TRIZ

iTrader: (14)

Ask me your questions DX/LX header/exhaust questions!!!
This will be updated as information is needed.


First many people with DX/LX’s want to know what header will work.
First, the EX header wont bolt up to your existing stock exhaust. Second, you WILL loose your cat. Here are your header options if your cool with your peashooter exhaust and no cat:
Kamakazi – part number: ??
OBX – part number: 10-1602-3D

Will an EX header bolt up to the head of an DX/LX engine?
Yes, the bolt pattern on both the D17a1 (DX/LX) and D17a2 (EX) are the same.

So I should be all good right?
No. Just because the header connects to the head, doesn’t mean the other end of the exhaust has matched up- and let me tell you, it doesn’t. The LX header connects at a point several inches lower then the EX header does to the rest of the exhaust.

So what can I do?
You need to find some way to connect it. You have three options:

1. If you want an EX header and stock DX/LX exhaust w/o cat, then take it to a muffler shop and have them custom weld the two together. You will loose your cat of course, and you'll have to stare at the check engine light every time you drive your car because the sensors wont be taking readings they understand. To avoid this- see O2 extenders / defoulers.
   
2. If you want an EX header and stock DX/LX exhaust with a cat, buy a cat and take it to a muffler shop and they will connect the header to the rest of the exhaust and weld the cat in line. This is kind of stupid- see backpressure. You'll also run a check engine light. To avoid this- see O2 extenders / defoulers.
   
3. If you want an EX header, and an aftermarket exhaust you have two options.

• Buy a stock EX downpipe to connect to the EX header, along with some O2 sensor extension cables or defoulers. Specs: It starts off with an internal diameter (ID) of 2.00" and tapers down to 1.70" ID, finishing with an exit ID of 1.85". This is what I consider the best option if you want to avoid buying the RT downpipe (see below).
• Buy the Random-Tech downpipe from Dezod to connect to the EX header, along with some 02 sensor extension cables or defoulers. This is the best option if you cant find a EX downpipe.

What is a cat back?
Essentially this is a full exhaust from the cat converter in the downpipe on back, including the muffler, and usually includes an inline resonator as well.

What is a downpipe?
The pipe that connects the end of the header to the rest of the exhaust. This will have a cat in it. If there is no cat, it is called a test pipe- these are usually reserved for turbo applications.

Where can I get 02 extension cables?
This is where I got mine: Casper Electronics. (***link updated by admin*** and your get three dif size options for O2 extention cables) I purchased a 24-inch, and a 12-inch because there are two sensors. While I wasn’t able to, I have been told that some have been able to connect one of the first O2 sensors without the 12-inch extender cable. If you want to splice in wire to lengthen the cables thats up to you, but its creates the potential for more things to go wrong, plus the O2 sensor has a specific voltage so a change in resistance can trigger a CEL. I've also found O2 extension cables here: PasswordJDM or Club RSX

Defoulers
First off lets explain the two O2 sensors. The primary is prior to the cat and exists for air/fuel into. The secondary is after the cat and reads for a working catalyst. A defouler pulls your sensor (usually only need this for the secondary) out of the exhaust stream. This is used by people running race headers with out cats, or cats that are non-functioning. With a defouler, your ecu will not throw a CEL (check engine light). Two options are available- straight or angled. With an angled defouler the sensor will pick up less of a signal and may save you from needed an O2 extension cable under certain circumstances. For more info on how-to, check this out: https://www.civicforums.com/forums/7...simulator.html

Will an EX’s exhaust hangers need to me modified in order for them to hang from my DX/LX points?
No. Thankfully no hanger bending is required at all when putting an EX exhaust on your DX/LX. Even the original rubber donut’s are reused.

Hold on, this is going to get technical for a second

Backpressure
Backpressure is basically some sort of restriction on the air volume/exhaust coming out. A good exhaust system has the right amount of backpressure. Imagine if nobody ran an exhaust system- everyone’s car would be super loud and also yield more performance right? Wrong- they would actually loose power due to no back pressure- that’s why exhausts are important tricky little bastards.

• With more backpressure, you’ll have better bottom end (this means you’ll be able to accelerate better at low RPM’s). More bottom end is best if your staying away from the track and the strip and not driving like an idiot, or if you just want good fuel efficiency why driving in the city driving.
• With less backpressure you sacrifice bottom end for top end power. This is best if your on the track most of the time. This is best if your on the track most of the time and need power at high RPM’s.

