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 Post subject: Exhaust
PostPosted: Sat Nov 11, 2017 5:48 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7698
Location: Hope, B.C Canada
Don't want to hijack the other post (I do that a lot by accident just answering questions) so will move the exhaust thing to here.
In a previous post very loud DG pipe type exhaust was discussed. I will cut and paste that part from the other thread and post it here.

Canadian oddy:
methodical wrote: I must say, it is much louder...much. I will need to wear ear plugs under my helmet from now on. It's not DG (lack of silencer loud) but it's close.


Hey meth you may have to make a custom muffler.
I had a formula car with a peripheral port rotary Engine. A rotary is actually a two stroke. It screamed and the exhaust was so hot you could see it glow on a sunny day as I went down the straight. Mufflers only lasted two races and I had to make my own. I did contact Jim Downing in Atlanta. He ran IMSA rotary cars. He told me if I could build a muffler to 105db that lasts and didn't create back pressure he would make me a millionaire. I did a lot of research and even bought a noise meter. Had to because the faggots would make us run 105db or we would get black flagged if over. I got a book on gun silencers and it was very helpful as well. Basically high frequency don't go around corners well. I built corners into my mufflers but this also creates back pressure which is deadly to power on a rotary. It was a give and take. You could not use packing because it would just burn out in a few laps. There were guys running very long straight through mufflers with packing that were successful but my issue was that I had a formula car and the Engine is at the back like an oddy. Not much room for a long muffler. Since our two strokes don't really run that hot that far back I bet you could use some packing to prevent "pinging" and two corners to kill the high frequencies. The most effective mufflers I ran were the non packing spiral core. I bet this would work well on the oddy.
Just a few thoughts.
This is what I basically made for my race car: http://www.jegs.com/p/Moroso/Moroso-Spi ... 9/10002/-1
One of these with a narrowed end to fit the pipe and a choked off exit. This would prevent high frequencies from escaping.

go oddy: Would mini resonator have an impact as well? Cancel out the higher annoying frequencies.
CO, I guess it's unlikely but I'll ask anyway, did anyone try that on the race circuit?
Then next question would be, does a two stroke resonator exist? Maybe touring sleds, more comfort than performance in that crowd.

Canadian oddy: Not sure about that mini resonator use on the race track. I never noticed it on any car but then again I had no time to look around and spy. I was just to busy trying to keep my car running.


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 Post subject: Re: Exhaust
PostPosted: Sat Nov 11, 2017 5:54 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7698
Location: Hope, B.C Canada
Well I just looked at some pics of resonators on the net and yes I did see those at the track a lot. They were still very loud but the piston Engine race cars were a lot quieter with those. Probably because the exhaust must go around a valve and not just dump out an open hole like a rotary Engine. The only rotaries that were successful with these were the sedan type cars (street cars) and they ran very long units. Any formula car had issues because of the restricted space. Short resonators won't work. They would probably work on an oddy but I would put a spiral in the core. A straight hole won't kill high frequency. I bet money a resonator with a spiral core would work well.


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 Post subject: Re: Exhaust
PostPosted: Sat Nov 11, 2017 5:58 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7698
Location: Hope, B.C Canada
A combination of these:


Attachments:
resonator.jpg
resonator.jpg [ 12.39 KiB | Viewed 276 times ]
spiral.jpg
spiral.jpg [ 13.77 KiB | Viewed 276 times ]
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 Post subject: Re: Exhaust
PostPosted: Sat Nov 11, 2017 6:05 pm 
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Joined: Tue Jan 17, 2012 3:19 am
Posts: 7698
Location: Hope, B.C Canada
Just in case anyone gets any bright ideas on silencers I would like to dispel some myths.
You can not "silence" a large caliber weapon that is putting out a round at super sonic speed. You can only silence a sub sonic round.
If you think you can silence your .30 cal with your captain nukem depleted uranium hollow points you are mistaken. Just have to throw that out there.
How do I know ----- don't ask.


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