Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 DB Noise Level for track days

My baffelectomy noise level was measured at 105.5db @ 4000 rpm (2/3rds) throttle.

The nice man at Croft let me on and told me where the hidden on circuit noise measuring equipment was so I could back off at the right time.

Where was the meter when they took the reading? That must have been at some distance

So it was not taken by someone inspecting the vehicle with a hand held meter? Wow, that would be what happens here if they checked. Just like emissions testing where they put a probe up the pipe.

That was very nice of the gentleman to tell you where to back off the throttle.

The usual method is to measure the noise at 45 degrees and half metre from the end of the exhaust at 3/4 max revs. The M3W does not have a red line on the rev counter so a dodge is to put an artificially low red line on the rev counter with a bit of red tape.

Thank you Rog

If conducting test to Motorsport UK regs for a circuit then yes 3/4 max rpm.
For hill climbs and sprints it is 2/3 max rpm.
Individual courses may have their own (lower) limits for non-competition days.

As Rog says, pit lane noise test 2/3rds revs (honest guv) @ 45degrees and half a meter plus on course random noise checking.

As I guess we all know, noise monitoring is not an exact science and so many things affect the final readings - weather conditions, position of the engine relative to the exhaust outlet, position of the vehicle relative to buildings, the meters themselves and indeed the operators. My Renault Spider (as I think I may have mentoined in a similar thread before) passed the Goodwood noise meter test one week at 96dB, yet failed the very next Saturday in the same place, with supposedly the same meter, but a different operator at 102dB. Bear in mind that a 3dB increase in reading is typically twice the sound pressure level, then you can see how ridiculous some testing processes are. I would never try to get anything other than a very rough idea of noise by using a different meter to the one the officials will use at the circuit. I have my own calibrated device and at 2/3's revs, 45-deg and 1/2m, readings vary from 97-102dB, so I can't even get consistency. However what I can do is put some track-day slip-on silencers onto the ends of (in my case) the G56 cans and these make a significant - and more importantly consistent - difference to the readings, with typically 3-4dB drop. I secure them with a clamp and also well hidden locating screw to keep even fussy Marshalls happy and always take them with me to a track event I do. Have only had to use them once, but well worth having in your back pocket as it were. Very little performance drop - certainly compared with being sent home

2.5" Slip-On Silencers

Great and yes that is exactly the sort of thing I was looking for