how does a dual valve thermostat work in car cooling?

[S0 What]

The 2nd (or 1st) part of the dual valve stat opens to allow hot water to the heater before it opens it to the rad so you get a hot engine, then hot heater and hot rad last of all, it's how some mdoern engines warm up quicker, older designes alowd the coolant to perminantly flow from the head into the hater rad which on cold days slows the engine heating (cos the heater rad acts as small engine rad cooling the water as it heats the air for cabin).

[Ozzie Osmond]

Engines which require a tighter control of temperature, as they are sensitive to "Thermal shock" caused by surges of coolant, may use a "constant inlet temperature" system. In this arrangement the inlet cooling to the engine is controlled by double-valve thermostat which mixes a re-circulating sensing flow with the radiator cooling flow. These employ a single capsule, but have two valve discs. Thus a very compact, and simple but effective, control function is achieved.

Says Wikipedia. There is a pic as well,

http://en.wikipedia.org/wiki/Wax_thermostatic_elem...

[Ozzie Osmond]

S0 What said:

The 2nd (or 1st) part of the dual valve stat opens to allow hot water to the heater before it opens it to the rad so you get a hot engine, then hot heater and hot rad last of all....

If that's right it's the first I've heard of it.

[Captain Muppet]

Ozzie Osmond said:

S0 What said:

The 2nd (or 1st) part of the dual valve stat opens to allow hot water to the heater before it opens it to the rad so you get a hot engine, then hot heater and hot rad last of all....

If that's right it's the first I've heard of it.

The first time I'd heard of it was the first time I'd heard of it too. But there are cars out there with this system, the Ford Fox is one, I think.

[anonymous-user]

If its a race car, and your thermostat is not fully open, your radiators too big!!

[tvrolet]

If its a race car why do you need a thermostat at all? Assuming the radiator is the right size can't you just use a restrictor plate (or old thermostat housing with the valve-bit removed)? Your going to be warming it up anyway before trashing it, and assuming its in the pits there's no airflow through the radiator so it doesn't add much to the warm-up time to have water circulating through the radiator even when cold. Plus the whole system warms up, not just the block until the thermostat opens.

[Krikkit]

maverickdrives said:

Max_Torque said:

If its a race car, and your thermostat is not fully open, your radiators too big!!

I am pretty sure the thermostat fully opens eventually so radiator is the right size.

I want to find out about both the scenarios, is there any advantage at all to the dual valve thermostat and does it reduce the lag caused by the wax? why use a dual valve rather than a single valve tstat?

Edited by maverickdrives on Thursday 9th January 17:55

The dual valve system smooths the temperature changes as the stat opens and closes - it mixes the coolant from the water jacket/heater loop with the cooled radiator intake. Unless you know it specifically needs one, use a single valve.

[Captain Muppet]

maverickdrives said:

tvrolet said:

If its a race car why do you need a thermostat at all? Assuming the radiator is the right size can't you just use a restrictor plate (or old thermostat housing with the valve-bit removed)? Your going to be warming it up anyway before trashing it, and assuming its in the pits there's no airflow through the radiator so it doesn't add much to the warm-up time to have water circulating through the radiator even when cold. Plus the whole system warms up, not just the block until the thermostat opens.

I was wondering that too because its only one of them small formula race cars with small radiators so shouldn't take long to warm but my uni said I need to put a thermostat in the race car's cooling circuit so now I am trying to find out more about thermostats.

If they say you need one then use the thermostat layout from the engines original application.
Any deviation from a mature solution is a risk. It's not worth the hassle if the benfits won't be noticable.

[Monty Python]

In patent-speak:

"The cooling system is defined by two flow loops, one for the engine and the other for cooling purposes. An engine driven pump circulates a coolant through the engine block and cylinder heads. The pump also circulates coolant through the cooling loop which includes the engine oil cooler immediately upstream of a radiator and bypass line. The aftercooler is downstream of the radiator and bypass line. Placement of the oil cooler ahead of the radiator and bypass line produces a higher temperature potential which permits a reduction in radiator size in addition to other benefits. A flow control logic system embodied in a dual thermostat arrangement ahead of the radiator and bypass line minimizes mixing of bypass flow with radiator flow and reduces radiator flow rates to permit low aftercooler temperatures that hithertofore have not been achievable."

[andycaca]

if race car, ditch thermostat and mechanical pump. use craaaaaig david electric pump and related sensors tied into ecu to alter engine parameters according to cold/overheat scenario

not hard, much coolness. *wow*

[ads_green]

Some cars have dual stage thermostats for different running conditions.
For example, low engine temp gives better power and performance but higher emissions. Conversely, running a hot engine can give slightly better emissions and maybe extra economy.

On the V8 non FSI engines they have a multi stage thermostat that uses an internal electric heater to give the different openings.
The thermostat is a mainly a traditional stat set to a high temperature and when the car demands more power the ECU switches on the electric feed to the heating element. This gives the effect of opening the stat much earlier (as it's tricked into thinking the coolant is much hotter than it is) and so allowing a cooler coolant.