Converters Needed?
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From: Zanesville, Ohio
Bluegrass thanks for that info. Here in a few mins. I am going to start to weld these things back together. Will it hurt to use the dual pipes that were installed or should I use the factory Y and use a SI/DO.
Johngs, I am not sure as to why I only have 2 O2's could it be because I have the 4.6L instead of the 5.4L?
Johngs, I am not sure as to why I only have 2 O2's could it be because I have the 4.6L instead of the 5.4L?
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From: Fort Worth,Tx
Originally Posted by Bluegrass
I'm sorry if some one take me for a smart *** but do you all know what complexity you entered into by removing the OX sensors?
It is really deep and may not be worth while to do much explaining unless you want to know..
Just a few tidbits.
1. No Ox sensors makes the PCM go to fixed internal fuel tables that are very rich to protect the engine. That translates to really poor fuel milage.
2. The PCM looks at the rear sensors and does a compare to the front sensors as a way to access the condition of the cats. No cats equals total failure of that function and a cel/code report THAT YOU CANNOT get away from with any simple bypass method.
3. The stock system is tuned for the best overall average torque for the averge owner so it's not at all surprising low end is lost when other systems are installed..
And theres a lot more to it folks.
Your playing with a complex total system and thinking it's too simple.
It is really deep and may not be worth while to do much explaining unless you want to know..
Just a few tidbits.
1. No Ox sensors makes the PCM go to fixed internal fuel tables that are very rich to protect the engine. That translates to really poor fuel milage.
2. The PCM looks at the rear sensors and does a compare to the front sensors as a way to access the condition of the cats. No cats equals total failure of that function and a cel/code report THAT YOU CANNOT get away from with any simple bypass method.
3. The stock system is tuned for the best overall average torque for the averge owner so it's not at all surprising low end is lost when other systems are installed..
And theres a lot more to it folks.
Your playing with a complex total system and thinking it's too simple.
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From: Fort Worth,Tx
Originally Posted by guido874
Bluegrass thanks for that info. Here in a few mins. I am going to start to weld these things back together. Will it hurt to use the dual pipes that were installed or should I use the factory Y and use a SI/DO.
Johngs, I am not sure as to why I only have 2 O2's could it be because I have the 4.6L instead of the 5.4L?
Johngs, I am not sure as to why I only have 2 O2's could it be because I have the 4.6L instead of the 5.4L?
two on the manifolds and two after the cats stock on all of our trucks mustangs crown vics.
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From: Zanesville, Ohio
Well that is probably why I never noticed them, since they are on the manifold. I looked and I stand corrected 
Guess it pays to pay attention and look at things more closely. Thanks
Guess it pays to pay attention and look at things more closely. Thanks
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From: Fort Worth,Tx
Originally Posted by guido874
Well that is probably why I never noticed them, since they are on the manifold. I looked and I stand corrected Guess it pays to pay attention and look at things more closely. Thanks
Guess it pays to pay attention and look at things more closely. Thanksits all good lol no hard feelings atleast u noticed and admitted it hard characteristic to admit something like that
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From: Seabrook,NH
Originally Posted by Faster150
ford cats usually have about 1-2PSI of back pressure any more and ur cats are clogged any less and u will likely throw a CEL
The rear two just check for working cats based on oxygen levels and the front two are used to adjust your Air:Fuel ratio so you do not run on a canned value table. You can sim out the rears but you need the front ones for proper A:F ratios and proper performance. Just like myself, Bluegrass and others have pointed out several times in various threads.
Technical Article Contributor
Joined: Dec 1997
Posts: 9,417
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From: Windsor,Ontario,Canada
Faster150,
Stop with the backpressure BS. Read the second paragraph in the following link.
http://www.ssheaders.com/header.htm
JMC
Stop with the backpressure BS. Read the second paragraph in the following link.
http://www.ssheaders.com/header.htm
JMC
Senior Member
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From: Fort Worth,Tx
Originally Posted by JMC
Faster150,
Stop with the backpressure BS. Read the second paragraph in the following link.
http://www.ssheaders.com/header.htm
JMC
Stop with the backpressure BS. Read the second paragraph in the following link.
http://www.ssheaders.com/header.htm
JMC
A muffler is an ambiguity in the performance world, as it can have both good and bad effects on power output. Back pressure is essential for peak power in almost any application, even 6000hp alcohol-burning Top Fuel dragsters have some built-in back pressure. Before we begin this discussion, take note that 1 atmosphere is the pressure that air is at naturally (uncontained) at sea level.
hmm read that then tell me what u think....
