Powersource

I have LT's with a ORY and bought a 3" magnaflow awhile back to help with the exhaust smell at idle. Problem is, the cat is going to be farther back than I think it is designed to be in the exhaust system?

I can't find anything online that tells you the best location to make sure it heats up correctly and does the job it is intended to do. I know eventually it will warm up enough to start scrubbing, but just worried it isn't going to be optimal and might cause issues down the road.

6SpdLT1Z

An offroad y-pipe (ORY) doesn't have catalytic converters. That is why it's designed for "off-road" use. Are you running emissions? The air pump is used to heat up the catalytic converter faster. I'm sure if you mounted a cat behind your ORY you would be fine, but it begs the question, why didn't you order/custom fab a dual cat y-pipe if you wanted to retain the catalytic converters?

Powersource

No AIR, no EGR.

Initally, I wasn't worried about emissions but when you are sitting in traffic or idling it in the garage it fumes up pretty good. I've already started building a 304SS dual X pipe exhaust that dumps in front of the axles for track days. I rarely go, so 95% of the time is spent on the street.

I just wanted something to use the ORY with a cat and full exhaust so I can have a conversation with people in my car and not stink up the streets. My daughters hate the smell, and frankly the car is no fun if I can't enjoy it with them.

I guess the other option is to put in mini cats on each side of the Y if it doesn't seem to help much.

pgerst

It will "work" wherever you put it, maybe not as effectively as designed location. The catalyst typically starts to work about 600F with typical internal temps of 1200-1400; you get much hotter to 1800+ and you can melt the substrate and the catalyst material goes out the exhaust pipe. As the dual cat systems have the driver cat right up next to the manifold, not sure you can get too close (ignoring back pressure issues); conversely installing instead of a muffler might be too cold for opitmum catalyzing. Also I think relocating is technically illegal under fed law; in a smog state like CA, you have to have OEM or certified converters in the factory locations or you will fail a visual inspection.

Powersource

Thanks for the info!
Illinois doesn't really visually check anything unless they suspect something. Generally, they just plug it in, check for codes, and you are on your way. My car just smelled so strong that they asked flat out if I had cats on the car, then checked under to see.

I guess I'll give it a go and see what happens. Emissions is due up in March, so I need to get it running by then and make sure there are no codes or check lamps lit. Last time they nearly failed it because the ABS lamp was on.

bobdec

Powersource, my next mod if you call it that is to add a pair of cats to my LT's in the Y-Pipes close to the collectors as physically possible. Like you, the eye burning exhaust smell in the garage and near the car is like driving a 1950 dump truck and it's getting old. Wonder how we ever survived w/o cats years back. That smell is soothing at the track, but not in a DD. In answer to your question my stock '94 setup had a single cat at the end of the Y-Pipe, they actually joined in the front of the cat, just behind the bell housing.. But in my LT setup the Y's join way back after the transmission near the driveshaft tunnel and I would be reluctant to put a single cat back that far. It may get hot enough, but I'm not sure, never saw one that far back, maybe someone has tried it and can chime in. Also by going for a pair of cats I can use something smaller as there are only 2.9 liters (4 cylinders) feeding each cat.
With no cats today in a '97 your rear O2's must be programmed out, in some OBD2 emission test centers they do not allot non-ready conditions for emission equipment, depends on your state. Mine is OBD1 a different story, sniffer only.

Powersource

I'm running O2 sims for the downstream, no problems here in Illinois yet. I was under there today trying to find a decent place for it and if I put it right after the Y, it puts it right where the tunnel brace is/start of the driveshaft yoke. Still debating if I want to waste the single cat, or just bite the bullet, sell it and get the 2 smaller.

bluz28

Using 2 cats closer to the headers would be a lot more effective, and it would be less restrictive than 1 at the end of the y-pipe.

BTW, what Y-pipe are you using, and what's the diameter of the pipes, including the Y-pipe exit?
If its a lot like a LS1 Y-pipe then install passenger side cat is easy (plenty of room), but the driver side is limited for cat clearance.
IMO, If you carefully/slowly use a floor jack and a piece of 3-5" diameter thick wall metal plumbing pipe you can make a little more room to mount a cat on the driver side.

ascastil

I had a pacesetter ory with longtubes. Had an exhaust shop cut ypipe and weld in cats . It worked fine, had to use o2 extensions, but I didn't like the way it looked. Ditched that setup for true duals, no cats.

Powersource

Using the LPP Y pipe. 3" Any good places to grab mini cats?

bobdec

I was looking at these " Magnaflow 54959 " 9 3/4 inch long and 4 inch diameter that's only 1/2 inch wider than the Y-Pipe. They are good for up to 5.2 liters, OK if you are using 2 cats. The 59959 is good to 6.6 liters if you go w/only one cat. Also looking at Walker SS Mega Clamps 33272 Lap joint (for different size pipe slip connections) and 33278 Butt Joint (for same size pipe connections). Since you have to break open the exhaust whenever you do tranny or TQ work so using these clamps makes an easier break point than welding both ends of the cat to the Y. When I installed my Yank SS3200 it was a PITA, w/o a collar type of connection in the system I had to break the exhaust way back at the muffler to allow the engine/tranny to drop enough to get to the top tranny bolts, connections and cooling lines.

Powersource

Thanks Bobdec!


94109 is the cat I have here, rated to 6.2L.

If I weld that right to the merge, I am only a foot back from where the OEM would have been. To scrub out the stench, I think the single would do the trick.