hodge Posted July 10, 2012 Share Posted July 10, 2012 Hi guys Thought I'd start a thread on this cos I'm finding it interesting and confusing at the same time. My exhaust at present, in my opinion is too loud and is 1 of or the most annoying thing about my car. I'd like to make it a lot quieter but don't want to choke the power at all. I've read numerous threads about power loss after fitting smaller diameter exhausts. I'm just trying to find the medium between performance and noise. My current exhaust is a custom 1 which I made at work, consisting of the following:- Big single turbo - 4" downpipe - 4" midpipe - 3" HKS super Dragger catback the car made 778hp (hubs) with no restriction issues at all. Johnny.Gs big twin has just been dyno'd at 638hp (hubs) power stopped there because of exhaust restriction. 2 x 2.5in downpipes - 3" midpipe - 3" madallion catback Wangan Supra in japan, with bigger turbos made 839hp iirc 2 x 2.5in downpipes - 3" midpipe - 3" custom catback White T51 TRD widebody Jurgen sold 700hp 3" HKS downpipe - 3" midpipe - 3" HKS super Dragger I spoke to Jamie about all this sort of thing when I was making my exhaust and he told me he lost over 100hp just by fitting a 3" catback instead of his 4" I'd love some input as how your exhausts perform, restrictive and noise level wise. And maybe we can find the perfect setup for a quiet noise level minimum power restrictions. I know a full 4" system is the way to go for no restriction BUT, that's way way to loud for me. I'm considering having a new catback made in 3" same as my currect one but with 2 silencer boxes in, thoughts?? Also has anyone found any restriction by using an exhaust bung? Maybe if we could get a breakdown list of your systems and power figures and if your power was restricted my it. Cheers John Quote Link to comment Share on other sites More sharing options...
spikedjack Posted July 10, 2012 Share Posted July 10, 2012 Keep the diameter, install some resonator/silencer boxes? Quote Link to comment Share on other sites More sharing options...
Guigsy Posted July 10, 2012 Share Posted July 10, 2012 All i can add is i had a 4" dp, mid and catback (BL dp and mid, hks ti) and it was REDICULOUSLY loud. so much so that i hated driving the car. i swapped to a whiffin twin box and had it modified to fit the 4" mid pipe. and its now much better. just about right. my little gt35r is only pushing 520 bhp so a 4" was way overkill and i have not noticed a difference at all. other than it was far nicer to drive. when i asked about it paul whiffin said it shouldnt be a restriction untill well into the 700 range. Quote Link to comment Share on other sites More sharing options...
hodge Posted July 10, 2012 Author Share Posted July 10, 2012 Keep the diameter, install some resonator/silencer boxes? What is a resonator, and will silencer boxes produce a restriction. Quote Link to comment Share on other sites More sharing options...
hodge Posted July 10, 2012 Author Share Posted July 10, 2012 All i can add is i had a 4" dp, mid and catback (BL dp and mid, hks ti) and it was REDICULOUSLY loud. so much so that i hated driving the car. i swapped to a whiffin twin box and had it modified to fit the 4" mid pipe. and its now much better. just about right. my little gt35r is only pushing 520 bhp so a 4" was way overkill and i have not noticed a difference at all. other than it was far nicer to drive. when i asked about it paul whiffin said it shouldnt be a restriction untill well into the 700 range. So you've now got the same setup as me with 4" down and mid, 3" catback? Quote Link to comment Share on other sites More sharing options...
Hellstrom Posted July 10, 2012 Share Posted July 10, 2012 just mount an exhaust system with multiple silencers? Quote Link to comment Share on other sites More sharing options...
hodge Posted July 10, 2012 Author Share Posted July 10, 2012 just mount an exhaust system with multiple silencers? We've established that, but that's not what I'm trying to achieve with this thread. I'm wanting people's views and experiences on restrictions to power because of an exhaust. Quote Link to comment Share on other sites More sharing options...
hodge Posted July 10, 2012 Author Share Posted July 10, 2012 Found this an interesting read. http://www.modified.com/tech/modp-1102-exhaust-test-tech/index.html Quote Link to comment Share on other sites More sharing options...
Guigsy Posted July 10, 2012 Share Posted July 10, 2012 So you've now got the same setup as me with 4" down and mid, 3" catback? Yep but it's a twin box catback. Rater than just the one. Not an issue restriction wise for me but I don't know about you Quote Link to comment Share on other sites More sharing options...
hodge Posted July 11, 2012 Author Share Posted July 11, 2012 I've just spent the last hour or so reading posts on SF about exhausts. Most say it's the midpipe is the restrictive issue. Theres lots of guys on there running 4" downpipe - 4" midpipe and a 3" catback. Others use this setup but with an exhaust cutout/butterfly valve half way up the midpipe which opens at say 10 psi. Personally I don't fancy this at all. I'd imagine the noise on WOT would be horendous. I personally would prefer to hear the noise of my turbo spooling that a roar of a crazy loud exhaust. Quote Link to comment Share on other sites More sharing options...
hodge Posted July 11, 2012 Author Share Posted July 11, 2012 I've just spent the last hour or so reading posts on SF about exhausts. Most say it's the midpipe is the restrictive issue. Theres lots of guys on there running 4" downpipe - 4" midpipe and a 3" catback. Others use this setup but with an exhaust cutout/butterfly valve half way up the midpipe which opens at say 10 psi. Personally I don't fancy this at all. I'd imagine the noise on WOT would be horendous. I personally would prefer to hear the noise of my turbo spooling that a roar of a crazy loud exhaust. I'm going to call upto AAS (custom fabricators in Newcastle) and see what he recommends for my needs and I'll report back. Quote Link to comment Share on other sites More sharing options...
michel lane Posted July 11, 2012 Share Posted July 11, 2012 I went through a simular excercise, after hours of different setups, I reached my goal.I have a 4 inch sysems all the way through with 1resonator box and one silencer box . It brought the noise level down to 96db apposed to my 128db using my boostlogic system. I used the mid pipe and Downpipe and altered the rear section of the car. The two boxes were not the cheap resonators ad silencers you would normally buy, I used aero turbine units. Quote Link to comment Share on other sites More sharing options...
