does it have a cold water return pipe ?

[menostig]

My Sylva Phoenix had a water rail to take water back to the pump if the thermostat was closed. This meant water kept flowing so preventing: any localised heating before the thermostat had a chance to open, any water from forcing the thermostat open a little, phases of cold water then hot water hitting the thermostat.

Does the Ultima have this ?

I can't see it looking at my Sport. Has thermostat fat hose up to the swirl tank, right next to the water thermostat. But I can't see another take-off near the thermostat to run cold water back around the engine.

Am wondering why on a quiet run, water temp is stays at 60 (oil at 75), then blat it for a few minutes and water comes upto 80. Is the water pump just opening the termostat a little ?

cheers
Roger.

[CanAm Dave]

Hi Roger

Localised heating is the thermostats main job until the engine is up to temperature. It should never be bypassed or removed. The pump simply circulates the water around the block, heads and inlet manifold until the thermostat opens. Pressure from the pump can't open the thermostat.

Regards Dave

[Rubi]

CanAm Dave said:

Localised heating is the thermostats main job until the engine is up to temperature. It should never be bypassed or removed.

I agree but what I think Roger is saying is that the radiator should have a bypass - which I also agree with. If you have a heater then that is the bypass. Until the thermostat opens water circulates through the heater and back to the water pump inlet.

It is actually wrong to say that the thermostat "opens" it actually starts to open at a set temp and becomes fully open at a somewhat higher temp, it is not an on/off device. The thermostat finds an equilibrium point that means the engine runs at the right temp which is relatively stable (thus no thermal cycling). When you cane it harder and make more heat the stat opens further sending more water to the rad for cooling. When the temp gauge starts to climb above its normal running point then the stat is fully open - this only happens at low speeds. At anything over 30 mph in mine (up to 30deg ambient)the airflow through the rad means that the rad cools the water more than the engine heats it up and the thermostat closes (but not fully) to maintain a constant temp.

If you have no bypass what happens is that when the stat opens (which it does rapidly and by a large amount) a slug of relatively very cold water goes into the engine which soon finds its way back to the stat and shuts it! This can be seen by the temp gauge cycling between its opening temp and about 20 deg lower - this may be what Roger is describing. My engine used to do it when I shut the heater control valve such cycling is not good for the engine and especially not for the stat (which wears out very quickly under these operating conditions). I cured it by fitting the "H" pipe in the heater supply pipes that the factory told me was only needed for A/C equipped cars; I believe it is needed on all builds especially if your heater valve can stop the water flow through the heater, I guess that some may be better at this than others? Obviously if you have no heater (and run a SBC) then a coolant "loop" from the inlet manifold water jacket to the water pump inlet serves the same purpose and is a good idea. I suspect, but do not know, that the LSx range will have an integral bypass between the stat and water pump - as most modern engines do.



>> Edited by Rubi on Friday 19th May 22:48

[gtrclive]

Just fitted a EWP that flows 50gpm, and if you think about it, the Pump will pressurize the motor when the stat is closed and even when its open due to the apature in the stat can't flow that high. Higher pressure means less chance of air pockets less chance of boiling to higher boiling point etc etc... Actual flow will be some where near 20 - 30gpm, the rest keeps up the pressure in the engine...

At 3 Bar the boiling point of pure water is over 130c with contaminates i.e. normal drinking water mixed with Gycol it would be higher than that....

[GreenV8S]

gtrclive said:

Just fitted a EWP that flows 50gpm, and if you think about it, the Pump will pressurize the motor when the stat is closed and even when its open due to the apature in the stat can't flow that high. Higher pressure means less chance of air pockets less chance of boiling to higher boiling point etc etc... Actual flow will be some where near 20 - 30gpm, the rest keeps up the pressure in the engine... At 3 Bar the boiling point of pure water is over 130c with contaminates i.e. normal drinking water mixed with Gycol it would be higher than that....

I doubt that your EWP produces enough pressure to make a significant difference to the boiling point in the engine.

The ideal setup is with a stat that closes the bypass as it opens the flow to the radiator. If your bypass is *only* a restrictor then reducing the flow through the rad also reduces the flow through the engine. The engine might be fine in terms of average temperature, but not at all fine in terms of local hot spots and temperature variations. You really want masses of water flow at all times, and just vary how much of it goes through the rad.