95 dB noise limit

[Redawgleader]

Does anyone have experience with getting a Zetec or MZR to reliably emit only 95 dB during competitive racing? Using the bullet mufflers we purchased from Primus, our MZR cars were measured at around 100 dB at Rad Torque near Edmonton. No surprise there, the mufflers are very small. We participated in a sound test at Rocky Mountain Motorsports using Thrush Turbo mufflers, and the sound readings taken by RMM indicate we were in the 95 to 98 dB range. RMM has a strict 95 dB limit, and I suspect other tracks are trending in that direction. So, it seems the Thrush Turbo mufflers don't quite get there, despite being rather chunky. Wondering if there is a muffler that is more effective without being too chunky?

[BeerBudgetRacing]

Are you using a 'turn down' (or turn away) to direct the sound away from the sound station?
We use a direction adjustable 90 with the muffler.

[Redawgleader]

Are you using a 'turn down' (or turn away) to direct the sound away from the sound station?
We use a direction adjustable 90 with the muffler.

We do have 90’s. However, the sound metering folks are crafty - they have pick-ups on both sides of the track. Does aiming the 90s at the ground make a difference?

[BeerBudgetRacing]

We do have 90’s. However, the sound metering folks are crafty - they have pick-ups on both sides of the track. Does aiming the 90s at the ground make a difference?

I believe it does.
But if they are cheating, maybe straight back or 45 down would be better than aiming it at one of the pick-ups with a 90.

[Purple Frog]

Try aiming down. sound directed at wings or diffusers will be amplified.

Also... many who know where the sound station is, know when to lift.

[alangbaker]

Down here in Mission we run under a 95dB sound limit as well, so you might want to contact Ray Stec, kr 98, dillybar, or Michael Lensen on here.

They all either run or have run an FC at Mission.

I run FF Honda and for me, at shorty, SuperTrapp-style muffler from CIP1 intended for VW dune buggies has been perfect.

https://www.cip1.ca/vw-buggy-baja/ex...lers-stingers/

[Redawgleader]

We had success with noise abatement of our Elan/Mazda 2.0 cars at the first ever competitive race at Rocky Mountain Motorsports. As the RMM track had just been granted its operating certificate from the municipality and they were being monitored by the municipality for noise compliance, they asked that we take a very aggressive approach noise abatement, so they didn't get into hot water on their first day. We did have a 2" input Supertrapp baffle (without muffler) on hand in case we needed it, but we did not use it. We weren't sure how many baffles would allow for a balance between power performance (low back pressure) and noise abatement. Instead, we used a Thrush "Hush Thrush" muffler. We certainly didn't choose the Thrush for aerodynamics or esthetics. It appeared just like you might imagine - chunky and clunky. We tacked a downturn 90 onto the end for good measure, also. However ugly it was, it did achieve noise compliance. Feedback from the track said we were between 90 and 92 dB. Even after we ditched the 90 degree in a follow-on session. We did NOT notice a performance loss from the Thrush, though there may have been loss that we could not detect by 'feel'. The motor spun right up to redline under load. And we seemed to achieve about the same outcomes as we did with a small bottle style muffler on our prior outings at other tracks. The Smetaniuk team used a muffler/baffle combo from California Import Parts (CIP1) on their Zetec, but it seemed like they struggled to find the right balance between power and sound. They started aggressively (as advised by the track) with a small number of baffles but couldn't spin past about 5,500 if I recall correctly. Adding baffles improved their performance, but I don't think they found a happy balance before they ran into some other issues.