[iflylikeaneagle]

ok before ppl fly off the handle about how bad removing a cat is....i have to remove it per SCCA rules....this is a race only jetta mk4

Now back to my question.....when i remove the cat and the downstream 02 sensor i know im going to throw a CEL. Therefore i was wondering if anyone knew that ohm resistor and how i could put it in line to "trick" the ECM into thinking the cat and o2 sensor are there and working properly. All help is greatly appreciated guys. Thanks

might help to add that this is a 2.0l n/a aeg engine

 

[Vixen]

So it's a 2.0 naturally aspirated race MK4 jetta...? What kind of numbers do you put down and what kind of racing are we talking?

As for tricking your computer into thinking the cat is there... I'm not too sure about that. I'm not very keen on the electrical workings of these things yet, but I'm sure someone will chime in haha.

 

[iflylikeaneagle]

Its SCCA club road racing....im putting the car together for next season and trying to build it to the GTL specs. pretty much every thing on the car is custom so far...i had rules i had to build the car to though. The roll cage took me the better part of a week to design, bend, and weld in. they allow some engine work but not tons...the piston we had made by JE for the size bore and compression i wanted...again not too radical but much better than stock. The rods are manley, nuspeed cam, crane valve springs...i massaged the hell out of the head (3 angle valve job and nitrited valves...you would not believe how "dirty" the stock ports are. I have yet to put it on the dyno cuz i want to have everything done before i spend the money to take it to the tune shop but i need to figure out this cat situation soon

 

[vr king13]

I run SCCA also I race at NJ Motor Sports Park. I run ITA with a MK III a 92 jetta GLi 16v 2.0 But as far as the down stream o2 just drill a hole or if there allready is one. Leave it plugged in and screw the light. The main reading come from the first one that regulates all the mixtures. the second just tell the ecu that the cat is there it will throw a code but but dont worry about it. There is no resistor cuz the O2 sensors give off millivolts not ohms. Dont even try to trik it it will be fine.

 

[iversonbaby]

...i massaged the hell out of the head

Thats what she said.................sorry just had to point out the gheyness of that remark hehe im so childish hmm or a guy. ill go with both today

 

[Boost Addicted]

Agreed. O2's are a half volt system anyway, so readings are pretty precise inbtwn 0 and .5. And like he said, the primary O2 influences AFR's, not the secondary.

What kind of compression are you running?

 

[iflylikeaneagle]

im about 12:1 and i run only 104 octane...i was gonna run a standalone ECM...any ideas? I was thinkin motec but i dont know
and what does the downstream o2 sensor need to not send a code....ie hotter than the upstream or is it the afr or what?

 

[Boost Addicted]

Dunno bout stand alone's... I went through hell getting my buddy's Evo 9 to run on a stand alone lol, I've discontinued my SA tuning offerings haha.

But uhh.. you'd have to find a way to trick the ECU into seeing what it wants to see, voltage wise. You'd have to find out what kind of voltage the O2 reads when proper emissions are detected.. You'd need to apply a precise power source, not a resistance feed. It'd be difficult.

Just deal with the code and light for the time being and erase it when finished?

 

[vr king13]

Agreed, it would be next to impossible to trik it out. the second O2 runs at about 0.465 volts on average with a good cat u would have to reproduce that signal and have it flucuate alittle. Good luck with that. Maybee a watch battery, but i dont even know what they run at. As far aa a SA system if u dont know how to tune it dont even get it just run vw's ecu reprogram it but get it to mach ur cams that ur running. techtoniks or GIAC

 

[Zachattack01007]

Won't the computer read a high voltage if you run catless? I have heard if you use a diode inline with the O2 sensor it will drop the voltage enough to read a standard level and turn you CEL off. Not completely sure. I am hoping to try it this weekend.

 

[Skimmer0220]

Stop bumping old threads!!!!

 

[KiDGiB]

One hell of a first post too.