supradanturbo Posted March 10, 2020 Share Posted March 10, 2020 I have a 4” single box exhaust on my single turbo car. My car has a crazy histall converter aswell so the car is always at 3k plus rpm when driving. The noise is most noticeable at idle and cold start. I am toying with the idea of fitting a mid box to the exhaust. 1st idea. Fitting a mid box either 6”round roughly 14” long or an oval that will fit. 2nd idea. Making a removable baffle that will fit into the end of the rear box. With multiple layers of baffling and a restriction on the outlet. Also a turn down. I know that I won’t be able to see any boost with the restrictive baffle, but it would just be for leaving home and cold start etc. Does anyone have an experience with a twin box 4”exhaust and does it make enough of a difference to be worth it ? Also the same question with a baffle? Any info would be appreciated. Quote Link to comment Share on other sites More sharing options...
Hamilton Posted March 10, 2020 Share Posted March 10, 2020 Can't help I'm afraid but I have the same exhaust and the noise level sometimes bothers me, so I'd be interested in ideas as well. Quote Link to comment Share on other sites More sharing options...
Peter P Posted March 10, 2020 Share Posted March 10, 2020 Hi mate, Not running a single (yet), but due to fit a Whifbitz 4” twin box setup shortly. Happy to give some feedback once it’s on the car if that helps? Hopefully not ages away, but thought I’d mention it. Had the same concerns over the single box option myself, hence opting for the twin setup. Whether it makes a lot of difference I’m not sure. Certainly seemed like that was the feedback from others on here. Cheers, Pete Quote Link to comment Share on other sites More sharing options...
Noz Posted March 10, 2020 Share Posted March 10, 2020 I'd fit an exhaust control valve over a baffle. Pain in the ass getting out the car. I run a 4" valve in my mid pipe. As my 4.5" exhaust system was too loud. Reduces the volume loads. Neighbours appreciated it too. I used a manual one rather than electronic. No reason why I just didnt have an electronic variant available when I needed it that moment. Quote Link to comment Share on other sites More sharing options...
Mike2JZ Posted March 10, 2020 Share Posted March 10, 2020 I've got a whifbitz twin 4'' on mine. It's still loud as hell, but compared to 4'' single its a lot deeper noise. I wouldn't go from a single to twin box if you are expecting it to shut it up. Exhaust baffle or control valve is the best way. I use a baffle personally but it is a pain Quote Link to comment Share on other sites More sharing options...
fullthrottle Posted March 10, 2020 Share Posted March 10, 2020 I went from a single box to a twin box system and it made it a lot better to drive at cruising speeds Quote Link to comment Share on other sites More sharing options...
supradanturbo Posted March 10, 2020 Author Share Posted March 10, 2020 Thanks for the reply’s. My thoughts on the twin box is it’s going to change the tone rather than the volume of the exhaust. Quote Link to comment Share on other sites More sharing options...
herbiemercman Posted March 11, 2020 Share Posted March 11, 2020 My grandson had an easy fit noise reduction baffle on his Subaru WRX Impretsa, it was well designed as you could just push it in and just turn it 20 deg and it locked in, just like a "bayonet" fitting. The car also had two MAPs for different octane fuels, not sure if this also assisted the exhaust baffle? Herbie. Quote Link to comment Share on other sites More sharing options...
Noz Posted March 11, 2020 Share Posted March 11, 2020 I can barely hear my exhaust on cruise with valve shut. Sounds loud as hell with it open. Controllable exhaust note is a very useful addition. Quote Link to comment Share on other sites More sharing options...
supradanturbo Posted March 11, 2020 Author Share Posted March 11, 2020 With the valve shut. Is the full exhaust still 4” all the way ? Quote Link to comment Share on other sites More sharing options...