Exploring the stock downpipe
The stock downpipe seems like its 2.25 inches thick, but its really not because its double walled which gives it the appearance that its bigger then it really is. I believe I measured it at 1.75” when I did my swap.

Whats the best exhaust diamater?
A lot of people say the max they would go with out having extensive motor work done is 2.25”, which others will say that 2” is best. The theory behind saying that 2” is best is that its .25” larger then the downpipe, which should be more then efficient.
The whole thing with exhausts is to not bother increasing one section of pipe unless the others after it are increased as well. You don’t want to have a large downpipe that goes to a small mid pipe, then to a huge muffler with a 5-inch tip. The fact is your exhaust will only be as efficient as the smallest. It’s a thin line, and without dyno sheets for both size exhausts from the same car that are tested in the same conditions, there really isn’t any factual proof that I can give you that can back this up.

Sectional exhaust piping
The sectional piping are pretty similar no matter what exhaust system your looking at, size is the only difference. Exhaust systems tend to be much louder without a cat then system with a cat. To counter act this you can purchase a silencer that sits inside the muffler outlet to restrict the sounds but can/will also restrict the air coming out. Regardless if you choose to run a silencer or not, you’re going to be polluting the earth like crazy.

“Whoa cool, a packaged deal!!”
There are a few setups offered as “packaged deals” or “all in ones.” Be weary. Many of them leave you with out a cat converter. You might be tricked to thinking there is one in the system your looking at because the manufacturers like to place a resonator in the place where the cat would traditionally go to trick you. These are called test pipe.

Conclusion
So… in conclusion don’t worry about a 2.5” exhaust unless your boosting or you figure out how to do some seriously amazing NA work. You will be ok with 2.25” piping, that’s what I have- but that’s the max I’d go with. With 2” you’ll be good and will have a little more bottom end, although you’ll get a increase in top end from the stock exhaust but also a hardly noticeable decrease in top end from what your would experience with a 2.25”. Being I am running a 1.75” to a 2.25” I can say that you’ll be fine, although I think you might get better performance if you had a 2” pipe the rest of the way back.

Additional notes:
The DX/LX exhaust has spring loaded bolts that connect the end of the header to the rest of the exhaust system; these are kind of a pain in the butt to reach but they come off eventually.

If your having trouble getting the exhaust hangers out of the rubber donuts, use a little lube that’s not corrosive to rubber, like white lithium grease that you can pick up at Napa like shops.

Jack your car up and get it on 4 jack stands so you can slide under the entire car with out any problems. Double check that the car is jacked correctly so that you don’t crush yourself.

Use extreme caution when loosening the header from the head of the engine. Use a crisscross loosening patter to prevent warping. Do not loosen one nut all the way, and move to the next, this is horrible for your head. If your having trouble loosening the nuts (which was my case), tap/hit the end of the wrench with a hammer. This is a lot better then using all your might to loosen the nuts- I cracked several sockets when trying to muscle it.

Removing your cat is illegal in most states. Also in some others modifying your exhaust is as well. Check your states requirements, before proceeding.


Questions answered:
I keep hearing that you do need an EX sway bar if you're doing an LX to EX exhaust swap, and i hear that you dont. Im doing the cat back, header, and hi-flow cat--will i need one?
You will if you are going to be using the stock cat.. but I couldnt tell you about the high flow cat- I know they are thinner so it might work, but I dont know if they are thin enough. Only way to find out is if you go and do it... if it doesnt fit, then you just need to get an ex sway or an rsx sway.


For you 8th Gen guys
This is all I got for ya. Thank FGcoupe:

On models 06-07' there is no header to mount onto the cylinder head,
instead they have changed this design using an integrated exhaust manifold.
So, this is a single 2.5" pipe with the 2-bed CAT (Closed couple catalytic converter) as part of it. You cannot remove the CAT material but other alternatives would be to purchase the WeaponR downpipe which in this case removes the CAT all together and uses a defouler to trick the CEL.

