the BMW 520/4 E12

Stromberg 175 CD-2S: installed in the VOLVO PV 544, motor B 18 A

Stromberg 175 CD-2SE: built into the VOLVO 1800S, engine B 20 B; for USA, Canada and some European markets

  • 175 = suction tube diameter 1.75 inches corresponds to 44.4 mm
  • CD = Constant Depression (constant negative pressure)
  • T = temperature-controlled automatic start
  • U = idle system with recirculation and recirculation
  • E = emission (reducing exhaust gas)

literature

  • Cross-section through the engine technology, Volume 309: Repair instructions for Mercedes-Benz 123 series (from 1976 to May 1980) , Verlag Bucheli, Zug (Switzerland), page 30 f.

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