I think that the testing that Tony and Jones have done, has shown that the main problem that has affected Steve and Dan has been found, and rectified. The results are pretty conclusive.
The clue came with Tony’s pressure testing on his own car. The graph that he produced (post #299) showed that the pressure at the thermostat housing, fell as the rpm went up. That showed the possibility, that because of the temp of the water, and the negative pressure, at the thermostat housing, the coolant could boil.
As John (SVX Commuter) says, and I respect that John has been with pumps long enough to have found all the problems. The boiling starts to build steam or vapour at the centre of the impeller, to implead the flow. This then reduces the flow of coolant through the engine. The engine starts to heat up, and the coolant entering the pump, increases in temperature, so it will boil earlier at the same negative pressure. This is a compounding effect, the more vapour entering the pump, will further reduce the flow through the engine to the result, of the coolant in the block boiling.
The vapour is the result of temp and pressure, and does not leave the pump.. As the vapour rises up the impeller vanes, the pressure increases and the vapour condenses back to water. The pressure in the engine block will remain high, even though the flow is reducing.
The testing that Tony has done with the test rig has shown that when the inlet to the pump is increased, the negative pressure at the pump is reduced, and Steve has proven the theory with an excellent result in the buggy. This is the best testing we could have wished for. Racing in very high temps, and sustained high rpms, the only difference to Dan’s car (besides the car)
was a different radiator.
With what we have learned, if Tom uses the modified thermostat housing, Dan will have the same results as Steve.
The modified top pipes should be retained to ensure, that with the increased flow that the thermostat mod will allow, there will be even flow through the two sides.
Harvey.