Midpipe-This is the section of piping that connects the exhaust to the CAT,
Megan Racing has a mandrel bent section to improve flow. This is bolted
to exhaust manifold with x2 springs/bolts.

ultimatetuner10

iTrader: (5)

just skimming i think you forgot one thing. the sedan bumper on our car has a small cutout at the bottom, but the coupe has a larger one. i believe coupe exhausts hang slightly higher than sedan so they sit flush with the bumper. therefore, on the sedan, a coupe exhaust will either need extended hangers, or the sedan bumper will have to be cut to accomodate the higher angle of the coupe...this is just what I heard and managed to assumingly put together in my head so double check before you put it into the main post. also, do a bit of info about o2 defoulers as we were saying in the other thread. il put this thread on my desktop and check it daily (cause i know i wont find it otherwise unless its stickied) and try to help you respond to questions

by the way
HAVING NO CATS IN MOST STATES IS ILLEGAL, AND WE DO NOT ASSUME ANY RESPONSIBILITY FOR YOUR MODIFICATIONS. THIS IS WRITTEN AS ONLY A GUIDE. PLEASE REMEMBER THAT REMOVING YOUR CATALYRIC CONVERTER IS NOT ROAD LEGAL, SO BY DOING SO YOU ARE MODIFYING YOUR SYSTEM ON YOUR OWN FREE WILL

i duno how its really supposed to sound, but i dont want someone getting a ticket for their exhaust and then trying to blame you and saying that "he told me so"

MisterFrankieJ

iTrader: (2)

The first o2 sensor doesn't need one if you stretch it. Get a 24 inch one for the second one. I got 12 and ended up having to extend it more.

speedfoos

iTrader: (17)

Easiest way to do this, like Triz said, is buy an EX header and catback exhaust.

Then go to Summit Racing and buy 2-1/4" inlet/outlet Magnaflow hi-flow cat. It's a real cat (not a test pipe), is OBD-2A compliant and costs $70. While you're there, buy a 4' length of 2-1/4" pipe ($10-12) and a 2-1/4" formed flange for $5 (P/N: WLK-31885) .

We're at $85 plus shipping right now.

Then head over to Mandrel Bending Solutions Ebay store (Click this), buy these items:
1 piece of 2-1/4" U-bend pipe - $12
1 three-bolt 2-14" flange - $4.25
1 two-bolt and 1 three-bolt gasket - $6 ($3/each)
1 oxygen sensor bung for your post cat sensor -$4
1 L-shaped hanger - $1.76

That's $33 plus shipping from Mandrel Bend Solutions. The whole new, truly 2-1/4" downpipe and real high-flow cat has just cost you $120 plus shipping for the parts. You will reuse those spring bolts already on your car.

Now take your new EX header, catback system, and box of exhaust parts to the nearest non-chain muffler shop. Point to the box of parts and the car and say, "I want all this stuff on my car, and I want all the stuff that's currently on my car put in these boxes. I'll be back in two hours, here's $150."

Go stuff some food down your gullet, have a beer, and then come back to your brand new, **** sounding exhaust.

I'll get your pics in a second Triz. I'm pissed off at the car and don't feel like going outside right now.

ultimatetuner10

iTrader: (5)

TRIZ here is defouler info

https://www.civicforums.com/forums/7...simulator.html

not done by me

speedfoos

iTrader: (17)

The cat is closer to the engine because of the cat "light-off". The catalyst element inside needs to reach a certain temperature to function properly - burning up all the contaminants in the exhaust stream - and to do this quickly, it needs to be as close to the exhaust ports as reasonably possible. The closer it is to the motor, the hotter the exhaust stream, facilitating the cat light-off. It has nothing to do with wire length.

Mr. MMA. If you are not going to do a custom exhaust setup, then you need everything forward of the midpipe section on an EX. The difference between the LX and EX - from head to midpipe (1st part of a catback system) - is that there are different components of varying length. The LX header is longer than the EX header, and as such, the LX downpipe (which goes between the header and midpipe) is shorter than the EX downpipe. Make sense?

speedfoos

iTrader: (17)

Here's a good link to how a catalytic converter functions.

http://www.aa1car.com/library/converter.htm

The light-off temperature occurs between 400-600 degrees. Copied from that link is the explanation for why a P0420 pops up.

"On 1996 and newer vehicles with OBD II onboard diagnostics, the OBD II system has a catalyst monitor to keep an eye on converter operating efficiency. The OBD II system compares O2 sensor readings upstream and downstream of the converter. If the downstream readings start to match those of the upstream O2 sensor, it indicates a drop off in operating efficiency and sets a catalyst code P0420. Other converter faults may set codes ranging from P0420 to P0439"

There is a delay built-in to account for the time it takes for a cat to reach operating (aka light-off) temperature so you don't throw a code every time you do a cold start on the car.

Be careful what you suggest on cats for every exhaust runner. The enviro-***** might think it's a good idea.... But there are a couple reasons they don't do this.

1. It's expensive to stuff the individual runners with enough catalyst material to be effective. Think of how much surface area is in that 14"x 4" cat and now figure how much of each individual runner would have to be stuffed to reach that same surface area. Not to mention how would you get in to the small runner and secure it so the engine vibrations don't just knock it loose.

