Intake manifold - Diaphragm intake manifold -MALOSSI 2-hole diaphragm- Vespa V50, PV125 - AW=28,5mm

MALOSSI diaphragm intake manifold 2-hole with 28.5 mm connection for Vespa V50 and PV125

A diaphragm intake manifold regulates the mixture supply automatically, independently of the intake timing of the crankshaft. This opens up several possibilities for using a reed valve intake in a sensible way. For example, it is ideal for continuing to use an engine housing with a defective rotary valve intake surface.

In this case, the sealing function that would otherwise be performed by the rotary intake valve is taken over by a valve integrated in the intake manifold (colloquially known as a diaphragm). As a result, the engine housing can be milled open without regard to the former sealing surface and a significantly larger intake surface can be realized. This significantly improves the degree of filling of the crankcase, especially in the upper speed range. For all tinkering fans, this offers the possibility of using carburetors with a cross-section of more than 24 mm. This is particularly interesting for very high-revving engine set-ups (e.g. Malossi 136cc or machined Polini 133cc).

Diaphragm intake for tuning setups suitable for everyday use

If you want to build a normal engine, a 24 mm intake cross-section is sufficient. With the right cylinder and exhaust, speeds of over 120 km/h can be achieved, taking the fun factor of a Smallframe to a whole new level. As with the rotary valve intake manifolds, it is important to select the correct manifold to match the engine housing or chassis mounting method. To ensure good filling of the crankcase, a racing crankshaft should be installed. This has longer opening times and thus reduces the flow resistance that would occur with a normal crankshaft with short intake timing to a minimum. Furthermore, the inside of the housing in the inlet area can be freed from all interfering edges (rotary vane sealing surface). This results in good engine elasticity and further reduced flow resistance.

Limits of the full cheek crankshaft at the housing diaphragm intake

If you want to run a full cheek

crankshaft

in conjunction with a housing diaphragm intake, you have to dig deep into your bag of tricks. In this case, the crank web is constantly in the gas flow, preventing the engine from delivering its full power in the upper speed range. This requires massive welding and milling work on the engine housing, which does not necessarily make the engine any better. Cylinders that can draw in their mixture independently of the crankcase are much better suited to the full cheek. We therefore offer the 136cc Malossi cylinder, which can take in the fresh gas either via the crankcase or directly with an optionally available intake manifold. This enables it not only to make very good use of a full cheek, but also to deliver very high power at a high engine speed.