Reducing car noise to meet Bedford noise limits
Discussion
My car is getting close to the limits at Bedford. I am almost certain it is not exhaust noise but the noise of the turbo-charged engine itself. Those I have overtaken have said they could hear it was my car coming up behind with it's 'awesome soundtrack'. Not so awesome to the Bedford autodrome organisers who wave a noise board at me every now and again but have not black flagged me (presumably because I short-shift after seeing the board.
Ultimately, I am thinking of fitting some sound deadening under the bonnet (my car has no sound deadening anywhere at all presently). Has anyone else had similar issues (presumably with a turbo car) and used a sound deadening product that can take the heat under the bonnet of a tuned turbo-charged car? Basically I can find products online but an independent recommendation is well worth having.
This clip is from inside the cabin but I think you'll see why I think it's the turbo not the exhaust causing the noise.
http://m.youtube.com/watch?v=PFUqPnx1U9k
Thanks.
Ultimately, I am thinking of fitting some sound deadening under the bonnet (my car has no sound deadening anywhere at all presently). Has anyone else had similar issues (presumably with a turbo car) and used a sound deadening product that can take the heat under the bonnet of a tuned turbo-charged car? Basically I can find products online but an independent recommendation is well worth having.
This clip is from inside the cabin but I think you'll see why I think it's the turbo not the exhaust causing the noise.
http://m.youtube.com/watch?v=PFUqPnx1U9k
Thanks.
Turbos mute induction noise and exhaust noise, what car is it, does it have a silly exhaust on it as its almost always exhaust noise other than on hugely high revving normally aspirated stuff when intake noise can be high.
Just watched the video, that's not normal noise that sounds like a restriction it's like when a baffle is fitted to a fart can exhaust it basically turns it into a whistle. Sounds almost the same as when I had to fit a the restricter / baffle in my exhaust on my mr2 turbo, it had a 3.5" apexi Hayabusa through pipe with no silencing at all, 110dB but dropped to 97dB with the restricter that was a metal plate with a 1.5" diameter pipe welded on the end that got shoved up the exhaust tip. Other reason could be the intake is too restricted dragging air in or too small a turbo being over spun.
Just watched the video, that's not normal noise that sounds like a restriction it's like when a baffle is fitted to a fart can exhaust it basically turns it into a whistle. Sounds almost the same as when I had to fit a the restricter / baffle in my exhaust on my mr2 turbo, it had a 3.5" apexi Hayabusa through pipe with no silencing at all, 110dB but dropped to 97dB with the restricter that was a metal plate with a 1.5" diameter pipe welded on the end that got shoved up the exhaust tip. Other reason could be the intake is too restricted dragging air in or too small a turbo being over spun.
Edited by Herman Toothrot on Sunday 15th December 10:01
That sounds like turbo intake to me. It could be benign and simply caused by design of the turbo plumbing/filter, but also could be a number of unpleasant things like overboosting ,bearings, leaking gaskets, leaking pipes etc.
My money would be that its the airbox design causing the noise - maybe look at changing the airbox/filtering...that kind of noise isn't going to go away with some sound insulating material.
My money would be that its the airbox design causing the noise - maybe look at changing the airbox/filtering...that kind of noise isn't going to go away with some sound insulating material.
The engine was build (4k ago for the previous owner) by a reputable firm who checked the condition of everything going on the car so I'm not inclined to jump to the conclusion that all hell is about to break loose under the bonnet. I have a feeling it's the (high) pitch of the noise carrying and causing the noise meters to pick it up. I'm not tripping the noise meter, just getting close so only need to take a few db of it!
Thanks.
Thanks.
Masher
your best bet is doing a google search for the bedford noise management plan and print off a copy and take it with you. Their end of day black flag is against little known official policy, which states in the rules of the circuit that you are allowed back on if you make an alteration to your exhaust. I think they do this so they don't have to keep track of noisier cars - it's easier just to ban them from the track straight away as they've already paid for the day anyway.
