Also what about the 5" Magnaflow, any good?[/QUOTE]

In the latest Diesel Power Mag there is an article on the Magniflow. They put it on a stock truck, and it gained (if memory serves correct) 17hp and 22.5lbft of torque AT THE WHEELS!
That's pretty impressive if you ask me.
I just called MBRP a couple of days ago to ask about the new 5" system. This is what I was told. "The sound is very agressive." I asked if it was down right loud and would drone on the highway. "It's much louder than our 4" system and if you don't want loud you should consider one of our other options."

I'm wondering how much of the increase they got with the Magniflow test was from the removal of the stock cat and muffler. I have been kicking around the idea of removing my cat and replacing my muffler with a Donaldson.
Any opinions on that idea?

 

The Magnaflow is loud, I had one for about 2 weeks.

 

see, this is the thing that frustrates me about this site - everyone's opinion is different. If you read 97on22s thread about the 5" Magnaflow he put on, he says it's quiet. Loud to one guy is not loud to another. I really don't care if it's a little loud around town. It's that dreaded highway drone with a 10,000lb load at 70 - 80mph that I fear. I don't want to spend $600 to find out I hate it!

 

ok i know everyone's opinion is different but i think you just have to try it out yourself and see and just take everyone else's opinions with a grain of salt. now here's my opinion and the facts as i stated earlier on here. going from 3.5" to a 4" exhaust will reduce backpressure up to 98% now that being said, in my opinion, anything over that (4" that is) is just wasting money really because you're not gaining a whole lot after that. and with that you won't have to worry about the droning either and it'll sound good too. so there's my 2 cents and if you want a 5" exhaust system and you've got the money just go on ahead and get it and see for yourself what ya think.
good luck!

 

am I mistaken or is the factory system on the 05's already 4"? Downpipe and all?

 

I have an 05 G56 QC short bed. I went the cheapest route to get a good exhaust. I bought an MBRP cat delete pipe ($60) and muffler replacement($150).
The new muffler is straight through. It does not appear to have much more restriction that a straight pipe. The truck drives much better. There is a significant reduction in turbo lag. The truck feels a lot faster because of the reduction in turbo lag. I can not tell if there is more peak HP of torque.
Removing the factory pipe was very difficult. The clamps crush the outer and inner exhaust pipe and I had to cut the pipe in three pieces to get it out.
The MBRP parts were perfectly bent and proper length. I cut the tailpipe so that i could tuck the tailpipe in a llitle more than stock. I think that it sounds great but I think that most people would say that it is pretty loud. It really sounds off at WOT above 2000 RPM. I will get pictures and video later.

 

no you are not mistaken. it is 4" all the way. i was just stating that interesting fact to help him make up his mind and to let everyone know. that's why i said it. so ya, but you are right on the money!

 

where did you get your cat delete pipe? I guess this would work to put on the cat delete and then the cool duals? i really like the look of the dual side pipes.

 

i think ppl confuse loud INSIDE versus loud with the windows down versus loud outside if your driving past someone. my setup is a 4" downpipe into a 5" piece that dumps out in front of the rear tire. no drone, not loud inside until you get about 2200rpms then it goes away. it all depends on what you want...outside...its loud no matter what rpms.

 

I agree everyone's opinion is different, but none the less the 5" Magnaflow is loud. Around town it's OK with the windows up, but as soon as you start to lean on it people 200 feet up the street turn around to see what's crashing behind them, and it had alot of drone at about 70 mph.

 

Dude
Did you read my post above. An actual dyno pull on a stock '05 changing only the exhaust from stock to the Magnaflow resulted in 17hp and 20.5lbft of torque at the wheels. The larger downpipe and complete system should allow the turbo to spool faster as well. It should also reduce EGT numbers. Those two things were not tested, however, only the power increases. In my opinion, that's not wasting money. If you make only this one mod to your truck and pull up next to another '05 that is stock, you know you've got the advantage. That's money well spent.

 

ya i did read it man i just wanted to state that fact. it doesn't even apply to the 3rd generations. i just read and quoted it from "diesel power" magazine.

 

I got the MBRP 4", and Im not real sure about how I'll like the sound. Im give n it a try though!

 

I realize that there is a 98% reduction of back flow from 3.5" to 4", but the fact remains that they picked up substantial power going from the stock 4" to the Magnaflow 5".
How does this not apply to 3rd gens? An 05' is a third gen. This test wasn't on an '01 or something, it was on a brand new truck.
The dyno doesn't lie.
FACT! - A 5" exhaust will benefit over the stock factory 4" exhaust.

 

i dont know and i dont care any more i'm tired of arguing about it because now i'm freaking confused. i'm unsubscribing from this thread!!!