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More Exhaust Questions: Muffler reccomendations...


MadManMike
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Hey Guys,

 

Back story:

6 months ago took my pathfinder into the local Japanese auto repair place to look at the loss of power I have been having and the horrible 11mpg.

 

They said that there was a bunch of back pressure on my engine and it was caused by the fact that my muffler was plugged and my Catalytic converter was probably responsible for clogging it. They recommended a full catback exhaust system and quoted me some crazy price.

 

New story:

I am on spring break so I had time to take my car into a local exhaust shop and get a quote on a catback.

They looked at it and said that they didn't think my catalytic converters were bad just that my muffler was bad. Told me they would replace the muffler with a so called "Turbo muffler" and install a new tailpipe for $180.

 

Questions:

Why does my pathfinder have 2 catalytic converters? This is news to me. Does this mean if I want to replace my converter with a magnaflow I am going to need 2 of them? are both the converters the same?

 

Any recommendations for a muffler? or is a muffler just a muffler...

 

Oh and also they said I need new plug wires... recommendations for plug wires?

 

-Mike

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Perhaps it was a California model?? :shrug:

 

In Washington I'm sure you could just run 1 cat and pass emissions. Magnaflows are good so get the same for the muffler. I have one and like it.

 

I haven't bought plug wires for 10 years so I can't help you there. Hint, when you need to do a tune up, buy another vehicle that has just been tuned... :D

 

B

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You only need one cat here in Washington to pass. I put a Magnaflow hi-flow cat on mine and it woke it up pretty good.

 

NGK plugs and wires are very good for the money.

Edited by Kingman
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My ca model only has one cat, I think a P.O. prolly had trouble with emission and thought that would fix it, I knew a kid who's dad put 5 cats on for the very same reason.

1 magnaflow cat and 1 magnaflow 2" or 2.25" mufler should do you fine

Edited by MY1PATH
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my 3.5 has 3 cats, two precats in the exhaust manifolds, and one main after the y-pipe. I know the precats in the 3.5 are notorious for getting clogged up, think due to burning oil. Headers get rid of precats.

 

Not sure if this help, just throwing it out there.

 

 

J

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So I got off my lazy butt and got underneath to take some pics...

 

Looks like for some strange reason I have a smaller pre-cat after the Y and a regular cat after that.

 

On the left is the CAT and the right is the Pre-CAT

3384131238_161d0c38ae.jpg

 

Up close of what I believe to be a Pre-CAT

3384130962_08d77f26d9.jpg

 

Any other 95 owners have a setup like this?

-Mike

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Looks to me like all it's doing is reducing flow and taking away some efficiency. Power, fuel mileage...

 

I say get rid of all but the mandatory one and use 2.25" piping with a magnaflow or flowmaster, or whatever muffler.

Edited by Kingman
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Questions:

Why does my pathfinder have 2 catalytic converters? This is news to me. Does this mean if I want to replace my converter with a magnaflow I am going to need 2 of them? are both the converters the same?

 

Any recommendations for a muffler? or is a muffler just a muffler...

 

Oh and also they said I need new plug wires... recommendations for plug wires?

 

-Mike

Mufflers range between size, sound level and composition. If you want one that will last forever but costs more initially then get a stainless steel one. A retailer should be able to help you pick one out that's fairly close to stock if you want.

 

Having two cats is not uncommon the least bit. Never looked into the reason for having a pre-cat so I couldn't tell you why. If it were me, I would get rid of the precat and put in a new "main" cat.

 

As for plug wires.. just don't cheap out :crossedwires:

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Mufflers range between size, sound level and composition. If you want one that will last forever but costs more initially then get a stainless steel one.

 

The problem with stainless is I can't weld it my self... I don't have TIG only ARC and Oxy/Acetylene.

Suppose I could find someone to weld it up for me.

 

-Mike

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The problem with stainless is I can't weld it my self... I don't have TIG only ARC and Oxy/Acetylene.

Suppose I could find someone to weld it up for me.

 

-Mike

Personally, I would just clamp it on if the rest of the exhaust is ok. I don't think it would be worth it to get it welded to the stock exhaust.

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Simple, yet effective muffler system:

 

1. Starting at the end of your manifolds, take crime there back out... But save it for parts...

2. Go to advance auto parts, get a flange kit, then an adapter to go up to 2" or 2.5"(max)

3. Get a thrush turbo muffler (it's like $20 and reversable- 2 sounds in one)

4. Get various lengths of straight pipe( depending on where you want it to exit at)

5. Get a universal sport cat(legal in CA I believe)

6. Put the cat about 3-6" closer to the manifold

7. Put the muffler 3-16" back from the cat (affects loudness and tone)

8. Get a curve piece and make it come out the side of the car...

9. If you live in NC/SC- hidden exhaust is illegal on non lifted vehicles, if you have a lift 3" or more then put a down pipe after the muffler cause you can see the tip making it legal

 

That is what I will be doing... Cheap and effective...

 

Hope it helps...

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Depends on how much of the exhaust will be 2". If it will be bumped up to 2" or 2.5" right off the manifold, then yes it will be beneficial. Stock exhaust systems usually restrict around 20% of flow - so 80% efficiency, with the tubing size, manifold set up, type of muffler and catalytic converter(s) used. That's if you were going to redo the entire exhaust system.

