THE EXHAUST VALVE

TKART Staff

11 November 2016

In recent years, with the transition from 100 cc to TAGs, another component has appeared on kart engines: the exhaust valve. A system to accompany the function of the traditional silencer

WHAT IS IT?

HOW DOES IT WORK?

IN PRACTICE

As can easily be deduced from the name, an “exhaust valve”, or “power valve”, is a valve located on the cylinder on the exhaust side, above the pipe.
Physically it has a main body, generally made of plastic, but may also be aluminium, which contains membranes. On one side is a plastic thumbwheel acting on a spring for valve adjustment, while on the other side there is a steel body, like a guillotine, which fits inside the exhaust

pipe. The two parts are connected by a membrane that, together with the spring, adjusts the valve opening.
Raising and lowering the guillotine body adjusts the opening.
Nowadays, the valve is simplified on new OK engines, while in the past it was more complex in both form and during “tuning”. In fact, adjustment relied on both the main guillotine body and the presence of two side guillotine bodies that acted on the exhaust port’s side boosts.

THE EXHAUST VALVE IS A SYSTEM THAT IS IN ADDITION TO THE SILENCER AND ALLOWS A KIND OF VARIABLE ADJUSTMENT BASED ON ENGINE SPEED

The components of the exhaust valve

WHAT IS IT?

HOW DOES IT WORK?

IN PRACTICE

SECTION OF THE ENGINE WITH THE EXHAUST VALVE

OVERVIEW

EXPLOSION

As is well known, unlike 4-stroke engines, 2-strokes do not have traditional valves, with the piston itself acting as an opening and closing valve for the transfer and exhaust ports. Simplifying the concept to the extreme, the ideal engine should have an exhaust port that opens late at low revs to take advantage of all the thrust provided by the exhaust gases in the combustion chamber, while opening early at high revs (when the engine cycle is faster) to allow exhaust gases out quickly.