2. Balance between emissions and power. It's a trade-off. Sure, if you run 8 cats in a row, your exhaust stream will be as clean as a whistle, but holy back-pressure Batman. Nissan and some other manufacturers do something similar. For instance, my 2004 Frontier has 4 (count em 4) cats. Two coming off each cylinder bank. Luckily the secondary O2 sensor is before the secondary cat so I can remove it without having to worry about tripping a code, but Nissan decided cleaner exhaust was better than more power.

Make sense?

ProjectMayhemR

iTrader: (1)

Yes it will fit into the Dx exhaust routing space under the car. The sway bar should be replaced because the Dx one rubs against the pipe and causes horrible vibration especially in the cold (personal experience). As far as the O2 sensors are concerned just get the extensions, new wiring and sensors will cost more. I did my swap for under $500 for new quality parts, but since you want a cat it will probably cost more. I would set aside $800 to $1000 for everything. Anymore questions?

sdaidoji

iTrader: (1)

I just came across this.
Thought it would be good for a visual of the system.
(credit to trustdestruction on hondacivicforums)
DX/LX/CX/HX Exhaust Layout
(please note that components in the picture may not exactly match yours in color, etc.; however, this is the same layout)



The headers available for 96-00 Civics are only made for Civic EX’s (except for one made by Magnaflow, but I am not going to talk about that because it is not as good as an EX header). Civic EX’s have a regular exhaust manifold, with the catalytic converter located directly after the exhaust manifold.

If you have an aftermarket catback exhaust on your DX/LX/CX/HX, then chances are, your catback looks like the one in the first diagram, but has a short removable ~16" section of piping, located where the catalytic converter is on the EX layout. In this case, when you get the EX catalytic converter, you just replace that short ~16" pipe with the catalytic converter. This ~16" section of piping is essentially a test pipe.

EX Exhaust Layout
(please note that components in the picture may not exactly match yours in color, etc.; however, this is the same layout)
[my personal note: illustration below have a problem: primary o2 sensor is in the downpipe, not the header!]



There’s two things you can do - a wrong way and a right way.

The wrong way:
Install the EX header onto your car, and leave the catalytic converter completely out of the equation.

This is a bad idea for a few reasons:
1. It is illegal, and if caught, you will be penalized.
2. You will throw a CEL (check engine light) and the car will run in limp mode (limited power, bad gas mileage lower rev limiter, etc.) because the secondary O2 sensor will think that the catalytic converter isn’t working, or you may not be able to hook up the secondary O2 sensor at all.
3. Instead of CO2, NOx, and H2O, your exhaust will spew out hydrocarbons and poisonous carbon monoxide gas.
4. You will fail emissions/smog/inspection/etc.
5. A test pipe gives you only ~1WHP over a high flow catalytic converter. 1WHP isn't worth breaking the law and/or failing smog.
6. You will be polluting our air even worse than it is already being polluted.

The right way:
Convert to the EX exhaust layout by installing the EX header, installing an EX catalytic converter located directly after the header, and using an O2 sensor wire harness extension to relocate the O2 sensor to it’s new location on the EX catalytic converter.
You can convert using bolt on parts designed for an EX, or you can cut and weld the exhaust parts together as needed. You can have your original catalytic converter cut off and welded directly after the header if you want. The advantage to bolt on parts is that anyone can do it themselves with simple hand tools, and different pieces can be taken apart in the future if necessary.
Any method will work, as long as the finished product has this layout:

Converted Exhaust Layout
(please note that components in the picture may not exactly match yours in color, etc.; however, this is the same layout)
[my personal note: illustration below have a problem: primary o2 sensor is in the downpipe, not the header!]



Items needed:
-EX catalytic converter
-EX header (a.k.a. exhaust manifold)
-O2 sensor extension wire harness
-EX aftermarket or stock catback exhaust (aftermarket DX, LX, CX, HX catback exhaust will work if it has the removable ~16" section that I mentioned earlier. If it doesn't have that section, the only thing you can do is cut the piping and weld the catalytic converter to the mid-pipe of the catback exhaust.)

xRiCeBoYx

iTrader: (22)

You have 2 O2 sensors in the OEM exhaust mani/cat assembly
First one is pre-cat, and that will read the exhaust gases leaving the head, and will be an input into air fuel ratio. Thread that directly into the exhaust manifold. You mess with this one, you'll get erratic AFRs and the car will likely run like crap.
Second one is post cat. This one monitors catalyst efficiency. If it reads something it doesn't like (e.g. you go catless), your car is gonna throw a P0420 code, catalyst system under efficiency threshold. If you go catless or aftermarket cat, the best way to avoid a check engine light is a mechanical O2 simulator (I'll discuss this below).

