[Mk2] [Turbo] Another Exhaust question - Flow Vs Noise

[parker455]

Hi guys,

I'm currently running a decatted 95 rev 3 turbo with a Nur Spec, and like all owners of the Nur.. Neighbours are getting miffed and I'll be tracking the car soon, so noise limits need cutting. I've already got a bung for it but you can feel the increased backpressure, I'm also concerned with the 92db drive-by limit at snett.

What sort of options do I have with a high-flowing exhaust, with acceptible noise levels?

There's a HKS Hi-power in the classifieds now that tempts me. The nur spec is a lovely exhaust though. Single exit preferred.

Thanks folks!

[SonicSW20]

Fujitsubo Legalis R, no louder than stock according to the data, will just be a different tonality:

https://www.fujitsubo.co.jp/prods/detai ... 3/00000385

Not a single exist though, and I know you like a single exit!

That HKS Hi-Power fits the bill.

Bear in mind the drive-by tests are normally measured at a greater distance than static.

http://www.snetterton.co.uk/media/97529 ... 010_rm.pdf

Snetterton measure at 20 metres. If you car passes the static test at 0.5M / 2M, it is highly unlikely to exceed the drive-by limit, as SPL follows the inverse square law with distance from the source. So, a 102dB source measured at 0.5M will be only 70dB at 20M. There are of course other factors, this rule assumes a free field situation where there is nothing to reflect off, and you have to consider tyre noise etc.

If you can pass the static test, you'll have no problem with the driveby.

[parker455]

Cheers Gaz!

I reckon it'll pass the static, as reports are around 103/4db static with the bung, my bung is from an Evo nur spec so I think the bung is slightly longer than the one for the 2.

I'm just weighing up the options, I'd really like the HKS but also concerned on flow as the pipe diameter is 2.5'' as opposed to the nur's 80mm all the way through.

3 Piece sytem, polished SUS304 stainless steel

80mm bore pipwork

114.3mm Tailpipe

Note: Due to the large sizes of certain Nur Spec R exhausts carriage charges to Europe and other worldwide destinations vary greatly. Please enquire.

98DB with baffle inserted

Removable baffle included

I assume they measure the noise with a cat on aswell..[/quote]

[Nic]

This is the mid pipe from my Blitz NUR R with a stainless steel Jetex silencer welded into it. It's reduced the noise level a fair bit with hardly any effect on performance.

[SonicSW20]

Yes, I would imagine they would measure it with the cat unless the system includes a decat section out of the box.

Tony had problems passing static with a bung at Castle Combe earlier this year, though he's not convinced they measured it properly. As we've discussed before, they are supposed to measure at a 45 degree angle to the exhaust exit. On most systems, this would be 45 degrees from the rear of the car, however the Nur Spec already exits at an angle, so technically they should measure 45 degrees from the plane the exhaust sits in. If measured in line with the exit, the measured value will be a few dB higher.

[parker455]

Nic, that looks like a good option, did you have a dyno run before/after?

I was thinking the same thing Gaz, I remember Tony telling me about it, wonder how they'll measure it at snett.

[SonicSW20]

Welding in another silencer is a good option, not sure how much it will cost though. Cost of the silencer plus a couple hours labor, I guess?

[parker455]

Welding in another silencer is a good option, not sure how much it will cost though. Cost of the silencer plus a couple hours labor, I guess?

That's what I'm trying to factor in, would be easier selling and buying a different exhaust. I don't fancy my welding skills on it haha.

[SonicSW20]

Easy job for any custom exhaust place, must be one near you?

[Nic]

Nic, that looks like a good option, did you have a dyno run before/after?

No sorry no dyno runs, I doubt there'd be more than a few hp's in it though. It's definitely a LOT less restrictive than fitting a tail pipe bung which has a noticeable effect on performance.

The stainless Jetex silencer cost me £70 and my tame welder charged me £20 to fit it. See part number U457600R here: http://www.jetex.co.uk/website/custom_p ... a=3.0+inch

[androo007]

£ for £ i'd just swap the exhaust. At least you can sell on the old one.

Once a neighbour is p!ss3d..... they dont let it go so i'd just get rid and get a quieter one.

Legaris R imho wasnt any improvement over stock. No increase felt on bum dyno and you miss that roar.

I've got your / my old JASMA twins, which give a nice medium sound - maybe could look for something similar? I guess what is for sale atm.....

[Nic]

Welding in another silencer is a good option, not sure how much it will cost though. Cost of the silencer plus a couple hours labor, I guess?

The fabrication work took less than an hour, a simple jig was made to keep the flanges aligned in the correct orientation, the silencer and piping were cut to length and then welded together.

[parker455]

@ Andy - That's what I was thinking, do love the look of the nur spec I must admit, always gets comments. But if it was £90 to have the silencer stuck in there I don't think it's too bad at all.

This certain neighbour is a xxx in all aspects, he's moving soon so hopefully he goes.

There was alot on that car I wish I hadn't sold now, but needs must etc.

Near me there's Hayward + Scott, who will be mad money, or a local welders that I'm using to tig my sill up tomorrow, I'll ask him what he can do.

Any vids of the nur with the silencer in there?

[Race Idiot]

I doubt youd be restricted by a 2.5 exhaust on a ct20

[Nic]

do love the look of the nur spec I must admit, always gets comments. But if it was £90 to have the silencer stuck in there I don't think it's too bad at all.

The main reason for doing it the way I did was because I love the look of the NUR R. Ground clearance was also a concern, I have a lot of speed bumps around me and I knew the NUR R was okay. I also bought 2 new gaskets and new stainless bolts.

Any vids of the nur with the silencer in there?

I'll see if I can get some at the weekend.

[parker455]

Lovely, thanks Nic.

I'll take the pics to the welder tomorrow and see what he can do for me!

[androo007]

If not... swappy swappy with me

[parker455]

Any luck on the sound clip at all? I've found a welder that'll do it for 20-30 quid

[Nic]

Images and videos taken with an iPad so quality is not the best.

Click to view video - Idling

iPad 45 degrees from exhaust and around 1m away.

Click to view video - Revving

On this image you can just see the extra silencer behind the resonator.

[parker455]

Excellent thanks mate! Much appreciated. Sounds alot more of a tuner-y sound with the silencer, rather than just a loud noise. I like it.

I'm likely to go down this route, not sure if I want to do it before the trackday or not, I'm not going to be racing people just out to enjoy it. Will stick the bung in tomorrow and see what I think. I definitely think it pulls power noticeably