GS400V8

iTrader: (4)

Here are the pics some of us have been curious about, and myself very curious about.
Originally looking down the muffler through the exhaust tip, I saw a perforated pipe.
I thought it was a typical good flowing two or three pipe turbo muffler loaded with fiberglass packing material.
It turns out that it has no packing material, but a series of chambers with Helmholtz style cancelation, and two small sections of isolated glass-pack style pipes.

Exhaust flow:
Chamber I -
The entry pipe dumps a lot of pressure waves into here.
It is an isolated chamber that mainly cancels sound waves. No other exhaust exits or enters here.
Chamber II - The entry pipe has perforations here, but not many.
If I had to guess what size hole is made from these, I would say 1.75" or 2.00" inches.
Chamber III - Chamber II is forced into here from the main entry. This is another sound cancelation chamber and goes out through the final exit pipe.
The final exit pipe is perforated and covered in fiberglass but shielded and sealed around it with thin metal. It is like a glass pack.
Interestingly enough, the entry pipe in chamber III has another glass pack type section in it, and is very small about 4" long.
This small section also has a few small holes in it that go into the chamber III.

I would not suggest cutting them the way I did if you plan on modifying these.
I would cut the sections out of the top where you want to modify because the chamber walls are welded to the thick inner steel shell.
I used an air hammer to break those welds, and it punches holes through the shell.

SoCal Cyco

iTrader: (20)

those look extremely restrictive...

eicca

A 2" straight pipe should prevent torque loss then...

bruceb58

Not always. For example, on Harleys, straight pipe exhausts always generate less HP and torque than when there are mufflers.

newgsman

iTrader: (4)

It might be restrictive at full throttle but it really works well for low speed response and all around driveability. I recently took my Borla mufflers off and when back to stock. I find the stock mufflers really bring to life the low speed torque of the V8. This I believe, is what Lexus wanted this car to be all about. With the stock mufflers the car is a real joy to drive through rush hour traffic because you can pass whenever you want and also maintain good gap control effortlessly by simply modulating the throttle. I recently drove a friends Tesla and I find the GS400 with stock muffler is almost as quiet and provides very similar electric motor Tesla like torque response.