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post #1 of (permalink) Old 04-10-2003, 10:01 PM Thread Starter
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Running 4.0 without cat or muffler?

I'm slowly creeping toward getting my YJ back and running, but was curious if I could drive it without a cat or muffler on it? Will it run ok like that as long as the O2 sensor is plugged in? I probably wouldn't drive it anywhere other than the exhaust shop. I just don't wanna ruin anything or have problems with the FI. Also, what is inside of a catylitic converter? I tipped mine over and a bunch of white, clumpy stuff came out. Only way I can describe it is like dryer lint, only in LARGER quanities. It also had some gold looking flakes in it. I didn't keep trying to dump out this stuff, since I got a nice pile. But I bet I didn't get half of it out. Thanks!
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post #2 of (permalink) Old 04-10-2003, 11:02 PM
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Re: Running 4.0 without cat or muffler?

Here's what I found about cat's from one of <font color="green"> LEVE'S </font color> favorite websites. How Catalytic Converters Work and here's a pix from page 3 of this article.

Thanks again <font color="green"> LEVE </font color> for your knowledge and sticking around. If you were in Denver I'd buy you a root beer.


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post #3 of (permalink) Old 04-10-2003, 11:21 PM
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Re: Running 4.0 without cat or muffler?

</font><blockquote><font class="small">In reply to:</font><hr />
but was curious if I could drive it without a cat or muffler on it?

[/ QUOTE ]1. Engines work best with a little back-pressure.
2. Without the back-pressure cold air can get up to the valves,
3. That has spelled disaster for the valves...
4. However I ain't got a clue how long it takes.
5. Me, I'd take the chance... and drive it to the muffler shop
6. As long as it ain't 50 miles away.
7. However, I'd straight pipe it to get it to the shop,
8. And avoid not having anything past the down-pipe.
9. BigUgyl, If I ever get to Denver... I'll take ya up on the Root-beer.
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post #4 of (permalink) Old 04-10-2003, 11:37 PM Thread Starter
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Re: Running 4.0 without cat or muffler?

Thanks for the info guys. What exactly do you mean by #8 on your list? Just so nothing is there to take a beating from the exhaust pressure/gas/heat since there's no muffler and it's straight pipe? See any issues that would effect the FI system?
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post #5 of (permalink) Old 04-10-2003, 11:40 PM
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Re: Running 4.0 without cat or muffler?

1. If there system's open at the down-pipe,
2. The distance from the valves to the system exit it minimal...
3. Cold air can, and does enter the system,
4. And this is what warps valves.
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post #6 of (permalink) Old 04-10-2003, 11:53 PM
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Re: Running 4.0 without cat or muffler?

I agree with <font color="green"> LEVE </font color> on the distance. We started an engine on the dyno and the right bank's header was just finger tight. After starting it it fell off completely and we bent a couple of valves. we usually have aleast, I think 15-20 inches of downpipe on stock exhaust manifolds, before going out the exhaust hose. The exhaust hose is about 5 inch dia. To stay away from warping anything. L8r,



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post #7 of (permalink) Old 04-11-2003, 08:46 AM
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Re: Running 4.0 without cat or muffler?

I would say that you should be fine driving it a short distance... But don't do it when people are trying to sleep, cause it will be loud.
It would serve you well to get some flex exahust pipe and just rig it up to the header and run it to the rear of your jeep. not only will that help keep the valves happy, but also will keep the fumes out of your head. It is probably not a great Idea to dump fumes right out the header/manafold. Because that dump is pretty close to where you will be sitting, and it si not good stuff to breath. I myself would like to hear a I6 run with a streight pipe. You will probably get lots of funny looks.
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