I have not tested any aftermarket "airboxes" for 90-up C4s, however, I baselined my existing intake system in preparation for testing the Jeal airbox. Based on that test, I question the idea that the ZR1 and other C4s using the 90-up air filter assy. have the same restriction problem as do C5s and require an aftermarket airbox for improved performance.
My existing air intake system consists of a production air filter housing, a K&N filter element, a DRM "open element" air filter top and a stock intake air duct fitted with an aluminum brace to prevent duct-collapse.
I've run that set-up on the Dynojet many times at the 390-410 rwhp level.
To see if there was a need for a better airbox, during one test session I removed the air filter assembly and ran the test with just the intake air duct installed.
There was no performance change in running with no air filter assy. at all vs. running a slightly-modified, production air filter assy.
This test seems to indicate that, excepting those that generate a slight ram air effect at very high speed, at least up to the 500hp level, *no* aftermarket airbox is capible of a performance improvement.
Comments?