I was looking to book my first track day at Bedford with a 101 db(A) limit.

Just tested it using an iphone app and registered 101.3dB, the exhaust has a couple of slight leaks on the joins, would 101.3db be a straight fail.
Any tips, would the couple of blows increase noise. I wont' be able to afford a new exhaust this summer so would be a bit gutting if I can't get it down.

Mike

I wouldn't rely on a phone app to be at all accurate.
If in doubt cut some strips of steel from maybe 1/2, 3/4 and an inch wide and long enough to partly cover the end of the tailpipe and back along an inch or so, plus a jubilee clip. Take it all with you, if you fail add a strip and re-test. That will quieten down an exhaust effectively and get you on track. And costs 50p.

Another though, but never tried in practice. To help with drive-by limits I have wondered about using a 90degree temporary bend at the end, pointing straight down at the tarmac rather than potentially at the detector...would that bounce sound in all directions?

I was wondering if angling down rather than horizontal would make a different to the static as well?

I have wondered that. After all the sound is usually 1m at 45degrees (or is it 1/2m?)
But if pointed at the ground, especialy dead vertical, the sound would move in all directions. Half away from the tester...
Not sure how effective it would be. One way to find out.....

Just a thought, if pointed straight down, would it not then send any oil from the exhaust down onto the road that your tyre was about to run over ?

I wondered about sending the sound under and across to the other side, but i guess it might just bounce off the road and get amplified by car and road towards where the tester might be ?

Jason

I think if you have oil coming out of the exhaust, you have bigger problems than noise

a racer trick is to get a bit of step down pipe like a reducer step down and put it inside the exhaust with the narrow end facing the engine, the fat end needs to fit snug inside the exhaust tube
its is quite effective and dosent kill too much flow i have put one inside between the 4 branch and single silencer but can usually get away without it if ts less than 100-105db

you can by them but a simple pipe offcut is much cheaper

i also got myself a 2nd hand sound meter for IVA and for checking for pre track and motorsport events