rmpage

Last week I finally got my Magnaflow cat installed by the shop I take my car to. I've been meaning to get this done for a while, as I already eliminated all other possible restrictions I could in my car's respiratory tract (CAI, header, catback for now) some time ago.



The cat I used was #54309 on the right side of this page (round one, 3" piping size). I got it from the guys that installed it for $110. It's a universal model so I paid another $50 for an hour of labor to have flanges welded on and an O2 sensor bung put in. The rear flange is a standard triangular pattern, so they had some there in the shop they used. The front flange is a proprietary Honda pattern. For this one, I took my old OE exhaust manifold, which I still had, and zapped the flange off of it with a plasma cutter and took it with me so I didn't have to fab up a new one.

The OE cat is huge, especially for the gas flow of our engine pushes (the K24 pushes a little more than 300 CFM at 7000 RPM if my math is correct). The OE cat on my 4.6L V8 Dakota was smaller than this. The Magnaflow is a lot smaller. The OE cat, if you look into one end, shows very little light through the fine mesh screens inside - just a tiny dot. I can see the outline of my hand if I wave it in front of the Magnaflow, which has much wider holes in its catalyst. Ideally I'd like to hook up each one to a blower with a pressure gauge and record the backpressure of each at a given flow rate, but I don't know if I'll get the chance to do that. Anyway, just by a minute of inspection side by side, it is easy to see how restrictive the OE cat is as opposed to the new one.

One of my concerns was avoiding a CEL. With the OE cat, the secondary O2 sensor bung is in the center of the body. This means that when the O2 sensor plugs in, it sits deep inside the catalyst itself. The bung on the Magnaflow is welded into the pipe behind the catalyst. I was afraid that the O2 sensor, normally designed to be partially obstructed by the catalyst material, would be in full exposure to the exhaust stream and would therefore read an unacceptably high level of byproducts. Thankfully this was not the case. After a day of driving, there was no CEL.

Whatever volume the engine aspirates it will need to exhale with the addition of the mass of fuel it is ingesting for combustion. This means that, if you want to give it a good amount of breathing room for not a lot of money, the catalytic converter has got to go, especially if you want to realize full benefit from your CAI/header and have your $850 catback be more than an expensive ornament that does almost nothing for performance. Yes, it is emissions-legal. One of the great things about a OBD2 vehicle like the TSX is that emissions are checked via the OBD2 port at the inspection station, not by cornholing your tailpipe with the probe. No lights = you're good to go.

I was going to wait to post this until I could do a before/after dyno and post the result, but that's going to have to wait. For now all I'll say that the power increase from this is addition gave me more than anything else aside from the Hondata reflash - way more than my CAI. Exhaust note is only a hair louder. I can think of a lot worse things you can do with $160.

Given the gains this provided I'm tempted to just say screw the cat, go for a test pipe/O2 sensor sim and see what that gives me.

Merged info with pics...

First, here is the OE cat. The left side of the pic is the side that bolts to the downpipe, facing the engine. Note how huge the cat is, and the secondary O2 sensor bung that places the sensor bulb deep inside the catalyst itself:



Front side, bolts onto downpipe. This is the proprietary Honda flange that you either must fabricate an analog of, or do like I did and use one from my old OE downpipe:



Rear side, standard 3 bolt flange:




Here is the Magnaflow installed. As you can see it is much smaller than the OE cat. It also weighs about 1/3:



Front weld:



Rear weld, secondary O2 sensor visible on distant side of pipe:

BlackTSXer

Thanks for the info!!

Triz08

nice write-up! Where did you get the cat installed? Do you think a place like meineke would install a custom test pipe??? Im very interested in doing this. Just hoping my exhuast wont get hella loud or raspy with a straight through test pipe.

kaikai114

are you planning to do a dyno?

rmpage

The shop I usually frequent did mine: www.enhancedstreetperformance.com but yeah, any muffler shop can easily do this mod for you. Or a test pipe, whatever.
Yessir. I'm going to get a back-to-back comparison, and maybe a 3-way with a test pipe too. I'm also going to get some photos. It might take a while, but I'll keep bumping this thread. JTso talked about doing this too so he might beat me to it if he gets his big bore TB project done soon.

CGTSX2004

iTrader: (1)

Nice work, rmpage. You keep this up and you're going to have to start doing engine internals soon to make more NA power.

