Snorkeldepth

So, as I was removing my e-brake cable this evening I was imagining my new exhaust routing. I can see it coming down each side of the 5 speed with the right side wrapping around the back of the transfer case. But, it looks like I'd need to move the cat back to get a nice Y joint. How close can the cat be to the muffler and not cause problems?

CoedNaked

Wouldn't you want your cat closer to the engine to help keep it hot(ter) ?? (could be wrong).

AH64ID

They do work better hotter, I would move it foreword....but if you move it aft it wont hurt the muffler..

oly884

Don't move it too far forward otherwise it'll melt the cat and probably catch stuff on fire.

The cat where it is right now runs at about 600*C so don't move it too much further or else bad things will happen.

Snorkeldepth

Thanks guys. It can't go forward because the exhaust will be routed from the right side around the back of the transfer case. That's why it looks like I'll need to push the cat back a bit so that the connection between the right and left sides of the exhaust off the headers will be a smooth transition and not so much like a right angle. This connection needs to be in front of the cat. If this configuration won't work then I'll need to think more about the under the tranny routing like Downey's crossover.

Bobakazi

600*Celsius? I know they get real hot, but that is 1112*Fahrenheit! I just do not know. Are you sure?

eric-the-red

Snorkeldepth, one used car I bought had an aftermarket exhaust with the cats positioned further back than stock, and I had a hard time at emissions testing getting them hot enough to pass. I had to idle the car around 2500 rpm in the line-up to get them hot enough. They were about 8-10" back from the stock location. Everything seemed OK during normal driving, no CEL came up. Just something to keep in mind.

And Bobakazi, 600 C is correct, quoted from randomtechnology.com

"Under normal operating conditions, the catalytic process doesn’t begin until temperatures inside a converter reach 500 to 600 degrees (F). If air/fuel ratio is on target, and the exhaust is free of contaminants, internal converter temperature stays at about 1200 degrees. But when unburned fuel enters the picture, temperatures can reach 2200 degrees and either burn the precious metals out of the washcoat, or literally cause a melt down of the bricks. Extremely high temperatures can also result in destruction of the mat that's wedged between the bricks to the converter case.

Oil and antifreeze also cause elevated temperatures, but as the converter tries to burn (oxidize) these compounds, a residue, which plugs up the bricks is formed. At this point, the converter not only looses its effectiveness, it also becomes very restrictive to exhaust flow, which kills horsepower. "

Bobakazi

Learn something new every day. Thanks!

HUTCHSTACO

relocate it into the trash

AH64ID

I did that once, could have been the worst mod I did on my 95 (aside from the ranch arms).... it was stinky and loud....

Snorkeldepth

Great info Eric. I guess I'll do some more figuring. Thanks

Injohneer

Actually, I would relocate it to the trash, too. Yeah it makes it a little louder, but if your fuel/air is good, it won't stink.

Besides, if you 4x4 in grass/brush much, it isn't a bad idea to lose the cat. Your exhaust won't have that potential firestarter in it anymore.

Snorkeldepth

All the leaves are brown, and the sky is grey . . . . I went for a walk . . on a winters day . . . . . California dreamin' . . . where the cats must stay . . .




The SCAQMD doesn't take kindly to cat removal and southern California air quality needs a break. So, the cat stays and needs a comfy home under the truck.

Injohneer

well... if I understand things correctly, you can't even move the cat (much less REmove it), if you want to abide by California laws.... so tell them that you took it to your vet to have it neutered.

Snorkeldepth

Hmmm . . . I'll have to check if moving the cat would get me in trouble with the law. I guess there may be an "any tampering" proscription. But, I'm guessing that moving the cat a few inches would probably never be detected unless it posed a problem with emissions at smog check time and someone got real creative. Especially since I'll be installing a CARB certified header. Assuming some well meaning government official decided to cite me . . . my gut tells me I'd probably win that lawsuit because they'd probably have to show that I "tampered" (I'll check the definition) with the system in a way that made a significant change in the emission control system. I wonder if there's a difference in the distance from the exhaust manifold to the cat in extra cab and/or long bed models over my std. cab short bed. Hmmmm . .. . sorry for thinking aloud

Snorkeldepth

Does anyone recognize this truck? I can't remember where I found this photo. I had filed it away and just found it again.

Snorkeldepth

Well, I dropped off the headers this evening to have the 3 bolt flanges welded on.

The new 3.0 goes in next week. So, the exhaust will get designed and installed before the end of next week.

I still want to go with the configuration like the photo above.

How important is O2 sensor placement. Can it move towards the rear 3 or 4 inches without any problems?

From what I've read 2 1/4" tubing from the headers back is probably good. Any reason to reconsider 2 1/2"?

I'm going to use the Downey gaskets unless I'm persuaded otherwise. I've been assured that if I'm diligent in torquing and re-torquing the headers I won't have a problem.

Anything else I should be thinking about as far as this exhaust project goes?

Red3.slow

Yeah I should have kept the cat on my 95' I hacked off most of the exaust and put a dumped glass pack. Its damn loud.