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505 Tech: 3" Exhaust fabrication
9-20-04
The 3" exhaust project is finally underway. After having the parts for almost 2 months i've finally got the willpower to spend some good hours under the dark oily sludge that is the bottom of my 505. It's really allot of fun. :-) Hopefully it'll pay off in one way or another. So far the one part that looks really tricky is the clearance above the rear crossmember. Hopefully that will work out... i know there's gonna be some "frustration" involved.
The bends are all 3" aluminized mandrel bends from jcwhitney.com. The muffler is an aluminized magnaflow straight through. I was impressed with the construction of the magnaflow. Since it's offset in, center out, the exhaust travels through a mandrel bent perforated tube in the middle. You can see through it if you look down the pipe, although there is of course a little obstruction because of the mild bend in there. It does a pretty good job of muffling, i had it installed on the stock system already with a reducer cone, waiting to do the full 3". The tone is a little bit monotonous but it's really really deep... could be good depending on what you're looking for. It tends to resonate in the cabin a little bit, but not too bad. When you open up the throttle it really sounds happy and free flowing. It doesn't get all that much louder, it just sounds really content reving up.
I started by mounting the cat where it should be located, this will give me a good point to work off of. I'm going cat-back to start, and to try and get that crossmember situation out of the way early. Watch me end up doing a side-exit... Hmm, it would be much easier with more tolerance for error. Look at the clearance over the crossmember. It's hard to see in the pic, but the side of the exhaust pipe is resting against the torque tube, and the crossmember, and has probably a little more than 1/4" of room to move around. I can already see that being a rattle-nightmare, not to mention a pain to put together in the first place. Getting the pipe over the crossmember with more bends welded on is not going to be easy, and might be impossible. I keep starring at the passenger side in front of the crossmember... you see why. There's plenty of room there to work with, i'd just need to find a muffler small enough. Noise would be the main issue here. Still deciding what to do..
I liked the hangers i recieved from jcwhitney. They are just generic things but allow for a little flex. I cut them down really short to fit the cat, drilled some new holes, and welded some mounts on the cat to bolt up nicely. I like the way it came out. Seems nice and strong/durable but flexible... Allot better than the hack job that some muffler shop did when they put on that cat for the previous owner. You can see the stock downpipe is still on the car in front of the cat. I lost my 10mm open end. yay.
My welds aren't that great but i'm getting better :-). I'm using flux core so it's pretty splattery and difficult compared to the one time i've been able to do a true mig weld (SO CLEAN...).
9-25-04
I ended up doing the side exit exhaust.. i was too scared of the pipe over the crossmember. So i ordered a dynomax bullet race muffler because it was the only one small enough to fit in the cubby in front of the crossmember. I figured it would be loud, but thought what the heck it's worth a try. Well, it is LOUD. I feel rather disappointed because just when i thought i was done cutting/welding pipes and laying under my car fitting them, i'm not. The car is unacceptably loud for street use. It really sounds mean... if it were a race car. Lots of pops, lots of burble, a bunch of turbo noise in the exhaust when you start rolling, lots more mid-high frequencies when it revs up compared to the stock system with no muffler. It really sounds "open," maybe because it is. Anyway, as far as performance, gtech says i shaved .2 seconds off my 50-70mph passing time... that's fairly significant, althuogh peak tq/hp numbers didn't show any improvement. That's only from one run though, so i can't be 100% sure it was accurate.
so, after driving around the block a few times, my head is POUNDING. It's really that loud. I don't think i could carry on a conversation with a passenger. Oh well, at least i have a "race setup" now :-).
So, i hacked my downpipe a few inches below the o2 sensor since i don't have any way to connect 3" piping to the turbo itself. So i had to use the top of the stock downpipe and then expand it to 3" on the way down. I fit some more pipes to connect to the cat. The routing turned out rather nicely, even though my welds were still suffering at this point. After i got the front half finished including the cat, i just had to fire it up to hear it. I recorded a couple sound clips too :-).
Sound Clips
Catalytic converter only
With dynomax bullet muffler
If you'd like to know why the dynomax bullet doesn't reduce sound levels all that much.. well i think it's pretty obvious here :-).
The next day i installed the side exit portion of the exhaust. I had to cut a little more off the pipe after the cat, and then fit an elbow toward the passenger side as you can see. By this time my welding is getting ALLOT better. It's still splattering like crazy but i never have to patch and the bead isn't nearly as ugly as before. I was lookin for an easy way to mount this thing without doing drilling and such. I ended up with some threaded rod, some nuts and washers and some creativity. It turned out nicely for a temp solution.
The finished (for now) product
Well, i think i'll take a short break before i do the rear mount and put on the magnaflow. I'm sure then the volume will be at an acceptable level. It'll be nice to drive around and not get a headache from it. But in order to get to that point, i'm gonna have to get a hell of allot of pipe sawing/welding/under-the-car headaches... I'm looking forward to that.
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