Fun with cats! Meow!

[azn2nr]

if the title was too confusing baciscly i didnt pass imissions and i missed by alot. so i ordered a magnaflow high flow 3in 3 out cat universial oval style. its gonna be on a test pipe so ill take it out as soon as i pass emmisions.

the problem is that its rated for a v8 350+ 6k gvw car. how much performance will i be loosing with this cat. and should it be enough to help me pass emmissions.

for reference im allowed 1.2 co2 and i had about 10.12 at 2500 rpm

[91White-T]

Thats strange, both my legacys passed no problem catless, are you sure there's not something else wrong?

[legacy92ej22t]

Ya, our engines run pretty damn clean even without a cat. That reading seems off.

[JasonGrahn]

yeah, your title sucks. Edit it or I will.

[vrg3]

I agree that something else is probably wrong. Several board members have passed emissions without cats on their turbos. And your car's number isn't even close to the acceptable amount.

A catalytic converter actually probably won't reduce your carbon dioxide output.... In fact, it might increase them, since it converts carbon monoxide into carbon dioxide.

Wait... I thought CO2 had a minimum required quantity during the test to make sure there weren't exhaust leaks... or something like that. Are you sure you aren't thinking of CO?

[azn2nr]

thanks for catching that V its co in % that im thinking of. my co2 and o2 look just fine.

im running catless right now. someone said that it may be an injector problem which i would consider a non problem since id rather run rich than lean.

but back to the orignal question. how much powerloss will i encounter wiht a cat this size

thanks for the edit jason, i had trouble finding my post.

[azn2nr]

i just went and talked to a master mechanic and he told me to look at o2 sensor and a bad maf. he said that if my maf was bad id get bad mileage, which i am but i atributed that to the bigger turbo.

thoughts

[DLC]

That edit would be mine

A turbo won't change mileage unless you use it a lot, which you probably do. I wouldn't expect to pass catless if you've changed the turbo or even gone intercooled. Granted, there are a lot of variables to account for, but the farther from stock, the more chances you have to be out of tune.

[vrg3]

Unless they're testing your car under load, your turbo and intercooling setup shouldn't make an iota of difference in an emissions test. They're basically just intake restrictions, but at that level of flow even that's not really important.

It's true that the oxygen sensor and MAF sensor would have the greatest impact on carbon monoxide. But the MAF sensor actually shouldn't be that relevant unless it's really gunked up, since under low load things should be running closed loop.

So, yeah, check your oxygen sensor first. Carbon monoxide is generally an indication that you're running a bit rich.

[azn2nr]

how do you check the o2.

i should note that when i installed the tbe i couldnt unplug the o2 sensor, i was only able to twist it out of the bung. something was wrong with the clip and it wouldnt come out no matter how much i poked it with a screwdriver or squezed it. ive had it out before but it just wouldnt come out that time. also it was a little strech to get it in but i got it.

how would you damage an o2 sensor???

[vrg3]

The most basic check is to measure the signal coming from the sensor with a voltmeter or with my scan tool. It should always be between about 0 and about 1 volts, and at idle it should bounce around 0.5 volts.

You can damage a sensor by banging it around, by damaging its wires, or by contaminating it with silicone, lead, or just exhaust crud.

If you didn't buy this sensor recently, you probably should just buy a new one. Get one for a non-turbo Legacy and it'll have longer wires.

[azn2nr]

will it just snap right into the clip

[vrg3]

If you get one meant for a 90-94 non-turbo Legacy, yes, it has the same connector.

In fact, I think all OBD-1 Legacies and Imprezas use the same connector. And the rear sensor on OBD-II models up through 98 or something, too.

[azn2nr]

few last questions.

shouldnt the car throw codes for bad maf or o2 and shouldnt the car not run with a bad maf???

[vrg3]

A bad MAF sensor should keep the engine from running and throw a code, but a dirty one might not.

A bad oxygen sensor might or might not throw a code. Even if it does turn on the CEL, it might only happen for a few seconds every once in a while.

Was your car warm during the emissions test? If your sensor is the one from the factory its heater is almost certainly dead, in which case it will only work when the exhaust is nice and hot.

[azn2nr]

it should of been warm. the guy that did the test reved it up pretty high for fun before he started testing it.

[vrg3]

Just revving it up a couple of times doesn't warm up the car. Did you have the coolant and oil hot, and drive the car hard just before the test?

[azn2nr]

yes

[douglas vincent]

While this may seem total ghetto, I monitor my MAF signal and O2 signal via two multimeters jambed into the drinkholders. I just tapped into the signal wires of each of the parts and grounded out somewhere else, and then ran these wires to the testing clips of the multimeteres.

MAF signal should be at about .8 on average at idle, and climb as you open the throttle, up to almost 5 as you hit full boost.

O2 signal should be at about .7 ish while cruising with the occasional dip down to the negative side. WOT should = .8 constant or better. Idle should be .7, .7 .7 - - .3. .7 - .2 ie, it bounces around.

[vrg3]

While cruising it actually should act just like it acts at idle -- bouncing around above and below 0.5 volts.

[azn2nr]

im gonna add the cat to clean it up and an o2 just because its a good idea after soo long. but 02 sensors are expensive and install is too, sucks when you cant get shit apart

[vrg3]

If you want to do some wiring and are willing to deal with an oxygen sensor that doesn't work unless the exhaust is hot, you could use a ~$20 universal 1-wire sensor.

[BAC5.2]

Install is expensive?

I was unaware that a 22mm open ended wrench was expensive...

If I took my car to be emissions tested, I would be HEATED if the monkey doing the test started revving my car.

[vrg3]

They're supposed to rev the engine for a bit. It's part of the test cycle.

[BAC5.2]

He said the guy was doing it for fun, revving pretty high, before the test started.

The test, at least in Moco, calls for 3,000 RPM sustained.