Cat Placement

[98hd]

Building the exhaust for my '90 c1500 w/ ls1, and want to install a set of cat converters. I know they need to be fairly close to the outlet of the manifold so they get hot enough to function. Does anyone have an idea of how far away is too far?

I'm running truck manifolds, and as of now the cats would fit nice about 16" from the outlet, but I'm afraid that might be too far back. If I do a little tweaking I can probably move them up to about 12" downstream.

Planning on using 2 magnaflow 2.5" in/out universal 3 way cats.

I was going to just run a single cat after I Y the exhaust together, but it was too much of a PITA to run the driver side pipe under the trans by the front of the pan, using a few mandrel bends. So I want to run 2 cats and bring the drivers side pipe over to the pass. side under the tailshaft of the trans, Y them together, toss on a muffler and either dump it under the bed or run it out in front of the tire, if I can get enough clearance not to crush it hanging there.

[RedHeartbeat]

the 18" won't be a problem, they will get plenty hot.

[gearheadnate]

Yeah, 18" or less will be fine

[98hd]

Cool, that makes me feel better, now if my parts will get here I can get to work on it.

[txarkitekt]

<div class='quotetop'>QUOTE(98hd &#064; Apr 6 2007, 06&#58;07 PM) [snapback]88846[/snapback]</div>

Building the exhaust for my &#39;90 c1500 w/ ls1, and want to install a set of cat converters. I know they need to be fairly close to the outlet of the manifold so they get hot enough to function. Does anyone have an idea of how far away is too far?

I&#39;m running truck manifolds, and as of now the cats would fit nice about 16" from the outlet, but I&#39;m afraid that might be too far back. If I do a little tweaking I can probably move them up to about 12" downstream.

Planning on using 2 magnaflow 2.5" in/out universal 3 way cats.

I was going to just run a single cat after I Y the exhaust together, but it was too much of a PITA to run the driver side pipe under the trans by the front of the pan, using a few mandrel bends. So I want to run 2 cats and bring the drivers side pipe over to the pass. side under the tailshaft of the trans, Y them together, toss on a muffler and either dump it under the bed or run it out in front of the tire, if I can get enough clearance not to crush it hanging there.
[/b]

I am not sure how you are going to harness up everything (wiring harness from donor vehicle?), but I know that if you don&#39;t position the O2 sensors in the exact spacing between the cats, then you will have a CEL.

[98hd]

<div class='quotetop'>QUOTE(txarkitekt &#064; Apr 9 2007, 01&#58;58 PM) [snapback]89246[/snapback]</div>

I am not sure how you are going to harness up everything (wiring harness from donor vehicle?), but I know that if you don&#39;t position the O2 sensors in the exact spacing between the cats, then you will have a CEL.
[/b]

I"m using a nelson harness, and it only uses front sensors.

[txarkitekt]

<div class='quotetop'>QUOTE(98hd &#064; Apr 9 2007, 03&#58;08 PM) [snapback]89249[/snapback]</div>

I"m using a nelson harness, and it only uses front sensors.
[/b]

I&#39;d ask Allen what to do about the O2 sensor placement...His harness may have been set up so that you don&#39;t have to worry about the 02 sensor placement.

[98hd]

<div class='quotetop'>QUOTE(txarkitekt &#064; Apr 9 2007, 02&#58;19 PM) [snapback]89250[/snapback]</div>

I&#39;d ask Allen what to do about the O2 sensor placement...His harness may have been set up so that you don&#39;t have to worry about the 02 sensor placement.
[/b]

I had planned on it, still waiting on him to call me so I can order a tune.