I have read somewhere to get a bit more noise they drilled holes in the airbox.
My questions are, where do you drill the holes, how large
and how many? How much extra noise do you get?
I have a K&N panel filter fitted and a MX-5 parts stainless exhaust.
Unfortunatly, I have been made redundant and have far too much time on my hands.
Thanks,
Jeff
Yes, I did this before fitting a K&N induction kit. It does work in the noise department
. Just remember to drill the holes in the air box before the air filter, otherwise you will suck dirty air into the engine.
The old air box is in the garage somewhere - I could take some photo’s if you want. But really, just drill lots of 1 inch holes.
iddy
Both my Mk1s have the Swiss Cheese modified airbox, I think they sound great and work just as well with the K&N panel filter as a far more expensive induction kit, I recently tried a K&N Typhoon in place of a drilled airbox and removed and sold it after about a 10 min run…
They also look a lot more stock (insurance) than after-market induction systems.
I used a 22mm and 12mm wood-boring flat drill bit and probably managed to get anout 12-14 holes (cold side, front and base only, away from the exhaust, and rear side) and be sure to de-burr the hole edges and vacuum all the plastic swarf away. I have spare un-holy airboxes to put back on when I become elderly…
Dr. Eunos
Hi, just been sniffing around for some info on this.
Ive just stuffed a K&N panel filter in my mk2.5 1.8 and have noticed around a 5% increase in sound but overall the engine runs a lot smoother and throttle response is much better. Howver, I wanted me noise so, having pcked up a spare air box, want to drill it.
Ive seen the advice as cold side, etc but where exactly should I drill? Im daft with this stuff tbh and dont want to get it wrong. As I look at the engine stood in front of the car with the bonnet up, should I drill below the filter on the right hand side? Also, can I do it with the air box lid off but the bottom half of the box still on the car?
Im not after McDonalds loud, just a nice induction noise. If all else fails, ill buy a Typhoon. 
Many thanks in advance.
Yes. The side away from the engine and it’s heat. I did the front too on mine.
No, don’t try drilling it while still in the car. It’s only a two minute job to take out. Drill the front and cold side as said before. If you aren’t in a rush I’ll take some photo’s of my old box this weekend for you.
iddy
One of the items on my " to do " list is to replace the K&N cone filter ( which I hate ) with a standard air box and performance panel filter, I will probably drill it as I would like a little intake roar, and I will drill on the cold side of the box.
I know a guy who drilled the air box on an early SRi cavalier, he claimed doing so actually harmed his performance! ( although it did sound good ) anyone got any views on that one?
Cheers mate, that would be good. Ive seen pics of the MK1 drilled box but not the MK2.5 which Im running. Im just heading out now to remove the snorkel which leaves a big gap on the side of the box. Just to see. Some pics would be appreciated though mate. Got my drill all charged ready. Im gonna go for a few 20mm ones as theyre easier to tape over if it goes to cock.
Thanks.
Just be aware, by drilling the standard air box your car will sound like a vacuum cleaner when idling. I drilled mine and regretted it instantly!
I’ve done it on both my mk1s and on previous cars too. Never had any problems at all. No issues with an idling noise.
Make sure you drill a good amount of holes with a 20mm drill or it won’t be worth it. I reckon I probably have 25ish. The worse that will happen is that you don’t like it and will have to tape over them.
Only problem I’ve had is using more petrol as I keep putting my foot down to hear the noise 
Yeah, I hadnt thought of that. One thing I hadnt considered before buying the car was how much extra fuel Id use taking the long way everywhere.
Ahhh well, Ill drill it tomorrow and if its bad Ill bang the new one Ive got on.
Not much space to fit 25 20mm holes on a Mk2 box as far as I can see.
wish i had seen this thread before i splashed out on a K&N air filter, ive still got my old air box , might give it go ,
keep injoying the 5 thing all
Is the air box on the NA 1.6 and 1.8 the same?
You might be right. I think maybe I had a 10mm bit.
oops, I only just noticed you have a MK2.5 - I’m running a MK1.
iddy
Haha Mal, at the moment the air filter on my supercharged R2-Ltd is one of these below and the J2-Ltd has an un-drilled airbox (for now) with a Pipercross foam filter installed, how times change. It is true that a drilled airbox with a standard Mazda filter does sound a bit odd, but with a decent panel filter like a K&N or Pipercross they sound really good.
OK… Do I assume that both are identical and interchangeable? 
Yes the boxes themselves are interchangeable, lids are not 