Luxluc Posted July 11, 2012 Share Posted July 11, 2012 which is why the 4" mid/down pipe to 3" system definitely makes sense to me. I'm not sure on this mate. A turbo comes normally with a given flange diameter. Medium sized turbos generally come in 3", while the big ones use 4" flanges. The flange diameter is defined through various characteristics, one is the exhaust gas flow that the turbo is able to push towards the exhaust. Therefore, a 4" DP/MP connected to a 3" exhaust doesn't seem to be logic, as the gases will go quickly through the MP/DP, and then be slowed down when entering the exhaust. A 3" DP/MP combo, connected to a 3"+ exhaust should be more free flowing, as the bends on numerous 3" systems are nevertheless slowing down the gas flow. The best for me is an exhaust system that is as straight as possible .. therefore I went for the Whifbitz 4" Ti unit which is almost straight. Quote Link to comment Share on other sites More sharing options...
sdistc Posted July 11, 2012 Share Posted July 11, 2012 After having my car's bum up in the air to get at the diff, I have had a chance to look at my exhaust again - I know it's 4" dump, but think it's also 4" to the midpipe and only 3" or 3.25" (Blitz Nur spec), including 1 resonator, back from where the 2nd cat would be. Flows decently well, but sounds too loud for mine - so was considering what Michel has done, and adding another silencer or resonator. Quote Link to comment Share on other sites More sharing options...
johnny g Posted July 11, 2012 Share Posted July 11, 2012 If the exhaust cut out doesn't do what I want, then I'll enquiring with Michel about his exhaust. Quote Link to comment Share on other sites More sharing options...
supraGZaerotop Posted July 11, 2012 Share Posted July 11, 2012 (edited) ive got a veilside evolution exhaust, came over from japan on the car, and i love it, not that loud just a nice deep sound, one of them exhausts thats just sweet when you gun it but quiet enough not to draw unwanted attention to yourself, i havint fitted the double decat yet tho Edited July 11, 2012 by supraGZaerotop (see edit history) Quote Link to comment Share on other sites More sharing options...
johnny g Posted July 11, 2012 Share Posted July 11, 2012 ive got a veilside evolution exhaust, came over from japan on the car, and i love it, not that loud just nice deep sound, one of them exhausts that just sweet when you gun it but quite enough not to draw unwanted attention to yourself, i havint fitted the double decat yet tho Oh that'll certainly change it! Quote Link to comment Share on other sites More sharing options...
supraGZaerotop Posted July 11, 2012 Share Posted July 11, 2012 ;)Oh that'll certainly change it! Quote Link to comment Share on other sites More sharing options...
supraGZaerotop Posted July 11, 2012 Share Posted July 11, 2012 ive got a 1.2 bar RR with the car, but im thinking il get a 1bar RR to be on the safer side, Quote Link to comment Share on other sites More sharing options...
CanisLupus Posted July 11, 2012 Share Posted July 11, 2012 You could go with silencers like theese here: Click they are 89mm ID and really do lower the noise level considerably especially the Simons Grand Quote Link to comment Share on other sites More sharing options...
Nic Posted July 11, 2012 Share Posted July 11, 2012 You could cut out the small resonator and fit another silencer in it's place. I have a brand new stainless steel 3" Jetex silencer I was going to sell that would fit. http://www.boostaholic.com/supra/drager/drager2.jpghttps://www.jetex.co.uk/jetex/store/images/uploads/u457600rlarge.jpg You could go with silencers like theese here: Click they are 89mm ID and really do lower the noise level considerably especially the Simons Grand The middle one on that link is the same silencer I've got available. Quote Link to comment Share on other sites More sharing options...
CanisLupus Posted July 11, 2012 Share Posted July 11, 2012 You're right Nic didn't notice that Quote Link to comment Share on other sites More sharing options...
hodge Posted July 11, 2012 Author Share Posted July 11, 2012 I'm not sure on this mate. A turbo comes normally with a given flange diameter. Medium sized turbos generally come in 3", while the big ones use 4" flanges. The flange diameter is defined through various characteristics, one is the exhaust gas flow that the turbo is able to push towards the exhaust. Therefore, a 4" DP/MP connected to a 3" exhaust doesn't seem to be logic, as the gases will go quickly through the MP/DP, and then be slowed down when entering the exhaust. A 3" DP/MP combo, connected to a 3"+ exhaust should be more free flowing, as the bends on numerous 3" systems are nevertheless slowing down the gas flow. The best for me is an exhaust system that is as straight as possible .. therefore I went for the Whifbitz 4" Ti unit which is almost straight. I'm running a 4" downpipe and midpipe into a 3" catback and have no restrictions as yet at my power levels at all. It's just 2 damn loud. Quote Link to comment Share on other sites More sharing options...
Luxluc Posted July 11, 2012 Share Posted July 11, 2012 (edited) Do you think it's the 4" DP/MP that make such a difference in Db? My 3" DP/MP with the HKS Dragger exhaust (3.7" piping) wasn't that loud. Edited July 11, 2012 by Luxluc (see edit history) Quote Link to comment Share on other sites More sharing options...
