Cold Air Intake and Short Ram Intake....
Which is better? Cold air or more air? The answer is "both." You want to have more filter area, but you also want to be bringing in cool air from outside of the engine bay. How much cooler? Well, see for yourself.
In all of the following pictures, the fender well where the air filter is housed is represented by the Temp Gauge on the left while the engine bay's temperature is represented on the right.
I warmed up the car to normal operating temperature (allowed the fans to come on twice) and then drove around for a while before officially starting to record the temperatures. Outside ambient temperature during the test was about 60 degrees F (it was much more chilly today than it's been for a while).
First: Allowed to idle for 5 minutes
The underhood temperature fluctuated between 130 and 135 which coincided with the fans coming on. It was definitely interesting to watch
Second: Cruise for 7-10 minutes at 45 mph
Both temperatures dropped significantly. The fender temp went as low as 65. But they both leveled off around these temps (67 and 89) before I finally took the pic.
Third: Cruise at lower, neighborhood speeds. 30 mph for about 10 minutes.
Engine bay temp rose back up though it was still quite cooler than at idle. The fender temp rose, at most, a mere 5 degrees.
UPDATE
Took a trip to Simi Valley today. 70-80 mph the whole way (30 minutes on the highway) at 75 degrees ambient temperature.
Cruise at Highway Speeds for 30 minutes
The temp leveled off and stayed at this temp even as the outside temperature rose from the beach to the valley. It also stayed fairly steady while the engine was under load while going up a steep 3-mile grade...
Heat Soak Max
After a 30 minute highway run and sitting outside in 75 degree weather, this was the max temp reached in the fender well and under the hood...
Night time cruise home on Highway (30 minutes, same route)
Temperature was about 60 degrees at 70-80 mph the whole way.
Now for my setup:
C25a Manual Tranny with Homemade CAI:
Cold Air Intake is built from 4 90 degree elbows of PVC
Now for some Mythbusting:
It has been debated on many a car forum whether PVC is suitable for intake construction. It's a well known fact that when heated, PVC can melt, deform, and (worst of all) start to release fumes that can be toxic to both engine and occupant. Some say it WILL AND DOES happen, while others argue that the engine bay just doesn't get hot enough.
Well I decided to go straight to the horse's mouth. I asked a contractor what the temp rating of this PVC was. He was stumped. He called the manufacturer and we were informed that this particular PVC is rated up to 180 degrees for safe use. At 210+ degrees it will start to release the fumes. As the temps continue to rise, it will start to lose its shape and eventually start to melt.
One thing that I found interesting was that the company also produces ABS and stated that although it has a higher temperature rating, once it DOES begin to melt is releases fumes that are FAR MORE TOXIC than those released by PVC. Hmmmm.....
So if your car ever catches fire, head for the hills...or at least inform the fire department of the health hazard.
Anyhow, this material will only be temporary for me as I have something better waiting in the wings. But I digress...
I have another part to this un-scientific experiment that I will have to add to this thread at a later time. In short, I will be adding cold air to the stock air box in an attempt to stop biting my nails thinking about hydrolock come the first heavy rain storm.
For now, though, it looks like CAI > SRI (but I didn't have to tell you that now did I?)