mp5 header
- Thread starter brennan
- Start date
7
70
What?!?
Who ever told you that has no idea what he's talking about.
An after-market header will change around the plumbing of the exhaust, but you will still be able to have all emission control systems on your car. They will just be in different places.
It won't screw anything up in the engine.
Who ever told you that has no idea what he's talking about.
An after-market header will change around the plumbing of the exhaust, but you will still be able to have all emission control systems on your car. They will just be in different places.
It won't screw anything up in the engine.
freekwonder
Contributor
- :
- Datsun 510/Nissan Frontier
about the only thing that will happen, is if you get a header that removes the cat. it will set off the check engine light. and if you dont fix it. after a period of time it will put the motor in limp mode, and you will screw up your o2 sensor thats about it.
mazdamp3_18
Member
- :
- 06 gti, 06 evo IX
our car will go into limp mode after a while????? if i reset it with obd 2 will this stop it from going into limp mode....
Mine did the "limp" mode
I removed the contents of the first cat about a month ago. My O2 sensor come on immediately. About 3 weeks later, the battery light started coming on and going off. When I went in to get my oil changed, they looked at it and told me the altenator was bad. So they replaced it and it still did it. Then I told them that I hollowed out the first cat and they said that if the check engine light was on fot too long it would make the engine act funny. Since then I've wired a 100ohm resistor inline with he 2nd O2 sensor and it still does it. I'm thinking of getting the 2nd O2 sensor relocated behind the 2nd cat. I'm tired of seeing the CEL. Does anyone else have any suggestions? Please let me know.
I removed the contents of the first cat about a month ago. My O2 sensor come on immediately. About 3 weeks later, the battery light started coming on and going off. When I went in to get my oil changed, they looked at it and told me the altenator was bad. So they replaced it and it still did it. Then I told them that I hollowed out the first cat and they said that if the check engine light was on fot too long it would make the engine act funny. Since then I've wired a 100ohm resistor inline with he 2nd O2 sensor and it still does it. I'm thinking of getting the 2nd O2 sensor relocated behind the 2nd cat. I'm tired of seeing the CEL. Does anyone else have any suggestions? Please let me know.
My cat is off of my car and the CEL is on now saying catalyst is not effective. I am putting a High flow cat on my car very soon but I hvae not had any problems out of it so far and it has been 4 weeks now. I'm going to put the Catalyst on and maybe move the second O2 to behind the catalyst.
I wonder why my engine did that then. When I talked to the tech a the dealer, he said that his diagnostic computer was saying the check engine light was on because I hadn't reinstalled the air temp sensor into the custom CAI I had made. He did something to it that kept it off for almost a month. I don't know what he did though. So I went home and drilled a hole for the air temp sensor and put it in. But the CEL still comes on. I'm not sure why though. I think I'm going to go back and see if they can hook it up the the computer again to see what's causing it now.
freekwonder
Contributor
- :
- Datsun 510/Nissan Frontier
i dont know how it is on the MP3, thats how it worked on the zx2 (both have odbII). If the CEL was on for a long period of time it put the motor in limp mode (safe mod). if you dont want to worry about it here is a little trick to trick the 2nd O2 sensor. its written for a mustang, but it should work on our car also. we are going to do it to my buddies zx2, he got pissed cuase he ran a 17.7 were stock zx2 should run run mid to high 15's, and he has a i/h, msd ignition. so we are going to see if it will help.
http://www.zx2racing.com/mods/mods_mil.htm
http://www.zx2racing.com/mods/mods_mil.htm
That is exactly the info I was looking for about a month ago when I did this. I didn't even think about putting a capacitor on there. That is a great idea. I'll be doing this to my MP3 this weekend. If anyone else wants to do this to their primary cat, it was kinda worth it to empty out the first cat. I saw power gains only at the higher rpm range(5000 to 7000). But there was a noticable loss in torque at lower rpm. There was also a noticable difference in the tone of the exhaust. It was very easy to do also. Just don't cross thread the bolt on the down pipe like I did. The new stud was only $3.00 though.
rodslinger
Member
The sensor modification does work. New OBDII standards pretty much make all O2 sensor operation the same. I have done this on several cars and the light never came back on or set a hard code in the computer. The mod is for the SECOND sensor. If you do this to the first sensor, you WILL screw up operation of the car. I had my own diagram up for a while but the wire colors are probably different. I haven't been under my P5 yet to see.