Noz Posted March 11, 2020 Share Posted March 11, 2020 Not sure what you mean. My dump valve wont go off with it fully shut and power is noticeably reduced. With it shut you are turning the 4 inch into a forced surface around around gaps of the butterfly valve. It's like the power has been reduced top end by the torque improves slightly. Surprisingly. The turbo spools quicker but I cant build any power due to lack of flow through the engine. With it fully open I doubt youd notice a difference to it now. With it shut it's a big change as expected. If you want it quiet constantly even when driving a valve wont solve your issues. If it's just for late night driving or early mornings for your neighbours. Then open her up and enjoy the roar, its perfect. Quote Link to comment Share on other sites More sharing options...
Swampy442 Posted March 11, 2020 Share Posted March 11, 2020 Why on earth do you need a 4" exhaust?! A resonator would help you no end Quote Link to comment Share on other sites More sharing options...
Mo Reviews Posted March 11, 2020 Share Posted March 11, 2020 Not sure what you mean. My dump valve wont go off with it fully shut and power is noticeably reduced. With it shut you are turning the 4 inch into a forced surface around around gaps of the butterfly valve. It's like the power has been reduced top end by the torque improves slightly. Surprisingly. The turbo spools quicker but I cant build any power due to lack of flow through the engine. With it fully open I doubt youd notice a difference to it now. With it shut it's a big change as expected. If you want it quiet constantly even when driving a valve wont solve your issues. If it's just for late night driving or early mornings for your neighbours. Then open her up and enjoy the roar, its perfect. Do you have any issues with your EGT with that set up? Quote Link to comment Share on other sites More sharing options...
fullthrottle Posted March 12, 2020 Share Posted March 12, 2020 (edited) Not sure what you mean. My dump valve wont go off with it fully shut and power is noticeably reduced. With it shut you are turning the 4 inch into a forced surface around around gaps of the butterfly valve. It's like the power has been reduced top end by the torque improves slightly. Surprisingly. The turbo spools quicker but I cant build any power due to lack of flow through the engine. With it fully open I doubt youd notice a difference to it now. With it shut it's a big change as expected. If you want it quiet constantly even when driving a valve wont solve your issues. If it's just for late night driving or early mornings for your neighbours. Then open her up and enjoy the roar, its perfect. The trouble with a butterfly flap on a supra is i don't supposed its connected to the throttle pedal position?? And therefore driving with it closed will only increase engine temperatures and in the end more engine stress. The butterfly system is a good idea in theory and has been used on yamaha r1 on the exhaust side and bmw diesel cars on the inlet side all to increase midrange torque but in reality they always get removed and remapped. Edited March 12, 2020 by fullthrottle (see edit history) Quote Link to comment Share on other sites More sharing options...
Noz Posted March 12, 2020 Share Posted March 12, 2020 Do you have any issues with your EGT with that set up? Never had any warnings come up no. When I'm next out I'll see what difference it makes. The trouble with a butterfly flap on a supra is i don't supposed its connected to the throttle pedal position?? And therefore driving with it closed will only increase engine temperatures and in the end more engine stress. The butterfly system is a good idea in theory and has been used on yamaha r1 on the exhaust side and bmw diesel cars on the inlet side all to increase midrange torque but in reality they always get removed and remapped. You're over thinking it. The situations where you drive with it closed are also the same times you reduce throttle usage and desire less noise. We arent talking about drag racing with it shut dont forget. If the desire is to have the ability to reduce exhaust flow while also adjusting driving behaviour then I think it's well suited. If you want a quieter all round driving experience it's not the right choice. You can link an electronic ECV to an ecu output but let's refer back to the original request for advice which was specific events which in turn, would not see excessive driving on a closed valve. Which is counterintuitive and an unlikely combination. Quote Link to comment Share on other sites More sharing options...
supradanturbo Posted March 12, 2020 Author Share Posted March 12, 2020 As I originally stated. The use of the exhaust bung would just be for leaving home early etc. Performance reduction is not a consideration. Quote Link to comment Share on other sites More sharing options...
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