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Discussion Starter #1
Background:

2007 Si Sedan/Nor Cal/Sea level.

I installed a DCRH with Strutking angled non-fouler (sp). Threw one CEL within 150 miles, reset the ECU and haven't had a CEL since. (1800+ mi).

Question(s):

Is the rich smell of my exhaust the result of not having a cat, or has the ECU ajusted my air/fuel ratio too rich?

If its becase there is no cat, I can live with it. But if the ECU has my motor running rich, can the air/fuel ratio be adjusted? Am I doing harm to my motor if too rich? Does the motor/ecu need to be tuned or adjusted after the install of a header?

Forgive me if this has been covered in another forum. I searched, but couldn't find one that addressed this particular issue.

Any insight would be helpful. :box:
 

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i believe that the odor comes from not having a cat. i read somewhere that a race header doesn't effect the afr much if any at all on the k20z3. the k20a2 needed to be tuned with a race header in order to get rid of a slight lean condition.
 

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Any car you remove the cat from will stink. There is no Catalyst to bind the harmfull chemicals to, so it spits it right out. Theres a bunch of different types of metals inside the cat like platinum, almuminum, copper, and some other high tech stuff - when you remove this, there is nothing for the "stinky" bad particles to bind to.
I'm not familiar with the non-fouler but i assume its some sort of resistor to trick the ECU?
 

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Discussion Starter #5
I'm not familiar with the non-fouler but i assume its some sort of resistor to trick the ECU?

From what I understand, the sole purpose of the non-fouler is to decrease the amount of expelled gases the secondary O2 sensor is able to detect. Thus, "tricking" the ECU into thinking there is a functioning cat still on the vehicle.

My question is this, does the secondary O2 sensor send any other information to the ECU besides simply detecting a difference between before-cat exhaust and after-cat exhaust? For instance, is the secondary O2 sensor actually breaking down the composition of the exhaust and telling the ECU to make air/fuel changes based on whatever it detects?

I must know!!!! Help me. :box:
 

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Background:

2007 Si Sedan/Nor Cal/Sea level.

I installed a DCRH with Strutking angled non-fouler (sp). Threw one CEL within 150 miles, reset the ECU and haven't had a CEL since. (1800+ mi).

Question(s):

Is the rich smell of my exhaust the result of not having a cat, or has the ECU ajusted my air/fuel ratio too rich?

If its becase there is no cat, I can live with it. But if the ECU has my motor running rich, can the air/fuel ratio be adjusted? Am I doing harm to my motor if too rich? Does the motor/ecu need to be tuned or adjusted after the install of a header?

Forgive me if this has been covered in another forum. I searched, but couldn't find one that addressed this particular issue.

Any insight would be helpful. :box:
Did you reset your ECU properly?

The smell you are smelling is a combo of the cat being gone, and the fact that your car is still adjusting to the header.

When you first reset the ECU, especially with the DCRH, your car will run pig rich, and you will smell a lot of gas. This will probably go away.

I would however get your AF ratios checked, as I myself am running a bit lean with the DCRH.

-Freq
 

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^what happens if i do not reset the ECU after installing the header?
Your car might not adjust right to the new part. Supposedly the ECU will eventually figure it out anyway, but a lot of people recommend resetting the ECU. I myself can't really tell a difference, and neither does the dyno.


-Freq
 

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Discussion Starter #9
Thanks for reply Freq. Its been 2000 +/- since install of DCRH. How long does my car need to adjust? How long after your install did the 'rich' tendancy last?

How/where do I get my A/F ratios checked?

I'm not sure I want to walk into HONDA sevice dept. and say "Hey, I just installed this race header, will you check my A/F ratio?" I'm sweatn' even goin back for an oil change with this header on.

Legal implications aside, doesn't the install of a Header compromise the warranty somehow?
 

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^Just reset the ECU after putting in a non-fouler. When I had my DCRH it smelled pretty bad with a slight fuel smell.

Your car will not change your afr based on your secondary O2 sensor. Your O2 sensor will just tell your ECU that something is not right because you have a stronger exhaust going through due to having your race header on.

The only thing that will happen is the car will throw a CEL warning you. The car will not change the AFR as a result of the CEL though.
 

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Discussion Starter #11
Your car will not change your afr based on your secondary O2 sensor.
Thank you vetkiller. I was hoping that was the case.

BTW, how do check and/or adjust AFR? Dealership only? Can you buy a special tool? Will I need to be ASE certified to understand any of this information? :box:
 

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I think a scanguage might, but you should ask those guys that are boosted because I know they have AFR guages.

No, it's pretty straight forward. I think we run around 11.5-12 stock but I could be wrong. I would just do some research online and use the search tool on here to find the right thread. I know someone posted a dyno graph for a stock si on one of the threads in here and I think it showed an AFR on the bottom for you.

I really would not worry about AFR unless you are running an aftermarket intake (other than xfactors), are boosted or have some other more invasive modification. The exhause itself is not going to do anything except help your engine exhale better.

In fact, I have a RT high flow cat (AJP versioin) and am running a CEL right now due to taking out the non-fouler that I had. I thought that I would not need it with the new cat but I guess I was mistaken. Not a big deal or a hard fix though.
 
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