Nissan Australia

Custom Air Box Lid

Every now and then you come across an extraordinary individual who sees something on the Patrol that can be improved on then goes out and creates a wonderful piece of kit that really is a work of art.

TD42T custom billet airbox lid

I came across Bruce Robinson on the Patrol 4X4 forums in May 2009 after reading his write up on an aluminium billet airbox lid that he had designed and built himself. Now most people knew that the standard TD42T airbox lid was quite asthmatic in its airflow and some had tried to alleviate this by buying and fitting a lid from a ZD30 (including myself) or even customising their existing lid by replacing the outlet with poly pipe. The ZD30 lid looked like it would be an improvement over the standard TD42T unit because there appeared to be less restriction but testing revealed it was only marginally better than the TD42T lid. It also had a square flange at the end so an adaptor plate was required to adapt the standard ducting up to the airbox lid. This coupled with the fact that the angle of the top of the pipe was different to the standard lid so different pipe work to the turbo was required for a decent fit which still left you out of pocket quite a few dollars.

The pieces

The assembled product

After conducting flow tests on the standard airbox lid, Bruce thought that he could fabricate something that would offer much better airflow over the standard unit. The end result of his efforts was a totally new airbox lid fabricated from aluminium billet with a larger diameter outlet with less restrictions. Flow tests showed that there was 40% less restriction when compared to the factory lid and airbox when a Donaldson filter was used.

Flow tests - Standard TD42T lid      Flow tests - Custom TD42T lid

The test result were done in a controlled environment and at the same time so that factors such as air temperature, humidity and air pressure were all the same:

Test 1: Airbox assembled with new Donaldson Filter.

Stock 4.2L 214CFM @ 8" water
Stock 3.0L 224CFM @ 8" water
Custom Billet 260CFM @ 8" water

8" water is constant which means higher CFM is better.

Test 2: Airbox assembled with new Donaldson Filter and airflow set to 393CFM which is the maximum amount the flow bench can flow.

Stock 4.2L 393CFM @ 25" water
Stock 3.0L 393CFM @ 22.7" water
Custom Billet 393CFM @ 17.3" water

393CFM is constant which means lower water is better because it is less restrictive.

Test 3: Lid only comparison and airflow set to 393CFM which is the maximum amount the flow bench can flow.

Stock 4.2L 393CFM @ 17.9" water
Stock 3.0L 393CFM @ 17.7" water
Custom Billet 393CFM @ 7.4" water

393CFM is constant which means lower water is better because it is less restrictive.

Flow tests - Standard TD42T airbox with Donaldson filter

Flow tests - Custom TD42T lid with standard airbox & Donaldson filter

As you can see by the above results, Bruce's custom airbox lid definitely outperforms both the factory and ZD30 lids which means that Patrol owners can definitely benefit from this modification. Not only can you expect slightly better performance in both power and torque but Bruce has also noticed better fuel economy when towing as well. Since I have fitted the new airbox lid, I have definitely noticed improvement across the rev range especially higher up in the range.

The new lid comes complete with all components required to swap out your existing lid in minutes as well as instructions explaining everything in detail. Utilising the same clips and seals as the factory unit, you can be safe in knowing that Bruce's lid is both secure and airtight in its fitment. He is also in the process of sourcing an adaptor plate so the lid can be utilised on Patrols with the ZD30 engine.

If you would like to find out more about Bruce's custom billet airbox lid then you can email him direct.