I wouldnt' put both the sensors behind the cat. That is just too much for nothing. They need to have a reading before and after the cat. Or just do this mod to the rear one and you should be good. I know form experience that you lose some torque from making the 1st cat high flow. You also gain some top end hp though. It's give and take. Turbo will solve that though!
rodslinger
Member
Moving the sensors isn't going to fix anything. It will likely make it the same or worse. Especially if you move the first one. The primary sensor is to monitor exhaust A/F ratio. The second sensor is in place to monitor catalytic converter performance. If you move the first one downstream of the catalyst, you really screw up the A/F reading the ECM gets. Probably melt down a piston to boot. You move the second one and you are still going to get a CEL as the second catalyst performs a slightly different function than the first. Most cars with OBDII that upgrade to a high flow cat still trigger a CEL. Aftermarket converters don't perform the same way as OEM units. Take a look and see if any OBDII certified converters are out other than the one that came on your car. If you change or remove the primary converter, the only way to eliminate the CEL is to mod the input signal from the second sensor (which is explained in this thread) or remove the CEL lamp completely. You MUST use a CEL eliminator if you do anything to the catalyst. Make your own. It's easy. Parts are about $2 from Radio Shack.
Rodslinger is right. The first sensor needs to be prior to any catalyst, cuz its monitoring F/A mixture for the ECU. As a general rule, the further down the pipe you put it, the richer your mixture will end up. Not by enough to worry about though. So other than being before the cat, it doesnt really matter where you put it.
The 2nd O2 is just there to monitor emissions. It has no bearing on mixture control at all, just emissions monitoring. As such, its expected input to the ECU is in a very narrow band, so any change in exhaust configuration can set the CEL due to an out of spec reading from the 2nd O2 sensor. You may still be able to pass a state exhaust gas analyzer test, but youll fail for the CEL. This is the major difference between OBDI and OBDII, which is supposed to alert you to a problem with your catalyst and emissions. Ive even seen a clogged EGRV knock the 2nd sensor of spec even though the ECU didnt pick up the EGR problem.
Some states go as far as to inspect the 2nd sensor to ensure that it hasnt been removed and defeated. If you are unfortunate enough to live in one of these states, the trick installation is to remove the 2nd sensor gut it, install the necessary resistors, weld it up and reinstall it in the same bung. I recently saw these in Summits catalog for late model GM V8s. Theyre priced at like $80, which made me think about marketing the same thing for imports.
My advice is to probe the harness of the 2nd sensor with a DVM before monkeying with the exhaust. That will document a baseline for later, when you can install the necessary electronics directly into the harness and nix the 2nd sensor, catalyst and boss altogether. Thats only if you live in the right state, cuz youll still need to pass inspection. Thats one thing I love about Floida no vehicle inspections at all!
The 2nd O2 is just there to monitor emissions. It has no bearing on mixture control at all, just emissions monitoring. As such, its expected input to the ECU is in a very narrow band, so any change in exhaust configuration can set the CEL due to an out of spec reading from the 2nd O2 sensor. You may still be able to pass a state exhaust gas analyzer test, but youll fail for the CEL. This is the major difference between OBDI and OBDII, which is supposed to alert you to a problem with your catalyst and emissions. Ive even seen a clogged EGRV knock the 2nd sensor of spec even though the ECU didnt pick up the EGR problem.
Some states go as far as to inspect the 2nd sensor to ensure that it hasnt been removed and defeated. If you are unfortunate enough to live in one of these states, the trick installation is to remove the 2nd sensor gut it, install the necessary resistors, weld it up and reinstall it in the same bung. I recently saw these in Summits catalog for late model GM V8s. Theyre priced at like $80, which made me think about marketing the same thing for imports.
My advice is to probe the harness of the 2nd sensor with a DVM before monkeying with the exhaust. That will document a baseline for later, when you can install the necessary electronics directly into the harness and nix the 2nd sensor, catalyst and boss altogether. Thats only if you live in the right state, cuz youll still need to pass inspection. Thats one thing I love about Floida no vehicle inspections at all!
rodslinger
Member
You don't need to remove the second sensor to mod the signal except to modify the wiring. The resistor/capacitor combo keeps the voltage above the 450mv reference making the computer think the catalyst is doing it's job. It's the same for all OBDII vehicles. But the second O2 sensor MUST remain in place and functional. If you gut it, the mod won't work. The sensor itself is what generates the signal voltage to begin with.
All you have to do is.
1)Remove catalyst.
2)Install resistor/capacitor on sensor signal/ground wire.
I'll get proper wire colors tonight and place a proper wiring diagram tomorrow with Radio Shack part numbers.
All you have to do is.
1)Remove catalyst.
2)Install resistor/capacitor on sensor signal/ground wire.
I'll get proper wire colors tonight and place a proper wiring diagram tomorrow with Radio Shack part numbers.
