What Size exhaust 4" or 5" ?

[onebadf150]

I can't find a solid answer on this one. I run a full 4" deleted on my 6.4l and it runs great, but I see alot of guy's with 6.7l running 5" why is that?

My father's regular cab fx4 that he ordered just came in and he wanted to clean up the exhaust. So on the list was SDP 4" downpipe but what size exhaust to finish out.

pro and cons of 4" and 5" on a 6.7l?

muffler or no muffler?

thanks

Nick

 

[WHY NOT]

It's just for the sound mainly. 5" will have a deeper tone. Toss in a muffler to help quite it down in the cab and when towing and such.

 

[onebadf150]

It's just for the sound mainly. 5" will have a deeper tone. Toss in a muffler to help quite it down in the cab and when towing and such.

great info thanks!

 

[onebadf150]

What is the quietest in cab setup when deleted?

 

[Rowdy]

Well 5" is a deeper tone but we also get 5" for future plans of bigger turbos and duel fuelers, etc. If you plan on going 600Hp plus then the 5" is needed. If not 4" is plenty. I have 5" MBRP stainless straight piped and at cruising speeds it's not loud at all in the cab. I would say its no louder than my wife's Tahoe with a flow master. Now if you stomp on it she will talk to you then! But I love it! So if you want it quiter get the muffler with the exhaust kit. It will cut down on the cab noise.

 

[onebadf150]

Well 5" is a deeper tone but we also get 5" for future plans of bigger turbos and duel fuelers, etc. If you plan on going 600Hp plus then the 5" is needed. If not 4" is plenty. I have 5" MBRP stainless straight piped and at cruising speeds it's not loud at all in the cab. I would say its no louder than my wife's Tahoe with a flow master. Now if you stomp on it she will talk to you then! But I love it! So if you want it quiter get the muffler with the exhaust kit. It will cut down on the cab noise.

Thanks brother

 

[Built 6.7]

I would just go with a 5 inch right off the bat, or you will be like me I have a 4 inch on my truck and outgrew it

 

[TheBigNasty]

I highly doubt you will see any appreciable difference in power between 4 and 5".

 

[Rowdy]

I highly doubt you will see any appreciable difference in power between 4 and 5".

I think that lower EGT's is defiantly an appreciable difference!

 

[TheBigNasty]

You have proof of this?

 

[powerstrokin15]

I doubt 4" is that much different, and 600+ HP would be fine on a 4"... the 5" will have a deeper tone to it. both our 6.7s have 5" exhausts with mufflers, and you can barely even notice it when cruising, but has a nice tone when wide open. straight pipe naturally has the best sound-but you'll notice more of a drone than with a muffler.


Sent looking at my blown up 6.4

 

[onebadf150]

I doubt 4" is that much different, and 600+ HP would be fine on a 4"... the 5" will have a deeper tone to it. both our 6.7s have 5" exhausts with mufflers, and you can barely even notice it when cruising, but has a nice tone when wide open. straight pipe naturally has the best sound-but you'll notice more of a drone than with a muffler.


Sent looking at my blown up 6.4

What exhaust system are you running that exactly what my father wants? Did you experience and low end power loss due to the 5" exhaust sizing? I've heard but don't have proof that a 5" exhaust could cause a loss low end power and hurt mileage. I don't really believe it.

 

[powerstrokin15]

no. it's not gonna hurt a thing.... running a 5" stainless flopro with muffler


Sent looking at my blown up 6.4

 

[Rowdy]

Best bet is prolly gonna be ask an expert. Every one is gonna have a different opinion. My personnel experience is I have had 4" and 5" I notice that my EGT's are lower with the 5" especially when towing heavy loads (27' toy hauler full of water and gear with my can am commander in it cruise set at 80mph) . Yes the 4" is sufficient for most people and most applications but I Don't under stand why any one would say there would be no difference going from 4"to 5". So is there no difference going from 3" to 4"? Then why do we even put exhaust systems on? :morons:

 

[powerstrokin15]

there probably is. yes. but is there a huge difference? I don't think so. did you notice 100* or more? the price difference and even sound of 4" is preferred by some people.

I got a good example-you know shones truck? makes what-1000hp on fuel. he has dual exhausts. which come in 4" only. unless he got them custom made or runs 5" until the axle and reduces.

we could probably get away with a 3" if it didn't have a pancaked down pipe, Cat, DPF, urea in some cases, and restrictive muffler from the factory...


I sell these kits every day..


Sent looking at my blown up 6.4

 

[CATDiezel]

I think that lower EGT's is defiantly an appreciable difference!

There are 1000hp engines running 4" all day long. Twice the cubes to boot!

 

[Rowdy]

There are 1000hp engines running 4" all day long. Twice the cubes to boot!

Yep 4" exhaust is the BEST wished I would have got 4"! :thumbup:

 

[TheBigNasty]

I have a feeling if 6" exhaust systems were readily available and marketed in the latest issue of diesel power, you'd be telling us 5" is junk and 6" is the only way to go.

There's nothing wrong with 5", I have 5" on mine for the look and sound. Fact is though, it's not necessary for any power these engines will ever see.

 

[dieselpower]

Get whatever you want. 5" will probably have a deeper tone, but as was stated, will not be necessary for flow.

All the air has to go through a 3.5" (or 4") downpipe anyways.

Sent from my MB886 using Tapatalk 2

 

[Rowdy]

I have a feeling if 6" exhaust systems were readily available and marketed in the latest issue of diesel power, you'd be telling us 5" is junk and 6" is the only way to go.

There's nothing wrong with 5", I have 5" on mine for the look and sound. Fact is though, it's not necessary for any power these engines will ever see.

Lol:blah: Yeah I am thinking about cutting holes in the bed so I can run 8" stacks! :bs: