Ive heard of a lot of people on this forum passing smog with unique set ups, im wondering if anyone has ever passed smog with 1 aftermarket highflow cat? for example: downpipe+highflow mid cat/no air pump or high flow mid cat+downpipe with air pump... anybodys smog story is welcome!

 

People have passed in CA with the Bonez downpipe, Hi-flo and the airpump hooked up in the past. However, some have also failed with the same setup. There was never any determination as to whether the emissions testing got stricter which resulted in some of them failing, or if there were other reasons.

 

I've heard of people passing smog (this year) with an aftermarket downpipe, stock cat and stock airpump. I've heard of people failing with aftermarket cats, then swapping back to a (used) stock cat and passing. Didn't hear if that car had an airpump or not.

Either way, fresh oil and fresh spark plugs help, and the cat converter works best when it's warm so you might want to do some hard driving before the smog test and try to get on the rollers as soon as possible.

 

make sure your engine is in great running order upgrade the spark plugs the wires the air filter run high octane gas (all things youll be doing anyway) and you should beable to pass. Hell i etested cleaner then almost every car in the local csmart group last year so I am feeling pretty confident about the downpipe this year

 

the stock cat, even a 100,000mile used one is usually better than an aftermarket.

fd's will pass with just the factory main cat no problem, as long as the air pump and air control valve are working right

aftermarket cat will probably pass, its just not as clean as stock

 

he's right I failed with a leaky acv, actually it turned out to be a gasket coming from the air pump to the LIM. After fixing it, it passed in 1 shot even with my downpipe. An airpump is very important on a stock car with the stock main cat.

 

My FD:
stock intake ports and mild exhaust ports
GT35R turbo
Bonez cat
working air pump with air flowing directly to the cat
With my testing map passes Texas dyno emmisions testing.

 

I passed in MD running the PowerFC base map, a streetport, stock twins, 3" all the way back (no precat) with a 3" highflow cat on the first time up. No change to fuel, etc.

 

hrm, my car passed on 3 inch downpipe, stock cat and stock catback, but this is in CT so im not sure about Cali.

 

usually CA smog is stricter than other states, but an FD should be able to pass with a DP and OEM cat + air pump. Also, you can run the PFC base map and that might help as well if you're normally running above 10psi on stock twins.

 

With a downpipe, Bonez hi-flow cat and air pump I have passed Tx smog for the last five years with no problems at all.