18-10-2019, 07:26 PM
The top of the overflow is only 1/4" below the top of the filler neck.
While I was out measuring this, I took some other measurements. The current water depth (cold) in the top tank is 3/4". An ideal level would seem to give a depth of about 1 1/2" - so actually only 3/4" difference - not as much as I thought - and with the thermal expansion from garage to working temperature it would perhaps be a bit less (by about 1/4"?) when hot.
The volume of water needed to raise the level from 3/4" to 1 1/2" is only about 3/4" x 12" x 4" = 36 cu inches.
This is equivalent to about 600cc or 0.6kg of water, which has the capacity to absorb 4200 x 20 x 0.6 = 50,000 joules if raised from a normal working temperature of 80 C to 100 C. Whilst 50,000 joules might sound a lot, it is the equivalent of only 1kW (1.4 horsepower) for 50 seconds - not much of a buffer against the engine working harder on a hill.
Seems that circulation is the key to cooling, and 3/4" in the top tank is plenty for that.
Colin
While I was out measuring this, I took some other measurements. The current water depth (cold) in the top tank is 3/4". An ideal level would seem to give a depth of about 1 1/2" - so actually only 3/4" difference - not as much as I thought - and with the thermal expansion from garage to working temperature it would perhaps be a bit less (by about 1/4"?) when hot.
The volume of water needed to raise the level from 3/4" to 1 1/2" is only about 3/4" x 12" x 4" = 36 cu inches.
This is equivalent to about 600cc or 0.6kg of water, which has the capacity to absorb 4200 x 20 x 0.6 = 50,000 joules if raised from a normal working temperature of 80 C to 100 C. Whilst 50,000 joules might sound a lot, it is the equivalent of only 1kW (1.4 horsepower) for 50 seconds - not much of a buffer against the engine working harder on a hill.
Seems that circulation is the key to cooling, and 3/4" in the top tank is plenty for that.
Colin