Well, I have no Cat on my truck and it runs like a striped *** ape. It is loud and I do enjoy it, but I was wondering if I should install a high flow cat to get some low end back and a little deeper sound, or if it's a waste of money. No emissions out here. Any educated thoughts?

 

I run a gutted cat with a flowmaster muffler (I forget the series number) it's the best of both worlds imo. The muffler provides sufficient backpressure to give back the low end I lost from hollowing the cat out.

 

ya i took mineoff and ypipped it with flowmaster super 10..

 

i had my longtubes and with no cats and when i put on highflow cats , i was surprised with the amount of power i got back . i say its worth it my .02

 

If you guys are getting power back from adding back pressure, your exhaust system is not doing it's job, likely too big. Back pressure is an extremely poor bandaid for an improperly sized system. The key is velocity, not back pressure. On most heavy trucks like we drive with engines between 300-360 c.i. a good mandrel bent system with a smooth flowing y-pipe leading to a 3" single in/single out is the best all around but if you have to have duals, under 330 c.i. use no more than 2.25" pipes, really 2" tailpipes would usually work better. On the 350-360 c.i. stuff 2.5" up front with 2.25" tails. That keeps the exhaust velocity higher as it cools moving back through the system. You can always use big tips for the look.

 

smaller pipes sounds like sh*T sound like farting ! the cat smooths it out and makes a nice gain .

 

Bigger pipes do tend to sound better I was just pointing out from a torque and horsepower perspective, to a point smaller makes more torque, bigger has the potential to make more power but moves it up the rpm band. If the convertor added power then it also changed the sound. You can get the same basic sound with smaller tubing as with adding back pressure, but with more power and better mpg. Does cost more though. Not knocking anybody's choices, just looking at the potential of more power.

 

he does have some mods though , i would think 2.25 would choke ?

 

I absolutely can't stand the sound of small pipes. A lot of the college kids around here run them for the loudness, but I think they sound like crap. Might as well run a fart pipe.

On my old Chevy I ran 2.5" back to the mufflers, and 3" tailpipes. That sounded pretty good. A larger tailpipe will give you a deeper, throatier sound, and not be quite so obnoxiously loud.

I must be getting old.

 

Backpressure is bad guys, period. Scavenging is not.

Heat generates a region of low pressure which creates a conveyer effect pulling out what the cylinders are pushing out... The exhaust needs to be open enough NOT to create backpressure, but small enough to get hot enough to create that heat- which creates scavenging.

Cats get hot. Really hot. Hotter than your headers or manifold hot, and is 'sposed to, to do its job. They generate a good portion of the scavenging that creates the low end. Exhaust is tricky business, getting the pipe diameter and bends, cat and muffler right and balanced to allow suitable hp/tq for your application LONG before obtaining the sound you want is even considered.