Mark Steitle wrote:
Paul,
From past statements I have been convinced of the benefits of removing
the thermostat and controlling temps with cowl flaps.
What I'm wondering is if I should replace the thermostat with a
restrictor plate, or leave it "wide open".
Over the years I have heard & read differing opinions on whether or not
a cooling system restrictor (such as a thermostat) is
beneficial or not to cooling of an engine. Lynn Hannover recently
stated that he runs a 5/8" restrictor in his 13B race engines
and doesn't have a problem with overheating. This makes some sense as
the typical thermostat has a fairly small passage-way for
coolant to pass through.
I got to questioning this again yesterday after reading an article on
cooling systems at (don't laugh)
http://www.grapeaperacing.com/GrapeApeRacing/tech/coolingmods.cfm that
explains that having a restrictor in the cooling system
actually raises the boiling point of the coolant to close to 300 degrees
F by creating 40-45 lbs of pressure between the pump
and the restrictor. If this is true, it seems like this would be highly
desirable.
Here's what they say about system pressures, "The pressure in the block
is higher than the radiator pressure, this is because
the pump is building pressure due to the thermostat being a restriction.
This pressure raises the boiling point of the coolant
and reduces the chance of steam pockets, so never run with out a
thermostat (or some form of restriction). The radiator cap will
usually hold 15-18 psi, if the radiator holds the system at 15 psi, the
boiling point of plain water will be raised to 250° F.
The water pump can then make an additional 40-45 psi in the engine and
bring that boiling point close to 300° F. So as you can
see, pressure is important."
They also state, "Most people seem to think that all a cooling system
needs to do is keep the engine from overheating. But what
is not realized is if the engine runs too cool, thermal efficiency is
lost and power is reduced."
So, I'm wondering... do I want high pressures, or high flow. It doesn't
seem like I can have both at the same time.
Mark S.
You want high pressure and high flow. I kind of doubt those 40 to 45 psi
numbers in
the block. For the sake of argument lets assume those numbers are correct.
They are easy
to measure however.
Simple solution. Get a higher pressure cap for the rad or put the 20 psi
pressure cap
on the other side of the rad on the inlet side of the pump. Let the rad be
your restrictor.
It is a restrictor anyway. Why add work for the pump?
Paul Lamar
Ah Come on Paul - you know better than that - a restrictor just upstream
of the pump ????? You would be running the pump rotor in a bubble, and go
down in a cloud of steam and melted aluminum. Besides which if the
radiator or exit is that restrictve, you would probably blow the top
tank - I vote with some restriction where the thermostat goes - tho
I doubt the pressures are that high - Vance
Plenty of people for the last 100 years have run their engines with no
thermostat or restrictor other than the radiator just before the pump and
the worst thing that happens is the engine runs too cool. I have done
it many times myself with the two dozen cars I have owned in the last
50 years. Now I want to warn the new guys don't try this with a Mazda rotary
as it has a special thermostat that when closed opens a pump bypass
passage. If you remove the thermostat on a Mazda rotary engine you
must block this passage.
Paul Lamar
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