I dont want to gut the cats anymore, I want to stay legal, and not effect the exhaust flow like mentioned in my last post, so my newest idea is, how about getting bigger hi-flow cats? Say 3 inch ones instead of the 2.5inch ones? Would that cause the same exhaust turbulence problems, or could I see some extra airflow thru them?

 

I would just leave it how it is your truck is LOUD already and sounds real nice if anything turn them out in front of the rear tires like you were talking about before as far as getting bigger cats I have no clue just be more of a hassle I think but thats me haha good luck with whatever you do -Scot-

 

Not worth the $$$ or effort IMO. It probably won't noticably change sound and will great turbulance because of the oversized converter.

 

on a steet driven motor you will probably see a decrease in performance when going from 2.5 inch pipe to 3 inch pipe especally in the low rpm range where you are going to need it with a 4x4 truck.

 

Besides, the cross section of the cats would still be the same regardless of the pipe size feeding into them.

 

Yes thats a good point. I really am sick of myself always wanting a differnt noise, its getting really old. I am going to get those 5 x 24 inch tips that MR.Man has, and call it a day, and leaving my system alone!

 

i have headers on my 400 with a magnaflow 3" in and out cat flanged directly on the end of each header. i would be pretty sure that 4 cyls are not restricted at all, flowing thru 3" on each side. by the way, it's 3" of tru dual all the way out the rear and it sounds pretty cool, well to me at least, but that's all that really matters. to each his own.

 

its not a matter of notenough flow, but to much space, there fore not creating proper backpressure, which is actually neccesary for an engine to run.

 

NO. The engine does NOT need backpressure to run right.

Backpressure = restriction. How is that good for an engine?

Go read about proper exhaust systems, not about ancient wives tales.

 

Backpressure/no back pressure has been an argument on hear for quite some time and maybe just maybe we can clear it up but i seriously doubt it..Ok so removing the cat can give you hp but will cause a loss of torque..Your engine needs a certain amount of backpressure to give maximum torque where the cam comes on. To say, in the 460 stock engine, the peak torque is 442@2170 RPM. Removing backpressure may decrease this somewhat. I've saw dyno number that when you drop the exhaust torque numbers will go down. So, if youwant top end, then the less restriction the better, but some is needed or maximum torque. This relates to intake systems also.Thats whysome cars like the Taurus SHO use dual intake runners for eachcylinder. This to to maximize the resonance of the intake to low and high RPMs for the most torque and hp. I believe it's long runners forlow end, short runners for high end.But for a turbocharged/supercharged/blowen vechicle is a whole differt story..Since its a 6000 pound truck without torque it cannot get going hence the more torque it has the faster it will get up and going..So if the exahaust is to free flowing/not enough backpressure it will not get the performance he is looking for.

 

Velocity is important, NOT backpressure. Making max velocity at the powerband you want makes good torque where you want it. Most exhaust systems make max velocity flow in the midrange, which is better than bottom end torque for all but the people who just want to lug an engine. Since the mid is stronger people equate that as a loss of low end. Not True. I dont deal with how someone "thinks" it made a difference, I like dynos. They are the proof.

Eveeyone acts like using a bigger exhaust is gonna kill power. Its a 460 people!! It will make low end torque REGARDLESS of what exhaust is installed. The engine makes power, not the exhaust.

Oh, and I have seen plenty of dyno sheets that show a torque gain with a loss of backpressure. You are right though, this will never be universally agreed on. Too many people choose to listen to mis-informed or unknowing "mechanics" or experts rather than looking at exhaust design rationally. These are the same people that buy the Tornado and other snake oil products.

 

I think Brad hit it right on the head. I think the system I have now is perfect for this vehicle, I was only originally doing it for sound. I like the way my system, is, the true dual is 2.5 inch, a great compromise for low end and top end, the collectors on my tri-y headers is 2.5inch so theres a good torque size on the truck, but its free flowing enoug so that when I am going 65 70 mph on the high way I barely need to keep my foot on the gas because the top end can breathe so easily. Its all preference, when I use to run a single 3 inch into a dual 2 1/4, the truck seem to have a little more bite off the line, but nothing overly noticable, but not nearly as a good as a top end, especially since i added the headers and cam

 

Kens64 do you personally have a 460 v8??? i know for a fact when the exhaust is dropped that the power from 0-60 is by far less than even the stock system..

 

Just take a look at the exhaust part.. When they do put a free flowing exhaust 2 free flowing mufflers and 2 high flow cats the torque drops..What do you think would happend if the cats and or mufflers were gone in performance wise???

 

You have to be kidding me. You are talking about a 1% change? Thats well within the dynos MARGIN OF ERROR, air temp, etc. LOL!!! You would never notice 1% (4.7 ft/lbs at the time) if your life depended on it. Give me a break.

Not to mention, peak power numbers are not something to go by, unless you are building a dyno queen. Its power under the curve thats important. So what Im saying is what if there was a ton of torque made under the peak numbers? That would never show if you are only publishing peak power. Peak numbers and drivability numbers are NOT the same.

Not to mention there was never a stock system on this truck at the time of testing.

"The Flowmaster/Random exhaust replaced PREVIOUSLY INSTALLED aftermarket dual system blah blah."

You have no argument yet... but keep trying.