Coolant in motorbikes

The same in oil the coolant is important to know any specifications. 

Motul INUGEL

• Density 20ºC 1,070 gr/ml
• pH (100%, Mettler) 7,0 – 8,50
• Freeze Point -37ºC
• Colour yellow
• Boiling Point  +145ºC  

Castrol Motorcycle Coolant

• Colour  blour/green
• pH, n ASTM D1287 - 8.0
• ASTM D1121 ml 0.1N HCl 10
• Density  @ 15°C ASTM D4052 - 1.03
• Freeze Point ASTM D3321 ºC -25

One infortation that is important in the coolant is the Specific Heat Capacity, that it is "storage" heat capacity.

Engine provide X heat, and with more Specific Heat Capacity this means that needs more time to increase the temperature.

The problem is that the volume is not infinite, and it needs transmit heat to air surrounding, that it is not infinite but it is close. Therefore we need transmit heat between engine and the air, and coolant is only a transmission medium, and it is not a heat storage.

The typical coolant are mixture between:

• Ethylene glycol 2.4 J/(g•ºC)
• Water 4.2 J/(g•ºC)

and the Specific Heat is between those values:

If coolant have more Specific Heat Capacity.

• Advantages: more control temperature and more constant temperature
• Disadvantages: less heat transfer to air in the radiator and need more radiator surface.

Coolant with less Specific Heat Capacity is opposite.

Normally if you want extract more heat to use coolant with less Specific Heat Capacity, but you take the risk

Conclusion

With high Specific Heat Capacity, temperature changes are slower but the work temperature is higher when working.

With low Specific Heat Capacity,  temperature changes are quicker but the work temperature is lower when working, but the air stop pass trought the radiator the temperature increase quicker, for example in traffic jam or any situation when the vehicle is stopped with the engine heat.

Which is better?

The better is testing, but the normal is, if it design show 50% (vehicle manual), and you test 75% or 25%, and it depend of vehicle use, but one important thing, radiator must be clean outside and inside it.