johny Posted April 15, 2023 Report Share Posted April 15, 2023 Ive just bought one of these to stuff up my Vitesse tail pipe! Well I get popping and banging plus although not a sports system it could be quieter so Im hoping this will help. Standby for the result... Link to comment Share on other sites More sharing options...
Pete Lewis Posted April 15, 2023 Report Share Posted April 15, 2023 popping and back pops on overun are you sure it doesnt want a bit more advance ??? that sounds a bit retarded Pete Link to comment Share on other sites More sharing options...
johny Posted April 15, 2023 Author Report Share Posted April 15, 2023 Well timing set to standard and drives beautifully but is a larger diameter mk2 exhaust bodged😁 to a mk1 manifold so no centre box. I havent checked compression so maybe valves not sealing 100% but also its a bit too noisy for me now that Im old... Link to comment Share on other sites More sharing options...
johny Posted April 15, 2023 Author Report Share Posted April 15, 2023 The item fits neatly in the tailpipe and is adjustable for back pressure which I feel is probably my issue.... Link to comment Share on other sites More sharing options...
cliff.b Posted April 15, 2023 Report Share Posted April 15, 2023 1 hour ago, Pete Lewis said: popping and back pops on overun are you sure it doesnt want a bit more advance ??? that sounds a bit retarded Pete I got popping & banging on the overrun when my vac advance unit seized up. Presume it should advance on a closed throttle but wasn't doing so. Link to comment Share on other sites More sharing options...
johny Posted April 15, 2023 Author Report Share Posted April 15, 2023 Think its partial opening that gives the advance as when cruising to improve fuel consumption. Certainly I dont get much advance if I check my dynamic timing at idle with the vac still connected. I suspect that after market SS exhausts dont have as much baffling inside as the originals did... Link to comment Share on other sites More sharing options...
johny Posted April 15, 2023 Author Report Share Posted April 15, 2023 My motorbike did the same thing (popping) when I changed from the standard exhaust to a sports one☹️ Possibly worsens fuel consumption as well because unburnt fuel gets sucked past the exhaust valves before they get a chance to close... Link to comment Share on other sites More sharing options...
cliff.b Posted April 15, 2023 Report Share Posted April 15, 2023 5 minutes ago, johny said: Think its partial opening that gives the advance as when cruising to improve fuel consumption. Certainly I dont get much advance if I check my dynamic timing at idle with the vac still connected. I suspect that after market SS exhausts dont have as much baffling inside as the originals did... I assumed it was the closing the throttle at highish revs that caused the vacuum advance just when you need it. Certainly replacing my faulty vac advance cured the popping etc on my car. Link to comment Share on other sites More sharing options...
johny Posted April 15, 2023 Author Report Share Posted April 15, 2023 It certainly does something to timing on closed throttle but thats not its purpose because many cars including some Triumphs dont have vac advance. Presumibly they dont worry about optimising cruising fuel consumption.... Link to comment Share on other sites More sharing options...
Pete Lewis Posted April 15, 2023 Report Share Posted April 15, 2023 (edited) the vac unit only works at a cruising throttle when most vac is generated from a small hole very close to the throttle plate its purely an economy device nothing to do with performance add around 4mpg to a cruise , has no effect if you drive it like you stole it shouldnt develop much at idle and nowt at full throttle if the spring inside has failed then the base plate can float about and have mind of its own changing the timing as the base position is unstable Pete Edited April 15, 2023 by Pete Lewis Link to comment Share on other sites More sharing options...
johny Posted April 15, 2023 Author Report Share Posted April 15, 2023 Makes you wonder why vac isnt used on some models or are they sports cars that probably wont do much cruising? Link to comment Share on other sites More sharing options...
Pete Lewis Posted April 15, 2023 Report Share Posted April 15, 2023 maybe on some performance cars you just cant improve the MPG ??? we have the vac unit on pretty much every bread and butter uk car built from the mid 50s Pete Link to comment Share on other sites More sharing options...
johny Posted April 15, 2023 Author Report Share Posted April 15, 2023 Ah maybe Im thinking of PI which of course is a different kettle of fish... Link to comment Share on other sites More sharing options...
