Jeep CRD airbox mod

Diesels need good airflow. After doing my muffler/exhaust upgrade I wanted to modify the airbox for better flow.

'tired_old_dave' at the LOST KJ CRD forums modified his air intake by using a 3" PVC pipe adapter and a 3"-to-4" PVC pipe rubber repair piece to give the airbox a larger inlet. I decided to copy his idea but I decided to do the whole thing in 4".

I bought the parts at Lowes for $8.48 and it took about 10 minutes to do.

The Jeep engineers did a good job for the most part. With the grille off you can see the fresh air intake goes straight into the airbox. However... get there it has to go through a small opening and turn 90*.

Not a very big opening. I'm guestimating around 6 square inches.

The first step is to remove the duct from the airbox.

I expected to fight with bolts and stuff to remove the airbox but it just popped out of its holders.

This is/was an adapter for 4" schedule 40 PVC pipe to 4" 'sewer' PVC pipe (Lowes P/N 24128). I trimmed the extra off with a chopsaw.

I traced for the larger hole...

...and cut it out with a jigsaw. Took about 90 seconds.

There's no reason to enlarge the hole with 'old_tired_dave's' 3" version.

Perfect fit.

The second piece used in this mod is a 4" PVC pipe rubber repair boot (Lowes P/N 23477). Put the airbox back in, insert the PVC adapter, and slip the rubber boot on. To the uninformed this looks stock.

The factory fresh air duct (green arrow) still feeds into the new airbox intake (red arrow), but now the airbox can draw all the additional air it needs. I've doubled the cross sectional area of the intake.

I removed the intake blockoff piece for better symmetry of the grille and to give a more direct route for the fresh air. If this happens to let too much stuff in the fresh air intake I can always pop it back on.

The Liberty ran A LOT better when I upgraded the exhaust. I don't know if the stock airbox is a restriction, but if it was it isn't now! And all for $8.48 and 10 minutes.

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