Straight pipe/Cat. delete review...

[e9nine]

I had a severely clogged cat that was hindering the car a lot. The car was run rich for a while by the PO then me. I got a used front pipe section that had straight pipes replace the cat and boy what a noticable increase in perf. :shock: on the butt dyno and by comparison in 1st, 2nd and 3rd.

My cat. must have been the exception among bad cats that I have heard of since the diff. is so noticeable now. The car smells funny as is expected and it is noticably louder. Being that i have a new factory OEM muffler the car sounds loud, less throatier and high strung when you get on the gas. I have a univ. Catco cat. converter that I will have put on soon as I don't like how the car is loud...it has gotten noticably louder over a 24hr period so its now broken in with the muffler I guess...

One other variable is weight. You save a few lbs (didn't measure) with any aftermarket cat or straight pipes over the stock setup.

I am not yet sure on which setup to modify. Even though it will be cheaper to modify the "new" setup, I might pay extra to have the old one modified and run a resonator on the "new" one to quieten it. I'll keep the cat for inspection and other procedures :twisted:

IMHO straight pipes are best combined with an aftermarket muffler for better sounds. Straight pipes and OEM mufflers are not worth it (to me). Straight pipes can also land you in trouble with the law and whatnot...do so at your own risk

[Rob]

Great info. However, on some exhaust systems (like yours) where the cat is the major restriction, and test pipe can be beneficial even with the rest of the exhaust system remaining stock.

[SlammedE30]

Running without a catalyst rules. Here's my dyno, before exhaust, and after. I have a custom exhaust from the downpipes back, 3" piping with 2 Borla mufflers. Headers are ceramic coated and getting installed on Tuesday, dyno soon after. So we shall see what kind of a difference the headers make.


Sorry if I jacked your thread too much.
-Ted

[e9nine]

u didn't jack the thread...positive contribution towards the matter at hand is welcome... There's a lot of misconception about cat delete and I just wanted to chip in on my personal experience..

I look forward to your new graph with the headers!!

[Stu]

I represent the no-cat crowd.

I have OBD-2 stainless S50 exhaust manifolds with everything custom past that, a 2.5" pipe with a straight-through resonator and a 3" muffler. I love not having a cat. I love the smell, it kicks ass. :D The performance is great, and deleting the cat on M50's makes the sound during the VANOS changeover absolutely sweeeeeeeeet! 8)

[Rob]

ain't no VTEC though stu, and never will be :P

[Brew]

So you guys without cats........ can you shoot flames on hard shifts? :twisted:

I'm thinking about doing the no-cat, custom exhaust thing eventually. How much did you guys pay for the custom bent piping and muffler?

[rwh11385]

hmmmm, sounds sweet!

its tight not being in california for this shit! I'm in indiana and am pretty sure there are no emissions test ever here. Is there any site that gives info on State's EPA info or such? I'm assuming SC, NJ, and WA are pretty cool if Stu, Ted, and e9nine are getting away with it.

Somewhat on topic: There's a HOT chick co-worker of mine who drives a straight-piped 95 M3! Sounds means as hell. :twisted:

[SlammedE30]

My state does have emission testing, so I will have to have a catalyst fabricated when it is time for testing (every two years). I could also get a PO Box outside of town where emission testing isn't required, but I'd just rather get something fabbed up. I have not seen flames, but I am running stock exhaust manifolds right now, so maybe after the headers, but I'm betting the system is too long for the flames to come out the tailpipes. I'll post the graph as soon as I get it (Can you believe I actually have to break-in my headers! It's the coating actually, but the stuff is sweet, good up to 2000 degrees F)
-Ted

[Brew]

I remember some of the guys on e3s with m3's and no-cat saying that they sometimes saw bright flashes in their rear-view as they shifted hard at night. I'm willing to bet the 3 liter can shoot out some nice ones. Just watch that rear valence. :o

[EtaSport]

Maryland has some of the most stupid emissions laws. We have got vehicles to pass without catalytic convertors. Most notable is our v8 jeep (185k). The convertor was trash so we put a straight pipe on it, did a major tune-up and ran a mix of 30 percent alcohol/70 percent 87 octane fuel and it passed our state standards.

I ran my old fiero without a cat, and when we rebuilt the 460 in our truck we used straight exhaust.

I did find however, that the jeep ran better with a catco hi-flow convertor. I recommend these to everyone. I had one on my fiero, and we have two on our truck now. They dont restrict flow and noise very much, and help with backpressure and emissions. Best bang for the buck. I am going to try and replace the cat on my 325 with one of these when I get a chance. Just added cat back system (resonator delete) and a turbo muffler. Cat is next.

jon

[derek w]

Do you guys running w/o cats notice that your car backfires or pops when rowing thru the first 3 gears on a "spirited" run? This is a factory, but gutted cat..

[Jonathan M3]

I gained a good bit of lowend torque(+12lb/ft@2200rpms) when I removed the cat.(BAS headers w/ offroad pipe) on my previous eta. It did make the car much more raspy though, which I didn't really care for.


As for shooting flames out the exhaust between shifts, you'll need some high duration cam(s) for that. ;)

[Digitalwave]

Don't forget that even if your state doesn't have emissions testing, you can still land a VERY hefty fine for removing the cats.

[e9nine]

Don't forget that even if your state doesn't have emissions testing, you can still land a VERY hefty fine for removing the cats.

Yeah I hope not to get caught, I don't go to watch street races and don't hang in spots where you have cops pull you over to pop your hood etc. I might just add mid a resonator or the Catco sometime soon though..