Header / exshaust mod. questions
 

Anyone have experience with removing the primary cats and using a header? I'm wanting more power and sound from my 2000 S, but don't want to break the bank. Please share your mods and suggestions.

There's about a million posts on this, give or take one or two. Use the Search function, with "header", "exhaust", etc. What may be the forum's longest thread is on exhausts/headers:

http://986forum.com/forums/performance-technical-chat/7248-performance-exhaust-header-boxster.html

(You're welcome, Che.)

With doing some research and shopping around you can do quite a bit without breaking the bank. You might rattle it a bit along the way though.

I believe the problem with that is that the Cat needs to be close enough to the exhaust manifold to be at the right temp for the Cat to actually work. Then you also have the extra set of O2 sensors that will cause problems. You can lose the secondary rear Cats but you need a set of primary Cats attached to the header.

I have O2 sensors in my Dansk headers and extended the second O2 sensors behind the secondary cats and everything's fine. No CEL or any other problems.

You really won't get any power gains by installing header and removing the primary cats.
In order to get anything more out of the Boxster engine, you have to improve the breathing (intake) and the exhaust while at the same time you tell the car's computer what you've done (remap the ECU).

I installed a hi-flo air intake, bored out the throttle body, installed headers (only one set of cats), modified my muffler t PSE specs (45% free flow) and remapped the ECU while increasing rev limiter to 7100 rpm.
With all that my car went from 201 to about 235HP. Before I remapped the ECU but after I had installed everything listed, the only noticeable difference was "maybe" a little better low-end torque.

Happy Boxstering,
Pedro

So, Pedro after you did the mods you felt nothing, but after you reprogrammed the ECU to match the mods, you felt something? I understand the concept, just trying to understand your post better.

Thats pretty funny Pedro,I have these 3 mods without my ECU remapped and gained nearly 30HP on the dyno. You may check my dyno results for proof.I put 209HP and 172TQ to the wheels. With a 15% loss thats about 246HP to the crank and 246 minus 217 equals 29HP gain.

An ECU remap isn't required to get at least some gain. The stock map contains enough data to accomodate the greater flow from even headers alone. I didn't get mine remapped until about a year ago, but had headers for at least 4 years. Frankly the remap did not boost power much, but helped with throttle response. I think the intake made a bigger difference. But headers are the biggest bang for the buck on this car. The stock manifolds are so very restrictive.

I don't doubt your results and you shouldn't doubt mine either.
I have a '98 2.5 non e-gas car.
The ECU in the 2.7 may have the latitude to relearn your mods, not so the 2.5.
Happy Boxstering,
Pedro

Pedro, I think the only reason anyone doubted you is because you made a blanket and general statement as to Boxsters in general. You did not qualify your original comment with that you have a 1998 2.5 non e-gas engine.

I think the difference between you two has to do with the difference between Pedro's 5.2.2 DME and rule1's 7.2 DME... the 7.2 is much more capable...

pedro - i have two questions for you. to what diameter did you bore the throttle body and who did you use to tune your ECU? at 94HP / L, i think you're at the limit of what the 2.5 can do without head work or forced induction.