Scooter Posted August 12, 2012 Share Posted August 12, 2012 (edited) Ok following on from the thread below I went about (yesterday) removing the whole manifold and 1st cat as advised http://www.mkivsupra.net/vbb/showthread.php?274628-HELP-1st-decat-Whats-the-best-way-to-do-it all went well the 1st cat was removed ok and new decat pipe added. I had to leave one of the decat joints slightly loose to get the cast manifolds to go back on, then I did this up from below and popped the decat to 2nd cat bolts in and went out for a test drive. It was then that at anything more than cruising throttle I get a whistle/hiss, it annoyed me and I first replaced the decat to 2nd cat join with a brand new crush gasket, but no change. (fine at idle and no hiss apparent on blipping the throttle only on the road and under load does it do it) Fast forward to today when I have completely removed the manifold again, removed and refitted the 1st cat and exhaust pasted as well as the gaskets the new joints. I also changed the manifold to head gaskets for some newer ones I had in the spares bin and then refitted everything and also pasted the decat to 2nd cat join. (I'm emphasising this as I'm convinced there is no exhaust leak?) Still I have this whistle/hiss. I should say at this point that I have a stock exhaust back so things are quiet in general which obviously makes this easier to hear and it's got me annoyed!! What I'm wondering is if this is related to the decat pipe in some way and that is may pass in time once 'bedded in' (massive wishful thinking!) or that it's a characteristic of these pipes (but bar one thread I can't find and evidence of hissing)? Had a good look around the intake as well to check that was all tight and that is wasn't induction noise......... I'll appreciate any advice it will all be coming off and going back to stock next week if I can't sort it out! cheers Edited August 12, 2012 by Scooter (see edit history) Quote Link to comment Share on other sites More sharing options...
Nic Posted August 12, 2012 Share Posted August 12, 2012 A hiss/whistle under load would suggest it's on the intake side to me rather than the exhaust side, a leak on the exhaust side you'd hear a definite exhaust blowing sound at idle or when blipping the throttle. Quote Link to comment Share on other sites More sharing options...
Scooter Posted August 12, 2012 Author Share Posted August 12, 2012 it is very odd, I just fitted an old blitz filter to see if I'd disturbed something on the stock intake. Took it for a spin and it's the same (just with more induction roar as expected from the non stock intake). When I got back, from idle I built the revs up and up slowly to near 5000rpm and it was fine nothing to suggest a normal exhaust blow, a quick blip does give a little hiss/squeek but it's barely noticeable, normal driving and anything over a hint of throttle and in it comes all the way up the rev range ie it's there almost non stop, stops instantly on lift off (I say instantly as it's almost a tiny dump valve effect where you hear it for a fraction of the time after lifting off) Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.