Agreed, that's my general answer. ;) And indeed it does work on a street car. I find it hilarious when people remove the carpets and stereo out of their daily driver to save 20 lbs.

If you race though, I see your point completely. If you want to be competitive, you need an edge wherever possible. If that's the case, the best parts are often not bought, they are fabricated. In this case, you could build a light weight exhaust system. In fact I started to mention this in my previous post, but I've got a feeling you are looking for "where can I buy a PNP exhaust" rather than the best. The best will not be bought anywhere. You'll have to build it yourself or have a fabricator build it. Something like thin wall stainless would be light and durable. I built my exhaust. It's about as heavy as the stock exhaust, but it's all 3" and very quiet.

I dunno about NB's being a pig though. My base model is 2200 stock IIRC, and around 2150-2200 right now turbocharged. I haven't done anything too radical by any means. Still carry a spare, still have all the creature comforts, etc. NA's aren't that much lighter....

FWIW, I ran open downpipe for a while, it was too loud for my taste but not unbearable. I bought a 2.5" resonated testpipe for a 93-97 323/MX3/626 off ebay for $7 and it bolted up perfect. It really quieted the car down a lot. Our local autocross is pretty strict w/ sound limits and I didn't have any problem. It wouldn't pass a visual check for a cat but might keep it quiet enough that you wouldn't get harassed in the first place.

Link to testpipe: eBay Motors: 93-97 323/MX3/626 Racing High Flow Cat Resonator 94 95 (item 120362683353 end time Feb-11-09 11:46:29 PST)

I have no affiliation w/ the seller, but quality seemed good and price is excellent.

Pat - I think the two big reasons I am considering the idea proposed in this thread are that first, no pipe is going to be lighter than any pipe, so eliminating as much as possible seems ideal, and also that for myself not only are my goals DIY but also to spend as little $$ as possible. In some areas this cannot be done and I gladly accepted the cost of getting the proper part - my mspnp for example, but in this case, grabbing a spare cat and hollowing it out completely and then welding a short 9" straight through cherry bomb muffler and turn down to that would cost a total of like.. 50 bucks, and it (I think) should perform as well if not better in terms of spool and power output than any full exhaust. And that sounds good to me. I was thinking the NB's were more in the 2300-2400 lb range, but I've been wrong once or twice in the past...

pdexta -thanks for that idea. On that note, does anyone have any input on wether these resonated straight through type deals with all the little holes inside has any negative effect on airflow through the pipe for a turbo compared to just say, a pipe? The glasspack I am considering has this same resonated design.
http://209.200.64.237/images/auto/6756.jpg

-Ryan

nope it won't hurt flow. unless it's smaller diameter than your DP or you stick your weiner in it.

too bad.. I so enjoy the hot exhaust gas 'blow' job

OK, pulled the exhaust and cat off and drove around open downpipe...

NOPE! That's not going to work! Hahaha it is wayyyy too loud and the whole car vibrates all the time. If this was strictly a race car exclusively for the track it'd be dope...

Ok, so I am going to try to find a cheap as hell aftermarket cat in 2.5" in/out for the miata - does anyone have a suggestion on where to get one? Cheap as hell b/c then I won't feel bad gutting it...

Then I'm going to get flanges, a glasspack, and a turn-down tip from summit and weld this all in the order of downpipe -> cat -> glasspack -> turn down right before the rear axle...

-Ryan

Ya summit usualy has some really cheap ones in any configuration you want. Ive got a 3" and it doesnt seem to dog my spool that i can tell.

That's a resonator in the picture. A glasspack will dampen sound waves more than a resonator but they only last 1-3 years. I have 3 very long louvered glasspacks under my car for exhaust pipe, and then a straight thru magnaflow muffler. I cranked the car and ran it a few times with an open downpipe and with 3 glasspacks only. The glasspacks alone probably reduce the volume you hear by 20%. That's some, but not a ton. I mean, just a piece of pipe to the rear where the glasspacks stop would help 8% probably. So they're worth it for me. Main reason I used them is because they filter out higher frequencies more as to make it less raspy. My exhaust is very very deep and "different" than your typical 4 cylinder. But the magnaflow works very well. It makes for a larger noise % reduction than the 3 glasspacks combined. I never would have believed that until I saw it, but in my case, it's true.

There's a lot that can be done to make exhaust quiet. Turn downs often make it louder. You want at least 1' of straight pipe before it exits for maximum quietness.

But you can't have it all. You want quiet, cheap, easy, simple, light. You don't get that many choices.

lol I just don't want stupid loud - but loud is ok... quiet I don't need. You said you want 1' of straight pipe before it exits - do you mean after the muffler/glasspack or whatever? I think I can work that in just fine. The cat I'm lookin at is 12" long, then the glasspack is 16" long and then I can do about 12" of pipe before the turn down before the rear axle.

-Ryan

here's what I used to do. make a test pipe with an old cat from the junkyard. don't waste your money for a new one. cut the flanges off. beat a piece of pipe through the fuckin thing that is the right length and weld the flanges onto the pipe. you don't have to gut it cause jamming the pipe through will take care of that.
mix up a good solution of brine(realy salty water) and spray the thing down. this helps to make it rust and cover up your fresh welds. esier to pass a visual that way. I accept no responsability for this though. do it at your own risk cause the fine is pretty heavy if you get caught.

I've found everything I need except for flanges. Does anyone know where I can find a 2.5" flange for a decent price? Summit has no flanges.. the downpipe flange has ~3 1/8" from center of bolt hole to center of bolt hole.

V-bands > flanges. I know you want cheap, and I'm 100% for cheap. But I HATE flanges for exhaust pipe. FWIW, if you're trying to connect 2 pieces of pipe together, they make these cheap band clamps. Picture a huge hose clamp/ t-bolt mix that clamps over both pipes and when you tighten it, they're connected and sealed. I got one at the end of my downpipe where it connects to the rest of the exhaust. Works great, no leaks, no warping, no stipped bolts, etc. And the clamp was like 7 dollars on summit racing.

The v-bands are 3-peice kits, am I correct in assuming you weld one of the connectors onto the ends of each of the pipes you're connecting and then the clamp fits over the two?

I would still need the 2.5" flange to mate whatever I'm making to the outlet of the begi downpipe.. but a v-band between the cat and glasspack could be possible... I'm thinking maybe just weld the cat to glasspack to turndown and have the only flange be the one to the dp.. welds > v-bands > flanges ;)

i have two things going for me living in california with a modified miata:

i'm a big, dumb-looking midwestern white guy

i have greying hair.

win-win.

Try driving through Irvine in a slammed '84 Rabbit GTi with tinted windows and primer spots, holding a driver's license with a Santa Ana address. Good times.

If you run a cat and a glass pack it wont be to loud I ran with no cat and it was loud but the cat will def quiet that down a bit.

just do a side pipe in front of the rear tire. its carb legal and no worries

how the hell is that legal?

^^Who let the 'tard in?