Luxluc Posted July 11, 2012 Share Posted July 11, 2012 Interesting thread John; I have been thinking about this too, since I plan my next setup. I have a PHR 3" midpipe/downpipe combo, combined to a 4" Whifbitz Ti exhaust. My Supra pushed 651 rhhp with my old HKS Super Dragger exhaust still in place. I'm not sure what the restrictions of my actual setup are (3" DP/MP and 4" exhaust), but I guess I will have to go for 4" DP/MP when I go for more power. You're right though that the bigger exhaust are a lot louder ... my 4" Ti is way louder than the HKS one. Quote Link to comment Share on other sites More sharing options...
johnny g Posted July 11, 2012 Share Posted July 11, 2012 Wait and see how I get on with my exhaust cut out mate. Am just waiting for Sound Performance to give me a price for the cut out and solenoid shipped. I'll be able to keep the Tanabe then. Quote Link to comment Share on other sites More sharing options...
tooquicktostop Posted July 11, 2012 Share Posted July 11, 2012 Not that I belong in the thread too much but for those chasing bigger BPU power I had issues on the dyno with my exhaust, it's a whifbitz 2.5" decat, no restrictior ring (that made it worse) 2.5" cat back. Nice and quiet but at 1.2bar we had to stop as it was restricting so much it was getting hot, big bpu needs a free flowing exhaust Quote Link to comment Share on other sites More sharing options...
mellonman Posted July 11, 2012 Share Posted July 11, 2012 I went through a simular excercise, after hours of different setups, I reached my goal.I have a 4 inch sysems all the way through with 1resonator box and one silencer box . It brought the noise level down to 96db apposed to my 128db using my boostlogic system. I used the mid pipe and Downpipe and altered the rear section of the car. The two boxes were not the cheap resonators ad silencers you would normally buy, I used aero turbine units. this is what i would of thought to be the best set up as the 4" pipe gives you the flow that you loose fitting the silencer's, so probably flows better then the 3" just quieter Quote Link to comment Share on other sites More sharing options...
Luxluc Posted July 11, 2012 Share Posted July 11, 2012 There are power restrictions with 3" DP/MP combo's. Out of interest, what have people been pushing as a max on 3" DP/MP? Quote Link to comment Share on other sites More sharing options...
mark newman Posted July 11, 2012 Share Posted July 11, 2012 There are power restrictions with 3" DP/MP combo's. Out of interest, what have people been pushing as a max on 3" DP/MP? I have the 3'' bhp is around the 900 bhp Quote Link to comment Share on other sites More sharing options...
hodge Posted July 11, 2012 Author Share Posted July 11, 2012 Just to clarify, what's the difference between a resonator and a silencer? Quote Link to comment Share on other sites More sharing options...
hodge Posted July 11, 2012 Author Share Posted July 11, 2012 I have the 3'' bhp is around the 900 bhp Does your turbo have a 3" outlet Mark? I think the restriction issue is when you have say a 4" outlet and reduce down to 3", and get a bottleneck effect. Quote Link to comment Share on other sites More sharing options...
Luxluc Posted July 11, 2012 Share Posted July 11, 2012 Does your turbo have a 3" outlet Mark? I think the restriction issue is when you have say a 4" outlet and reduce down to 3", and get a bottleneck effect. Yes John. Mark and myself are running the same turbo. It comes with a 3" flange on the turbo. I think Jamie (P) has to got a 3"-4" adaptor to get his new turbo (which came with a 3" flange too) connected to the 4" MP. I guess the other way round (bottle-neck) would severely reduce the flow and limit the power and torque considerably. Quote Link to comment Share on other sites More sharing options...
hodge Posted July 11, 2012 Author Share Posted July 11, 2012 Ahhh ok, cheers Luc Anyone else found there power restricted by there exhaust and what setup were you using at the time? Quote Link to comment Share on other sites More sharing options...
Guest ugp Posted July 11, 2012 Share Posted July 11, 2012 Just to clarify, what's the difference between a resonator and a silencer? Silencer kills the noise without blocking flow. Glass packs and motorcycle exhaust. The flow goes through UNBLOCKED, but the air pressure wave gets delayed by the holes inside the pipe. (Just like the gun.) Resonator, the pipe gets wide then narrow. The air wave speeds up, low pressure, at the wide spot then slows back down, high pressure, when leaving. Less vibrations and at a lower pitch. (Found on late '50 and early '60 cars.) Quote Link to comment Share on other sites More sharing options...
Noz Posted July 11, 2012 Share Posted July 11, 2012 I rang up about a 4" exhaust for my car. For the new engine my plan of attack is get the breathing spot on instead of go crazy on boost. Matey said he had an m3 running 1000bhp on a 3" and that would suffice, yet I see some 3" systems on here struggle I try and look at it like wire when you have different value resistors in a circuit. With the exhaust having nothing beyong it I would imagine a 3" pipe with straight through exit would have alot less restriction through it than a 3" mid/down pipe leading into another system which is why the 4" mid/down pipe to 3" system definitely makes sense to me. 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 Quote Link to comment Share on other sites More sharing options...
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