jeepsrock said:
Hey 8mud i never said about running a cooler stat.
You said a high flow stat would help at temps around 219 (full open), so wouldnt that be overall helpful ?
pete
Possible a bit, but the restrictions seem to be more prevalent, at other spots in the system (like the bottom of the radiator, in an old unit). Surface area of the radiator (layers) seems to help some, but the greatest boon in my experience is with increased air flow. Possibly turning the pump at a higher RP M's (smaller pulley?) to increase flow could be a benefit at low RP M'S, low flow does seems to be slightly apparent at low RPM´s in my XJ's.
Just a theoretical thought or two, the object is to move excess heat, from the inside to the outside of the motor. Increased surface area in the heat exchanger (extra layers can do this), moving more air through the heat exchanger can do this. But it´s doubtful moving more coolant through the heat exchanger, by increasing flow at the thermostat, is gonna help much (pump RPM, would seem to have a larger influence anyway). The efficiency of the heat exchanger is the temperature drop between the inlet and outlet. The coolant rarely gets all the way down to anywhere near air (ambient) temperature. So pushing the coolant quicker through the exchanger isn't actually gonna do much, if it actually works, the thermo is probably gonna slow down the flow anyway. If it pushes the coolant through before it has time to loose maximum heat, it will actually exit at a somewhat higher temperature, it doesn't exit at anywhere near ambient (air temp) anyway.
Fine tuning the system, with a high flow thermostat, may have a benefit, but it´s doubtful, the benefit would be where it could be used. At higher RP M's on a fairly hot motor. I´m just skeptical of the benefits.
Air flow, surface area and pump RP M's (flow) would seem to be more important than a possible restrictions at thermostat full open temperatures. If there was actually a restriction in that area, the top hose would probably have a tendency to collapse.
I think high flow thermostats, may be holdover from the old Chevy's that seemed to benefit from increased coolant flow (around the thermostat and elbow area). But guys did take that too far also. They would remove the thermostat all together and at sustained high RPM´s the system would push the coolant through the radiator, before it could give up much heat and this would actually cause higher engine temperatures. Until the system stabilized, if it ever did.
Most of this is just theory, I´m not an XJ cooling guru, but have worked on a few building sized systems.