...but it looks so cool!!!

Interesting muffling stories.

 

Muffling the Mazda race engine.

 

My first attempt was on a rear engined car. Why not a simple formed glass pack that had worked so well on piston engined car? Lasts about 10 miles at speed. No glass left in muffler. Sound level back above 105 Db.

 

The limit at 50 feet. Turned the curved tip tube, down at the track, had the driver lift going past the sound equipment. No problems until the last lap. The remaining shell melted into two pieces.

The rear engined car has a short system similar to the aircraft.

 

Built a muffler from .062 truck exhaust pipe, packed with Lava rock. Its heavy but really kills off the sound.

Got through the next weekend with a warning after the race. Got two hits from sound on the last two laps.

 

No Lava rock in the muffler. Center tube melted  at the inlet end.

 

Rebuilt the muffler with a piece of a house jack as the center tube. Very heavy. Replaced the Lava rock with kitchen scouring pads (the real fine stuff). Got through the weekend but no pads left in the muffler.

 

Went back to $8.00 glass packs. Two per weekend. Drop them into the dumpster on the way home.

 

For the front engined car, (full length of the car system) i used a Flowmaster (looks like a big suit case) muffler. Very good sound control. Went to Sebring. During the race the muffler swelled up like a giant pillow.

All of the many baffles were at the rear bulkhead blocking much of the flow. During the week, I rebuilt the muffler. Cut off the top. Welded in the baffles, and installed through pins of 1/2" diameter behind each baffle.

The already heavy muffler was then really heavy. I moved the rebuilt muffler to the rear of the car, behind the axle housing. I built another house jack muffler, this time about 40" long. Installed that right at the collector.

 

Got through the weekend at West Palm Beach. Center tube of the front muffler melted in two again.

 

The current muffler is huge (4" ID center tube) Very heavy, stainless all around. Filled with course stainless swarf. The headers are .140" mild steel, with a blast tube providing ambient air to the tubes. The engine is tuned to maintain EGTs below 1600 degrees. Same exhaust parts for 8 years. No problems. 

 

Mild steel is not very strong at 1600-1800 degrees. The supersonic shock waves slow to subsonic in the muffler and the pressure spikes inside the muffler, will beat it to pieces.

 

Round mufflers last way longer than flat mufflers.

 

Mild steel muffler disintegrate with out regard to shape.

 

Round and stainless works best for life length, but not sound control. Mine is just below the new 103 Db limit.

 

Flat mufflers work best for sound control, but have short lives. The Spin Tech looked like a winner with the many fins connecting the top and bottom. I would go in that direction even if I have to build a bit of streamling onto it.

 

If it is going to last a long time, it will probably be a bit heavy. Because there is no free lunch.

 

Best sound control was the Flowmaster, with a "V" shaped baffle that splits the incoming shock wave into two parts and then aims the two halves directly at each other, so as to kill off much of the sound energy while adding little resistance to flow.

 

If it isn't stainless, don't bother. Save your money.

 

The picture is the Guppy Mazda powered rear engine.

 

Lynn E. Hanover