So.. you mentioned swapping in a header for a D17A, which, to my understanding, should be the same as a D17A2 -- the EX exhaust setup. If it isn't, then the rest of this post will be all for naught. lol
Here's a comparison of the two exhaust systems, via a nice little doodle I did waaaayyy back when

Your OEM D17A1 LX/DX setup is on the bottom, and the D17A2 EX setup (and presumably the D17A) is on top. The axle-back portions are identical, and everything upstream of that is different. The D17A1 exhaust manifold reaches a bit further downstream, connects to a longer B-pipe (a.k.a. mid-pipe), then connects to the axle back. The D17A2 has a much shorter exhaust manifold (header), that goes into a separate downpipe that houses the catalytic converter, then to a much shorter B-pipe, then to the axle back.

Why am I explaining all this? The biggest "hurdle" will be the O2 sensor placement (to which your post wants to address). The pre-cat O2 sensor in the D17A2 (and presumably D17A) exhaust is much further downstream, and the post cat is even further (it's physically located just about directly below the shifter assembly). Splicing wires hasn't had much luck with the D17 engines, since sensor choice is a really, really finicky thing with these engines. If it's universal, forget about it. It'll throw a code. If it's not OEM, you got like a 50/50 shot if it'll like it. More expensive OEM? It'll love it. O2 sensor extension harness are a thing, and likely the best course of action to take to get them to reach.

Now, onto the "to plug the O2 sensor bung or plug the sensor into the hole" question. We already addressed the pre-cat one. Plug that sucker directly into the pre-cat bung and call it a day. The post-cat, however, especially if you go catless, won't like it, and your car will illuminate a nice orange light on your dash. It won't affect performance, so if you don't mind the light and you don't need emissions testing, plug it straight into the pipe and call it a day. However, if you hate orange lights on your dash and need all those lights to clear to pass emissions, a mechanical O2 simulator is where it's at. I can personally attest that a mechanical O2 simulator passes OBD emissions testing (at least here in Clark County, Nevada). We don't require visual inspection for yearly check ups. Basically, it's a spark plug non-fouler screwed into the O2 sensor bung, then you screw the O2 sensor into that. It pulls the sensing portion of the O2 sensor out of the exhaust stream to trick your ECU into thinking that all is happy with regards to hippy emissions requirements. Here's a link on the forum of how to make that mechanical O2 simulator. It'll cost you a whopping $5 at AutoZone. Packaging will be different since that thread is now 16 years old, but that part number in the top left corner still works. I did it 2 years ago on my friend's Odyssey.

Now..... you mentioned an LX catback with an EX header. This kinda poses a couple problems. The EX header has zero O2 sensor bungs, since the cat is in the downpipe, and the LX catback will have zero O2 sensor bungs, as well, since the cat is integrated into the OEM exhaust manifold. The only way to alleviate this with this setup is to have a muffler shop weld in a couple of random O2 sensor bungs probably 18-24" apart along the front portion of the cat back, then O2 sensor extension harnesses to let them reach.

An alternative solution is to buy the aforementioned EX header, then mate it to an EX catted or catless downpipe, then to an EX (sedan) cat-back. Or go full on custom with whatever muffler the exhaust/muffler shop has to offer (or you bring in)

A third alternative is to find an LX header, catted or not, then mate that to your aforementioned LX catback. That'll have your O2 sensor bungs, and just do the mechanical O2 simulator on the 2nd one. If you buy a legit DX/LX cat-back, the mid-pipe should have that little kink at the end to mate to a D17A1 header.

hope this helps!

edit 1: proofreading, bc I suck sometimes.

edit 2: I should note that, once upon a time, I found a long 18mm spark plug non-fouler that fit the O2 sensor just fine, no drilling involved. It was also like $3-4. I have not seen them since. It was legit the length of 2 of the short ones (pictured in the DIY guide) screwed into each other.

edit 3: I suck a lot sometimes. Another alternative added


__________________

I would also like to go on record and apologize if this all sounds really remedial or like I'm talking down at you. That is not my intention. My intention is to spread knowledge, and to explain it so that people of every level of knowledge looking at this thread in the future with similar questions will be able to understand this without having to revive a long since dead thread.