5" vs. 4" inch exhaust - Diesel Forum

Roach45 · 03-07-2009, 12:13 PM

Howdy,
Does anyone know what the pros or cons are to having a 5 inch system over a 4 inch? Does the additional inch make that big of deal, or is it just a waste of money? My main reason for putting a larger exhaust system on is to lower my EGT's when towing our toy hauler, plus I like the sound

Thanx,
Roach

Spoolin'6.0 · 03-07-2009, 01:00 PM

i have a 5inch mbrp cat delete and it sounds fing awesome most people say the bigger diameter and lower the egts and the 5 inch is way louder then the 4 inch but thats just me i would go with a 5 in ebay has them for $500-600 all day long thats where i got mine 550 to my door

NavyF350 · 03-07-2009, 01:24 PM

5" stack is the way to go

JimmyDee · 03-07-2009, 05:16 PM

Most of the oldtimers on this site will agree that there is no advantage to going to a 5" exhaust. They may look good and sound great but there will not be a significant decrease in EGT with the 5".
Now if you are going to 400-500 HP, maybe but that is a different story.
Jim

StrokinTiger · 04-02-2009, 02:28 AM

Quote:

Originally Posted by JimmyDee

Most of the oldtimers on this site will agree that there is no advantage to going to a 5" exhaust. They may look good and sound great but there will not be a significant decrease in EGT with the 5".Now if you are going to 400-500 HP, maybe but that is a different story.
Jim

That is the main issue.....if you aren't running stacked chips...then you don't really want to do a 5 inch exhaust. The problem with doing a 5 with no cats AND NO PROGRAMMERS is that you will actually LOSE torque and hp.

Chuckdogg6.0 · 04-02-2009, 05:55 AM

Try searching the forums for more information. I see this issue being covered a few times a month.

lubbockguy1979 · 04-02-2009, 01:28 PM

The 5" exaust will change the power band by moving up a few rpms. The egt difference is negligable unless you are in the 500hp+. The main difference is how loud it will be. A lot of people are running 500+ with 4". Losing the cat and miffler on a stock exaust will be compareable to a 4" with a muffler. A 5" exaust with out a tuner shouldn't give a noticable loss of hp. That argument is like the loss or back pressure on a turbo diesel thing. With a free flowing exaust your turbo will spool faster. Also on that note you will have better performance with some egts. Hot air in the turbo makes it work better.... Of course I don't mean 1300+ degree air but hot air has more energy than cold air for pushing the turbo.

fxdwgi · 04-02-2009, 05:27 PM

Quote:

Originally Posted by StrokinTiger

That is the main issue.....if you aren't running stacked chips...then you don't really want to do a 5 inch exhaust. The problem with doing a 5 with no cats AND NO PROGRAMMERS is that you will actually LOSE torque and hp.

Quote:

Originally Posted by lubbockguy1979

The 5" exaust will change the power band by moving up a few rpms. The egt difference is negligable unless you are in the 500hp+. The main difference is how loud it will be. A lot of people are running 500+ with 4". Losing the cat and miffler on a stock exaust will be compareable to a 4" with a muffler. A 5" exaust with out a tuner shouldn't give a noticable loss of hp. That argument is like the loss or back pressure on a turbo diesel thing.

It is completely obvious that these posters know nothing of how a turbo engine works.

The difference between 4" or 5" is nothing but looks and sound.

.

lubbockguy1979 · 04-02-2009, 07:45 PM

Quote:

Originally Posted by fxdwgi

It is completely obvious that these posters know nothing of how a turbo engine works.

The difference between 4" or 5" is nothing but looks and sound.

.

so since i know absolutely nothing about a turbo diesel then explain to me why the "only" difference is looks and sound? a larger diameter pipe will flow more cfm's? more cfm = more flow? less restriction less heat? based on that awnser i question you knowldge. i simply stated that by allowing more flow it pushes up the rpm band of the engine. this is peak tq and hp. the egt difference is negligable and only a issue if you are able to get enough fuel and air (there are not alot of 6.0 engines above 700hp probably a hand full and in that area it would likely help egts) a stock 3.5" exaust straight piped will significantly lower egts and that is comparible to a 4" with stock cat and muffler. if you are looking at making more noise straight pipe will do this. the last part of my post was refering to the idea that the 6.0 needs back pressure to opperate corectly and this is not true. with a larger or freer flowing exaust the turbo will spool fater.
where is it exactly that you can teach me something?