Having said all that all the soundproofing in the bonnet shouldn't be needed - most turbo exhausts have to be very free flowing so I bet its the exhaust unless its a strange noise. I'd recommend fitting a 90 degree bend onto your exhaust exit aiming RHS, as most of the noise meters are on the left. Wth a bolt on attachment its an easy alteration you can add and remove as needed for when you're at bedford.
your best bet is doing a google search for the bedford noise management plan and print off a copy and take it with you. Their end of day black flag is against little known official policy, which states in the rules of the circuit that you are allowed back on if you make an alteration to your exhaust. I think they do this so they don't have to keep track of noisier cars - it's easier just to ban them from the track straight away as they've already paid for the day anyway.
Having said all that all the soundproofing in the bonnet shouldn't be needed - most turbo exhausts have to be very free flowing so I bet its the exhaust unless its a strange noise. I'd recommend fitting a 90 degree bend onto your exhaust exit aiming RHS, as most of the noise meters are on the left. Wth a bolt on attachment its an easy alteration you can add and remove as needed for when you're at bedford.
Herman Toothrot said:
Had another listen It's a high pressure through a small gap noise I'm 100% sure, it's either a) bad design somewhere, restriction b) boost leak
Pretty sure it's not boost leak but could be peculiar air flow causing a whistle. Runs fantastically so I'm thinking whatever it is is not affecting performance but is causing noise. Masher964 said:
Pretty sure it's not boost leak but could be peculiar air flow causing a whistle. Runs fantastically so I'm thinking whatever it is is not affecting performance but is causing noise.
If it was overboosting it would feel like its running fantastically....until the point the engine goes pop. I think its down to airbox design though. What kind of boost is it running?that is definitely on the intake side. how is your airfilter and intake plumbed into the turbo. is it in a sealed box with a restriction not allowing enough air into it?
maybe you need a larger air filter (assuming its a cone). my car used to whistle like that with a sub 3" intake. now i have a 4" straight pipe from the filter to the turbo and all you can hear now is the angry exhaust note
maybe you need a larger air filter (assuming its a cone). my car used to whistle like that with a sub 3" intake. now i have a 4" straight pipe from the filter to the turbo and all you can hear now is the angry exhaust note
What turbo is it? Some come with baffles fitted to the front to take away the whistling noise, it may have been removed at some point.
http://dodgeram.org/tech/dsl/FAQ/figures/silencer....
http://dodgeram.org/tech/dsl/FAQ/figures/silencer-...
Cone filters and a short intake path can make a lot of noise, also if you have metal intake piping then that can amplify the noise as well.
http://dodgeram.org/tech/dsl/FAQ/figures/silencer....
http://dodgeram.org/tech/dsl/FAQ/figures/silencer-...
Cone filters and a short intake path can make a lot of noise, also if you have metal intake piping then that can amplify the noise as well.
I'll look for a pic later. Basically it is a Porsche 944 that has been taken from 2.5L NA to 2.8 turbo. As far as I am aware, the turbo is standard and runs 1.2 bar and the air intake was a cone, just behind the intercooler, but has been replaced by the standard air box to allow it to take cooler air from the wing. Changing the air box has made no difference to anything at all other than the reassurance it's taking in cold air. Interesting comment on pipework... I'll have a look. Thanks.
I don't have a variable boost but a high / low toggle switch. Frankly, I never use the low setting! I like the way you're thinking though. Lower noise with less boost might help indicate where the noise is being generated. As you can hear on the video, the noise is clearly turbo related.
just for giggles, heres what my car sounds like from the inside 
http://www.youtube.com/watch?v=P2hidwFypbU
a little bit of launch control at the start to build boost, then 4WD grip on kumho v70 tyres
http://www.youtube.com/watch?v=P2hidwFypbU
a little bit of launch control at the start to build boost, then 4WD grip on kumho v70 tyres
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