EJeff8

It's tempting to go straight. I don't need to worry about emissions. My converter died so it gives me a reason to do it. Or should I do a high flow cat? Me and my friend don't think the cat holds that much "back pressure" so it wouldnt throw my engine too far out of wack. A high flow cat in my problem would just be for sound purposes right? Opinions welcome.

I have a Y8 with stock header, dead stock cat and a catback Greddy EVO2 2.25" exhaust.

clean92ex

Depends whether your cars obd1 or obd2. Guessing from your pic its gonna be obd2, which has a post cat o2 sensor. Running a straight pipe is going to make your car run rich and possibly throw a cel. A high flow cat shouldn't do that and won't have your car running rich

EJeff8

Ah. The secondary o2 does relatively nothing though right?

EsotericImage

iTrader: (8)

If you need a cat for visual inspection from a cop. Votionspeed.com sells fakes that are straight thru. A CEL eliminater will solve your CEL Problem.

clean92ex

It still plays alittle role tho. I'm pretty sure it's gonna throw a code for your pre cat sensor not working properly, but it won't make it run much noticibly richer

EJeff8

Hey, Eso! Just the guy I was looking for haha. I doubt a damn cop would ever want to bend down under my car. My dad had a high *** straight 350 and was never questioned about a cat. What's a CEL eliminator? And I might still go high flow, idk. What's your take? And how rich would I run straight?

lunareg

it wont be terribly noticable performace wise, but you will notice that your going thru gas faster. honestly if your cat is bad right now you should already be throwing that cel.

EJeff8

^I did a jump and it just gave me Cat converter, but nothing more specific than that.

EJeff8

Does this mean that a straight really won't be too beneficial or too bad?

lunareg

I meant the rich conditions, but that would also apply to straight pipe. The only thing you prolly would notice is that its louder.

-__-

my cat also died lol. i had severe power loss cuz it was very clogged. so i juts hollowed it out. my car is OBD-2 and im still throwing the catalytic converter code. Also running a little rich. I might jump back to obd-1

EJeff8

yeah, this does turn me away from it. A high flow cat would keep the rich conditions fairly close to stock, will keep the CEL off and still allow me to keep a nice sound and maybeee a performance boost. I'll probably go high flow even though I don't need to pass emissions. It's just the best option I think.

lunareg

yeah im not positive how it will work with a high-flow I havent used one before, but that o2 after cat is basically checking with the one on the down pipe to see if there is a difference in emissions. So the high flow would have to have some sort of exhaust cleaning put into it to keep the light off.

EJeff8

^I think it's still a fully functional cat, just built for performance more than emissions. That's how people pass with them.

chucky420

Get a straight pipe and a "check engine light eliminator". It's a little threaded bung that installs where the sensor used to go and then the sensor threads into it. It has a small hole allowing a smaller amount of exhaust to reach the sensor, effectively tricking it into giving a correct reading. I was scheptical, but I've seen them work on multiple cars. Eliminates the code 0420 (67) as long as your secondary HO2 sensor is still working. Noticeable power gain, increase in sound (louder). That sensor has no effect on fuel trim at all. It is just in place th monitor the catalyst. All fuel trim is controlled using the primary as a reference.

EJeff8

^Cool. Well, now what I'm worried about is what "louder" truely is, because I like the sound my GReddy offers and what is the power gain realistically?

chucky420

It's only a little bit louder, maybe a little deeper. As long as you have a muffler, it won't be too bad at all. The sound seems a little deeper at low rpm and I couldn't tell a difference at high rpm. Never seen before and after on a dyno, so I'm not sure about numbers. The power gain is best described by how your car feels when you're low on gas or if you inflate your tires above 40psi (a little quicker). To get an idea, drop your tire pressure to 25psi and go for a quick spin, then inflate to 40psi and compare. That's roughly the kind of gain in power I'm referring. You can feel the difference.

Da-Risin-Smoke

Cat deletes change the powerband.

You lose some low end torque and gain more top end.

EJeff8

^.This is what I've heard. Definitely tough to choose between.