I was looking to open up my air intake but I wanted to keep the stock airbox as it provides cold air from inside the fender vs. a cone filter that only pulls in hot air from the engine compartment. I did think the snorkel was undersized, especially now that I have installed a 3# pulley, and after reading about the extra solenoid controlled flap in the airbox on the 4.2 cars I decided to work on a a larger 4" round snorkel to feed the stock airbox.

I ended up using 4" aluminum flex duct in order to easily get around the plumbing fittings on my intercooler reservoir that I installed in front of the airbox. Without the tank in the way a 4" solid duct may fit instead of flex duct fine if anyone else wants to try this mod. With the rubber boot removed the duct easily extends down into the fender void and then sweeps into the airbox. At the airbox I fashioned a 4" collar to fit around the top of the snorkel opening and then cut out the airbox below it to create a larger inlet (kind of a 4" oval).

After I connected the duct to the airbox I wrapped insulation fabric around the duct to minimize heat soak and then covered the insulation for a clean look. Total cost $5, total time 3.5 hours.

I don't hear any difference in sound from the stock unit - all I still hear is the blower whine. Now I can't wait to see if can I feel any difference under full throttle

 

nice

 

Now get rid of those snorkel things sticking off the intake (they are silencers, but rob some flow)

See photo of where I removed some off my XJ8 (these are in different places than the XJR, but perform the same silencing functions)

 

What does it sound like without the snorkel things ? I always thought they looked kinda funny so they must perform some valuable function.

 

Their "valuable" function was to silence the noises of the intake at different frequencies. Honestly, I don't hear much difference and I have sensitive ears. The only slight difference I hear is a tiny bit more roar under full throttle when the engine is spooling up, but I like and want that, so it is a win/win for me.