After logging temperatures at the Ridge, I decided to run some air flow visualization experiments using wool tufts and a GoPro.
Observations from data-logging engine parameters:
IAT – 150 F
ECT – 165 F
AMBIENT – 80 F
Engine coolant temperature stabilizes around 165 F on track and will rise to 200 F when idling in pits.
IAT drops to about 90 F during warm up lap and stabilizes to 140-155 F depending on load and speed.
Car uses a custom V-Mount intercooler/radiator with an inlet duct separating the two and an outlet duct on the intercooler that vents to hood vents covered with perforated aluminum (50-59% open area).
Observations from wool tuft testing:
All three hood vents are flowing out the hood as expected. There was some concern that the vent near the windshield could be in a zone of high pressure and result in airflow into the engine bay. The wool tufts in this area are clearly being blown out of the vent and the tufts on the non-vented side are in attached flow. A center tuft at the base of the windshield is curling under as one would expect as the flow stagnates at the junction between the hood and windshield base. Video was taken at multiple speeds with flow patterns stabilizing above 30 mph. The still frame photo below doesn’t quite give the whole picture like the video but this particular frame is a good average.
After reviewing data-logs and airflow tests, my goal was to reduce air intake temperatures and I don’t mind sacrificing some flow to the radiator to do so as it runs cooler than required.
Modifications made:
– Remove the perforated aluminum from the vents used for intercooler exhaust. This would gain 40-50% area for flow.
– Add hood vents to drivers side to promote flow through that side of the engine bay where the air filter/inlet resides in order to minimize inlet temperatures pre-supercharger
– Add trailing edge ducts to the hood vents to improve flow conditions
– Extend intercooler inlet duct to divert more ambient air flow to the intercooler at the expense of airflow diverted away from radiator.
Testing performed at PIR after modifications:
IAT – 156 F
ECT – 170 F
AMBIENT – 80 F
Engine coolant temperature increased a small amount to 170 F
IAT drops to about 90 F during warm up lap and stabilizes to 140-155 F depending on load and speed. No significant change.
Conclusions
With drivers side hood vents, inlet air temperature is close to ambient. Additional airflow through intercooler provided by revised inlet ducting and increased exit area did not significantly reduce IAT’s. Note: tests were not done back-to-back and the conditions were not the same. Different tracks, similar ambient temperatures. In order to reduce IAT’s, I will likely need to replace the intercooler core with one that has higher efficiency and/or capacity.
Sector One Design 
Very nice write up, have you thought about adding a gurney flap in front of your hood vents.
Yes, I have and plan to do more testing soon. I’m currently changing the intake air temperature sensor with a fast response sensor mounted in the charge pipe vs the stock AP1 sensor mounted in the intake manifold. Once complete and results are validated, I’ll resume duct and airflow testing as I think this will give me more accurate results.
In your opinion which vents are the most useful for airflow out of the engine bay? I’ve been thinking about doing the largest on each side, like your drivers side, plus the center for a total of 5 vents. Seems like these are the lowest pressure zones on the hood.
I agree. Vents closest to the front have lowest pressure and will be the most effective. I was surprised by the flow out of the rear side vents as there should be stagnation at the base of the windshield, and there may be in the center. The sides likely get a lot of air speed spilling off in front of the windshield so it ends up low pressure as well.