Noz Posted July 11, 2012 Share Posted July 11, 2012 I'm running a 4" downpipe and midpipe into a 3" catback and have no restrictions as yet at my power levels at all. It's just 2 damn loud. Do you think running the same system, 3" or all the way 4" would make a difference on a dyno? Quote Link to comment Share on other sites More sharing options...
dandan Posted July 11, 2012 Share Posted July 11, 2012 (edited) If you decide to add an unrestrictive silencer to the 3" then give me a shout mate. I've got this one for sale now (I went 4" rather than trying to quieter on my old 3" Nur Spec) Edited October 2, 2013 by dandan (see edit history) Quote Link to comment Share on other sites More sharing options...
Luxluc Posted July 11, 2012 Share Posted July 11, 2012 Which 4" did you go for Dan? Quote Link to comment Share on other sites More sharing options...
David P Posted July 11, 2012 Share Posted July 11, 2012 I like these Moroso spiral silencers, they are small enough for an easy fit and reduce by about 7dB each. http://www.moroso.com/catalog/categorydisplay.asp?CatCode=35054 Quote Link to comment Share on other sites More sharing options...
dandan Posted July 11, 2012 Share Posted July 11, 2012 (edited) Which 4" did you go for Dan? Custom setup as I wanted completely unrestricted and quiet. The only way to do that was with an electric cutout to give me 2 options after the 4" DP/MP, and short 4" exhaust section: 1) Valve open - Dump straight out near the diff - 90dB at idle, 103dB at 5000rpm 2) Valve shut - Passes through a 3" silencer and the the 3" back box - 83.5dB at idle, 96dB at 5000rpm The decibel meter was 500mm from the tailpipe for these readings. Edited October 2, 2013 by dandan (see edit history) Quote Link to comment Share on other sites More sharing options...
hodge Posted July 11, 2012 Author Share Posted July 11, 2012 My first stop is going to be AAS on Friday to see what they can reccomend and what they can make for me. Another issue is ground Clearence. I'm wondering if they can make me an oval 4" midpipe and a 3" catback with 2 silencers in and a back box. Ot even a silencer in the midpipe, odviously ground Clearence permitting. I'm thinking I'm going to raise the car maybe 1/2 inch all round too, just to aid Clearence. Quote Link to comment Share on other sites More sharing options...
hodge Posted July 11, 2012 Author Share Posted July 11, 2012 Custom setup as I wanted completely unrestricted and quiet. The only way to do that was with an electric cutout to give me 2 options after the 4" DP/MP, and short 4" exhaust section: 1) Valve open - Dump straight out near the diff - 90dB at idle, 103dB at 5000rpm 2) Valve shut - Passes through a 3" silencer and the the 3" back box - 83.5dB at idle, 96dB at 5000rpm The decibel meter was 500mm from the tailpipe for these readings. http://i828.photobucket.com/albums/zz202/danc8000/Exhaust/CIMG3760a.jpg Hey Dan. Why have you heat wrapped the catback part of the exhaust, are you having issues with stuff under the car getting too hot. I've been thinking about wrapping my midpipe, after I've been driving the car for say an hour, the heat makes my shifter swell and becomes very stiff. No issues with gear change but just isn't as free as it should be. Quote Link to comment Share on other sites More sharing options...
michel lane Posted July 12, 2012 Share Posted July 12, 2012 John you can always try my exhaust on your car if you wish , its got a 4inch v band , but i have a convertor kicking around. It will give you a good starting point. Quote Link to comment Share on other sites More sharing options...
dandan Posted July 12, 2012 Share Posted July 12, 2012 Hey Dan. Why have you heat wrapped the catback part of the exhaust, are you having issues with stuff under the car getting too hot. I've been thinking about wrapping my midpipe, after I've been driving the car for say an hour, the heat makes my shifter swell and becomes very stiff. No issues with gear change but just isn't as free as it should be. It was just to take help knock the noise levels down a touch John - not intentionally a heat thing. I never had any heat issues when it wasn't wrapped but I don't remember driving it that "hard" before I wrapped it so I'm not sure if anything would happen like you said. Quote Link to comment Share on other sites More sharing options...
hodge Posted July 12, 2012 Author Share Posted July 12, 2012 It was just to take help knock the noise levels down a touch John - not intentionally a heat thing. I never had any heat issues when it wasn't wrapped but I don't remember driving it that "hard" before I wrapped it so I'm not sure if anything would happen like you said. I never thought of heat wrap to reduce noise. Would you have said its made much difference? Quote Link to comment Share on other sites More sharing options...
hodge Posted July 12, 2012 Author Share Posted July 12, 2012 John you can always try my exhaust on your car if you wish , its got a 4inch v band , but i have a convertor kicking around. It will give you a good starting point. Thanks Michel. I think I've tried most of your car on mine whilst fault finding Your a top bloke. I do think I should call over and help get the thing back together again. Quote Link to comment Share on other sites More sharing options...
michel lane Posted July 12, 2012 Share Posted July 12, 2012 would love your help next year , I just dont have the time this year unfrotunately. The exhaust is there if you would like to try it anytime. Quote Link to comment Share on other sites More sharing options...
black_widow87 Posted March 18, 2013 Share Posted March 18, 2013 Been thinking about changing my exhaust system, currently running 3" downpipe/midpipe then 3.5" whifbitz cat-back, would reducing the whifbitz system to 3" cause much (if any) restriction? Im assuming the noise level will be reduced if reduced to 3". Quote Link to comment Share on other sites More sharing options...
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