Boxster Exhaust Modifications

Exhaust systems are a compromise design, just like everything else in a car. The designers try to reduce the "backpressure" of the system as much as possible (to ensure that the exhaust flows out smoothly for more power) without allowing too much noise to escape. They also have to consider weight, exhaust temperatures, corrosion, protection against damage from debris in the road, cost, etc. Since you may not care as much about some of these issues as Porsche thinks you do, you can modify your Boxster's exhaust to suit your needs. By reducing the backpressure you can add some more power to your car's engine, though you should expect to add some more noise too.

High-Performance Mufflers

There are a number of good mufflers available for the Boxster, most of which have documented increases in power (and noise), on the order of 5-12 hp. See the "Boxster Links" page for some of these vendors. This modification is legal in the Boxster's SCCA class (any muffler is allowed as long as you don't change anything else in the exhaust system from the catalytic converter to the engine).

I replaced the standard muffler on my Boxster with an aftermarket muffler from Tech-EFX as part of my attempt to squeeze a little extra power out of the Boxster's engine. It's commonly called the "Korda" exhaust because Jeff Korda builds these. It's actually just a regular Boxster muffler that they cut open and modify internally. So the external appearance is identical except for the welding (which is on the top and out of sight), unless you buy one with the optional twin tips. And it's made of stainless steel and fits perfectly of course!

Tech-EFX claims 10 extra horsepower with the Korda. I've done a few acceleration tests with the new muffler so I could compare the performance with the stock muffler. So far it seems to have helped reduce my e.t.s by a tenth of a second or two. And Greg Reddick posted a dyno test of this muffler that seems to show an 8 hp gain, measured at the rear wheels. That would be roughly 10 hp at the flywheel (which is how advertised power is measured). Seems possible.

Tech-EFX "Korda" dyno graph printout with before/after lines (measured at the rear wheels of course). Sorry about the poor quality.

I like the sound a lot, though I know that it won't please all the people all the time (and even I sometimes find it a little annoying). It sounds deeper and slightly louder at all times, but at certain speeds and throttle positions it is virtually unchanged. This muffler mostly seems to have affected noise during medium throttle at rpms below 3000 which wasn't what I expected. At engine speeds below 2000 rpms it is noticeably louder and deeper, and burbles a bit. Between 2000 to 3000 rpms, especially at moderate throttle positions, it is significantly louder, and sometimes it starts to "buzz" to the point where you get that "bee-in-the-ear" feeling. The buzzy sound once actually set off the alarm in a minivan I passed at low speeds! I know this makes it seem that it must be much louder, yet it isn't somehow. And I really like the sound, especially at full throttle; it sounds really good without losing any of that great howl that the stock muffler provides, but is deeper. I love to get on the gas in tunnels and under overpasses!

Exhaust "Headers"

These are an improvement over stock exhaust manifolds in that they are usually "equal-length" manifolds... that is, each tube running from its respective exhaust port in the cylinder head to a collector is the same length. That length can be chosen to favor a specific rpm range of the engine so that extra power is produced around that rpm range through a "ram" type of effect.

The only manufacturer of headers for the Boxster that I know of is B&B Fabrication. They sell them through Performance. They don't advertise a power increase, but I'd estimate the improvement at 10 hp or so.

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