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Catalytic converter

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skyhigh4by

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Was thinking about installing a magnaflow spun cat due to them only being 8" long and small diameter. Problem is my exhaust is dual 2.5 from the long tubes all the way back to the y-pipe just past the tcase where it goes to 3" and a single muffler. Right after the y is the only spot I could fit a cat but I'm afraid that's going to be too far from the motor for it to function at all or last as long as it should?? The next problem is that if installed there it would be directly infront of the muffler. If the cat gets really hot will it burn up the muffler?

It doesn't have to pass any kind of emissions testing or anything. Mainly I would just like to cut down the fumes a bit and eliminate some of the raspy sound I get from not having any type of resonator besides the one muffler. My other option was to add a flowmaster or dynomax race bullet type muffler in front of my muffler. I have about 10" of length to fit something in. I know that wouldn't help emissions at all but should eliminate rasp I hope
 
I don't recall seeing the inlet temperatures required to "light off" a specific converter, but I do recall seeing something that the outlet temp was 800* when working right. Good thinking on the muffler, I had not considered that, at least on the K5 there is not a lot of distance between the converter and muffler as stock. ( edit: from what I found searching now, looks like inlet and outlet temp is dependent on much, as I figured: http://www.aa1car.com/library/converter.htm http://www.researchgate.net/post/Catalytic_converter_exhaust_temperature-anyone_know )

Just an idea, can you call or email magnaflow and ask them? The inlet temp requirements are probably different depending on cat manufacturer and cat design, I for one would be interested to know as well. If you need someone to call from the US let me know a part number and I will try.

As an aside, the EPA here prevents you from even *adding* a cat where one did not exist before, and I'm sure that is due to the variables that need considered to do it properly.

I too plan on running a converter, but I've got to figure out where in the system it needs to be just as you do. I plan to run it where the factory one was if I can get away with it, since the shielding for the floor is already present there.

If we know what the inlet temp requirement is, worst case you assemble the exhaust up to the point where you want to run the converter, and use a temp crayon of the proper rating to see if your inlet temp will be ok there.
 
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skyhigh4by said:
Was thinking about installing a magnaflow spun cat due to them only being 8" long and small diameter. Problem is my exhaust is dual 2.5 from the long tubes all the way back to the y-pipe just past the tcase where it goes to 3" and a single muffler. Right after the y is the only spot I could fit a cat but I'm afraid that's going to be too far from the motor for it to function at all or last as long as it should?? The next problem is that if installed there it would be directly infront of the muffler. If the cat gets really hot will it burn up the muffler?

It doesn't have to pass any kind of emissions testing or anything. Mainly I would just like to cut down the fumes a bit and eliminate some of the raspy sound I get from not having any type of resonator besides the one muffler. My other option was to add a flowmaster or dynomax race bullet type muffler in front of my muffler. I have about 10" of length to fit something in. I know that wouldn't help emissions at all but should eliminate rasp I hope
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Right after the Y is fine. Thats where the stock location is on my 350 k5. You definitely want it in front (closer to motor) of the muffler. The muffler wont burn up. They really don't have anything to burn up inside. A good cat should last 10 years if you dont have any issues...that being said make sure you dont have a misfire and run it around like that. It will burn the cat up real fast.
 
I understand that the stock setup is right after the y but my y-pipe setup is much longer than stock. Mine doesn't pass under the engine/trans anywhere. It goes all the way down both sides of trans/tcase and then crosses over behind the tcase and meets in a y. The y-pipe is pretty much inline with the tcase rear output. A long ways further back than stock. I will try to contact magnaflow and see what they have to say
 
It shouldnt have any effect against the cat, in fact its probably better in terms of heat for longevity. Its not like the exhaust gasses will slip by because its out farther.

I forgot to mention that my setup passed smog here and with the exhaust pipe adapters my cat is pretty much inline with the transfer case so im not far from your position.
 
I just spoke with a rep at magnaflow and I took a guess that my y pipe is about 4 ft from the headers and he thought that would be too far for it to be effective. Suggested about 2.5-3ft from header collector to be effective. I'll have to actually measure and see where I'm at.
 
Cats need to be hot to work properly, that's why you drive around for 20 mins before a smog test.
 
My y is actually closer to 5ft from header collector upon second look. I could put a cat closer on the driver side but unfortunately the passenger side has too many bends to fit one in anywhere. Guess I'll continue going cat less and try a small bullet type muffler further down the line to control the raspy sound
 
I run 2 cheap cats - 1 right after each header collector.
 
Any chance anyone has taken temp readings of their headers at the collectors? I'm curious to see what they run in that location.

It would seem that if you didn't merge the pipes close to the engine, you'd have plenty of room for a converter on each side.
 
dyeager535 said:
Any chance anyone has taken temp readings of their headers at the collectors? I'm curious to see what they run in that location.

It would seem that if you didn't merge the pipes close to the engine, you'd have plenty of room for a converter on each side.
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I'll shoot the temp of various points of my exhaust later tonight if I get a chance. I just picked up a flowmaster 10 series and it's going in as a resonator right after my muffler. I stuck it on the tailpipe temporarily for trial and it seems to have eliminated the rasp sounds. It's cleaner and deeper sounding with the 10 on there.
 
Cool, I'd appreciate it.

Did Magnaflow give you an inlet temp range that the cat(s) you inquired about like to see? Seems like there are a fair number of variables that could influence converter operaton besides just distance from the engine...inlet temp would likely seem the most important variable to know.
 
No I didn't get that info. It wasn't hard to get hold of a tech there though. Maybe just give them a call.

The air/fuel ratio is going to play a pretty big role in temps as well and I know mine runs a bit rich at low rpm and lean up higher. It will give a ballpark idea but everyone is gonna be a bit different I think.
 
skyhigh4by said:
I'll shoot the temp of various points of my exhaust later tonight if I get a chance. I just picked up a flowmaster 10 series and it's going in as a resonator right after my muffler. I stuck it on the tailpipe temporarily for trial and it seems to have eliminated the rasp sounds. It's cleaner and deeper sounding with the 10 on there.
Click to expand...

I've done that as well, I have the spun-type convertors a few inches behind the collectors. The welder is paying for itself real quick.
 
I recently added cats to my burb. I was concerned about getting them far enough forward, and in the end there was not enough room to get them in there. the only room I had was behind the t case. they seem to be working fine though.

made the exhaust much quiter than I expected. Changed the power more than I expected too, exhaust sure smells purty though
 
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