new headers

[hazmat456]

so I finally broke down and called in a order to Bob a couple of weeks ago,he said that I should have my new headers by the end of this week, and I sure hope so because the mounty is all torn down and sitting ready for them.I tore off the secondary cats and muffler,finally rusted out after 182000 and ordered a thrush 2.25 duel in single out muffler and some straight 2.25 pipe. So I know that length of primaries and collector make a difference on where your power is but dose the y-pipe or in my case the muffler?
I want to keep the stock tail-pipe and resonator (re:glass pack) but dose it make a difference if the muffler is moved forward from the stock location?

 

[Mountaineer1113]

so I finally broke down and called in a order to Bob a couple of weeks ago,he said that I should have my new headers by the end of this week, and I sure hope so because the mounty is all torn down and sitting ready for them.I tore off the secondary cats and muffler,finally rusted out after 182000 and ordered a thrush 2.25 duel in single out muffler and some straight 2.25 pipe. So I know that length of primaries and collector make a difference on where your power is but dose the y-pipe or in my case the muffler?
I want to keep the stock tail-pipe and resonator (re:glass pack) but dose it make a difference if the muffler is moved forward from the stock location?

Well, from my experience, when I had the muffler further from the cat, the exhaust note was more raspy. As far as power is concerned it shouldn't matter where the muffler is because the amount of flow will still be the same.

 

[Electrohacker]

Well, from my experience, when I had the muffler further from the cat, the exhaust note was more raspy. As far as power is concerned it shouldn't matter where the muffler is because the amount of flow will still be the same.

not completely true

more pipe = more static pressure and more resistance... technically... but I am referring to a very small number

 

[hazmat456]

Well, from my experience, when I had the muffler further from the cat, the exhaust note was more raspy. As far as power is concerned it shouldn't matter where the muffler is because the amount of flow will still be the same.

well there has to be some connection between where the power band is and where the pipes merge, after all there are formulas for primary length and diameter the longer the lower your power comes on,intake runner length=shorter more power at the top end
however I have two conflicting thoughts on this,I know that I need to maintain some back-pressure,and after loosing the secondary cats, that means move the merge point forward because a single pipe will offer more resistance than two pipes
but if the merge point follows the same rules as everything else
or am I just over analyzing because it won't make enough difference to notice

 

[Mountaineer1113]

well there has to be some connection between where the power band is and where the pipes merge, after all there are formulas for primary length and diameter the longer the lower your power comes on,intake runner length=shorter more power at the top end
however I have two conflicting thoughts on this, I know that I need to maintain some back-pressure ,and after loosing the secondary cats, that means move the merge point forward because a single pipe will offer more resistance than two pipes
but if the merge point follows the same rules as everything else
or am I just over analyzing because it won't make enough difference to notice

IMHO opinion, I don't think that ANY "backpressure" is good for any engine. From what I've read and studied, exhaust is all about velocity and flow. The pressure in the exhaust shouldn't be in the form of any restrictions.

http://www.ehow.com/list_5806222_flow-characteristics-exhaust-manifolds.html

But you're right on sizing and merging of exhaust pipes, there's always a better combination for a certain powerband. Longer primaries of the header are better suited for low to midrange torque and vice versa. Not too sure about the downpipes but from what I think, as long as they have a smooth merge it should flow nicely for any powerband.

 

[TNTEXPLORER]

After all this reading, I still have a question if I may, I have just bought an Explorer for $500, needs some engine tranny and trans case work, including exhaust, what would be a nice exhaust system for a 97 with a 5.0 and I do plan on doing engine mods to attempt around 300 to 350hp?

 

[Heavymentill]

IMHO opinion, I don't think that ANY "backpressure" is good for any engine. From what I've read and studied, exhaust is all about velocity and flow. The pressure in the exhaust shouldn't be in the form of any restrictions.

The small amount of back pressure caused by the exhaust system is desirable so that the combustion chamber stays hot enough for a more complete combustion. A small amount of back pressure about 2 3/4 lbs keeps the air-fuel mixture from going out the exhaust during valve overlap and results in a denser air-fuel charge in the cylinder.

 

[Mountaineer1113]

The small amount of back pressure caused by the exhaust system is desirable so that the combustion chamber stays hot enough for a more complete combustion. A small amount of back pressure about 2 3/4 lbs keeps the air-fuel mixture from going out the exhaust during valve overlap and results in a denser air-fuel charge in the cylinder.

Supporting evidence?

What you're describing sounds a little like Reversion which is also bad.

 

[Heavymentill]

Supporting evidence?

What you're describing sounds a little like Reversion which is also bad.

Ever seen a dragster where flames shoot out the headers? You want combustion to take place in the cylinders not the exhaust. On a side note the restriction the exhaust system provides also keeps the exhaust system hot after the engine is shut off so that cold air can not enter and warp an exhaust valve.

 

[hazmat456]

well reversion is bad, but the long exhaust pipe when merged correctly the opposite is true.
The velocity of the exhaust gasses will help pull the next exhaust pulse out,it's a siphoning effect, reversion happens when two or more pulses collide and reverse, this is usually the result of a bad manifold design or reving a motor past the header's designed capacity.

 

[celly]

Soooo, are they there yet?

 

[hazmat456]

Nope still waiting for the headers,Bob said that he would be sending them when he hit my card and it's been about a week now,just over, since the charge showed up soo hopefully it will be back up n running by the weekend

 

[Mountaineer1113]

well reversion is bad, but the long exhaust pipe when merged correctly the opposite is true.
The velocity of the exhaust gasses will help pull the next exhaust pulse out,it's a siphoning effect, reversion happens when two or more pulses collide and reverse, this is usually the result of a bad manifold design or reving a motor past the header's designed capacity.

That's true! This is called Scavenging. You want an empty for a cylinder for the next clean air/fuel mixture to enter. The exhaust valve is closed once the new fresh air/fuel mixture is in the cylinder so I don't understand why you think there's a need for there to be "backpressure". It's just a restriction in the exhaust. A lot of people remove any restriction (i.e. cat converters, swapping to high flow mufflers or x/h-pipes) in the exhaust just for the simple purpose of hp numbers.

 

[hazmat456]

well I guess we call it back pressure when what we are really trying to do is optimize the exhaust velocity to a giving rpm range, it's a generic term.

 

[hazmat456]

well I finally got the headers last week, went for my first long drive last night. After not driving the vehicle for more than two months it's hard to see to much of a difference,passing is better,but I think that my torque converter lock-up needs some service. Slight peddle pressure, especially in traffic will cause it to unlock when I don't think it should. Overall the truck is smoother and quieter(a good thing)yet still has a nice note to it

 

[66427]

Congrats on th TM's...

From everything I have read regarding H and X pipes, closer to the manifolds will increase torque, further back will increase horspower. I would assume a similar effect with the 2 to 1 muffler.

I would keep it in the stock location and add an H pipe where the cats used to be.