I am seeing underhood temps of 77 to 81F when the car is running and taking on air (motion), and the A/C is off. These seem to be average for when the car is moving and outside temps are in the 75 to 85F range. In other words, as long as there is motion, and the A/C condensor is not venting heat, the Airbox is seeing air that is the same temp as the environment.
However, the A/C Condenser is a tremendous source of under-hood heat, and whenever the A/C is active, the temp is prone to go up when speed is low, stop and go, or idling at stoplights.
I suspect the same for the radiator and to a lesser degree, the intercooler. These aren't controllable; we have to have them functional all the time.
A "Ram Air" system that would allow air to be "Captured" in front of the Condenser is the answer we are looking for. As long as the Condensor and Radiator are functioning, there will be hot air coming into the engine compartment, and entering the airbox, or whatever intake system that is being used.
This looks like a job for some A/C ductwork from a junkyard that will be able to act as a "funnel" in front of the condensor and duct air back to the airbox inlet. Ram Air would be the ticket. The space between the condensor and the frame that is filled with the "tar paper" would allow a duct like a dash defrost duct (wide and narrow) to divert air into a duct that could be plumbed into the air box. The source of air in front of the condensor would be unaffected by engine heat, and only affected by outside temperature. Even at idle, the duct should allow enough air to do the job.
Looks like a project to build an air flow sensor and do some measuring.
I also need to mention that I still have the rear weatherstrip installed under the hood, and I could possibly be getting different results when the A/C is on if it were removed.
The bottom line is that when the car isn't moving, under-hood temps will increase. Still pointing toward some kind of Ram Air ducting to keep a stable source of air that is the same temp as the outside environment (ambient).
Check out the mod (
http://www.ptcruiserlinks.com/forum/...?TOPIC_ID=2079 )concerning the overhead display dimming when lights are on and how to correct it. It is another easy one to do...