JTso

iTrader: (2)

Nice work! I wouldn't mind seeing some actual pics of the cat setup when you get a chance, especially the welding. If you ever deicided to go with a test pipe, I would highly recommend going with a Magnaflow straight through resonator instead. It will provide the flow you want without the raspy sound of a test pipe. I had one made for my other car to replace the cat. Below is an example of what it looks like (Btw, it's not my resonator).

Triz08

That looks alot better than the last test pipe i had on my old car. I'm really considering ordering whatever that picture is of.

Now, would you happen to know where i can order one of these resonator's at. I searched the magnaflow website but couldnt find any ones to order. And do you know the right length to get to replace the factory cat. Im not to sure of how much extra length the flanges will add when they get welded on.

Any extra info is appreciated. I'd like to do this as soon as i know what im doing and ordering.

Also, i dont know if it matters but i have dc headers and comptech exhuast. Not sure if that would cause the change the size of the test pipe that will be put on.

Triz08

By the way, is it illegal for muffler shops to replace the cat with a straight through pipe? I live in florida so we dont have emisions here.

Triz08

Ok, i found the magnaflow resonator you were talking about. Heres the link for them.

Triz08

Ok, well i found a website selling the magnaflow resonators. Heres the link.

Magnaflow Resonators

It shows that that the total length from the end of the inlet to the outlet is 20", but the high flow cat that Rmpage ordered is 13" in length. That seems it would be quite too big to fit without some cutting.

If any of those resonators would work on that website, please let me know what would be the best bet to choose.

BTW, heres the link for the Magnaflow cat that Rmpage has.

Magnaflow Cat 54309

drkangel348

very good info! thanks rmpage.

sauceman

It should be, but you know, some shops just do it anyway.

I got the cat removed and replaced with a test pipe on my wife's Tercel nowhere else than ... SAAQ vehicle inspection shop (Governing body for cars in Quebec)!

Triz08

Today i replaced my cat with a high flow cat at this muffler shop. Costed 180 installed. I was talking to them for

Triz08

Today i replaced my cat with a high flow cat at this muffler shop. Costed 180 installed. I was talking to them about them about putting a resonator or just a straight test pipe in there and they all didnt think it was too great of an idea with buying an O2 simulator to avoid getting a cel. So i just ended up putting a smaller in size high flow cat in there. They put the o2 sensor on the rear of the cat on the pipe.

First thing i noticed is that my exhuast sounded different. It's a bit louder in a good way. Im impressed with the sound. Performance wise, well, i cant tell too much for sure from driving today. I was driving for about an hour and a half before i got to the shop and my in-dash temp was reading 89 degrees. So its a very hot a humid day so my car isnt running great anyways. I did notice that acceleration feels a bit different, i guess a bit more floaty is a way to explain it. I'm going to be doing some more driving later tonight and test it out better.

Overall, I think for a mod this cheap, its good bang for the buck deal. Especially if you have a header/exhuast combo.


Question to anyone: Is it possible to loose power from adding a high-flow cat or a straight through test pipe? Also, does anyone know how this swap should affect gas mileage?

JTso

iTrader: (2)

So did they cut the flanges off the original cat and weld them to the new one?

Triz08

yeah they did. They didnt even remove the flanges at all. They made it seem very easy if you have a plasma gun.

kaikai114

can somebody provide a link to the basic layout of the exhaust system. I saw another thread that someone removed the resonator? So is the catalytic convertor just 1 step before the resonator closer to the engine? I'm interested in doing this, but I'm not sure if it's legal here in Southern California?

-KC

vwong

The catalytic convertor is #3 in the picture. The resonator is the round cylinder thingy in the exhaust pipe. I think the oval can just before the "Y" is also called resonator (or is it just another muffler?).

drkangel348

Resonator is before that oval shaped muffler.

Triz08

im getting horrible exhuast vibration noises now after replacing the cat. I know exactly where its touching also. Its right after the resonator, right before the y-shaped pipe, hitting the chasis and one little lip. Any ideas of what i can put over it to dampen the metal on metal clashing?

kaikai114

So removing the resonator should only give you that vroom sound instead of any increase in performance ?

JTso

iTrader: (2)

How would replacing the cat affect that area of the pipe? Is the aftermarket cat the same length as the stock one?

jonnerd154

IBtheInstallerFuggedUp

Matell

Uh-huh, sadly it sounds that way. Hence I think I'm going to take my time and wait for JTso's expert write up once he's done his swap. It will cost more but I'm planning on getting a shop to manufacture the front flange so the replacement cat will be "plug and play". In that case if it all gets fidizzled up you can just swap back to original.

I know it doesn't help you Triz, but any aftermarket cat should be much smaller than OEM so provided everything was installed properly, and none of the rubber hangers have come away it's odd to be having clashing near the resonator.

