13B REW Noise readings
 

What static and drive-by noise level readings have people had with their power and exhaust combinations?

For example, before I started to completely redo it, my 350-400 rwhp 13B REW with a Racing Beat dual resonated decat and HKS Hi Power catback that made 109 dB static; with an exhaust bung it made 105 dB static and didn't trigger drive-by sensors at 92 dB (at 20m).

I ask as I'm considering my exhaust options for 350-400 rwhp road and track day use where some information could save me a lot of time, aggravation and expense. Noise regulations here in the UK are typically 102-105 dB static and 89-92 dB drive-by (at 20m) with some tracks going as low as 98 dB and 87 dB respectively; AFAIK these are substantially lower than US limits, with even Laguna Seca being a breeze compared to, say, Bedford over here.

I currently have a Racing Beat dual resonated decat pipe and Racing Beat Revi catback for normal use and a standard Mazda cat for annual inspection emission tests. I haven't built my downpipe yet and am a way off having the engine running to do my own noise tests. Both the decat and cat back are 3" tubing with a reduction to 2.5" at the flanges, leaving me with the choices of running these as they are, replacing the end sections with 3" tubing and flanges with or without buying a true 3" RX8 cat (if there is such a thing) or buying a completely new system.

My default option is to get the end sections of the Racing Beat system changed to make it a true 3" all the way from turbo to back box exit and buy a couple of exhaust bungs. However, once I change the end sections the exhausts will be hard to sell on and the exhaust tips' internal flare may make bespoke bungs expensive.

I live in Connecticut so not many options for tracks in the area but here are their regulations from their own websites or from a club website that races at that track:

• The sound limit at Thompson Speedway is 100dB(Thompson Speedway site)
• Sound limits at NHMS [...] are 99 decibels(SCDA site)
• Sound limits at [...] Watkins Glen are 99 decibels(SCDA site)
• The sound limit at Lime Rock Park is 86 decibels.(SCDA site)

So yeah not sure what you're talking about being more restrictive in the UK. We have old cantankerous people that can't stand people having a good time here as well.

Also, have you asked around on rx7club.com? I feel like there are far more REWs that are in various race configurations(including exhaust changes) there then here.

Thanks.

I have looked at RX7 (FD) sound levels but found little useful as their single exit/single muffler arrangements are quite different to the twin exit/twin muffler arrangements that I'm looking at.

Gosh, 86 dB is pretty low. My aim was to illustrate why I'm interested and don't really want to spark a debate on who has the lowest limits. Decibels are a logarithmic scale where a 10 dB increase is a 10-fold increase, so your 100 and 99 dB levels are much louder than 92.