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make sidepipe quieter ???
I had to pass the yearly tecnical inspection with my 427 Contemporary Cobra featuring sidepipes. Last year I passed the inspection with under 90db noise, but this year after installing a new cam the volume is up to 96db. Flunked the test!!!.
Have to get back in a week with a quiter car. Can anybody let me know a quick fix to quiten the exhaust temporarily (just to pass the inspection) ? Maybe putting in a pack of steel wool , but how can I fix it inside the pipe? I do not want to do any welding. Help!!! |
Good question.
How about pulling 2 sparkplug wires before the test? John |
Hmmmmm !!!!
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Eljaro,
If your side pipes are easy to take off, just get a couple of the steel baffels they make to slide inside them. They come in two, three, and four per pod I believe. Instead of screwing them in permanent just take them back out after the test. I have a friend that uses them in his Daytona Coupe and they quited it down quite a bit with no loss of performance. Ron |
Bob Putnam posted this to a similar question a while ago...
Quote:
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The only thing I will be able to get here fast is the stainless steel wool used to clean metal pans and bowls.
I can push them down the four pipes of each header and hook them up to a stainless steel wire long enough so I can pull them out again. I suspect that the pads will end up beeing pushed way into the muffler section and not come out any more. I am trying to make a little basket filled with steel wool and join it to a long hook to be pushed in from the exhaust side to engage somewhere inside perforated tube inside the pipe. That shoul hold the steel wool basket in place. I would appreciate any comment on this. One tip a friend gave me is to go to the inspections in summer when the air is hot. With hot air apparently the exhaust noise gets muffled somehow. |
Never used them but Summit racing sells cone exhaust inserts. It is marketed to lower exhaust noise. I think they are about $50 for the pair. Give summit a call or visit their website.
http://www.summitracing.com/ FYI depending on a few different factors Steel wool can Burn! If you don't believe it, touch a 9V battery to a steel wool pad! Good luck! |
Also,
Someone I know would install the metal lid of an ice tea container where the collector gasket goes. The lid had a hole cut in it to allow exhaust out but since it restricted the flow it made it quiet enough to pass inspection each year. Worth a try I guess. |
Is this an idling sound test? If you advance the ignition timing a few degrees (4 degrees or so), it will quiet it significantly. The burn is more complete before the valve opens--the new cam is probably opening the valve a shade earlier. Do not run it at or near WOT with the timing advanced though, just drive it slow to the test, then home to reset it to original value.
Radio Shack has a dB meter for around $50 if you want to pre-test. Even changing the idle speed may do it, depending on the harmonics in your exhaust system. If it's a WOT test on a dyno or something, better stuff in the steel wool! Forrest |
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Try a perforated plate both prior to the muffler and at the end of the muffler. Cut out four circles - one front back each side. They will reduce the noise considerably. Expect a medium reduction in HP but they can be easily removed. If you make the plates in a cone shape with the base of the cone the size of the inside diamater of the pipe and the cone approximately 4'' high it will reduce noise. But they will not restrict the flow as the cone shape increases the opening for gases to move through. Again use the two cones each side. I can assure you that the steel wool will burn up very quickly as I have been down that path finding rusty balls and fibres when I pulled my side pipes apart. Bernie |
Eljaro Try a set of the Vortex cones that you will find in Jegs or summit. Put them inside the opening and put 3 screws to hold them in place. The other Idea is to put an under the car exhaust system on. Your running glass packs with side pipes not straight pipes or mufflers. Try the local Gas station for inspection, maybe you can work a deal:rolleyes: ;) Rick Lake
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I had the same problem when I changed the cam. One of the local tracks imposes noise restrictions and I solved the problem with a purchase from Summit. Vortex cones, as Rick Lake suggested. They aren't cheap, but worked on my small block. (I have a Factory Five with mufflers.) They are supposed to drop the level by 3-4 db and if that isn't enough, it would be easy to add some temporary steel wool to pass the test. Note: if you plan to take them out (as I do), bend the three tabs inward or you will have a tough time getting them out. They recommend welding them in, but do come with nuts and bolts to secure them. I use one only screwed in from the back. Worked for me.
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Thanks for all the suggestions, but the cones one seemed to me the most appropiate. I had something similar in mind and so I went and made this double cone with sharp edges cut out at the perimeter. I used a film can like in the picture. I pushed this botch-up inside the pipe at the output end, and voila, less noise . Enough to pass the inspection.
Once that is over I can just pull them out with a hook, even if I partially deform them, then bent then straight again and wait to use them next year again. Stefan Pietzsch http://www.clubcobra.com/photopost/d...tMurks-med.jpg |
Eljaro, very cool idea, glad it worked!
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SIDEPIPES
I JUST REMOVED THE FIBERGLASS THAT WAS WRAPPED AROUND THE BAFFELS INSIDE OF A PAIR OF EVERETT MORRISON SIDEPIPES. MADE IT LOUDER. SOOO IF YOU PUT SOME FIBERGLASS INTO THE PIPE BETWEEN THE HEADER AND SIDEPIPE, I THINK IT WILL DO THE TRICK.
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Eljaro
I mounted Vortex Insert cones with very good results. ( http://www.secureperformanceorder.co...ore/vortex.cfm ) Regards, Walter |
Leave the sidepipes alone and put in a SB.:LOL:
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what is a SB, Toni ?
Anyway, today I pushed in those self made silencer inserts and drove slowly off to the inspection. Noise was down from 96dB to 86dB at 2500rpm, the maximum permited being 82dB. The inspector was lenient though and did give the ok. The funny thing is that once I came back home I found one of those inserts lying in the driveway. The righ side one it was. Fortunately the inspector had measured the left side only . When I came home the left insert was gone also, probably during the fast drive back home. So the cheapy noise reducers work if they stay in place. I will probably stuff them with fiberglas next time and push them into the sidepipes right at the inspection station. Or get a set of vortex at summit. |
Come on Stefan - all we have around here are big blocks & small-er ones!:D
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