1993 Hi-flow catalytic converter exhaust question

[leitev8]

I have a 93 that the PO removed the cats and welded straight pipes in their place.
The problem is that I have terrible resonance above 3000RPM and there is a leak from one of the terrible welds he did it.
I have a pair of High-flow 3" cats from my Corvette days laying around.
The question is, should I install one catalytic converter or the pair?
I was going to install both of them, but I just saw that magnaflow offers a catted down-pipe kit (23120) that uses a single catalytic converter.
I would imagine that my high-flow cat outperforms the one magnaflow offers.
Let me know what you guys think.

 

[Rifleman]

As to your question, will your Corvette high flow cats fit. It would all depend on the size, and shape of the Corvette cats, based on that info you"ll know if they will fit where the original cats went. If it were me, and i lived where i didn't need to do emission testing, I'd leave the cats off. What i would do, I'd remove the exhaust, grind off the bad welds, weld the exhaust back together, and reinstall. As for your resonance problem, how do you know that issue is being caused by the exhaust tubes the previous owner installed? One thing I'd point out if you do try to install the Corvette cats. The factory cats were mounted REAL CLOSE to the passenger side floor board, so close that the factory cats came with a heat shield completely surrounding them. The heat sheild was not only installed to keep from overheating the floor board, but also to prevent fires while parked over vegetation.

 

[JaketheSSnake]

The magnaflow down pipe is meant to have a second cat bolted to it. I suppose 1 is better than none, but I'd go with 2. It sucks doing low speed offroad events and getting gassed out by someone running no cats. You'd still possibly get a little of that with only 1 cat I'm guessing. That's basically what made my mind up on replacing my worn out ones a few weeks ago with the magnaflow setup

 

[inkpot]

In the 90's cat technology was only up for one or two way cats. Federal law required 3 way cats, so they doubled them up. Modern cats are mostly all 3 way now. I am running a single 3 way cat with no problems. It passes smog every time. I do not have to do a visual or tailpipe, just OBD II plug.

 

[leitev8]

I think Ill try a single cat first.
I'm tired of the gas fumes already, that's why I want to put a cat in there.

 

[Rifleman]

Leitev8, just as an FYI, the 1FZ engine used in our trucks were not designed to have cats installed. They were only delivered with cats, EGR and other emission equipment in the North American market, because it was required by federal law in order to be sold here. Other 80 series Land Cruiser's sold around the world, didn't have that emission equipment installed on them.

 

[inkpot]

Leitev8, just as an FYI, the 1FZ engine used in our trucks were not designed to have cats installed. They were only delivered with cats, EGR and other emission equipment in the North American market, because it was required by federal law in order to be sold here. Other 80 series Land Cruiser's sold around the world, didn't have that emission equipment installed on them.

I'm pretty sure that Toyota engineers were quite aware of increasing North American smog standards way back in the 1960s and 1970s when cats were first developed/required.

 

[Tools R Us]

Leitev8, just as an FYI, the 1FZ engine used in our trucks were not designed to have cats installed. ...

How is an engine designed to have cats installed?

 

[inkpot]

I would think most differences would be programmed into the ECU. Like maybe running richer for more power, maybe 13:1? More aggressive timing schedule?

 

[Rifleman]

I'm pretty sure that Toyota engineers were quite aware of increasing North American smog standards way back in the 1960s and 1970s when cats were first developed/required.

Cats were fist developed for gasoline engines sometime around the mid 1950's, but did not come into wide spread use until the mid 1970's. The reason for the delay in the use of catalytic converters was due to the use of lead in gasoline, lead is a catalyst poison that effectively disables a catalytic converter from working. Once the lead was removed from gasoline around 1974, most car makers started installing them in the 1975 model year to meet the ever increasing federal emission standards.

 

[inkpot]

Cats were fist developed for gasoline engines sometime around the mid 1950's, but did not come into wide spread use until the mid 1970's. The reason for the delay in the use of catalytic converters was due to the use of lead in gasoline, lead is a catalyst poison that effectively disables a catalytic converter from working. Once the lead was removed from gasoline around 1974, most car makers started installing them in the 1975 model year to meet the ever increasing federal emission standards.

Cats were the simplest/most inexpensive way for auto manufacturers to meet the ever increasing smog standards.

 

[Rifleman]

How is an engine designed to have cats installed?

Timing curve, fuel and air metering, O2 sensors, ECM programing, exhaust system placement, all so the cats work within design parameters.

 

[Tools R Us]

Timing curve, fuel and air metering, O2 sensors, ECM programing, exhaust system placement, all so the cats work within design parameters.

Not the engine design, just the external tuning is optimized to to work with the cat. Even that isn't far from non-cat tuning.