Thermostat location advantages?

[zcarnut]

One difference between the earlier Nissan L-series engines and the later VG and KA series engines is the location of the water thermostat with respect to the water flow through the radiator.

 

The L-series engine has the thermostat at the water outlet of the block (or the inlet of the radiator) while in the VG and KA engines the thermostat is located at the water inlet of the engine (or the outlet of the radiator).

 

Can anyone shed some light as to why Nissan moved the thermostat?

 

One advantages I can think of is that by placing the thermostat at the inlet of the engine allows you to use a lower temperature thermostat (a typical VG thermostat is rated some 10 degrees less than a typical L-series one). This would allow the thermostat to open sooner, assuming equal thermostat masses. The thermostat is rated at a lower temperature because of the temperature drop across the radiator.

 

I can think of two reasons _not_ to re-locate the thermostat. First is that you are regulating the temperature of the water entering the engine instead of the temperature of the water leaving the engine which I would think would be a better indication of the heat being generated by the engine.

 

Second would be that the radiator would receive water at a higher temperature and pressure, thus placing more stress on the radiator.

 

Or maybe it doesn’t really matter where the thermostat is located?

 

Opinions anyone?

[johnc]

Manufacturing convenience?

[260DET]

It may allow the engine to warm up more quickly, by blocking cooler water from the radiator access to the engine.