I'm planning on putting in a High flow CAT soon, the question I have is should I go with a 3" down pipe or keep my stock. What are the pros and cons either way?

I put a 3" offroad (no cat) DP on my GTP before I sold it. Still with stock mufflers, the car sounded pretty mean

Unfortunately emissions standards require a cat for me :(

Where is everyone on this....

I don't think you'd really gain much performance wise from this. Want to hear from the others though.

I question how much of a gain could be had for any N/A I would think you would lose torque but would make it back up top. But for */C I would guess you could gain more; I've thought long and hard about getting one from hogan performance for myself. But I think tackleing the restrictive manifolds on our cars should come before any DP. I think I'm going to do a high flow cat right now and try to get a set of togs.

Ed

I have no numbers to back this up or disprove anything. That said, I can not see reason to putting a 3" downpipe on a stock or lightly modded L36. I would deffinately keep a cat in there. At most, I would suggest only a 2.5" downpipe, and for a lightly modded(cam, heads, rockers) engine. But this is all just what I think and I have no way to prove or disprove it. I'd leave the 2.25" downpipe and put a single 2.5" exhaust after the cat if it were my car, and I had a cam, heads, rockers, etc. Just my two cents.

I think you should leave it.
The bonneville DP isn't as restrictive as the GP'*.
If anything take the DP money and put it torwards PEMS.
Just my opinion.

Thanks for the feedback, I'd rather save the money for something else if there'* no bennefit from putting one in.

When you took yours off, did you look at it and compare it to the gp downpipe. Are you saying it because the diamteter is bigger or because of the fact of no u bend? Because i am thinking of going power log and rockers, but if i do the rear then i have to do a dp because of the 1995 thing. I would like to see a picture of the gp vs the bonneville dp.

I agree with Doug and Mike... your stock downpipe is probably fine at this point. After my heads and cam (though they were mild) I still wouldn't put a 3" downpipe on my L36. Like Doug said, I have no numbers to back this up, but I'm thinking a 3" pipe is far too big on an NA motor, unless it is highly modified and spinning up to 6500 rpm. Otherwise you're probably not creating enough exhaust volume to necessitate a big downpipe. It would kill your low end and barely do anything for the upper revs.