...I decided to try and shut my engine up for trackday noise reasons, by making an airbox. Never done any fibreglassing before, so thought I'd give it a go.

Since I'm only making one, I didn't want to do the whole buck/mold/item thing, so decided to have a go at a lost foam method.

So, first I carved out a shape in polystyrene and stuffed a mustard jar in the end: -


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Then covered it in masking tape: -


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Made the dining room stink with a layer of glass: -


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Then melted the polystyrene out with cellulose thinners and soaked the masking tape away. Then another layer of glass (actually, tissue) and a hole cut: -


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Offered up my original TTS back-plate for mounting: -


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Some more polystyrene and masking tape to allow making some mounts: -


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The completed mounts: -


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The completed box after trimming and another coat of resin inside to fix a couple of blemishes where the initial lay hadn't soaked through: -


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And in the engine bay: -


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The bonnet does go on, but does "touch" the box. I'll probably stick a thin layer of rubber under the bonnet to stop chafage/vibration.

And that's it - my first fibreglass "thing". Not had a chance to road test it yet, but for noise purposes it passes the "blip" test in the garage and is much quieter.

Quite pleased overall. Hopeful it won't affect the performance - gone for "big volume" rather than trying to tune with resonance so hoping it'll be no worse than the original sausage filter. I will be running a cold air hose too to keep the air round the filter cool.

Only thing is the outside isn't perfectly smooth, so "dressing" it would need a few mm filler in places where the top has overlapped the sides. Will be sticking with function over form for now. Might dress it over next winter if I get bored of beige, but that's adding weight - can't be having that

That is a quality first effort you have there.

Hopefully it will all work as you want in the performance and noise stakes.

very impressed. bit of gel coat painted on would give it the final touch

Looks great.

How much fibreglass mat and resin did you use and how much did it cost?

Might do one myself.

Len.

Looks nice. How thick did it end up, approx weight?

Very nice, how did you get the polystyrene so smooth? And how did you manage to clean up after

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Originally posted by maccmike
very impressed. bit of gel coat painted on would give it the final touch

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Haven't weighed it yet. Used about 3.5kg resin, but that includes the first abortion attempt (90 degree outside edges don't work!) and wastage. Guessing about 2kg but will weigh at the weekend out of interest. It's made of one layer or 450gsm and a layer of tissue, plenty sturdy enough for the job. Layed 3 layers of 450 for the mounting lip so its not likely to snap, but the box is supported at the other end by the filter too with a rubber spacer (read - coolant hose and cable tie

Because of the overlaps its a bit unevenat the edges. Not sure I'd want to remove enough material to level it enough for flowcoat to look smooth.

Discounting the failed effort, a 2.5kg resin kit from Leeds fibreglass (23 + vat), masking tape and a 3 quid polystyrene insulation tile from wickes is about what it cost.

Polystyrene was just glued, sawn with a wood saw then sanded with 80 grit by eye. Sweeping brush and a little help from mother nature for the bits I missed is how it was tidied!

that's good, if you mix pigment in with the resin you can have it coloured right through and no need for any gel coat, power paint works just as well

Excellent advice.

Well done, Great locost solution.

Just weighed it. 1.35kg for the box. 1.7kg including the filter itself. Lighter than I thought so quite pleased.

Thats really neat

Nice work Si

Looks ideal for taking a hose too the nose cone and mounting the filter there.

So I went for a play a couple of days ago, and did a crude comparison of the car accelerating with the airbox, versus without. Basically found a stretch of road, ran it both with and without the airbox, in 4th and 5th gear on separate runs. I recorded rpm over time using my Digidash for each run and plotted in Excel: -


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Basically, it seems that to all intents and purposes the airbox makes no perceivable difference to performance - which is exactly what I hoped for!

I will do a similar test when I run a cold air feed, see if that seems to make a difference.