Best high flow cat

I want a high flow cat that is loud and can pass smog in california. Doe any one know any brands that have louder high flow cats. Thanks john

I couldn't tell ya which hi flow cat is the best, because I personally haven't tested all of them out, but the Magnaflow has seemed to work well on another rig we have. And another thing, a cat will not make your exhaust louder. Get a Flowmaster 40 series or something similar, and that will make your exhaust louder. HTH.

A high flow cat won't do much for sound or performance (maybe 2hp). I bought one with high hopes but I was disappointed. The biggest advantage of the high flow unit was smaller dimesions that tucked up into the body more so rocks won't scape as easy.

Some people will think I'm full of it, but a straight pipe that is sized correctly will out flow any muffler, and that will have the biggest affect on sound and performance. The only reason I run a muffler is because I want a civilized sound.

I'm not into the "redneck truck" sound.

I've got a 2.5 in magnaflow unit on my XJ and it sounds good. I tried it without the cat (by-pass tube) and saw little to no difference. I passed smog testing last week and passed with flying colours. Hope this helps.

Phil

well i am in Mich an i cut off my cat and smacked on a flowmaster muffler, i wish i wouldnt have thrown away my cat, i dont like the sound, i was used to a throaty 350, huge difference. Dont know if that helps but, there

I too am happy with my magnaflow highflow cat. I have a Flowmaster 50 series DF, the magnaflow highflow cat, and 2.5" pipe from the downpipe back and it sounds great.

from talking to various engineers i know (my dad does fuel system programing ... he worked on the MDS program for DCX) him and other engineers say there is no big difference in your basic cat.

Get a universal fit catco one from summit or a magnaflow one both are like 50-80 bucks, will work great, and i went a few months with out a cat. I noticed no difference in performance with out one, and not much if any perceptable noise difference. For 50-80 bucks do it for the environement. And the people riding behind you on the trail will like the fumes burnt up better than huffing your dirty exhaust full of unburnt crap. Gitr done.

What year Jeep do you have well if it's a Cherokee then any cat will pass. At 5 years old the standers drop to a point you will have no problem as long as the rest of the engine/system is right and tight.
My 84 Cavalier has past 3 test with a gutted cat. That's with no acetone no additive or voodoo of any kind. Just a sweet running 4 banger.

The standards don't drop here in CA like that. In fact I think they get harder the older the vehicle. I've ran into several emission problems with great running, older cars and trucks. We have the most strict standards on our vehicles than any of the other states by far.

Yeah, and I'm tired of it. Lose the "visual" inspection, go right to the "sniffer" test, and I might be happy. Who cares how I pass, just so I pass, right?

Having said all that, I tend to use PFP "Universal" units listed for BB Chevvy - while it doesn't change the sound much (the Walker TurboII mufflers I use make it sound a little better, tho...) it does help with flow, even if it's just by "Butt Dyno" Standards. It feels quicker to me, and without spending a bunch of cash.

Correct - a stright pipe will outflow pretty much any muffler - that's simply physics. A striaight pipe also sounds a little obnoxious, so I don't run one (I prefer to announce myself, not drown out everyone else.)

5-90

I have a 93' 4-Banger and I had a Magnaflow Cat with a Flowmaster 50 and I was very disappointed. It lasted less than 2 years before having to be replaced due to failed emissions, which I hear is common. I looked at the warrenty and it was only for 1 year. I replaced it with a universal one from Advanced Auto with a 5 year warrenty and am more than pleased, at least in 2 years, if it fails again, it is a free replacement. Like others have mentioned the technician told me that there is no big difference in the cat's other than being more compact and a short life span.

I don't know who told you that, but its not common for Magnaflow cats to fail prematurely.

flyingphil said:

I've got a 2.5 in magnaflow unit on my XJ and it sounds good. I tried it without the cat (by-pass tube) and saw little to no difference. I passed smog testing last week and passed with flying colours. Hope this helps.

Phil

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I've had mine tested a few times since I got my magnaflow cat and mine too has passed everytime with surprisingly low numbers. Way below the allowed levels, and GA's new emmissions standards are pretty strict.

A few years ago I put a universal high flow cat in from summit I believe. It was like 80 bux!! Passed emissions (MA, pretty strict up here) with flying colors. They are cheap, and do their job...I don't think that they vary much by brand...the only variable really, IMO is the cost!!

Can't really tell with performance since I did a flowmaster at the same time.

Atl XJ said:

I don't know who told you that, but its not common for Magnaflow cats to fail prematurely.

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The emissions technicians at 2 different testing facilities told me that the high performance cat's fail prematurely. Based on my experience, I believe him. If they are as good as factory or even a universal, I'm curious why they don't warrenty them for longer than a year?

There are two schools of jetting or air/fuel mixing.
1. Run them lean very lean at least in normal mode. This is more common on old carbed and very early FI engines. If you have a plug gap of 55 or larger. If she false the NOx test with the timing right. If the idle was never quit right. If you have a slight bog in mid range. You got a lean burn engine. They would pass HO with colors but watch the NOx. My 84 Cav with TBI and a gutted cat is a prime example.
2. Run them a hair on the rich side. Small gap, better idle, Three stage cats, But HO and CO way up BEFORE the cat(s). Cats really come into play to pass many state tests. No gutted or weak cats will pass on them engines. Acetone and acts of God not with standing. The 4.0 as well as most engines made in the last 15-20 years fall into this category.
Note: Plus some computers and HP replacement chips are tuned to help pass "THE TEST" but over 35 MPH they tend to go for the power and poorer HO CO. If you new chip bogs a bit off the line. you got one of them.
Well, hope I have confused more people then I have helped.

JBFried67 said:

The emissions technicians at 2 different testing facilities told me that the high performance cat's fail prematurely. Based on my experience, I believe him. If they are as good as factory or even a universal, I'm curious why they don't warrenty them for longer than a year?

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Because they don't have to. If you read this thread you'll see that there isn't much difference in the design of modern catyltic converters. I only replaced mine because the factory one took a dump at 70K miles. It rattled like crazy at idle. I've already put almost that many miles on my Magnaflow, hopefully it will last a long time.