Why waste the heat from a muffler?
Here is an idea for using the heat in a muffler to charge batteries used to drive wheel hub motors in a hybrid vehicle. Water is pumped throught the muffler, turning it to steam, and driving a turbine which turns an alternator which charges the batteries through a pDC power controller. The power controller charges the batteries (in any configuration), and delivers power to the two 2000 watt hub motors in the rear wheels. Great for front wheel drive cars. Engage the electric wheels and you have power to get the beast moving, and maybe 50 or so miles on electric alone.
All using otherwise wasted heat.
Put that in your law of thermodynamics and smoke it!