StrokinTiger · 04-02-2009, 09:40 PM

Quote:

Originally Posted by fxdwgi

It is completely obvious that these posters know nothing of how a turbo engine works.

The difference between 4" or 5" is nothing but looks and sound.

.

lol lol lol!!!! Genius I tell ya......genius!

StrokinTiger · 04-02-2009, 09:45 PM

Quote:

Originally Posted by lubbockguy1979

e idea that the 6.0 needs back pressure to opperate corectly and this is not true. with a larger or freer flowing exaust the turbo will spool fater.

That is EXACTLY why I made my post.........backpressure....

Genius.....

fxdwgi · 04-02-2009, 09:58 PM

Quote:

Originally Posted by lubbockguy1979

so since i know absolutely nothing about a turbo diesel then explain to me why the "only" difference is looks and sound? a larger diameter pipe will flow more cfm's? more cfm = more flow? less restriction less heat? based on that awnser i question you knowldge. i simply stated that by allowing more flow it pushes up the rpm band of the engine. this is peak tq and hp. the egt difference is negligable and only a issue if you are able to get enough fuel and air (there are not alot of 6.0 engines above 700hp probably a hand full and in that area it would likely help egts) a stock 3.5" exaust straight piped will significantly lower egts and that is comparible to a 4" with stock cat and muffler. if you are looking at making more noise straight pipe will do this. the last part of my post was refering to the idea that the 6.0 needs back pressure to opperate corectly and this is not true. with a larger or freer flowing exaust the turbo will spool fater.
where is it exactly that you can teach me something?

Sure....I can explain it you....hold on.

1. The turbo provides the backpressure.
2. You could put a 10" exhaust pipe on the truck, you still have to reduce it to the turbo housing outlet.

Quote:

Originally Posted by StrokinTiger

lol lol lol!!!! Genius I tell ya......genius!

Nope...nobody is a genius with 6.0.....well except 1 guy at Ford and he even hates them.

Quote:

Originally Posted by StrokinTiger

That is EXACTLY why I made my post.........backpressure....

Genius.....

Which is made by the turbo..............Genius.

I await the responses.....

StrokinTiger · 04-02-2009, 10:23 PM

Quote:

Originally Posted by fxdwgi

Sure....I can explain it you....hold on.

1. The turbo provides the backpressure.
2. You could put a 10" exhaust pipe on the truck, you still have to reduce it to the turbo housing outlet.

Nope...nobody is a genius with 6.0.....well except 1 guy at Ford and he even hates them.

Which is made by the turbo..............Genius.

I await the responses.....

wait......I think you somehow missed the heavy doses of sarcasm in my last two posts.........

did you not notice that I pointed out that I was referring to backpressure, and even noted where the above poster had said that backpressure was not an issue on the 6.0?

I know how turbo works.....and I also know that the free-er flowing the exhuast, the better. In fact....if you could tow around a trailer with a huge vacuum cleaner on it hooked to your exhaust.....you would get even better performance and spooling.....

However....I was a believer in the rumor(which someone also mentioned above), that something was different on the 6.0, and that you could indeed "need" back pressure, even on the downside of the turbo. I was actually told this by a Ford tech....and by the guy that sold me my MBRP's at Truck Toyz.

Am I a genius? LOL, not by any means.....but I do like to refer to myself as one in a sarcastic response that pokes fun of.....myself.....

Btw....where is that little sarcasm emoticon when you need it......

lubbockguy1979 · 04-03-2009, 12:07 AM

There is no lesson to learn evidently? I never argued back pressure I simply stated the rumor or wives tale that keeps surfacing.... There is more of a difference then just looks and sound which is eactly what I pointed out. You have the basics. Now go study 6.0 little 7.3 grasshopper

fxdwgi · 04-03-2009, 08:42 AM

Quote:

Originally Posted by lubbockguy1979

There is no lesson to learn evidently? I never argued back pressure I simply stated the rumor or wives tale that keeps surfacing.... There is more of a difference then just looks and sound which is eactly what I pointed out. You have the basics. Now go study 6.0 little 7.3 grasshopper

Well since I work on these trucks for a living (ASE L2, Ford Senior Master, TRP) please educate a little grasshopper some more.

Also, how did you point out any change besides looks and sound?