Originally Posted by EPOS
Sorry, but that's just flat out wrong.
1. diesel engines have higher thermal efficiency compared to gas engines
2. has nothing to do with cooling
It is a dual stage intake, essentially there are 2 chambers to control the air velocity. I know it's hard to believe, but it is to improve torque at low RPM and help with higher RPM power as well, that's when that valve opens up and air is now being sucked in through that snorkel and into the secondary chamber, combining the 2 to make one big intake box.
Motorcycles incorporate intakes like this all the time and same goes for most race cars. The IS-F uses a dual stage intake box and I believe the NSX did as well.
If it were only about motor thermal efficiency, the dual stage intake snorkel would be directed to pull air from the same location that the main air filter feed air comes from. Compressing hot air is not how thermal efficiency is achieved as for every BTU you add from compressing the hot air, you need to remove it to a degree to achieve your combustion goals. Lowering charge temperatures are important.