Is it ok to run straight pipes from the cat back, no muffler at all? I will leave the cat on, from there the pipes will come to the back and come out to both sides and have double tips. I have done this on all my trucks before, it is very loud and sounds very good, has a mean rumble. I plan on doing this to my new truck but I want to make sure that with this brand new 2008 truck that it will not harm any parts of it.

 

Altho it might sound cool, to you anyway, the engine does require backpressure, and completely eliminating back pressure will actually decrease performance. I would wager a guess that it will void your warranty also.

 

i'd say just go with the smallest series you can get flowmaster.. whatever that is... if you want it loud.

keeping backpressure, but still almost straight pipe loud.

 

The straight pipes will be fine. The cat will provide more than enough back pressure.

 

I gotta disagree with the backpressure thing. I have seen quite a few dynos posted around on other sites and guys who are putting wide open (long tube headers, no cats, no muffler, 2 1/2"-3"pipes)exhaust and are getting better gains than those of us that are keeping the cats on and a muffler. Also if back pressure is a good thing why would peoplebe putting cutouts in between their cats and headers and opening them up when they get to the track and running better times with them open. Alot of people say you need backpressure for better performance, but after seeing these results I strongly disagree. Unfortionatly here in PA I need cats and a muffler to pass inspection, so straight pipes are not a option for me. Also with all that said some of the most powerful hemi trucks running right now have cats(highflow), and some have mufflers; but I think they are doing that for inspection/emission reasons, Im 99% sure that they also have the cutouts installed for track use though.

 

Here is SC we do not have inspections, legally it is supposed to have a cat though. From the two RAMs I have had before running straight pipes, I noticed gains in power. I want to make sure that by doing this to a brand new truck that it will not harm the motor. I have read from many sources that the cat alone produces enough back pressure.

 

Go back and look at your dyno results and you will see a substantial drop in torque with open pipes. Those that can run open exhaust have mods to make up for the loss in torque, like stall converters and steeper gears. Open exhaust will make power in the upper rpm range, but you will sacrifice on the bottom end. Even drag cars use torque tubes to add torque at launch, so having an open exhaust on a stock 2008 truck would be like fartin on a church bench, might be fun now, but you will regret it later.

As far as cut outs, if you have ever driven a HEMI truck with them, you will notice the throttle response will be lethargic and rpm will build much slower below 4000 rpm. Yes, i have driven them to see if I wanted to put them on my truck., I stayed with duels and flowmaster 50's.

Each to their own!

 

HorseApples, the truck is used just for driving, not racing or offroad. Will it be that bad to run straight pipes, will the MPG go down. If I have to get a muffler, what muffler should I get, i want the loudest one I can get.

 

The gas mileage will suffer somewhat with straight pipes, the O2 sensors will automatically send an impulse toadd fuel, thinking the mixture is lean without sufficient back pressure. This is an advantage at the drag strip, but a disadvantage on a street driven truck. The Flowmaster super 44 is a decible cannon! those things make massive volume. They make a deep rumble that will impress your friends and **** off your neighbors!

from flowmaster:











Super 44 -NEW!- Two Chamber Mufflers

Flowmaster’s NEW Super 44™ muffler with its 4” x 9.75” x 13” all black finish case offers distinct advantages over our original 40 Series™ muffler. Using the technology seen in our larger Super 40™ mufflers, the Super 44™ delivers a rich deep tone, an improved flow path radius, optimum internal flow and sound control, all created with Flowmaster’s Delta Flow® technology. It is the most aggressive, deepest sounding, highest performing four inch case street muffler we’ve ever built!

 

As for the warranty, my dealership said anything after the cat WILL NOT void the warranty. I removed the muffler and resonator to see what MDS would sound like with exhaust and I noticed a loss of low end torque and it was not that loud. I am running a super 44 3" in/ dual 2.5" out with turndowns and it is really loud. I have run single chamber flowmasters before and they are even louder than straight pipes. If it were me, I would run Cherry Bomb extreme single chambers or Flowmaster Delta Force Single Chambers. You may lose some lowend torque, but you have plenty to give up unless your towing.