This sounds a bit of a lashup if i am honest - all its going to do is pull in hot air direct from the manifold, which will make it st off the line. I won't dispute that it will make it noisy though

A k&n panel filter in the sealed airbox (no holes) and a custom air feed (ditch the snorkel) to the front of the car to catch the cold air would be much better and will sound good as well. Throttle response will be razor sharp and it will free up the rev range slightly. I know as that's what i am running and its relatively cheap but very effective. Will also clear the way for a strut brace if you are that way inclined, as usually its the snorkel that fouls the braces.

Ha ha ha 3-4mm? They need to be a good 5cm holes...

And no even with proper sized holes there'll be zero performance gain. You gain extremely little even with the best designed intake kits available, so drilling a few hole makes zero difference.

Had I seen this thread earlier, I could have told you that. Tried it myself. Made bugger all difference. Waste of time. And chances are, as someone else said, you'll now be sucking in hot air, so you'll have lost a couple of horses... not that you'll probably notice.

ETA: My holes were quite big too and I had lots of them.

Lol do yourself a favour and either leave it as standard or do it properly.

A k&n Panel filter will change the note slightly - but not to the extent you might expect. But the point still remains - you are drawing hot air from the manifold into the engine. Its probably performing worse now than it did at the beginning.

uprated panel filter and unmolested standard pipework - yes (This does make a small difference)
aftermarket air filter and heat shield - yes (Will make a lot more noise,with a cold air feed even better)
drilling airbox with tiny holes and generally wasting your time and ruining your parts - no (I can't see an upside to doing this at all)

thank-you all for your replies

it is interesting that there is a significant difference in the opinions provided before and after my little experiment

in addition to pistonhead's mazda forum , i also carefully read through the mx5 nutz thread, and the suggestion there was that drilling the airbox was of value, although not as good as getting an aftermarket induction kit

the nutz thread photos appeared have drilled holes of about 4 mm diameter,and suggested lots of holes meant lots more air and lots more induction roar

others here have suggested that i have either drilled too many holes or that the holes i have drilled are too small

what is actually responsible for causing the increased (for those who have achieved this holy
grail through drilling the airbox) induction roar?------the increased total airflow?, the sucking effect of air passing through the small/large holes?

at least one person here has had good results with only 5 holes, and another person has suggested larger holes (will 1 mm diam change really make a difference?)

also, it seems that the standard snorkle , is not really that far away from the drilled airbox, and i wonder if there is really that much effect from extra warm air getting through to the combustion chambers bearing in mind that :

1/ with the bonnet closed the airtemp at the snorkel intake will not be much different to that at the lower half of the airbox
2/the snorkel intake is still open , so lots of relatively cold air is still getting into the airbox
3/ the holes are too small to give an appreciable increase in induction roar, so presumably the volume of
"new" hot air getting into the airbox is small so should not appreciably affect the engine's output

at this stage , i am really more interested in people's thoughts as to the mechanics involved, and think that other newbies might benefit from further details before doing the same as i have done

so , over to the experts, but bear in mind that there are more than a few people who have claimed good results from this drilling procedure

The Nutz thread you speak of shows holes far far larger than 4mm, more like 4cm....

The added nose comes from bypassing the snorkel which is designed partly to reduce induction noise, (in conjunction with the rest if the intake tract.

The item which removes the mouse induction noise is the airbox it's self, so my putting holes in it, your bypassing 2 forms of sound suppression

How many miles?

^^^

Just make sure you clean and oil them.

I think the paper ones last 4 years or 36k miles at £14 for a Mazda one or about £6 for an aftermarket one.