Which part of the Engine Compartment has the highest air temperature?
 

Tair, not some solid piece

high, low?

center, LH side? RH side?

stopped or moving?

Air temp.? When at speed, engine compartment air temp. is pretty much ambient due to airflow. I placed a thermocouple sensor inside the air cleaner, then drove the car. Temp. was about the same as ambient.

Unknown when car is static, but I suspect anything above the exhaust system (heat exchangers/muffler, catalytic converter).

Blows up the claims of "cold air intake" unless the ambient temperature is "cold".

Sherwood

I took a 4 hr drive last weekend with air temperature never over 27 oC.

Tair an inch from the end of the oil filter got as high as 50 oC.

Tai in the RH rear carb throat (air cleaners & rain shields on) was always lower than that near the oil filter, but also always higher than the outside air by several oC, and never below 30 oC.

Type T thermocouples with a reader from Omega.
I didn't bother with my dataloggers, so these are spot readings.

What is your objective?

just curious

I would GUESS it is the area just above the sheet metal over the muffler or the catalytic converter. It might be the area above the engine fan shroud back near the firewall since it would likely get the least airflow.

One of the interesting questions, that would be hard to prove one way or the other without a lot of air temp sensors in hard to get to places.

I only plumbed in 2 thermocouple wires when I had the motor out, but I could set up a wireless data acquisition module (if I was that crazy...)

I think I might move one of the wires over to the rear sheet metal above the muffler next tho. Good idea.

I'm guessing I'm missing the point, but wouldn't the air around the hottest solid pieces (infra red) have the hottest air or be most influenced? At least you'd get an idea of relative differences within the compartment.

Would the 80-90 degree C oil filter radiate enough heat to affect the sensor 1 inch away??
Are you trying to relocate the injection air intake in the most favorable area?

Similarly, has anyone run engine compartment air pressure v ambient measurements with different deck lids?? I have seen numerous posts claiming small but noticeable reductions in oil temp, (and possibly power) going from standard engine lid to duck??
Sorry for the slight hijack
chris

I've got a temp sender in my engine bay that I move around frequently when testing things. Generally speaking, when the car is moving the entire engine bay is about the same temp. When the car is not moving the engine tin and intake get into heat soak. Cools down really quick once you start moving again. Interestingly, the back panel where the sound proofing pad resides does not get too much warmer than the rest of the engine bay. Apparently there is enough air movement that everything is cooled and sucked into the engine air fan. Air grill size makes a big difference. A turbo tail allows a lot more air in than a non-tail basic engine deck lid. Never tested a duck.

seems unlikely - I was going 50 to 60 mph most of the time and the sensor is soldered Tcple wire (i.e. small & bright metallic so little radiative loading)

the 50 oC figure was stopped, but still likely convective

I'm just doing this out of idle curiosity (this is what happens when scientists retire)

I have a std. sized grill tho the lid is FG not steel (unlikely to cause any effect); no duck

Again just a guess, but I bet the air intake is the coolest place. Only guess that because Porsche engineered the air intake there.

carb throat (air cleaners & rain shields on)

I have the non-tail basic engine deck lid.

Today's test was with the thermocouples outside the car (~19 oC) & just above the rear tin, behind the fan, & aft of the fan & cross bar (i.e. above the Monty muffler) - (~34 oC). So a 22 oC offset - at ~ 60 mph.