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DIY Air Filter Enclosure

Last year when i had my custom centre exit back box made by J’s Garage here in Norfolk,i popped over to my local track Snetterton to get the car decibel checked. I was told the exhaust would just scrape through but i wouldn’t pass the fly by due to the engine.

After trying to explain that the Supercharger noise is a higher frequency,it’ll sound louder than it actually is. The guy working there wasn’t having any of it,despite me also explaining i had done a track day at Snetterton AND Lotus Cars within the past 12 months.

So off i went,scratching my head thinking how can i get the noise down. I know with a single throttle body set up it would be loud anyway. But anyone who has heard my car (especially on wide open throttle) will know its quite loud.

So i finally got round to fitting Aran’s modified inlet for the MP45 Supercharger and i made an enclosure for the air filter

I first made a template from cardboard,the hardest part was making it curve the wheel arch as they’re not exactly level. Once i was happy with the shape i transferred that onto some 3mm aluminium. I managed to pick up the mounting hole for the PAS reservoir and OEM air box to fix the enclosure to the engine bay. A couple of 90deg brackets made out of angle iron i had kicking about,and a lick of paint and it was finished.

I ordered some fire retardant sound deadening from ebay. The thick foam has a reflective foil on one side and some ridiculously sticky adhesive on the other. I lined the inside of the enclosure including the engine bay itself. I also added some to the bonnet to act as the lid of the box.

Throttle response has improved and the AFR has come down a couple of digits while at WOT (wide open throttle). I arrived at a local meet recently and a couple of people mentioned they couldnt hear the supercharger,it was mainly exhaust noise (which i need to address at some point).

I’ve got a decibel tester here that i need to use and see what its like at various RPMs. Luckily i found the readings from when i went to Snetterton (we took some after we left). If all goes to plan and its reduced i can think about getting back out on track!

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