incl. VAT plus shipping costs
|used with carburettors brands:||Dellorto|
|used as atomiser in:||Dellorto SI|
|diameter head:||6 mm|
|total length:||26 mm|
function nozzle block SI
In the nozzle block area of the SI carburettor there is always a defined level of fuel (depending on the filling level in the float chamber). I.e. below the atomizer tube (which opens into the intake area of the carburetor) there is a petrol column. For this reason we also advise against the so-called float chamber spacers. These increase the filling level in the carburettor, but they also provide a higher level in the nozzle block area, which means that the premix can no longer work properly and possibly also petrol runs directly from the atomiser into the engine (spillage). The real problem is also not a too small volume of the float chamber, but a tuning via the air nozzle.
From the very bottom, the following fuel quantity is defined by the main nozzle. In the middle is half in the fuel, half in the air, the so-called mixing tube (e.g. BE3). From the top, the air nozzle defines the amount of incoming air.
The pre-foaming process in the mixing tube is very complex and strongly dependent on pressure and speed. The mixing tube has various cross holes. These are partly in the gasoline level, partly outside of it in the air area. Depending on size, quantity and positioning of the bore, this results in different pre-foaming behaviour.
It should be noted that there is generally no per se greasing or emaciating mixing tube.
As a rough guide value, a characteristic curve in relation to the speed of rotation can be shown.
BE4 - BE6 - BE5 - BE1 - BE3 - BE2
In this list, from left to right, the mixing tube is rather greasing at low speed and emaciating at high speed. The whole thing then tilts accordingly and becomes lean at low speed and greasy at high speed.
Attention: The mixing tubes have an effect over a very wide speed range. For example, a BE4 mixing tube greases strongly just above the idling slide valve position. A BE2, on the other hand, is relatively lean in the lower speed range, but greases strongly at the top.
The most common mixing tube BE3 covers 90% of all applications of the SI carburettor. In addition, the used gas slide should be checked here (see slide SI).
The combination air nozzle 160 with mixing tube BE3 is sufficient in almost all cases. If the filter bottom is drilled and/or a resonance exhaust is installed, the mixing tube can be changed to BE2 and the air nozzle to 140 if necessary.