BrEaK_AwaY

with headers that eliminate the cat, when you get your car tested for emmisions, will the computer that plugs into you car detect that it is gone? and wil you fail / pass the test?

DynomyteSW

you'll fail the visual inspection for sure once they look under the car. As for smog levels you never know it might pass the sniffer...

Thrawn

If you're throwing a CEL (check engine light), then yes, your ECU is detecting a problem with the cat due to the heated oxygen sensor's output being outside of normal parameters. So, any OBD2 reader will get that error code, (Bank 1, sensor 2). That will indicate to the tester that there is something wrong. If you've implanted the anti-fouler or any other technique to eliminate the CEL, then no, it will not detect that no cat is there. There is no sensor connected to the cat with the sole purpose of determining if its actually physically there or not, if that's what you're wondering. If there is no visual inspection in your area, then you'll also probably pass the sniffer as well even with a cat-less header.

BrEaK_AwaY

thats what i thought, i would install the anti-fouler when i get my headers then. thanks alot thrawn. i dont think they look under the hood... im pretty sure they just do the sniffer at the exaust tip and hook the cpu up to the cars ecu

BrEaK_AwaY

Another question i have on the headers is why does the CEL come on in the first place? is it because the cat is gone? or because it is allowing more airflow? or both? I want to ensure it wont hert my engine in any way

Thrawn

There are 2 sensors in the exhaust path, an air/fuel ratio sensor (on the exhaust manifold) and a heated oxygen sensor (on the s-pipe). The heated oxygen sensor is what's causing the problem. The heated O2 sensor outputs a certain voltage (between .1 volts and 1 volt) depending on what it's reading. With a stoic A/F ratio, given stock equipment, the signal it gets puts out about .5 volts. Increased airflow, increased oxygen in the exhaust gases, going past the sensor will affect the reading it gets and therefore its output. An aftermarket header affects it enough that its output goes past the pre-set threshold for that sensor, which could be an indication that the 1st cat is not doing it's job, so, the ECU throws a CEL. If you're worried about your engine, then your best bet would be to buy a Lambda and EGT meter. That way you can monitor the A/F ratio (to make its not too lean or rich) and the exhaust gas temperatures (should not see a huge spike in EGT, that would indicate a huge problem). Expensive, yes, but that's the cost of peace of mind. You could also take it to a dyno, and some shops should be able to provide you with both of those readings, but, that’s obviously a one time only deal, you couldn’t constantly monitor it.

BrEaK_AwaY

Thanks for your help, I think i will install my AF ratio gauge before i install my headers (which i havent bought yet) lol. I am assuming that same goes for intakes? it throws the CEL becuaase it is taking it more air?

matty-tC

hopefully the ecu seeing more air is going to send more fuel... and i don't think you'd have to worry about running so lean it detonates when you add just a header. stock the car runs 12.1 a/f or so... which is a few points rich already

BrEaK_AwaY

but if i were to add the anti-fouler the ecu wouldnt know that there is more air flowing, so it would have no need to send more fuel (in the ecu's mind), correct?

matty-tC

it wouldn't know as much air would be. may actually lean it up closer to what it should be (14.5-14.7 AF ratio). I haven't seen the dyno of an antifouler with the AF reading included though. that's the only reason i haven't bought one.. no proof!

BrEaK_AwaY

Im in the same boat Matty, Too many things could go wrong. the antifouler is just tricking the ecu... when it needs to be telling it to match that airflow with gas.

Thrawn

To my understanding, the A/F ratio sensor determines that, not the heated O2 sensor. It appears that the ECU takes input from the A/F sesnor (exhaust side) and MAF meter (intake side) to determine adjustments to the fuel maps. The heated O2 sensor is mainly to ensure that the cat is functioning properly. The anti-fouler effects the heated o2 sensor only.

I agree. I seriously doubt even a full I/H/E setup would throw the A/F off so much that the stock ECU couldn't adjust enough to ensure a safe A/F balance. A Lambda and EGT meter would be overkill for a N/A engine. But, for anyone that wants to be sure about the condition of things, that's what they would have to do.

BrEaK_AwaY

forgot about that thrawn, not its all starting to make sence.

acasanova

I dynoed my Alphawerks Header and Injen intake recently on hot ___ hell day here in South Florida 97 DEGREES!!! inside the shop lol their ac took a crap.. Take a look at the A/F ratios im using the antifouler mod. 4sp auto TC.


[/quote] Old dyno on a nice 80 degree day. Only mod was a K&N drop in filter, the Injen axleback is on the title ,but wasent installed at the time. A/F ratios are a bit rich as you can see.



[/quote] Recent dyno again disregard the title, temp is accurate 97 degree. Only mods were Alphawerks Header and Injen Short ram stock exhaust took off injen exhaust due to rasp . Second run the last run was the best at 141hp 144 tq but i couldnt get that saved. A/F ratio just a bit leaner.

tCarloRS1_0

I was under the impression that the purpose of a header was to facilitate the outflow of the exhaust...isnt the a/f ratio determined by the inflow of oxygen? if that be true i would think that the ecu would throw a CEL simply because the cat is no longer there therefore the 02 sensor isn't performing it's function.......if i am wrong please humble teachers, teach me

acasanova

My experience in this is limited but you are right. Thrawn gave a good explanation up top on this. My A/F ratios are decent if not a bit rich and this is with the antifouler mod.

hahaitzskippy

new headers usually mean that you wunt pass smog but i guess we already established that.

you can get a street legal exhaust and kinda work your way around emissions.

as the A/F ratio. the car sees taht more gas can be expelled so it trys to pull more air in with more gas burning thus producing more HP.

i also recently dynoed my car with the AW headers. +11hp/+10tq

https://www.scionlife.com/forums/vie...884&highlight=

matty-tC

the AF is determined by the mixture of air input and fuel input... you can only measure this AFTER the mixture has been made... the first sensor would be directly on the manifold. i need to get an antifouler if thrawn is right about the ecu only reading from that sensor.

boostedscion

its looking good, but wanting carb #

BrEaK_AwaY

agreed, i wont get one till its been carb approved