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From: St. Charles, MO
The truth about backpressure
Backpressure is always bad and does not increase the power or torque on any engine. Your engine will run best with no backpressure at all. I know, everybody says that you need backpressure. What you are looking for is a condition that simultaneously creates backpressure. Backpressure is the residual pressure within the exhaust system that is higher than atmospheric pressure. The backpressure is a pumping loss where the engine basically has to fight the phenomenon of backpressure to expel exghaust gasses. Those who are in favor of backpressure are partially right, but are confused on what to say. You do need something to create a backpressure condition in your exhaust, just without the backpressure.
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From: Fort Worth,Tx
Originally Posted by Zaairman
Backpressure is always bad and does not increase the power or torque on any engine. Your engine will run best with no backpressure at all. I know, everybody says that you need backpressure. What you are looking for is a condition that simultaneously creates backpressure. Backpressure is the residual pressure within the exhaust system that is higher than atmospheric pressure. The backpressure is a pumping loss where the engine basically has to fight the phenomenon of backpressure to expel exghaust gasses. Those who are in favor of backpressure are partially right, but are confused on what to say. You do need something to create a backpressure condition in your exhaust, just without the backpressure.
motorcycles need some back pressure any engine does that doesnt have overlap... or u will burn the valves and loose compression down in the lower RPMS
Senior Member
Joined: Jul 2004
Posts: 6,200
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From: Easton, Pa.
150, where in the world do you come up with your non-sence?
Do some study before you make these statements.
Back pressure means there would be exhaust gas left in the cylinders each cycle that sure don't add any power anytime.
Try running an engine on a dyno sometime and introduce some of it's own exhaust back into the engine's carb and watch the power drop. This is no bull ****.
I think your doing this to stur up others unless you really don't have accurate knowledge on all this.
At about 20 years old, i'm calling you on all this.
Do some study before you make these statements.
Back pressure means there would be exhaust gas left in the cylinders each cycle that sure don't add any power anytime.
Try running an engine on a dyno sometime and introduce some of it's own exhaust back into the engine's carb and watch the power drop. This is no bull ****.
I think your doing this to stur up others unless you really don't have accurate knowledge on all this.
At about 20 years old, i'm calling you on all this.
Last edited by Bluegrass; Aug 12, 2005 at 09:54 PM.
Technical Article Contributor
Joined: Dec 1997
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From: Windsor,Ontario,Canada
I guess you did not reat the second paragraph. You need to creat a vacuum in the system to properly scavenge the exhaust, or to be pushing so much out the pipes that the widest shortest route out of the head is desirable. See pic of top fuel drag car. Don't see a muffler do you?
JMC
JMC
Senior Member
Joined: Jan 2005
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From: Fort Worth,Tx
When you reduce back pressure, it is equivalent to increasing valve overlap, and when you increase back pressure, it is the same as decreasing the amount of valve overlap. That's why some people will say, "you need a muffler for torque", or, "you'll have more high-end, but less torque, if you run straight exhaust". They are right, but a muffler's purpose is to reduce sound output, not horsepower! By reducing back pressure in an exhaust system, you increase high-end horsepower at the cost of low-end torque.
https://www.f150online.com/forums/li...r/exhaust.html
https://www.f150online.com/forums/li...r/exhaust.html
Last edited by Faster150; Aug 13, 2005 at 03:59 AM.
Senior Member
Joined: Jan 2005
Posts: 5,389
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From: Fort Worth,Tx
Originally Posted by JMC
Faster150,
Stop with the backpressure BS. Read the second paragraph in the following link.
http://www.ssheaders.com/header.htm
JMC
Stop with the backpressure BS. Read the second paragraph in the following link.
http://www.ssheaders.com/header.htm
JMC
i did and it states clearly that....
The first misconception that needs to be cleared up is that a header relieves backpressure, but a certain amount of backpressure is needed for optimum performance.