Track days exhaust

bigbob · Post by **bigbob** » Thu Feb 06, 2014 5:51 pm

Any ideas/experience of getting exhaust noise down to 105db for up coming track day? Running twin 2 1/2" pipes with "cherry bombs" Suspect well over 105 at present!

JAYANDSHEL · Post by **JAYANDSHEL** » Thu Feb 06, 2014 6:01 pm

I have same concerns and was going to try Supertraps, they bolt into the tail pipe and are a selection of disc's that you add or take away to tune the noise. more disc's equals more noise.
I have not bought them yet but this is my plan

pushrod · Post by **pushrod** » Thu Feb 06, 2014 7:16 pm

Whilst I'm not saying you should do this now. When I used to rally back in the 70/80's if a car failed scrutineering due to a noisy exhaust we used to shove brillo pads up the tailpipe.

Marshals had to be careful on the event as the pads often shot out of the exhaust pipe when the car passed.

Ahh those were the days - no Health and Safety back then.

Lou.

bigbob · Post by **bigbob** » Fri Feb 07, 2014 10:37 am

I did wonder about these
https://www.merlinmotorsport.co.uk/p/me ... -ex-muff-4
Look easy to fit, but not sure if reduction would be enough.

H, Sunny 65 · Post by **H, Sunny 65** » Fri Feb 07, 2014 12:21 pm

Plenty of free APP's for smart phones, out there to measure db's.
I have a couple on my phone, not measured my Tiger noise yet, but may fire it up to over the weekend to see what noise it makes.
Wire wool in a coke can with holes over end and j/clip to end of pipes works for noise reduction. .[that method a bit more you Bob, than the fancy pipes you saw]
Harry

bigbob · Post by **bigbob** » Sun Feb 09, 2014 12:59 pm

I like your style. I think a pair of large beer cans would suit better though. But worried they would create a lot of back pressure & be a bugger to fit securely. But definitely worth investigating.

Tomaselli · Post by **Tomaselli** » Sun Feb 09, 2014 6:13 pm

Good idea Harry. I will try an App on my iPhone over the weekend. To get a fair comparison needed for track day regulations, how far away do you have to be with the decibel reader, and what revs needed from the engine?

Sure I won't have a problem

JAYANDSHEL · Post by **JAYANDSHEL** » Sun Feb 09, 2014 6:28 pm

Its measured 1meter away and at 45degrees vertical from the tailpipe.
revs depend on the tester/circuit sometimes they ask for the max revs and then work out 2/3 of that or they ask for 4500.
Jay

Tomaselli · Post by **Tomaselli** » Sun Feb 09, 2014 6:30 pm

Cheers, what revs do I need. Mine is awfully quiet until about 1000 rpm

Tomaselli · Post by **Tomaselli** » Sun Feb 09, 2014 10:22 pm

OK, I have it now - 4,500 rpm will be a challenge. Couple of brillo pads in a coke can might be the fix,

pushrod · Post by **pushrod** » Sun Feb 09, 2014 10:42 pm

According to the MSA regulations:

“the sound test shall be conducted as set out within these regulations with the engine running at 3/4 maximum speed, the sound level meter at a height of 0.5 metres above the ground (± 0.1 metre) located at 45° to and 0.5 metres distant from the exhaust”.

That way the scruitineer doesn’t kop a mouthful of Brillo Pad!

Incidentally if you have a Mk1Tiger ¾ maximum is around 3500rpm.
Oh and don’t rely on one of those phone apps as they usually max out at 105db.

Lou.

bigbob · Post by **bigbob** » Mon Feb 10, 2014 10:31 am

Apparently twin turbos tend to quieten down the exhaust. Seems like a good excuse to me.

V Mad · Post by **V Mad** » Sun Feb 23, 2014 6:51 pm

Just swap the rev counter for a 4-cylinder one. Halves the revs (oh no it doubles doesnt it? Maybe a 12 cyl one then)

I could easily recal a four to make it read much lower

Re wire wool, it is so fine it might catch fire. I bought some stainless steel pan scourers at Aldi that could be be worth a try?