28 replies to this topic

[FLD]

I've been giving a little thought to quietening my waggon. My attention has turned to the whine recently. Can someone explain to me why superchargers whine? My thoughts were along the lines of ...can we use exhaust silencer approaches to tackle induction noise? I'm guessing not. The other thought was...if the OE airbox is good at quietening the whine is it down to the surface both sides of the filter and as such if I put a larger, solid cone around the cone filter will that quieten it down a touch? I guess I need help from someone who knows about these things.

[I 8 a 4RE]

I dont know about these things ... but why would you want to silence it? In all honesty never driven a SC, but normally SC's are highly sexy in the noise dept.?

[techieboy]

I've got a modified OEM airbox to go back into mine Matt. It was meant to go in last weekend ahead of Donington tomorrow but, a part I was waiting for from Demon Tweeks didn't turn up until Tuesday, so that plan was scuppered. I'm hoping it will still have some kind of whine but that it will be massively attenuated which will hopefully help a bit more on track. Might sound a bit more like the muted noise of an unstressed Harrop. I guess the National @ Anglesey will be the next outing for it, so time pressure is off for now. Not sure what type of noise is worse regarding noise meters, the really deep but apparently not so loud bassy noise of the de-cat Tullet or the high pitched shriek from the 2.9" pulley equipped blower. G

[FLD]

Multiple reasons really. Trackday noise limits. Dont want to be heard from miles away like some chav saxo......and I guess I'm getting old!!!

[turbobob]

Well I always assumed it was a bearing / belt drive whine. But after Techie posted recently the airbox mod is supposed to help reduce the whine, I guessed my initial assumption was wrong

[techieboy]

Yep, not bearing/belt related. The charger is always spinning but it's only when the engine is under load that you get the noise. You can be cruising at 6000rpm and there's no noise until you start accelerating. I think it's the actual compression process itself and related to the way the two screws mesh together. In the Harrop TVS stuff, the screws were designed to minimise the noise and in something like the XF-R makes barely any noise at all.

[robin]

Get some ear plugs instead, i got some of those earplugs that they inject into your ears to make molds bit like what f1 drivers use and they are brilliant so i dont have to worry about noise

[techieboy]

Get some ear plugs instead, i got some of those earplugs that they inject into your ears to make molds bit like what f1 drivers use and they are brilliant so i dont have to worry about noise

Yep, just need to go around and stick them in the all the noise meters around the country. Sorted.

[Seb.F]

Afaik it's the vibration of the rotors. It happens more on load because of the ridiculously small tolerances the charger has which on load force components closer together. The induction is partly attributable to noise levels, however the main source is the charger itself I think.

[techieboy]

But as Exmantaa found, with a modified OEM airbox fitted, all of the whine goes. So I don't think it's purely mechanical noise from the charger itself.

[rsg]

Would a cone filter in an airbox, like the Honda S2000, give the breathing benefits but a quieter whine??

Edited by rsg, 02 June 2011 - 11:26 AM.

[Seb.F]

But as Exmantaa found, with a modified OEM airbox fitted, all of the whine goes. So I don't think it's purely mechanical noise from the charger itself.

I can't imagine he managed to completely exterminate it altogether though? The reason you can hear it is because evidently sound permeates air a lot better than metal, so the sound does escape through the intake, but I'm not sure exactly how much remains coming through the charger itself.

[techieboy]

No probably not altogether and I certainly wouldn't expect it to do that with a smaller pulley. But all of the noise is coming out of the induction side of the blower and if it's reduced to 90% of it's regular level, that's just background noise in comparison to the rattly piece of sh!t that is a Z22SE engine at high rpm. I've mounted an external mic on my camcorder on trackdays and if the mic is on the drivers side, you can barely hear the whine. If it's mounted on the passenger side, you can barely hear anything else.

[Winstar]

Afaik it's the vibration of the rotors. It happens more on load because of the ridiculously small tolerances the charger has which on load force components closer together. The induction is partly attributable to noise levels, however the main source is the charger itself I think.

Noise will be 'blade pass' where the pressure wave from the tip of the rotors hit a stationary object or each other, same as turbo whine/whistle. It'll be worse in the roots compressors (compared to the TVS) as the blades are not designed to cut though the air effiecently.

Would a cone filter in an airbox, like the Honda S2000, give the breathing benefits but a quieter whine??

yes but it would need to be deisgned to not restrict the flow to the cone filter, which would be the case as pictured

[FLD]

Hmmm, perhaps a 'viper' inlet filter system would be good.

[Mangham54]

Could you not always re-root the intake to feed from somewhere that isn't pointing at the driveby sensors? When I had a look at the space around my engine I wondered whether you could feed from the front part of the undertray with and additional NACA duct. When there was no airbox in the way it looked as though you could fashion a gentle 90* bend downwards towards the undertray. That way I would have thought the induction noise would be pointed at the floor and dissapated with the reflection on the tarmac and with the air that rushes under the car. However would there be a risk created by putting the intake into an area that would force air through the intake, or be too slow moving at high revs and defeat the benefit of the charger.

Edited by Mangham54, 02 June 2011 - 12:14 PM.

[smiley]

But as Exmantaa found, with a modified OEM airbox fitted, all of the whine goes. So I don't think it's purely mechanical noise from the charger itself.

I can't imagine he managed to completely exterminate it altogether though?

About 95% of the whine is gone. I was amazed when i drove it.

[Seb.F]

I guess for trackdays - it would suit. But I love the noise! I wouldn't want to completely eradicate it on day to day driving.

[TheStotts]

Should mask any super charger whine Caution: may destroy your ears

[Hark]

I've seen that one before. The guy's driving is sublime. The noise hurts. lol