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Discussion Starter #1 (Edited)
I just got a Magnaflow 3" SI/ 2.5" DO, going on a bone stock 4.7l. Is there any reason not to run 2.5" DO on my 4.7. If so, why? Ive read to stick with 2.25" on a 4.7, can someone give me a detailed explanation as to why?
 

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Because some people think they know everything there is to know about the 4.7....

If its a SI/DO, the DO doesnt really matter what size as much as the "in" part does.
You'll be fine man
 

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Nathan K said:
I just got a Magnaflow 3" SI/ 2.5" DO, going on a bone stock 4.7l. Is there any reason not to run 2.5" DO on my 4.7. If so, why? Ive read to stick with 2.25" on a 4.7, can someone give me a detailed explanation as to why?
The 2.25" you have read is in reguards to "True Duels"

What your doing will be fine!!!!<<<Sorry adam I'm having with-draws LOL!!!
 

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adamsredlines said:
Because some people think they know everything there is to know about the 4.7....

If its a SI/DO, the DO doesnt really matter what size as much as the "in" part does.
You'll be fine man
Well in your statment you just proved they at least "SOME PEOPLE" know more than you! :thatfunny

Are you going to add any of your "EXTENSIVE" experience to back up your lose lips? Or is your technical responce to his question limited to an attack on "SOME PEOPLE"?

I know your not going to go onpast experince because you dont have any of that.... so please enligten us on your "THEORY" as to why an system that is CLEARLY too large would do just fine?

SPEED SAFE, AIR RAM
 

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I, unlike SOMEONE on here, dont claim to be the know-all, god given gift to the 4.7 world. My technical experience with these engines is very limited, I've never claimed otherwise. I've never played up my experience with them trying to make others think I've torn these down and know whats going on inside them like SOMEONE.

And why take offense to a general statement, unless you think its YOU who thinks they know all...surely thats not the case?
 

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Nathan K said:
I just got a Magnaflow 3" SI/ 2.5" DO, going on a bone stock 4.7l. Is there any reason not to run 2.5" DO on my 4.7. If so, why? Ive read to stick with 2.25" on a 4.7, can someone give me a detailed explanation as to why?
Unfortunately 2.5" duals even on a "CAT BACK" will not be the best option for your 4.7L... Unlike "SOME PEOPLE" I will offer an explanation along with my statement.

The best exhaust system will promote the Scavenging effect and low end torque. In order to create "SCAVENGING" your system needs to promote HIGH VELOCITY all the way through it... This high velocity actual PULLS the exhaust gases through the system rather than being "PUSHED" out.

EXAMPLE:

Take a garden hose and drain your pool. You stick a long hose into your pool and suck on one end to get the water flowing.... Once the water starts you drop the hose and watch as the water continues to FLOW out the hose... and if you watch close you can actually see the water pick up speed... until the inner diameter of the hose limits this speed.

Now think of the pool as your cylinder, the hose as your exhaust system, the water as your exhaust gases.

If you where to use a short hose you would not be able to move the water out as quickly... because it will not create the needed velocity to create the needed speed.... it would lack the volume to continue the scavenging effect.

So in short, do not go too large in diameter... if you go true Duals keep them on the smaller side with same size tips... If you go dual cat back insure that the Volume of the 2 Dual out pipes do not exceed the volume of you single in... This will cost your performance...

The reason you hear many people say that a 3" singe out performs a dual out is because its too easy to go too large when you go dual out... everyone feels they need 2.5 pipe on a stock engine... and that’s on the too large end for most of out trucks... yes even the "HUGE" (348ci) 5.7L... The 4.7L guys should stay away from the dual 2.5 and go no larger than the 2.25.... That’s more than enough for the 287ci 4.7L....

Now in your case your adding the duals at the end of the muffler.... but the scavenging effect does NOT stop just after the muffler and by going LARGER you actual cause the gases to stop and then they must be PUSHED out becoming a restriction rather than helping with the performance.... In that case you would be better off DUMPING it after the muffler.

In my opinion the best system for the 4.7L would be a SINGLE 3" full length system.

But hey what do I know... just a little bit of theory of opperation that all. I clearly don't know everything... but I know more then "SOME PEOPLE"

SPEED SAFE, AIR RAM
 

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adamsredlines said:
I, unlike SOMEONE on here, dont claim to be the know-all, god given gift to the 4.7 world. My technical experience with these engines is very limited, I've never claimed otherwise. I've never played up my experience with them trying to make others think I've torn these down and know whats going on inside them like SOMEONE.

And why take offense to a general statement, unless you think its YOU who thinks they know all...surely thats not the case?
LOL... Yeah right dude, you know exactly what you where "IMPLYING"... Hows the truck running? Hopefully SCT will have it completed soon so you can lose some of your bitterness. Im sure with your list of mods you should be running some impressive times.

SPEED SAFE, AIR RAM
 

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adamsredlines said:
Its always good technical advice to compare an engine to a pool.
Your right, it does... if you cant GRASP the theory of opporation it does help to be able to understand the subject enough to brake it down to a level that can be understood by someone who does NOT understand the threory of opperation...

Are you disagreeing with the theory of opperation? Perhaps if you knew a "LITTLE BIT" of the THEORY of OPPERATION you would not be so quick to attack people who do. I certanly do not know everything... but I have built several Pontiac engines that have performed well for years... Along the way I did pick up a little bit. You would get a kick out of my 455 which will be belting out in the ball park of 650ft-lb at 3,000 RPMs... NA.

SPEED SAFE, AIR RAM
 

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Nathan K said:
I just got a Magnaflow 3" SI/ 2.5" DO, going on a bone stock 4.7l. Is there any reason not to run 2.5" DO on my 4.7. If so, why? Ive read to stick with 2.25" on a 4.7, can someone give me a detailed explanation as to why?
The setup wont really run any diff than a 3" si/so dumped exhaust, which alot of guys run..{It will sound better however if you exit on either side}

I'd say you would be just fine..

thats just me.


$
 

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AIR_RAM said:
Your right, it does... if you cant GRASP the theory of opporation it does help to be able to understand the subject enough to brake it down to a level that can be understood by someone who does NOT understand the threory of opperation...

Are you disagreeing with the theory of opperation? Perhaps if you knew a "LITTLE BIT" of the THEORY of OPPERATION you would not be so quick to attack people who do. I certanly do not know everything... but I have built several Pontiac engines that have performed well for years... Along the way I did pick up a little bit. You would get a kick out of my 455 which will be belting out in the ball park of 650ft-lb at 3,000 RPMs... NA.

SPEED SAFE, AIR RAM

I dont know I should take advice from someone on the "theory of opperation" who cant even spell it right...
And congrats on your 455, but that has nothing to do with the 287, completely different kind of motor.
 

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adamsredlines said:
I dont know I should take advice from someone on the "theory of opperation" who cant even spell it right...
And congrats on your 455, but that has nothing to do with the 287, completely different kind of motor.
Well if you think about it, why are you giving advice then... he clearly asked for a "DETAILED" explanation and you took the opportunity to attack "SOME PEOPLE" without even adding any of your extensive experience... He clearly asked for a DETAILED EXPLANATION... The theory of operation does not change. DE DE DEE!


SPEED SAFE, AIR RAM
 

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Again, I've never claimed to have extensive experience, I dont know why you keep implying that I've said I do. I offered my opinion and why, and SOMEONE jumped the gun, took offense, and once again, showed their true colors.
 

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Ok folks, time for a cooling off period.;)
 
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