Just watched the link above. You'll note that I mention "enclosed POD filter", in the link above they used an exposed POD filter at the back of the engine bay, I'm not surprised that it lost power sucking in hot air from the engine bay. It would be interesting to see the stock intake on that little 1.3 after a few power runs, I bet it would loose power too as the heat soak from the engine gets into that cold air intake system.
You'll note in my posts above I mentioned improvements in air intake temps (measured using the air intake sensor fitted in the car and what the PCM uses to adjust engine timing) and improvements in throttle response. These are real world improvements as the testing was done on the road, in traffic and not on a static dyno........
If you care to have a look at lets say the VS ecotec tune, the Spark advance Vs Air Intake table you'll note that the tune is based on 22 degrees C air intake temp, once the air temps get above this the PCM starts to pull out ignition timing depending on load. at 46 degree C your loosing between 2.8 degrees to 5.27 degrees timing depending on load. This is why I keep going on about minimising air intake temps as there are real world gains to be found.
As mentioned earlier, all this testing is done with brand new filters, a clean filter should flow more (if spec'd correctly) than the engine CFM requirements so there should be no difference in power output, now testing with dirty filters would be a LOT more interesting as this is what 99% of vehicles actually have.......
Another interesting test would be to use a water gauge across the air intake system as this would be a better way to see if the various intake types show much of a pressure drop and there for restriction.
Another test that should be carried out with the various intakes would be a engine acceleration rate test as this would show improvements on instant flow or what the driver of the vehicle would notice as throttle response.
