De-cat and O2 Sensor

[ItWasntMe]

I'm fitting the De-Cat tonight, but I don't have an O2 simulator. Is this going to make the EM light come on and/or any other problems?

Do I have to have a simulator or will it be alright?

 

[leejw87]

I'm fitting the De-Cat tonight, but I don't have an O2 simulator. Is this going to make the EM light come on and/or any other problems?

Do I have to have a simulator or will it be alright?

Your only gonna get the same Awnser i gave you, it might come on or it might not, you wont know until you drive it, chances are coz you havent really got any other breathing mods it should be ok, but as before if it does come on just buy a O2 Simulator or better yet stop being tight & get a K100/Kpro :xspank: :xstupid:

 

[ItWasntMe]

Oh ye of little faith eh?

Can't blame a man for asking for alternative answers!

Besides, you'd say anything to get me to mod the Teg! I just don't want to spend the evening making you fit it only for it to jump into 'Limp Home Mode' for the next few days!

It's gotta be up and running for Sunday!

You are indeed with Stupid. I'm your 'special' friend! :xwave:

 

[leejw87]

a O2 sensor wouldnt put it into limp home mode :xlol: it will just flag up a EML coz the secondary O2 will think the Cat is knackerded

 

[Stylesa]

and then it has to rely on long term adjustments from ecu, cos its no longer being fed short term adjustments as O2 sensor isnt there.

VT-Doo is your man for this sort of stuff.

 

[tricker_luke]

I recently fitted a decat and no eml came on, even when i got the car it had a decat/exhaust/intake and no kpro, and the light still wasnt on.

Is it just luck if it doesnt come on or cause problems?

 

[VT-Doo]

and then it has to rely on long term adjustments from ecu, cos its no longer being fed short term adjustments as O2 sensor isnt there.

VT-Doo is your man for this sort of stuff.

Hmmm, not quite.

OBD II engines use one O2 Sensor before the CAT and one after the CAT.
The function of the second O2 Sensor is to determine if the catalytic converter is working correctly. The ECU does this by looking at the difference between the two O2 Sensors. If the catalytic converter is functioning correctly there will be a reduction in the exhaust oxygen content as carbon monoxide and carbon dioxide is catalyzed in the CAT.

Correct, so what happens if you take that cat away and replace it with a straight pipe ("de-cat")?

IMHO the problem most people are having is with the O2 sensors. These are very sensitive and can be easily damaged, especially when changing CATs and exhausts.
Fitting a de-CAT shouldn‘t bring up a CEL if the proper care is taken not to touch the O2 sensor.

Sure if you kill your 02 sensor you get the cel, but fitting a de-cat means the second 02 sensor will get the same reading as the first one. Hence the cel people are puzzled about (the car thinks the cat is dead -> bad for the environment -> cel cel cel!).

Nice to see somebody on my wavelength

As some people have pointed out, not all ECU's will produce a CEL, at the end of the day every engine is different.

The thing to note is; the Secondary O2 Sensor does not to anything to the ECU except produce a CEL. It has no bearing on the Fuel Trims added by the ECU...The Primary O2 on the other hand...

 

[C&S Evo7]

Yep as Ian has said, primary is the one that does all the work, and the car will drive just fine with the second sensor getting the wrong signal it just put in the cel. another thing you could try is to get a sensor boss spacer. effectively this is a spacer (10mm long) that threads into the existing lambda boss and the lambda probe then threads into the spacer thus moving the sensor out of the direct flow of exhaust gas, this has worked for me in the past but i havent tried it on a honda.

 

[ItWasntMe]

The Primary O2 on the other hand...

primary is the one that does all the work

So is the Primary sensor affecting/changing anything when the de-cat is fitted then? Or is it just 'checking' the cat isn't knakered?

 

[dotty]

It is always a gamble meddling with CAT's without ECU adjustment, general rule of thumb is : Catback and induction is ok on the OE ECU, anything more then a adjustable ECU is required..

 

[VT-Doo]

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So is the Primary sensor affecting/changing anything when the de-cat is fitted then? Or is it just 'checking' the cat isn't knakered?

In simple terms;
The Primary O2 Sensor is continuously doing something.
The Secondary O2 Sensor only creates a CEL to let you know the CAT is knackered.[/size][/font]


READ THIS

 

[ItWasntMe]

^ Thanks. Read from start to finish!

So to clarify, is it recommended I reset the ECU now I've put the de-cat on to prevent it from running lean and/or calibrate it for the lack of cat?

 

[VT-Doo]

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Modifications will cause the engine to run lean at first but should be fine after a few runs, just don‘t go crazy on WOT once the mods have been done.

I always reset the ECU after any modifications made to the engine. By doing this you reset the Long Term Fuel Adjustment back to 0% causing it to re-adjust itself to the new fuelling that‘s required. Bare in mind that this is a linear adjustment at WOT and affects the entire range.

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[size="2"]On a separate note;[/size]

To ensure the life of a wideband it is highly recommended to make sure it‘s hot before starting the engine, I‘d do the same in a DC5 seeing as they can be a weak point.
To heat the O2 Sensor simply switch-on the ignition, wait for 30sec or so, you should be waiting for the fuel pump to prime anyhow.

 

[ItWasntMe]

That'll be a yes then.... :xcheers: