mellonman 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". Read this http://www.mkivsupra.net/vbb/showthread.php?278633-3-quot-vs-3-5-quot-exhaust-confirmed-results&highlight=results Link to comment Share on other sites More sharing options...
Luxluc 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". What power are you aiming for? Link to comment Share on other sites More sharing options...
black_widow87 Posted March 18, 2013 Share Posted March 18, 2013 I am not hunting for power as I'm only at approx 500bhp with the 3.5" system. Just wondering if dropping to a 3" cat-back would restrict my power. Link to comment Share on other sites More sharing options...
Paul Whiffin Posted March 19, 2013 Share Posted March 19, 2013 I am not hunting for power as I'm only at approx 500bhp with the 3.5" system. Just wondering if dropping to a 3" cat-back would restrict my power. No it won't, we run 750bhp cars on 3" exhausts. Link to comment Share on other sites More sharing options...
Parry_10 Posted March 31, 2013 Share Posted March 31, 2013 I have got phr 3" dp/mp and 4 inch cat back i'm looking to make around 700hp I don't think ill have a restriction issue. If I was to change the dp/mp for 4" would it gain anymore power over the 3 inch? If not it will be pointless me changing it as it will just make it louder and give less ground clearance. Link to comment Share on other sites More sharing options...
Rob_Mitchell Posted March 31, 2013 Share Posted March 31, 2013 A inch is alot when it comes to making a system breath/flow better. 4" full system sounds incredible BUT i do have stupid clearance issues with the custom 4" downpipe and midpipe as my boostlogic exhaust hangs mega low. Your be fine on the 3" downpipe and midpipe for 700bhp, i only went 4" as a bargain came up. Link to comment Share on other sites More sharing options...
Slutters Posted March 31, 2013 Share Posted March 31, 2013 I went for 4 inch downpipe into 3 inch for the rest. The gases only need to expand, in the downpipe once they are in the mid/rear section they begin to contract so they do not need the 4". Just going on what a friend of mine told me and the fact the there's a few 750HP cars on a 3 inch system. I think the big thing is making sure you don't have compression bends as these further reduce the pipe size. Anyway, heres mine: You can see the bottom where it goes to 3 inch here: Mid pipe 2.5 inch compression bend vs man 3 inch with added flexi and one final showing off picture Link to comment Share on other sites More sharing options...
Parry_10 Posted March 31, 2013 Share Posted March 31, 2013 cheers guys I know the 3" dp/mp is fine for 700hp and it is made by power house racing so I know it will be a good exhaust but I'm wondering if I change to 4" will I make more power than I would have and maybe the temps will be lower. Basically if it is going to be a benefit in anyway I would rather change now while I am in the middle of building the car rather than later on. Link to comment Share on other sites More sharing options...
Parry_10 Posted April 1, 2013 Share Posted April 1, 2013 anymore input on the above? Link to comment Share on other sites More sharing options...
supra steveo Posted April 1, 2013 Share Posted April 1, 2013 Subscribed, I am about to get all the mild steel pipe work cut off my HKS super drager and have it all replaced with stainless steel , just one question tho, if I don't have resonators put in will this damage my engine ? ( Well 2 questions ) Also if at the end of the second cat I have my apexi EVC butterfly valve to shut off the noise will that damage the turbos ? I put that in as the HKS sounded off at 93Db and that won a £30 ticket from the old bill when it was an N/A, the car is loads quieter now as a TT Link to comment Share on other sites More sharing options...
Paul Whiffin Posted April 2, 2013 Share Posted April 2, 2013 cheers guys I know the 3" dp/mp is fine for 700hp and it is made by power house racing so I know it will be a good exhaust but I'm wondering if I change to 4" will I make more power than I would have and maybe the temps will be lower. Basically if it is going to be a benefit in anyway I would rather change now while I am in the middle of building the car rather than later on. I'd leave it as it is, if you aren't going anymore than 700bhp there's not a lot of point. Link to comment Share on other sites More sharing options...
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