Silencer location, and Spintech v. Dynomax v. ?

[Marek]

Say the decibels are what limit the length of the jaunts in your Seven....

 

• Do I want a side or rear exit exhaust?
• Should I point the tip to the side, down, or to the rear?
• Anyone have experience with https://spintechmufflers.com ?  Either results or with fitment.

 

Currently I have a single 3" pipe (correctly sized for the 13b rotary) exiting the side of the car.  My experiment with a Supertrapp provided amusement, but failed as a solution.

[panamericano]

A turn down will spread the sound a bit.  I would guess that i you route to the rear, you would just add another silencer element there.

[MV8]

I've used a spintech many years ago before I had a better understanding of muffler design. Not a fan.

If you must use 3 inch, make a baffle insert the length of the straight section of 3 inch tube (essentially a tuneable glasspack and/or baffle that can be much more effective than a supertrap).

Make the opening in the center 2 inch. Small holes can be drilled around the edge if it isn't loud enough to suit. The insert is retained with a screw through the wall of the 3 inch tube to keep it in place.

If you want it quiet (for a rotary), transition to 2 inch at the engine in order to route out the back without losing too much ground clearance and allow tighter radius mandrel bends. Fit an oem type muffler transversely at the rear where it is not on display so much (because they are not pretty). I like Walkers. It is so tight you probably will need to cut off most of the muffler tubes for connecting the mandrel bends and butt weld.

If the side pipe uses a slip fit, the rear muffler and a baffle/glasspack insert could be used or tweaked for preference.

[speedwagon]

On my 85 NA engine I had 2ea 2" flow-masters in series and that made the noise tolerable. then I tried 2ea 3" Aero in series, not as quiet but OK until liquid fiberglass started running out the back.  Been a long process switching to the ported turbo engine, but I am planning on using the Aeros on it after making a couple of ports to stuff them with coarse steel wool.     I have also seen "holey steel" cones that can be inserted to further dampen the noise.  And I have never checked the exhaust temp. on a turbo rotary engine but my previous with high hp Corvairs was lots quieter and cooler as the turbo basically converts heat to HP. But the  "rx7club.com"  guys do not use fiberglass mufflers on the turbo cars.  Another route i am considering is blend from 3" round to 2X4 oval for the route to the rear.  It is the price one pays for having a 2 stroke engine.  john