Triangle42 Posted March 23, 2021 Report Share Posted March 23, 2021 What do you use to stay under the sound requirements? (m20) Also What size exhaust seems to be the sweet spot? I'm new to the BMW seen. Thanks in advanced Quote Link to comment Share on other sites More sharing options...
Technical Advisory Committee Andrew D Johnson Posted March 23, 2021 Technical Advisory Committee Report Share Posted March 23, 2021 It depends on the track, but there are many solutions. A basic 2.5" system with turbo muffler and a resonator would be easy, economical, sound good, and have good performance. You might be able to sneak a couple more hp from 3" but it also weighs more, is harder to package, etc. Quote Link to comment Share on other sites More sharing options...
55mini Posted March 23, 2021 Report Share Posted March 23, 2021 ^^^^^^ yeah what he said but not sure I would trust a Honda driver Oh wait he has spent many hours in Nate's car as an E30 M20.............now a Honda again. Man this is getting really confusing for an old guy to keep track of. 1 Quote Link to comment Share on other sites More sharing options...
enginerd Posted March 23, 2021 Report Share Posted March 23, 2021 (edited) We used 3” tubing with a single 3”x30” cheapo cherrybomb glass pack. Starts off reasonable in noise (but I don’t know a decibel figure... we never raced at a track with monitoring). Over the course of 3 events it gets gradually louder as the glass is burned out. By the time all the glass is gone you have a deafening monster (who else was at 2019 Indy???) that would have failed sound check from a mile away (but they weren’t enforcing sound at Indy). So, this is not the route you want to go unless you like replacing mufflers frequently... I went through 3 in about 4 years. In 2018 we raced at NCM and did not have any sound violations on a new muffler. Napkin math says that a 2.5” exhaust would not be any less powerful than the 3”... I pushed for 2.5” but I have teammates who like loud exhaust and I was overruled. A quality 2.5” x 24” all stainless “glass pack” would be my choice if building it again. I don’t think that setup would fail sound check, but again, having not been called out for sound I don’t really know how loud is too loud. Edited March 23, 2021 by enginerd Quote Link to comment Share on other sites More sharing options...
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