I've had the 3.4 for a little while and it just doesn't feel as strong as it did in the 996. In the 996, the 3.4 felt stronger as the rpm's went up. In the 986, it feels flat until about 3000 rpm and really kicks in at 4000 rpm. The only thing different between the 986 and the 996 are the intake and exhaust system. The 987 air box and MAF I used are very similar in size to the 996, so I don't think that's the problem. I think my problem is the factory 986 exhaust system. It doesn't take too long looking at the 986 exhaust to realize how restrictive it is. I had already gone with aftermarket headers and a Dansk sausage muffler, but I still used factory secondary pipes. Here's a picture of pipes used on the 986 and 996. (Still not using gloves!
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The smaller one is the factory secondary pipe used on the 986 and it measures only 36mm. That leads into the U pipe at 42mm which then leads into the Dansk muffler that looks to go back down to 36mmish. The large pipe is used throughout the 996 exhaust system and it is 52mm. That's a big problem to me that the 3.4 in the 996 gets these huge pipes but the 986 has these little pea shooters. I'm thinking that my power loss is because of these tiny pipes that I'm using and that leads me to my experiment. I'm going to build my own exhaust using what I have laying around. In my arsenal of exhaust parts are 996, 987 and Audi S4B5 pieces. After a lot of cutting up exhaust parts and some thinking, I ended up with this. I've gone with 52mm pipe all the way back to a modified 987 muffler. I've also eliminated the secondary 986 cat pipe. You might ask why am I using the 987 muffler? First off it's free, and secondly it uses larger pipes inside it. I didn't get a chance to measure them but I would guess it uses somewhere around 50mm tubes inside it. My main goal is flow and I think the 987 muffler can handle the 3.4. I also like the sound of the 987 muffler and it has catalytic convertors built into it. I don't live in a county that test emissions, but it makes me feel a little better that they're there.
Here's a normal 987 muffler
And here's a little taste of mine. I've got it almost complete and will post pics when I'm done fabricating
