At 12:39 PM 8/29/97 -0600, you wrote:
>
>Something's a bit off in this explanation.
>
>The guy's pump is running slower, so he gets higher temperatures. Makes
sense
>so far. But drilling holes in the thermostat cures the problem, by allowing
>some flow when it's closed? Wrong explanation. If he's too hot, the thing
>should be wide open, and the additional holes serve to decrease the
restriction
>at the thermostat, increasing the flow. Without knowing how many holes,
and how
>big the stock opening is, it's hard to say how much of a difference it
makes,
>but it must make some. And the car will take longer to warm up.
>
>Remember the discussions of a few weeks back. This result adds to the
evidence
>against those folks who want to slow the flow to improve the cooling.
>
>Stu
If you examine a stock thermostat, you will find a small ~1/16" hole to
releve pressure. The 1/8" holes likely allow enough uncontrolled or bypass
flow to allow the sensor bulb in the thermostat to sense the temperature
rise earlier and respond sooner, The heat energy is not input uniformly
over the parth of the coolant through the engine. Local hot spots will
occur, particularly under low flow conditions, and the bypass flow may
increase the overall "System Stability". The bypass flow will also reduce
the pressure drop at the thermostat under all conditions.
Unfortunately for "Stock" advocates, the factory designed pressure cap is
located on the WRONG side of the radiator for optimum performance. It
should have been mounted on the highest point of the lowest pressure point
in the system. Simply moving this cap from the left tank to the right tank
will bring the dynamic system pressure (in the engine) up by some 3 to 7
PSI. This simple change can make some marginal Tiger cooling systems fully
adequate.
Tom Hall
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