NonMember Posted April 16, 2023 Report Share Posted April 16, 2023 Most of the reason the PI didn't always have vacuum advance was that the manifold vacuum is 'noisy' - it pulses something rotten and upsets the disi 1 Link to comment Share on other sites More sharing options...
Colin Lindsay Posted April 16, 2023 Report Share Posted April 16, 2023 My lawnmower did it yesterday, a couple of pops on startup after emptying the grass box, about 30 minutes into the grass cutting - never thought anything of it then there was a bang like a gunshot and the spark plug blew clean out of the engine. No damage to threads so it's just worked loose. Link to comment Share on other sites More sharing options...
mark powell Posted April 17, 2023 Report Share Posted April 17, 2023 Any result on noise reduction? Let us know. 1 Link to comment Share on other sites More sharing options...
johny Posted April 18, 2023 Author Report Share Posted April 18, 2023 Well its a perfect fit in the tail pipe and Ive used it without the central plug because I think thatll be too restrictive. Just needs a good run now.... Link to comment Share on other sites More sharing options...
johny Posted April 23, 2023 Author Report Share Posted April 23, 2023 ok well had a run out and the exhaust is definitely quieter so I'll be keeping the baffle in place. The noise at the tail pipe is more 'blowy' now as is logical with a smaller exit but the drone on long journeys is reduced such that now wind rush is the dominant source of noise which with the Viteese aerodynamics is unavoidable. Ive realised the poppin and banging which is still present, although quieter now, is only when the engines cold so is probably, as suggested, due to a weak mixture after the choke has been pushed in. Next task will be to check fuel consumption as the effect on that, if any, could be interesting... Link to comment Share on other sites More sharing options...
Iain T Posted April 23, 2023 Report Share Posted April 23, 2023 (edited) Please let us know the mpg result. Did you notice any reduction in power? Iain Edited April 23, 2023 by Iain T Link to comment Share on other sites More sharing options...
johny Posted April 23, 2023 Author Report Share Posted April 23, 2023 No its ran really well but I suppose any drop of power would only be noticed at the top end which isnt somewhere I go😊Ive had 34mpg previously on long runs (non OD and standard diff) and I'll give it another check.... 1 Link to comment Share on other sites More sharing options...
mark powell Posted April 24, 2023 Report Share Posted April 24, 2023 I'll probably invest in a couple of these for my two. Both have custom (home assembled) stainless systems... Link to comment Share on other sites More sharing options...
johny Posted April 24, 2023 Author Report Share Posted April 24, 2023 Depends on matching one to your tail pipe diameter. 48mm was perfect for mine but I'll probably remove it sometimes so that people can get the full benefit of that lovely six sound😁 Link to comment Share on other sites More sharing options...
dannyb Posted April 24, 2023 Report Share Posted April 24, 2023 Got these a few years ago for my wheelbarrow exhausts but never used. Couldn't bring myself to drill the silencer ends. I was thinking of fitting a different back box. I fancy the gt6 box with twin pipes. Thinking it will quieten it down. At the moment I wear earplugs on long journeys. Danny Link to comment Share on other sites More sharing options...
johny Posted April 24, 2023 Author Report Share Posted April 24, 2023 They will quieten it down and then if you dont like the sound you can say the 6mm hole youve drilled in each tailpipe is a condensate drain👍 Link to comment Share on other sites More sharing options...
Iain T Posted April 24, 2023 Report Share Posted April 24, 2023 (edited) 1 hour ago, dannyb said: I was thinking of fitting a different back box. I fancy the gt6 box with twin pipes. Thinking it will quieten it down. At the moment I wear earplugs on long journeys. I've fitted extra sound deadening Dodo Mat pads and albeit short journeys so far it is quieter. I phoned Phoenix and they do a single tailpipe version but he said its even louder. What he did say was he could make an inline 3.5" diameter by 12" long silencer which would quieten things down. He quoted an approximate £100. The deadening pads cost £24 which is cheaper if they work. I put them on the front bulkhead and might put the rest on the rear seat bulkhead to reduce tailpipe boom. Iain Edited April 24, 2023 by Iain T Link to comment Share on other sites More sharing options...
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