Under Review | Vortex KZ 2016: the revolution

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VORTEX RKZ: THE REVOLUTION

Carlo Forni

29 February 2016

TYPE
Like most kart engines on the market, the RKZ is a 2-S. 4-stroke engines are still a small niche

125 CC

DISPLACEMENT
125 cc has been the standard for some time now, while in the past it used to be 100 cc

PUSH

START
Push-mode as in all KZ engines, with hand-release clutch and neutral to 2nd gear shifting

GEARBOX

TRANSMISSION
The RKZ belongs to the gearbox “family” of karting engines.
It has a 6 gear manual transmission

HOMOLOGATION
Certified under KZ homologation, just renewed and valid for the next 9 years, beginning in 2016

Vortex engines have been at the forefront for years, competing for the most prestigious titles. Thus, it would be normal to think that they would simply be looking to fine tune a winning engine. Not at all!

The new RKZ engine by Vortex is totally revolutionary compared to its predecessor: the cooling system, the cylinder angle, connecting rod length, flows and transfer ports are completely new, in order to obtain, right now, a faster engine than the ones previously available, and to be able to further improve it in the coming years. This revolution has led to high design and construction costs, it is up to the track (and consumers) to say whether the results make it worthwhile! The part that most revolutionizes the KZ class engines, which has always been a bit static, including the regulations that have not changed for years (which is good), is the free air cooling of the crankcase in the crankshaft area. The flow of air enters a hole positioned in front of the crankcase, under the carburetor, aided by a series made conveyor that is sold together with the engine. The air passes inside the crankcase through a conduit installed in the lower part, then up around the turning crank mechanism and then passing between it and the gear housing. The use of air is aimed at solving a very common problem in water-cooled kart engines: the fact that the temperature of the engines varies in the cooling circuit depending on several factors (running along straight or mixed stretches, having a greater grip, etc.). This oscillation varies the carburetion, with significant changes in performance and reliability risks.

Some of the photos of the innovative free air cooling system without its crankshaft, the main features of the Vortex RKZ engine

The cylinder head is a single piece and its fastening system uses 8 mm diameter lugs (below)

By basing the cooling of the crankcase on the air outside, in order to obtain a constant temperature when completing a circuit (even though the flow will vary), the carburetion is should remain more constant and the performance levels should be consistent.
Moreover, the fact that there is a flow of air from the outside between the crankshaft and the gearbox housing, instead of an inner flow of water, isolates the two parts of the crankcase much more, which is good for the crankshaft, which normally tends to heat up because it receives heat from the gearbox, reducing its efficiency. Furthermore, the air flow exits from under the exhaust, helping to cool the most critical part of the cylinder. The cooling water enters the cylinder on the exhaust side, improving the regulation of the pressure waves that are generated in this area. In any case, it has a cap that allows, where necessary, changes to be made to the flow of cooling water.
The Vortex revolution also involves the cylinder: the cylinder is always tilted forward in new generation engines; with the RKZ, it is instead installed in a fully vertical position. A solution that, according to the company, allows the flows to be optimised.