You don't have a Cusco Type II lower bar do you?

jonnerd154

Do the flanges HAVE to be TIG welded on, or would an unshielded wire feed arc be ok too?

I have a wirefeed arc and could make my own flanges then weld it all together.

Triz08

lol i dont have that lower bar. Well i have comptech exhuast and there is a spot on the chasis, a black little lip, that sticks down in front of the heat shield. My comptech piping right behind the resonator is where this could be seen. I put some A/C piping insulation around the lip today, it fixed it so far, just hoping it wont melt. Couldnt find anything else that would stop the rubbing. Any ideas on something high heat resistant that i could put there? theres only about 1/2" of room between the pipe and the little lip that sticks down.

JTso

iTrader: (2)

Post some pics of where the problem is...

Triz08

I just got back in after driving around with the insulation where i thought the problem was and it still is rattling. Im not sure if it just melted or if the problem is elsewhere. But i do know for a fact the noise is coming from the resonator area.

Later tonight ill put my car up on ramps and try to get a few pictures in.

Triz08

well just fixed it for good. The insulation i put on did melt. Ill take a pic of the area. All i did was got a vice grip and started bending the metal around the area back and forth til it got weak enough to break off. Will post some pics of the cat and the fixed area in 30 min.

Triz08

Heres a side shot of the high flow cat.


Heres where i had to break off the metal which was causing the noise. I broke off about 1/2" of the surronding metal.

Matell

Oh dear. Don't wan't to scare you but that doesn't look good. I can't see that region under my car without jacking it, which I'll probably be doing on the weekend, but from that photo it looks like you've torn out a hole in a stiffening member.

Hopefully someone with more experience can chime in and tell you it's "all good", and I'm gladly wrong, but to my engineering mind I think

Good luck!

AZTSX

ya im going with matell on this one... I think this may have been a very bad idea

rmpage

Pics of this setup are up here: https://acurazine.com/forums/showthread.php?t=23292

EuroR_SG

What does the secondary O2 sensor actually reads? outcoming "cleaned" air from the catalytic converter? I was intending to remove the cat and was told by the garage I can't do that coz it might cause a CEL and fugged the engine's reading.

rmpage

Yes. The secondary O2 sensor reads the amount of CO and NOX gases in the exhaust. As long as they are below a set amount as determined by the ECU's programming you won't get a CEL. Disconnecting the secondary O2 sensor will give you a CEL unless you install an O2 sensor simulator such as the one sold here.

Triz08

that tearing off of that little bit of metal did absolutely nothing to my car. Its not even strong metal. If i can easyily bend and break off pieces, then theres no way if taking the weight to keep my car stiff. Its a little lip that i just tore off. Not like my car is going to explode next time i drive it.

jonnerd154

Structural supports don't have to be solid titanium to be effective.

Matell

When you attacked that member it was static, and when statically loaded probably wasn't under much load at all. However most loading occurs to components when you're driving, ie dynamic loading. That is when you'll have dynamic loads placed on lateral(horizontal) structural members. This example is not realistic, but is all I could come up with quickly that wouldn't bore or confuse people with engineering speak . For example imagine you were fitting a strut tower bar to your car. When the cars horizontal and not moving on your garage floor it's a cinch, however if you to try to install it while the car was turning a corner you wouldn't be able to as the distortion of the chassis would prevent holes that were lined up in the garage from lining up.

You probably won't feel any difference while you drive, but hitting a pot hole, taking spped bumps fast, hard cornering especially if there's an upset in the road mid corner, will all contribute to allowing stress to concentrate around the weak point of that member where you've reduced its cross section. The end result could be warping or minor buckling, to complete failure and several more inches of compression of the rear passenger area in the event of a side impact.

If your happy with it, leave it as is. Otherwise forget the rice and fix the cause not the symptom. Have your exhaust system adjusted so it clears that area, and take you car to a good smash repair shop where they should cut out the damaged portion of the web, re-weld in a new section, and also weld a doubler over the new section.

I'm not shitting you or trying to make you paranoid as I'm a structural engineer on a fast jet military platform and would hate to have seen anybody unknowingly do something detrimental to their car although minor for the sake of a little bit of noise from the exhaust and the perception of a few more ponies that will never be of any use.

EuroR_SG

Hey thanks Rmpage. But I'm kinda confused with the variety of MIL eliminators in the market. I've seen from some forums that some of them don't really work. Had any our of forumers tried any of them? Any reliable ones to recommend??