1958 MGA - H4 SU CARBURETOR OPERATING PRINCIPLES - ANIMATIONS SHOW VARIABLE VENTURI AIR-FUEL CONTROL

This episode of Classic Cars - Driven By Data presents the basic operations of the H4 SU Carburetor as fitted to a 1958 MGA Mk1 with MGB 1800 engine. The key principles of operation are made clear with animations that show the process by which the SU carburetor achieves control of air:fuel mixture ratio over a wide range of engine load, engine speed and ambient conditions. The SU carburetor is a variable choke or variable venturi fuel air metering device. All adjustments are described, along with choke or cold start controls, accelerator or throttle controls as well as mixture adjustment. The need for, and operation of the dashpot or viscous damper are also described in detail, emphasizing the importance of the dashpot for transient operations, such as rapid changes in throttle or accelerator pedal position.
The motion of the main control piston is controlled by the differential pressure between the underside and topside of the piston. The source of these pressures is tracked through the hardware and fully explained.

[@360viewer]

Thanks, very useful for a new owner.

[@bladerunner6282]

for some reason i've never run across this video before.... it's an excellent explanation of how SU's work. of course, it's even of more useful, if you've had some familiarity with them in the past.

[@Unbuda.]

Gracias

[@markwatson6757]

Fantastic, easy to follow guide. Thank you.

[@walterholmes4609]

As to driving without oil in the dash pot. Some early MGBs had SU carbs where the brass nobs on top spontaneously loosened, especially at speed. Mostly it caused rough running. Pull over, tighten down and go. Without oil in the dashpot the engine will just stall out. BTW - if you need SU service and can't find anyone, try a custom motorcycle shop. Harley engine builders love them!

[@nalmeb]

Hi enjoyed the video about parts to the carburettor.
In fact I have just fitted a vacuum line too and from the carbs to distributor never had one fitted a previous owner had cut it off for reason unknown.
Just one thing which I had only just found out is the filters in the top off the fuel bowls where the fuels runs through might be worth mentioning?
Otherwise I would have loved to have found this 14 years ago when first bought my Mga 1500.
In fact I have just found out my carbs are from a 1600, dont think it affects the running of the engine.
Regards Tony

[@didiermusicvideo7987]

Une idée de la référence de la couleur de cette Mga ? Merci d'avance Didier