Out of all my modifications, the one I really wanted to get on the most was my Koni's and SuperH's in time for the Pocono Track day... Well things did not work out, but I did manage to get my header and cat-back exhaust on.
I found a nice deal on
www.thepartstrader.com for a Mugen header and exhuast a few months ago. I was initially just going to buy the exhaust from the guy, but at the last minute, I caved and bought the header too... At first, I kinda regretted spending all that money all at once, but now I'm glad I got both.
They are used, and the guy who sold them to me had a bunch of stuff that he sent with them, like used gaskets and mounting brackets and some stuff that I still don't know what it's for... I wanted to use all new gaskets to avoid possible leaks. Special thanks to James Chan for the info he gave me on the gaskets. If anyone cares, here's what I used:
1 new stock Honda exhaust manifold gasket
2 new stock Honda o-ring gaskets between the exhaust manifold and A-pipe
1 metal ring gasket on the A-pipe to cat that looked brand new that the seller had included (this is not the same as stock)
1 new stock Honda o-ring gasket on the cat to B-pipe
1 new generic 2.25" composite o-ring from Pep-Boys - seemed to fit pretty good...
Fitment of the piping was flawless. Every flange and hanger matched up perfectly. The heat shield around the cat was too small to accomodate the larger flanges of the Mugen A-pipe and B-pipe. We had to trim about 3/4" off of each end of the cat heat shield. My friend did the cutting and it looks beautiful... You can't even tell it's been modified.
As you can see we had some issues with the placement of the primary O2 sensor bung on the King Motorsports-modified A-pipe... On the stock pipe, the hole for this O2 sensor comes out of the side at 3 o'clock - keeping the wiring out of the way of just about everything. But the O2 bung King added came almost straight up out of the top. The O2 sensor fits OK, but now its wiring comes in contact with the steering rack assembly. I was afraid that over time, it might rub through the O2 sensor wiring, so I wrapped the wiring with several layers of a high-temp Teflon tape to try to prevent this. (If anyone has any ideas to better protect this O2 wire, please let me know...)
The only other issue I had was some rubbing and grinding that was only showing up when the exhaust was heated up. There was contact in two areas. One was the axel-back flange rubbing on the corner of heat shield just in front of the rear wheel well. That was easy to fix. That heat shield bends really easily. The right corner of the flange in the pic was contacting the shield. So I just bent the one corner out a little with pliers...
The other spot that was rubbing was actually part of the unit body behind the rear bumper. This had to be bent out of the way a little too, but the metal is *much* stiffer here and difficult to get at without removing the canister. I did a half-assed job in hammering, prying, and bending it. But it does not rub anymore.
I need to go back in there and put some paint over the area soon, because I stripped a good deal of the factory coat off with my body work. You can see my handiwork right above the canister hanger in the pic...
I have no other performance mods other than the Mugen header and cat-back now. And I can feel the combo making a pretty big difference already. I wish I had had the time to put on my AEM CAI too this weekend. The motor really sounds starved for air now. The stock air intake with resonator and all now makes a wicked sucking/air-induction sound at WOT...
I think the CAI will make another huge difference once I get it put on... As it stands now, the car feels much better in the mid-range through the top-end. At the top-end, the motor feels more willing to rev than it ever did before. And if nothing else, my car *sounds* alot faster now...
The sound is different than I thought it would be. It has a nice deep tone. But maybe I'm just getting too old, but I actually think it is a little loud for my taste. It's not loud at all when you first start the car and drive for a while, but after a good deal of driving on a warm day, it gets noticably louder as it gets hot. It sounds great when the exhaust is still cold (before you drive for about 30min or so.) The low-end (1000-3400rpm) is as quiet as stock, but with a nice deeper tone. The top end (5500-7500rpm) actually sounds only a little louder than stock to me too, but again with a deeper tone. Where the sound is most noticable to me is in the mid-range (3400-5500rpm). The exhaust seems to really resonate in this range - especially when you are getting on and off the throttle in gear like if you are cruising in traffic or stopping and starting a lot. The problem is after it warms up. It's really a pretty irritating sound to me when the exhaust is hot. It resonates loudly even if I just accelerate very gingerly.
Do you think it could be an exhaust leak that only apppears when the exhaust warms up and expands? Again, it only gets really loud after a good 30-45min of driving... Wierd...
Andrew
! Like everyone else that has the Mugen, I've got rubbing problems with the heat shield on the same spots. I may just have to do some bending and hammering too, if I have time 
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