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I was wondering, since I just put that race header on my car, would it make sense at all if I got a high-flow cat and got pipe and flanges welded on it so I could bolt it in place of my resonator on my DC exhaust? Or should it be near the front of the vehicle for some reason? Or would my car be even louder without the resonator?
I was wondering, since I just put that race header on my car, would it make sense at all if I got a high-flow cat and got pipe and flanges welded on it so I could bolt it in place of my resonator on my DC exhaust? Or should it be near the front of the vehicle for some reason? Or would my car be even louder without the resonator?
Its typically near the front of the vehicle closer to the engine is because its easier for the wires to reach where they need to go. If you put it back 3/4ths of the way where your resonator is, then you would have to run longer wires for your O2 sensors... a pretty easy fix. It owuld be a good idea to have a cat you can bolt in place like that.
Okay, I understand most of it now, thanks. But I'm wondering about the DX/LX exhaust past the down pipe. Is the pipe ID different from the EX? Is that what you mean by "keeping the stock exhaust for whatever reason," because ideally I would want an EX mid pipe and muffler? Or is the mid pipe and muffler on the EX the same ID and same specs as the DX/LX?
There's a guy selling a 1-piece 4-2-1 DC header for 120 in town. Is that a good deal? I wonder if it will line up on the 6th gens unlike the 7th gens. Then all I would need to do is shorten the mid pipe for the cat. I also found a stock EX setup on ebay starting at 20 dollars, so I may just go with that.
Oh and I also wanted to ask, can a cat be installed both ways, or is there a front and back?
Well whats the point of upgrading a header if your not going to upgrade the rest of the exhaust? I"m not sure about the ID diam of your civic's exhaust, but the exhaust pipes are pretty small- like 1.25 inches if that. You typically want to have larger exhaust pipes for better flow and performance, which is the main reason ppl upgrade the header in the first place, for better flow and performance. The main reason you would need to change it with a DX/LX is because there arent very many DX/LX specific exhausts out there to choose from, they are all LX.
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?
__________________
Quote:
Originally Posted by LogicWavelength
This thread (T.E.A.R.S.) was inspired by speedfoos. We all know about his very public and very obscene battle against his car's engine.
There's a good chance that I'm not going to answer your PM.
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?
Yeah, that's what I was wondering about. As far as the wires go, I could have just left them where they are in my race header, even though there's not a cat between them, they think there is. But I guess the cat would be pointless if it's affected by being too far down the exhaust stream.
Not so much pointless as inefficient. It will eventually reach light-off temperature, but depending on the type of emissions testing, it might not pass right away. They would have to hot test it.
__________________
Quote:
Originally Posted by LogicWavelength
This thread (T.E.A.R.S.) was inspired by speedfoos. We all know about his very public and very obscene battle against his car's engine.
There's a good chance that I'm not going to answer your PM.
Well, I'm not worried about testing, they don't do it in Michigan. I just thought maybe I should have a cat, even though I'm still probably putting out a fraction of the emissions of some vehicles.
Thanks for that info speedfoos, I had no idea about that. I figured it made more sense to have it closer, but never came across any reasoning saying it had to.
So at what point is light-off? And when you say light off, you mean any emissions codes that would come up because the cat is inefficient, would then go off because the cat is efficiently doing its job, or am I totally off on this?
And if thats the case, then why wouldnt they go ahead and put a mini cat in each of the exhaust runners, or build it into the exhaust port side of the engine some how? I'm sure there are performance drawbacks, but would this yielder less polution/ cleaner emission vehicles?
Well whats the point of upgrading a header if your not going to upgrade the rest of the exhaust? I"m not sure about the ID diam of your civic's exhaust, but the exhaust pipes are pretty small- like 1.25 inches if that. You typically want to have larger exhaust pipes for better flow and performance, which is the main reason ppl upgrade the header in the first place, for better flow and performance. The main reason you would need to change it with a DX/LX is because there arent very many DX/LX specific exhausts out there to choose from, they are all LX.
Well the point would be when you're in a situation like mine where your stock header is cracked, but you can't find a direct replacement nor have a desire to. So cheaply, I can replace it with an EX setup. Though the EX header is cast iron, if it cracks it can cheaply be replaced by a steel one.
Any way thanks for the help, I have a good idea what I will do. But other than my idea, could I redo the whole exhaust with aftermarket for under 500? Would you go with a cat back exhaust?
You could as long as you pick up some used parts to meet your budget instead of new parts. Most of the time theres just a few scrapes on them and a bolt missing- cosmetic and easy fixes. Def doable tho.
Thanks for that info speedfoos, I had no idea about that. I figured it made more sense to have it closer, but never came across any reasoning saying it had to.
So at what point is light-off? And when you say light off, you mean any emissions codes that would come up because the cat is inefficient, would then go off because the cat is efficiently doing its job, or am I totally off on this?
And if thats the case, then why wouldnt they go ahead and put a mini cat in each of the exhaust runners, or build it into the exhaust port side of the engine some how? I'm sure there are performance drawbacks, but would this yielder less polution/ cleaner emission vehicles?
Here's a good link to how a catalytic converter functions.
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-nazis 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?
__________________
Quote:
Originally Posted by LogicWavelength
This thread (T.E.A.R.S.) was inspired by speedfoos. We all know about his very public and very obscene battle against his car's engine.
There's a good chance that I'm not going to answer your PM.
You could as long as you pick up some used parts to meet your budget instead of new parts. Most of the time theres just a few scrapes on them and a bolt missing- cosmetic and easy fixes. Def doable tho.
