okay so i made myself a cat-delete section, my question is, why hasnt my check engine light come on yet? i thought obd2 cars are super sensitive to that sort of stuff? not that i want it on...but, is somthing wrong?
The only reason your ODB2 would wig out is if you removed the O2 sensors. Did you just bypass the cat and leave in the O2 sensors? Or are both sensors gone? Only one sensor gone?
When I still had the stock ECU my CEL was on all the time and I was under the assumption that it was because of the rear O2 sensor not liking what it was seeing. However I have to wonder just how effective cats are on modern cars. Aren't they supposed to reduce pollutants from exhaust gases? I've heard people talk about not needing cats anymore as long as the car is running properly since you should be burning off most everything and that the CO emissions aren't reduced hardly at all with or without cats on. Makes you wonder just what we need them for anymore. I can understand what they were doing on cars running leaded gas because TEL left airborne lead particles so that would certainly be a bad thing.
everyone ive talked to said the cel should be on...is my car running that clean? i remember when i put my exhaust on for the first time, it took about a week for the inside of my exhaust tip to turn black, it was shiny for about half the week. its running fine, and the exhaust reeks of catless awesomeness, mind blowing:???:
it takes a while. the ecu waits untill you are cruising and looks for a set rear 02 voltage. if it does not see 14.7 a/f, it makes a mental note. it will keep that fault in que for some period of time. (i forget but it's mesured in weeks) the next time it then looks for 14.7 and does not like what it sees you will get the inneficent cat CEL. it takes 2 faults to make a cel. open loop fueling targets 14.7 so a properly functing car could be fine for a while..
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Originally posted by DISCOPOPE it takes a while. the ecu waits untill you are cruising and looks for a set rear 02 voltage. if it does not see 14.7 a/f, it makes a mental note. it will keep that fault in que for some period of time. (i forget but it's mesured in weeks) the next time it then looks for 14.7 and does not like what it sees you will get the inneficent cat CEL. it takes 2 faults to make a cel. open loop fueling targets 14.7 so a properly functing car could be fine for a while.. <hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote"> i see, well thank you sir, i'll be looking for it then i can pull the bulb
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Originally posted by RallyNavvie When I still had the stock ECU my CEL was on all the time and I was under the assumption that it was because of the rear O2 sensor not liking what it was seeing. However I have to wonder just how effective cats are on modern cars. Aren't they supposed to reduce pollutants from exhaust gases?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote"> Well they surely do something, because without them my car smells like a motorboat.
Maybe 25 bucks, if my welder didnt quit working 2 minutes into hacking off my old cats...i had to gas weld the rest of it, it took about 3 1/2 hours, so i'll be welder-less for a while, perhaps fuji could chime in and see if he can help you out, hes a pipe welding nut
If you can find a pipe, I'll help find one for you too, and some hardware, then it's possible. Although I'll be a ghetto pipe, it'll be finction over form. I don't like crush bends so I don't wanna do it at my work. But I do have access to a pipe bender which bends like a mandral. I'm still working on my welding.
Just an additional viewpoint. The cat in my RS has been effectively dead for the past 2 years. I get a CEL light, but it does indeed take a while to trigger. After my last reset, I drove the car about 50miles over the course of 3 different drives and then did 5 AutoX runs and the light is still not on. It definitely can take a while and it will indeed come on during a steady state cruise. Interesting write-up Disco... When I had Todd pull the code, originally, he explained it in a similar manner, but slightly different... The O2 level in the exhaust is a function of the A/F ratio and the cat is intended to deplete the supply of the gas before exiting. The rear sensor looks for quick changes in what essentially is the A/F ratio. If the cat is dead, the constantly changing A/F ratio (remember, the cat is intended to damp these changes) will effectively make it through the cat and the ECU will recognize it and trigger the CEL. The cat acts as a low-pass filter (for you elctronics geeks) in that the A/F is always changing, but the cat filters out the quick changes and the sensor reads slow changes in the ratio. If you remove the filter, the quick changes are recognized by the ECU. This is also why the CEL fix works for cars without cats. The fix is a cap and a resistor which equates to what? A low pass filter (if used correctly). What the fix is doing is taking out all of the quick changes to the A/F ratio out of the signal line to the ECU. Presto, the ECU thinks there is a cat there. The ECU doesn't care what the actual voltage is (wrt the CEL), just how quickly it changes (let's stay out of the Calculus discussions). Make sense? I kind of rattled on a bit so I hope it is coherent enough to follow... Also, this may not be exactly accurate as I am going by memeory and my EE background.
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Chin Just an additional viewpoint. The cat in my RS has been effectively dead for the past 2 years. I get a CEL light, but it does indeed take a while to trigger. After my last reset, I drove the car about 50miles over the course of 3 different drives and then did 5 AutoX runs and the light is still not on. It definitely can take a while and it will indeed come on during a steady state cruise. Interesting write-up Disco... When I had Todd pull the code, originally, he explained it in a similar manner, but slightly different... The O2 level in the exhaust is a function of the A/F ratio and the cat is intended to deplete the supply of the gas before exiting. The rear sensor looks for quick changes in what essentially is the A/F ratio. If the cat is dead, the constantly changing A/F ratio (remember, the cat is intended to damp these changes) will effectively make it through the cat and the ECU will recognize it and trigger the CEL. The cat acts as a low-pass filter (for you elctronics geeks) in that the A/F is always changing, but the cat filters out the quick changes and the sensor reads slow changes in the ratio. If you remove the filter, the quick changes are recognized by the ECU. This is also why the CEL fix works for cars without cats. The fix is a cap and a resistor which equates to what? A low pass filter (if used correctly). What the fix is doing is taking out all of the quick changes to the A/F ratio out of the signal line to the ECU. Presto, the ECU thinks there is a cat there. The ECU doesn't care what the actual voltage is (wrt the CEL), just how quickly it changes (let's stay out of the Calculus discussions). Make sense? I kind of rattled on a bit so I hope it is coherent enough to follow... Also, this may not be exactly accurate as I am going by memeory and my EE background. <hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote"> nice!
yes, it's true it looks for the subtle fluctuations... a good cat will give blocks of similar voltage. at highway cruise it locks in solid.... faulty cats, or no cats will give a constantly fluxuating signal... mostly arround 14.7a/fr but off by a few tenths or so. i think if the ecu sees 14.7 24/7 4 weeks a month it gets pissed off. that may be why a hardcore resistor fix does not work on 04's(03's??year??)
