High flow cats and mufflers ,Are they worth it?

My cat in rattling really bad in my 92 xj and needs to be replaced. I was thinking about a high flow cat but are they worth it? Do they improve your MPG ? How much power gain do you get?

At the same time i was thinking about replacing the muffler with a 40 series flowmaster or a 40 delta series flowmaster. Is there any big difference ? This is a daily driver and i heard that a 40 series is to loud inside?

canadianwheeler said:

My cat in rattling really bad in my 92 xj and needs to be replaced. I was thinking about a high flow cat but are they worth it? Do they improve your MPG ? How much power gain do you get?

At the same time i was thinking about replacing the muffler with a 40 series flowmaster or a 40 delta series flowmaster. Is there any big difference ? This is a daily driver and i heard that a 40 series is to loud inside?

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I don't know about the cat, but I think they are only $10-20 USD more for the high flow when I has mine done. I have the 40 series flowmaster on my 4.0L in my 98' ZJ and it emitts a nice low rumble. You can hear it inside, but it isn't too loud or anything. I'd do it again. It will get your XJ noticed which can be a good or bad thing. :laugh3:

Troy

My shop wouldn't touch the jeep w/o the cat on it. I ended up ordering a Catco one, ebay, then put on the 40 delta flow. I originally had a magnaflow on there, but the flowmaster is definitley quieter inside, but much deeper outside. Go with this combination, you'll be happy!

Has anyone went with both the delta flow and original 40 series? Whats the difference?

canadianwheeler said:

Has anyone went with both the delta flow and original 40 series? Whats the difference?

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Buddy has regular 40 series on his YJ, 4.0, and it's louder than mine. But his is also 2 years old, my delta is only 2 months. I believe they get louder with time!

well its worth it if you are going to replace the failed original one. It wouldn't be the greatest investment if you want to feel the difference and be a drag racer. :laugh3: But if you buy a high performance muffler, you should get a highflow cat or you are not getting the full benefit of the new muffler.

I have a borla header, highflow cat, and the regular flowmaster 50 series (NOT the delta flow). I got the 50 series because thats what the tech guys at flowmaster recomended for my application, i got it with the rustys 2.5" exhaust kit. Since i did everything new from the hear to the exhuast tip, i did notice a slight difference in performance (around 30-60 it really pulls hard!) If you don't have a header or 2.5" pipes the whole way you won't notice a big difference at all. It will sound cool and you will have a highquality muffler though :wave:, when your stock exhaust manifold eventually cracks upgrade to a borla or banks and yer done.

Lastly the regular 50 series is a little loud under hard acceleration (not straight pipes or glass pack loud though) but louder than stock. The delta flow uses noice canellation to tune out some of the loud frequencies INSIDE the cabin. If it was available in 2002 i would have got a delta flow 50. Ilike the loud on the outside. :laugh3:

canadianwheeler said:

My cat in rattling really bad in my 92 xj and needs to be replaced. I was thinking about a high flow cat but are they worth it? Do they improve your MPG ? How much power gain do you get?

At the same time i was thinking about replacing the muffler with a 40 series flowmaster or a 40 delta series flowmaster. Is there any big difference ? This is a daily driver and i heard that a 40 series is to loud inside?

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I just installed a Magnaflow cat and Borla cat back system on my 94 HO a week ago.
I notice a lot more part throttle response, and it will boil the 29" tires with 3.07 gears.

It has a lower note than the Flowmaster stuff, and the there is only a dull hum inside around 2500-3000 RPM.

A lot less annoying than Flowmaster IMO, but it costs more.

On a related note, my XJ passed emissions no problem with the new system, so the high flow cat isn't going to be an issue.

IMHO, the most cost effective exhaust is a universal cat from an auto parts chain ($69 to $79) 2.25 in/out and a Dyno-Max cat back exhaust from many of the mail order places.($129 to $159). This combination netted me a 2 MPG increase and noticeable increase in power. Remember that an exhaust is vulnurable to trail damage so go cheap.

I installed a Random Tech cat a it shows a 27 h.p. gain on the dyno.....

Go with the Flowmaster. It acts like its own skid plate. Mines been beaten to death and been ripped off 3 timmes (2 on the xj and once on my grand wagoneer) and all it has is a small dent and a slight leak on the weld at the bottom.

If you're going to replace the entire exhaust, I recommend that you don't go with the Borla headers (you'll lose 2 inches of clearance).

Of course, Im the guy with no loot, but I just went out and bought a 20$ cherry bomb glass pack for my 2000XJ. I have no idea about gas mileage or power, but I do know that it emits a great sound. Purrz like a clean harley; enough to turn heads.
Brian

tttt

I just put on a new V-Force and got rid of my cat all toghether. The sound is very nice,Like a v-8 even Going without a cat helps the sound I think. does anyone know? Just curious. Is anyone else not runnig a cat?

sloppyjoe said:

...Just curious. Is anyone else not runnig a cat?

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Can't do that around here with the Vehicle Emissions Testing (VET). At the very least your jeep will fail & you will have to put the cat back on anyhow.

i hollowed out my cat, welded on a flowmaster 40, stock tail pipe, and still passed emissions!!! but right now i want to find a good tailpipe, either 2.5" or 3"!

i got 2.5in dynomax highflo cat from jegs like $49.99? and a thrush preformance something 2.5 in for $19.99 and a 2.5 tail pipe.....this sounds great....is soooo cheap....and i notice much more power

I have a 98 with 40 series and dual outlets. It is very loud but I love it. For now I am running no cat until emissions time (2 years away). The 40 series and no cat definetly has noticable power gain. Im going with a high flow cat once it's time though. If you dont mind some noise (enough to wake up the neighborhood) under acceleration go with the regular 40. At 50-70 all I can hear is my mud rovers.

aduke said:

i got 2.5in dynomax highflo cat from jegs like $49.99? and a thrush preformance something 2.5 in for $19.99 and a 2.5 tail pipe.....this sounds great....is soooo cheap....and i notice much more power

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Did you get the Thrush glasspack or the 'turbo' muffler? I used to run the glasspack and loved it. trying out the turbo as soon as it runs.

Keep in mind that the more freely your exhaust flows, the more your lowend performance will suffer.

Dean