Andrew Posted August 11 Report Share Posted August 11 Hello people. this question has been bugging me for years. The water pipe that runs through the exhaust manifold. What is the purpose of the hot exhaust gas heating the water pipe which I suppose it does. Is it to heat the water before it goes to the heater matrix. Or I am total wrong Andrew Link to comment Share on other sites More sharing options...
johny Posted August 11 Report Share Posted August 11 I suppose you mean the connections that are part of the aluminium inlet manifold? This is to heat the inlet manifold as soon as possible on a cold start as water is circulated through it before the thermostat opens and the radiator is put in service. This means that you have hot water available as soon as possible (including for the cabin heater if selected) which allows the choke control to be pushed in earlier improving emissions and fuel consumption. Afterwards the water flows into a metal pipe that runs behind the manifolds next to the block and whose only purpose is to return it to the water pump. Link to comment Share on other sites More sharing options...
DanMi Posted August 11 Report Share Posted August 11 there is no water pipe going through the exhaust manifold it goes through the inlet maifold to heat it to help running when cold Link to comment Share on other sites More sharing options...
Andrew Posted August 11 Author Report Share Posted August 11 Guys you are so right it does run through the inlet manifold my mistake. Thank you for the answers. What would happen if that pipe running through the inlet manifold was not there Link to comment Share on other sites More sharing options...
ed.h Posted August 12 Report Share Posted August 12 My theory is that the coolant passage in the intake manifold is there to maintain a relatively CONSISTENT temperature of the manifold. Warming the manifold quicker is just part of that goal. When adjusting mixture, the first step is to warm up the engine to operating temperature. Mixture setting will then be optimal at that manifold temp. Ed Link to comment Share on other sites More sharing options...
johny Posted August 12 Report Share Posted August 12 8 hours ago, Andrew said: Guys you are so right it does run through the inlet manifold my mistake. Thank you for the answers. What would happen if that pipe running through the inlet manifold was not there I have put a small valve in the rubber hose that supplies the manifold of my vitesse and usually have it closed so theres no flow through it or the heater. This is because I dont normally drive it in cold weather but do like to tour on the continent when the temperatures can be high and my thinking is that the pump output is better used through the engine and radiator. I cant say Ive notice much difference either with choke use or engine cooling but as long as I dont get any problems with the latter Im happy👍 Note I do open the valve from time to time to ensure the heater matrix gets flushed.... Link to comment Share on other sites More sharing options...
Andrew Posted August 12 Author Report Share Posted August 12 I like that idea. Link to comment Share on other sites More sharing options...
johny Posted August 13 Report Share Posted August 13 No sorry Ive just realised theres a big flaw in my idea! On a cold start because the thermostat is closed the only flow path is from the water pump through the head and block and back to the thermostat housing. Here it warms the thermostat wax bulb and temperature sensor before flowing out to the manifold (plus heater if selected) and back in the steel pipe to the pump suction. By cutting this flow Ive slowed the warm up process and even worse risked having hot spots in the engine☹️ Theres no problem once the engine is warm and the thermostat is open cos then theres a flow through the radiator but it would be a faff to have keep opening and closing my valve installation so it'll have to stay permanently open.... Link to comment Share on other sites More sharing options...
DanMi Posted August 13 Report Share Posted August 13 11 hours ago, johny said: No sorry Ive just realised theres a big flaw in my idea! On a cold start because the thermostat is closed the only flow path is from the water pump through the head and block and back to the thermostat housing. Here it warms the thermostat wax bulb and temperature sensor before flowing out to the manifold (plus heater if selected) and back in the steel pipe to the pump suction. By cutting this flow Ive slowed the warm up process and even worse risked having hot spots in the engine☹️ Theres no problem once the engine is warm and the thermostat is open cos then theres a flow through the radiator but it would be a faff to have keep opening and closing my valve installation so it'll have to stay permanently open.... Don't forget many eg mk1 spitfires did not have heated inlet manifolds and the heater was an optional extra. So that route was not there and it didn't cause any issue. There is a channel for water to circulate through the head and block even when thermostat is closed so you have just removed the heater system and that will have cause no slow in warm up and the water is circulating so no hotspots Link to comment Share on other sites More sharing options...
johny Posted August 13 Report Share Posted August 13 Its true theres a small hole in the water pump casing that goes from the thermostat chamber (return from head/block) directly to the pump suction but its pretty small😲 Link to comment Share on other sites More sharing options...
johny Posted August 13 Report Share Posted August 13 Here it is just next to the head return port and it might be enough to prevent hotspots on the 4 pot spitfire lump but the six? Link to comment Share on other sites More sharing options...
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