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Author: Subject: Additional bolt on 2nd Silencer for track days

posted on 4/12/19 at 10:16 PM Reply With Quote
Additional bolt on 2nd Silencer for track days

Last time I was on track often I was close to the drive by noise limit, I even got kicked off Brands Indy. That was 3 years ago so I bet noise limits have crept down further since.

With no time to be in the garage I am picking off little jobs and one was a better bolt on 2nd silencer to cut the noise, I have already solved the induction noise.

I drew out a design, sourced the parts and found a welder to join it all together. He has gone off plan a little, the 180deg pieces I provided caused too much trouble and he has welded bends himself. The welding is very good but I have hesitations with how much the tight bend at the bottom will restrict exhaust gases.

Anybody in the know care to wager if it will make a noticeable difference to power, torque or max RPM?

[Edited on 4/12/19 by bi22le]

Track days ARE the best thing since sliced bread, until I get a supercharger that is!

Please read my ring story:

Me doing a sub 56sec lap around Brands Indy. I need a geo set up!

View User's Profile View All Posts By User U2U Member

posted on 5/12/19 at 10:06 AM Reply With Quote
I can't answer your question but last year I arrived at Brands for a track evening and a few of the Caterham guys from the Magnificent Sevens series (Class H, power greater than 261bhp) had been 'testing' all day ahead of the coming weekends racing. They had a very similar arrangement to what you have done to bring the exhaust noise down for the day (which was really a trackday run by Javlin).

Needless to say that evening I got pulled for too much noise on drive by. The sound tester was very accommodating and said 'go and pretend to do something to you car for half an hour and then come back for a retest' which I did, I needed to cool down anyway. I passed the (static) retest and he said just short shift for the rest of the evening He wouldn't tell me where the drive by mics are but he did say 'at the points you will be reving high' hence the clue about short shifting.

I am not convinced that it was all exhaust noise though, my intake is an open filter out the side of the bonnet. Wide open roller barrels at >6krpm it makes quite an induction roar

I now have an airbox to fit over it if/when I get pulled again and even just sat on the drive the airbox makes a noticeable difference to the noise level when revving the engine.

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