I LUV all the sounds my MINI makes. Except one. The whistle.
Some of you are lucky enough to have never heard a MINI whistle. Every time I bring it up on NAM, inevitably someone tells me how much they LOVE the whine their supercharger makes. That, friends, is NOT the whistle to which I refer. Others say they LOVE the “whooshing” sound of air being sucked into the engine. That, friends, is ALSO NOT the whistle to which I refer.
When I’m giving Blimey just a bit of throttle – enough to very gently accelerate, maybe 10-15% open – from around 2500-3000 RPM, the bloke whistles like a tea kettle with a full head of steam. This is right at my common cruising speed around town. And it’s not a quiet, hidden little whistle. It’s sounds like the boiler is about to BLOW. It’s LOUD. And IRRITATING. Arghhhhh….This all started when I installed my Dinan intake and Alta hose. I LOVED the new amped-up supercharger whine. But the whistle came along for the ride. And it won’t leave.
I’ve read EVERYTHING I can find that’s been written about this symptom over the last 8 months. Across many, many posts. The most rational explanation I found was that it’s actually air whistling past the edge of the slightly open throttle. Given slight variations in the chamfer on the edge of the throttle plate, some do it, and some don’t. Being the throttle itself makes sense to me, because it happens at a very specific point in the accelerator, and I can modulate the sound with my toe on the pedal at that specific spot.
I’ve tried a UNI filter. Still whines. I’ve tried a K&N filter. Still whines. So today I decided to spend an hour or so and get medieval on its crass… noise.
I completely removed the Dinan airbox lid with the filter attached, leaving just the open Alta hose exposed. Then drove it. Still whistles, exactly the same as before.
So I removed the Alta hose. To a buck nekked exposed throttle. And drove it. Luckily didn’t happen upon any clouds of insects. Still whistles. Doesn’t sound quite as loud as before – because there’s nothing “piping” the sound into the open cowl cavity, so it’s more diffused by the time the sound gets to the cockpit – but it’s still there. If I had a hardtop, I MIGHT not hear it. I suspect it’s similar to what I’d have with a K&N or other “hot air intake” type design…
So, at this point, we can eliminate the intake or hose as the CAUSE of the whistle – though they can certainly contribute to the TRANSMISSION of the whistle into the cockpit.
I put the stock hose back on, and reinstalled the Dinan airbox. Still whistles. Probably 90% as loud as with the Alta hose, which makes sense – the larger, smoother silicone hose won’t muffle the sound as much as the ridgy stock rubber hose.
I plugged the top cowl intake on the Dinan box with a block of foam and some tape. No air coming or going through there anymore. Guess what? ALMOST no whistle. Of course, much less supercharger whine, too. At this point, the only whistle that’s making it to the cockpit is the amount that makes it through the enlarged cowl grommet in the lower half of the (stock) airbox. If you didn’t know it was there, you probably wouldn’t notice it.
So I’m going to run it like this for a few days and see what I think. Will I hear enough supercharger whine to be fun? Will the butt dyno feel any loss of power?
I’m thinking the only *real* solution here would be the JCW airbox – the “flap” would be closed at the RPM ranges where the whistle occurs – but the flap would open at high RPMs to let in more air and to let out more supercharger whine… I just have to decide if that’s worth the money… ugh.
Installed my JCW intake with AMSoil EaAU3570 Nanofilter and the whistle is almost entirely gone – I can only hear it when the top is down and the radio is off because I know when to listen for it… otherwise I would be blissfully ignorant of its existence… Gave up a little supercharger whine with the JCW – but to me it’s worth the trade-off – I’m a happy camper.