B1ack_Mi16 67 Posted February 4, 2007 Well, I've just finished a 2.5" stainless system: http://cortex.fa-s.ntnu.no/~kristian/205gt...07/CIMG0167.jpg http://cortex.fa-s.ntnu.no/~kristian/205gt...07/CIMG0172.jpg Spent quite some time to get it right. Problem is!! It's so noisy, I've never heard anything like it. Sounds like a Kawasaki Ninja with no exhaust muffler at all! So I really need to make another exhaust-system to get the noise down to an acceptable level. I wanna stay with 2.5" diameter, and could use some help regarding how to choose the right mufflers. The engine is 2.3 litres, and I've read somewhere before that the more displacement volume the bigger silencers are needed to keep the noise down. I have been looking at the Simons universal systems, as they're easily avaliable here in Norway. The centre muffler I've found is a round one with 125mm diameter and 420mm length. And the rear one (biggest they have) is oval, 140 / 220mm and 500mm length. Do you think this might be a reasonable choice and that the noise will be ok? They're both straight through mufflers with perforated pipe inside with damping material. It need to be able to get under the noise restrictions on trackdays, which I actually believe is 90dB at most trackdays, only some have 100db limit. Share this post Link to post Share on other sites
smckeown 1 Posted February 4, 2007 I reckon you have no hope of getting it under 90bs sport; i'd say a standard GTI is close to that! I read something from petert on another forum about using a smaller diameter tailpipe to reduce the noise. Share this post Link to post Share on other sites
petert 580 Posted February 5, 2007 Your noise problem is mostly coming from the diameter. Use 2.25" rather than 2.5". The later is perfect for a 5L V8. I use a slightly larger rear muffler too, 6" diameter x 21" long. If you're too stubborn to change the whole lot, try just changing the tailpipe down to 2.25", or even 2". 90dB is reasonably tough. We have 95dB here, which can be achieved with just a rear muffler and 2.25" system on a 205. Basically any muffler will get you through 95dB, so 100dB is a walk in the park. Share this post Link to post Share on other sites
niklas 1 Posted February 5, 2007 One other thing, you can reduce the diameter the longer back you get. For example use 2.5" up to the first muffler, use 2.25" to the second muffler and a 2" tailpipe. Also, you can probably get an even bigger second muffler but then they start to get heavy (Look at the second muffler on the 206 GTI180, it probably weighs 20 kg!!) Share this post Link to post Share on other sites
Mad Professor 7 Posted February 5, 2007 Oh hell mines getting a full 3" system with only a back box with in the next week or two, But then I don't do track days. On my 205 TT have a 2.5" full system atm, I would not say it's loud as such, but you can sure hear the car coming down the road. But I read somewhere on the internet that the turbo it's self is quite good a being a muffler, i don't know if that is true or not. 90dB - 100dB, thats quite some target you got, I'll have a word with my mate neal to makes custom zorst daly and see what he has to say. Share this post Link to post Share on other sites
petert 580 Posted February 5, 2007 (edited) Turbos are different though. They need a bigger pipe to help the turbo spool up and don't make as much noise as a N/A engine. A 3" exhaust would be a complete waste of money, even on a V8. Edited February 5, 2007 by petert Share this post Link to post Share on other sites
B1ack_Mi16 67 Posted February 5, 2007 Thanks for replies, I'm not sure wheter I'll go 2.25" actually as I "believe" I need 2.5" to get enough flow to produce 250bhp. I already have a standard Bosal system, for 205 1.6 GTi that's nice to use for street use (it's like less than 2" in the bends), but for track I wanna have 2.5". Engine analyzer suggest I need like 400cfm flow @ 28" water to get 250bhp. The mufflers in the stainless system flows like 500cfm, but that may be the whole problem to why I get too much noise too. I also believe the 3.8 / 3.2mm valve-lift @TDC is contributing to quite some extra sound. I can only get 2", 2.5" and 3.0" mufflers from Simons which is the brand I'm planning to get, I don't know any other brand selling universal mufflers over here. Petert are you sure 2.5" will be overkill even on a 2.3 litre engine? It's not like it's breating with VE of 90%, more like 110% I would guess, so it certainly will move quite some volumes of air. Share this post Link to post Share on other sites
petert 580 Posted February 5, 2007 Petert are you sure 2.5" will be overkill even on a 2.3 litre engine?It's not like it's breating with VE of 90%, more like 110% I would guess, so it certainly will move quite some volumes of air. I'm just comparing it to a 5L V8, which makes 300hp @ 6000 on a single 2.5" system. Let's say the V8 runs at 80% and it's being generous to run the 2.3L at 110%. It would only do that over a small range. ie V8: 0.8 x 6000 x 5.0 = 24000 2.3L: 1.1 x 7500 x 2.3 = 18975 Someone please correct me if my maths is wrong. The 2.5" pipe is 23% bigger. Share this post Link to post Share on other sites
B1ack_Mi16 67 Posted February 5, 2007 I'm just comparing it to a 5L V8, which makes 300hp @ 6000 on a single 2.5" system. Let's say the V8 runs at 80% and it's being generous to run the 2.3L at 110%. It would only do that over a small range. ie V8: 0.8 x 6000 x 5.0 = 24000 2.3L: 1.1 x 7500 x 2.3 = 18975 Someone please correct me if my maths is wrong. The 2.5" pipe is 23% bigger. Yes, and it's that small range that counts Well, I think I'll get a 2.5" system and see how it works out, must be better than the aeromuffler thingy anyway. And if still too noisy change rear silencer and piping to 2.25" as you suggest. As you say the exhaust temperatures and hence volume has probably been reduced significantly whan arriving at the rear muffler anyway. Share this post Link to post Share on other sites