 

I think the 2" inlet on a muffler is basically all you can use since stock pipe size is 1.875".

 

At that point, either have a shop weld the muffler on or take a hack saw and cut 4 slits in the end and clamp it down onto the stock exhaust pipe with an exhaust clamp. The material taken out of the pipe on the muffler when you cut it is perfect for mating to something slightly smaller.

Edited by Kingman
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I think for now I am just going to buy a cheap replacement muffler and clamp it on, that will get me through the rest of the school year. But I think I found my summer project :D

 

-Mike

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Really there is a way to make it work without welding but you will have leak problems possibly.

 

You can go to 2" with almost no problems, you just need to get an adapter from stock 1.875" to 2 or 2.5"... Then you will be fine.

 

And don't go any higher than 2.5" if you do make it bigger, cause you will have very little back pressure....

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Really there is a way to make it work without welding but you will have leak problems possibly.

 

You can go to 2" with almost no problems, you just need to get an adapter from stock 1.875" to 2 or 2.5"... Then you will be fine.

 

And don't go any higher than 2.5" if you do make it bigger, cause you will have very little back pressure....

 

You do not need an adapter. The way I said above is all that's needed. Just make sure that you only cut about an inch, if that into the inlet pipe on the muffler and make sure it's covering at least 2 inches of the stock pipe. No leaks of any kind, at least when I did mine earlier this year.

 

No engine likes back pressure. That is an old wife's tale that is not true. The less, the better. The piping sizes has to do with the efficient flow of exhaust and heat traveling down the pipe and mixing with cooler air, etc.

Edited by Kingman
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Didnt realize that you said that... I posted that last one by me from my ipod touch and could hardly read what you said....

 

I guess your was would work too... I was just suggesting a good way to up to a larger pipe... never thought about cutting slices in the pipe...

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Didnt realize that you said that... I posted that last one by me from my ipod touch and could hardly read what you said....

 

I guess your was would work too... I was just suggesting a good way to up to a larger pipe... never thought about cutting slices in the pipe...

 

Haha I have the same issue with my touch as well. Can be pretty frustrating sometimes...

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Having two cats is not uncommon the least bit. Never looked into the reason for having a pre-cat so I couldn't tell you why. If it were me, I would get rid of the precat and put in a new "main" cat.

 

Precats, since they're smaller, heat up before the main, reducing emissions while the main heats up.

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No engine likes back pressure. That is an old wife's tale that is not true. The less, the better. The piping sizes has to do with the efficient flow of exhaust and heat traveling down the pipe and mixing with cooler air, etc.

Try putting a 3" exhaust on our motors, and then say that. You're wrong.

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Try putting a 3" exhaust on our motors, and then say that. You're wrong.

 

That's not quite what I was getting at. I meant it as an engine being allowed to breathe easier is a happier one. More restricted, and it's less happy.

 

I like the analogy of blowing through straws. Small one and it's extremely hard to blow through (less than 1.5"), and a huge one it's like nothing and is way too much (more than 2.5"). A medium sized one, you can blow through it easy but the air has some force to it as well (2.25"-2.5")

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That's absolutely correct, you really want zero backpressure, no matter what engine. However, the trick is to balance the lack of backpressure with the need to maintain exhaust gas velocity. Otherwise we'd all be running 4" exhaust systems. A bigger displacement engine with higher airflow, higher compression/etc....can handle a larger diameter exhaust without a significant reduction in velocity, but a stock engine needs to be careful to not go too big.

 

I went with 2.5" as my main exhaust diameter based on previous experience (I've build a lot of road racing engines over the years). I used a Magnaflow 2.5" muffler (5" x 11" body and 22" long).

 

I extended the 2" primary tubes off hte manifolds to merge behind the transmission. I stuck two small Magnaflow cats further upstream (next the the tranny), and shielded them with .080" aluminum to keep radiant heat to a minimum. My torque has improved compared to stock, and higher rpm power is better as well. Mileage seems to be the same as before however.

 

HTH,

Bob

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Quick question...

 

So I ordered a cheap muffler just to use for now (one of the "trush turbo") mufflers on summit for $26... but of course I had to select the wrong model number when I ordered. The muffler I ordered is the same length as the stock but not nearly as big around. What would be the side effect of using this muffler? I could just send it back in exchange for one that I meant to order... but seeing that this is just a temporary job.. as long as it won't affect my vehicles performance.

 

-Mike

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9. If you live in NC/SC- hidden exhaust is illegal on non lifted vehicles, if you have a lift 3" or more then put a down pipe after the muffler cause you can see the tip making it legal

 

Ok. Why?? What difference does it make if you can see the tailpipe or not?

 

Granted, I live in California. We've made an entire industry out of meaningless and ultimately destructive regulations (eg: CARB).

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Ok. Why?? What difference does it make if you can see the tailpipe or not?

 

Granted, I live in California. We've made an entire industry out of meaningless and ultimately destructive regulations (eg: CARB).

 

Its one of those "stupid laws" that just doesnt make sense..... the whole reason why I am saying to put a down pipe is its a "loop hole".... You can see the exhaust if you lean down but from a regular view you cant.... so technically i am following the idiot law....

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