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WATER PUMP TRANSMISSION BELTS: THE TEST OF 4 DIFFERENT TYPES AND TIPS TO KNOW HOW AND WHEN TO USE THEM

Jacopo Colombo

24 January 2024 • 33 min. read

In kart engines that have a liquid cooling system (when the water pump is not "on board", i.e. not incorporated into the engine, but is instead external), the transmission system between the water pump and the axle plays a fundamental role in achieving the correct operating temperatures of the engine (to learn more, read "Technique | Cylinder cooling" and "Technique | The radiator") and, therefore, affects performance on the track. Over the years, several transmission systems have been developed (for a general overview, we recommend reading this "Must Have | Choose the best transmission system for your kart water pump"), each with its own peculiarities, strengths and weaknesses. But what are the differences in terms of flow rate of the water produced by the water pump and absorption of energy produced by the engine given by a system that uses O-Rings compared to a toothed belt? Or, what are the advantages (if any) provided by the most innovative systems such as the "Power Saver" by New-Line Racing? Thanks to the collaboration with the Italian company (a leading brand in the production of cooling systems for Racing karts), we tested and measured the performance ensured by the most popular transmission systems on the market with a special test bench. We have understood their differences and advise you when and how to use one solution over another.

test in points

Check the differences, in terms of water flow rate (from the radiator to the engine cylinder) and engine power consumption, recorded using the different water pump transmission systems.

With the support of New-Line Racing, we carried out five tests on three speed steps (50 km/h, 100 km/h and top speed) with a special test bench developed by the Italian company. The following were the drive belts used:

Rubber O-Ring
Extra grip heat-sealed O-Ring
HTD toothed belt
OK Power Saver belt (indicated for Direct Drive karts)
KZ Power Saver belt (indicated for Shifter karts)

New-Line Racing Headquarters - Fiorano Modenese (Modena) - Italy

In order to have perfectly comparable situations, we did not carry out a real test on the track. We carried out bench tests instead, where the weather conditions were uniform and did not affect the results of the tests.

IN THEORY

The pump

The pump pushes the cooled liquid from the radiator towards the cylinder head. The pump consists of three main elements: the volute (the internal body of the pump that defines the path of the liquid first in suction and then in delivery); the impeller (the internal part that, thanks to its rotation, pushes the coolant towards the cylinder of the engine); the axial pulley (which receives motion from the drive belt to transmit it to the impeller). We used the exact same pump in all the tests to check the efficiency of the various drive systems.

Water Pump Transmission System

The transmission system of the kart's water pump is the kinematics behind the circulation of water within the cooling circuit of the kart's 2-stroke engine. This consists of three main elements: the pulley on the axle (we have analysed some models in this "Must Have | 5 pulleys on the axle for the transmission of the kart water pump"), the drive belt and the axial pulley of the water pump. A crucial role in this system is played by the transmission belt, which must transfer the power absorbed by the engine as efficiently as possible, via the axle pulley, to the impeller of the water pump, by means of the pump pulley. To ensure that the operation of the water pump is optimised, it is essential to make sure that the transmission is installed in the correct way (to learn more, read "Technical Track Test | Water pump drive belts: how much do assembly errors affect the performance of the cooling system and the kart?") or select a transmission system that gives the best trade-off between the flow rate of the water generated and the power of the engine.

Power consumption

"Power consumption" refers to the energy consumed by the pump (but more generally by the entire transmission system) to move the water inside the cooling system. Having to move a large amount of liquid, the pump absorbs power from the engine, which instead of being directed to the wheels is "spent" to activate the pump and the cooling system. Therefore, the greater the amount of water that is moved in the system, the greater the power absorbed and, therefore, the lower the maximum speed that can be reached.

Water flow rate

In order to keep the engine in its ideal operating temperature range (around 50°C) so that it can give ideal performance, it is essential to ensure that there is always a correct flow rate of cooled liquid towards the head of the engine. It is important to emphasise that there is no minimum numerical value that allows you to identify a correct water flow rate in every situation. The reason is related to the innumerable number of factors that can affect the data. In fact, the optimal flow rate may depend on the speed of impact of the air on the radiator, on the average speed of the track (generally medium-slow tracks require a greater flow of water than fast ones, since the work of the pump is affected by the motion of the axle and therefore the slower the axle, the greater the amount of water that must be pushed towards the cylinder) or the outside temperature.

test WATER PUMP TRANSMISSION BELTS: THE TEST OF 4 DIFFERENT TYPES AND TIPS TO KNOW HOW AND WHEN TO USE THEM

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WATER PUMP TRANSMISSION BELTS: THE TEST OF 4 DIFFERENT TYPES AND TIPS TO KNOW HOW AND WHEN TO USE THEM