Motorsport Plumbing Systems: Sizing
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Sizing
03.56
| 00:00 | - The coolant system uses a range of different hose sizes to move the fluid for different functions like engine cooling, turbo cooling, overflow, and vehicle interior heating. |
| 00:11 | The size of the coolant hoses has a significant effect on how the fluid flows through the system as well as the pressure of the system which changes the boiling point of the coolant and therefore has an impact on its overall function. |
| 00:24 | Let's start with maybe the most important plumbing in the coolant system that has the most effect on the pressure of the coolant, the hoses connecting the engine to the radiator. |
| 00:34 | In most cases, radiator hose sizing can be determined by the size of the water necks on the engine and thermostat housing which will usually match those on the corresponding radiator neck. |
| 00:46 | This is the hose size the manufacturer determined and shouldn't need to be questioned. |
| 00:51 | You will notice however that the lower radiator hose is generally larger than the upper. |
| 00:56 | This is because on the traditional bottom up coolant system, the lower radiator hose feeds coolant to the water pump's suction side. |
| 01:06 | Since this is subject to a vacuum from the water pump, if the hose is too small, more vacuum will be pulled and at some point this can cause the hose to collapse. |
| 01:15 | A work around for this would be using an internal spring to reinforce the hose but ideally it should be large enough to prevent this happening in the first place. |
| 01:25 | More vacuum, AKA lower pressure reduces the boiling point of the coolant. |
| 01:30 | If it does boil, air bubbles will form and this, along with the higher velocity fluid seen in the smaller hose can lead to cavitation issues. |
| 01:40 | Essentially the pump can go into vapour lock where it loses the ability to move fluid through the system. |
| 01:46 | At the other end of the spectrum, if the hose is too big, the velocity could be too slow, which reduces the heat transfer to the fluid and therefore its cooling effect, all other things equal. |
| 01:58 | It also increases the mass of the fluid in the system which could be beneficial for cooling but will also increase the weight unecessarily. |
| 02:06 | Again, the factory sizes are a good starting point here and these have internal diameters anywhere between 1 to 2 inches. |
| 02:14 | Though the inner diameter of the overflow plumbing is of course smaller, typically under half an inch. |
| 02:20 | Unfortunately there's no hard and fast rule for calculating the correct size as every engine, water pump and application is going to have different requirements. |
| 02:29 | If we are working on a completely custom application then the sizes of similar factory setups are probably the best place to start. |
| 02:37 | In saying this, the thermostat when open is often the most restrictive part of the plumbing so the diameter of this can act as a good guide for the minimum size. |
| 02:48 | Electric water pumps more common in motorsport builds also tend to use between -16 to -20 AN size plumbing. |
| 02:56 | Likewise, coolant lines for a turbo or supercharger are going to be determined by the specifications of the manufacturer based on what they have found suitable for their product and the coolant ports will be sized accordingly. |
| 03:09 | So for us, it's just a matter of using whatever sizing they specify and plumbing the coolant to these ports. |
| 03:15 | In saying this, it's common to use -6 AN water lines or similar. |
| 03:20 | In summary, there's really no rule to follow for coolant plumbing size but the best method is usually following the factory sizing or something similar. |
| 03:28 | Too small a hose can result in vacuum and higher flow velocity, causing other issues so keep in mind that the radiator hose that feeds the suction side of the water pump is usually larger than the other hose. |
| 03:42 | For turbo or supercharger coolant lines it's always best to follow the supplier's specifications to ensure the component gets the cooling it requires for the best performance and to prevent damage. |
