heater bypass for better cooling?
 

check my thinking on this. the engine fan (old style) blows air out both side ducts , thru hoses into the heat exchangers, thru hoses to the flapper boxes. the air is then either directed to the cars cabin heating system or dumped out the side of the flapper boxes to atmosphere. would it not make more sense to block the sides of the flapper boxes to make them straight on/off controls. this way when no cabin heat is needed the airflow is all directed into cooling the engine. anyone have any thoughts? am I missing something? Don.

still hoping for some feedback. anyone?

Heat exchangers need airflow through them to keep them from getting too hot. The airflow through them actually keeps things a little cooler on the underside of the engine.

Headers are a different story: They are not enclosed, so they will cool much faster, especially with a high temp coating such as Jet Hot.

You would COOK yourself if you had all the heat directed to the cabin. I have my flapper boxes set half open and it can get uncomfortably warm especially when the hot air is blowing directly above the gas pedal.

I think he means to not let them vent to the atmospere or to the cabin, but to block all airflow at the flapper box location so that the entire volume of air from the main blower goes over the cylinders and heads.

On the 964, Porsche made a change where the rear heater blower would come on and circulate air through the heat exchanger to help engine cooling. I'm pretty sure it comes on even if the car is turned off -- preventing heat soak when you park a hot car.

I guess there would be two key questions: 1) Is the amount of air diverted to the heat exchangers significant, in terms of cooling the heads and cylinders, and 2) Does cooling the headers contribute in any meaningful way to cooling the engine when the car is in use?

My guess would be the answers are 'no,' and 'yes, a little.' and that that's why the factory chose to dump rather than block the heat exchanger airflow. But that's just a guess.

thanks guys! it's just possible that the engineers at porsche are a little bit smarter than I am and probably had a reason for doing it the way they did. I'm leaving well enough alone. thanks again for all the input, much appreciated. Don.