Unfortunately, the results as they relate to my primary goal were inconclusive, but I found out some interesting stuff anyway.

Goal:
I recently installed a J's Racing carbon fibre hood, and I was curious as to whether the vent really made a difference or not.

Method:
I borrowed some Thermochron iButtons by Dallas Semiconductor. They look exactly like watch batteries, but they're self contained temperature sensors with a clock and enough memory for 2048 readings. I taped them to various areas of my car, as shown below.

Yes, I know it's dirty. But it's clean now!

One on the front grill, to get the ambient air temp.


One on the airbox, just behind the radiator. Hot!


One above the airbox, behind the vent.


One near the battery.


One in the airbox.


One near the brake fluid reservoir.


To make it a worthwhile comparison, I drove the car both with the vent blocked, and open as above.


Here's the chart of the actual readings over the test period:


Timeline:
11:05am Initialize buttons. Block vent.
11:19am Have buttons installed.
11:28am Fire up engine. Do some regular street driving, 40-45mph.
11:40am WOT onto freeway entrance ramp. Cruise at ~75mph.
11:45am Exit freeway.
11:47am Park car in garage, shut off engine, leave hood closed.
12:01pm Remove vent blockage, fire up car, begin same drive as above.
12:14pm WOT onto freeway entrance ramp. Cruise at ~75mph.
12:19pm Exit freeway.
12:22pm Park car in garage. shut off engine, leave hood closed.
12:35pm Remove iButtons, pop 'em in the fridge for a sec to cool them off.

Results:
The reason I say the results are inconclusive is because of the tremendous amount of heat that was built up under the hood when I let it sit in my garage for 15 minutes after the first drive. It completely overrides the data for the second drive. At least having the vent just behind the radiator helped that area to cool, rather than remaining constant like when the vent was blocked.

That heat buildup is interesting, however - ever since seeing that, whenever I park the S2000 in the garage I open the hood to allow it to cool better. I'm sure the components were designed to withstand such temps, but I'd rather not stress them. Maybe even worthwhile to open up the airbox between autocross runs.

So what I'll try in the future is between runs, just jump out and tear off the blockage really quickly, and continue on driving. A longer route would be better too, of course.

I'd also like to do better on getting actual air temps rather than the temp of the plastic the sensors are taped to.

Questions:
Can anybody draw any other/different conclusions from the data?
Suggestions on methodology for the next experiment?
Am I wasting my time?

 

Using headerbandages should lower your tempratures, you should also get som performancegais and you would have a warmer exhaustsystem with higher exhausttempratures by the rearend.

 

[QUOTE]Originally posted by Elistan
[B]
Results:
The reason I say the results are inconclusive is because of the tremendous amount of heat that was built up under the hood when I let it sit in my garage for 15 minutes after the first drive.

 

If I put on a mugen or spoon thermostat to make my S run cooler it should make a difference right?

 

Perhaps you should conduct the experiment over a 2 day stretch -- one day with vent closed, the other with the vent open. First, check w/ the weather forecast to ensure that there will be no dramatic temp. changes. Then begin both experiments at the same time of the day.
You could also do it in a 4 day period -- 2 days open, 2 days closed, then average the readings.
This should effectively eliminate any interfering readings due to heat buildup from previous runs.

 

perhaps allow the engine bay to return to ambient temps before repeating the run for your next test? Also, the more tests the merrier, repeated results are worth more than a one-time shot.

 

I think the best thing to do is get the engine to heat soak conditions. Then do a measuring run with the vent covered, make sure the engine is back at heat soak conditions, and then do another run with the vent removed.

You want to measure max underhood temps. That's what's important in this test.