Displacement: 4,04 cc
R.P.M. (max power): 37.500 RPM
Practical range: 6.000-42.100 R.P.M.
Bore x stroke: 17,10x17,60 mm
Sleeve: 7 ports
Rear ball bearings: steel
Front ball bearings: steel
Crankshaft: 14 mm - turbo
Carburetor: plastic - 9 mm - reverse
Glowplug: Turbo (C6TGC)
Exhaust position: posteriore
Weight: 374 g
Fuel type: 25% nitro
The cooling heads of the ROMA.21 engines are made lighter by making aditional holes in the cooling fins. This reduces the overall mass of the engine.
The sleeve has 7 transfer ports and an exhaust with booster ports. The special shape and positioning of the ports, covered by a patent, improve the internal fluid-dynamics to obtain the maximum possible performance.
The Turbo SG crankshaft is made from high quality steel.
The inner shape of the gasket has a new shape, and with that more material. Together with a change in material these gaskets are more resistant to high temperatures.
The glowplug of engine is a Turbo type glowplug. Turbo glowplugs have a different shape than Standard glowplugs and therefor are not interchange able with engines that are using Standard glowplugs!
The rear cover presents a round shape to optimize the filling and reducing the dead spaces. the steel plate is to reduce friction and to expand the lifespan of the conrod.
The ignition timing is controlled with these little rings of various thickness. To change the ignition timing you can add or remove a ring of a certain thickness.
This carburettor is made from plastic and have a sliding throttle valve. (reverse type).