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my car has long tubes, will running open headers increase power or anything, or cause more harm than good...or no difference other than sound
 

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Bringing Yellow Back
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no, it will probably hurt you, you need back pressure
 

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my car was noticeably slower running open headers.
 

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I couldn't get past the sound long enough to try it. Man, these cars sound like complete ass with open headers.
 

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Head Unicorn
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Open headers will most definitely increase your ablitly to piss your neighbors off as well as yourself. Sounds like ass, loses power and is just plain pointless. Keep exhaust/mufflers, they help you not hurt you at low power levels like these cars make.
 

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Nile P. Pezdel of Pez Dispenser Inc. CCA
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Not that I would do it, but if the car was dyno tuned with open headers, would that show a gain?
 

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no, it will probably hurt you, you need back pressure
sorry bro, but thats a myth. a lot of hot rods have open headers and even top fuel dragsters... use some common sense.

I ran open LT's for a minute and when i revved it up it made people jump... :cool:
 

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Nile P. Pezdel of Pez Dispenser Inc. CCA
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sorry bro, but thats a myth. a lot of hot rods have open headers and even top fuel dragsters... use some common sense.

I ran open LT's for a minute and when i revved it up it made people jump... :cool:
A stock engine that can't adjust its fuel delivery will need backpressure to run properly. Lack of back pressure means more air is being sucked into the combustion chamber to compensate leading to lean conditions in the cylinders.

Source: The truth about exhaust backpressure and torque

Makes sense to me.
 

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!FACEPLATED!
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sorry bro, but thats a myth. a lot of hot rods have open headers and even top fuel dragsters... use some common sense.

I ran open LT's for a minute and when i revved it up it made people jump... :cool:
sorry to bust your bubble but it is not a myth with the 2v mod motor. Your comparison is like comparing apples to oranges, totally different animals
 

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9k All Day.
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but dont you have open headers f8l?
 

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Too Soon, Junior!
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Sadly very few people really understand compressible flow in terms of automotive exhaust discharge, so my humble appeal to all of you is please don't just post random info you've heard or read on the internet somewhere, since it's probably incorrect. By acoustically tuning the manifolds, the major players in exhaust flow are port discharge velocity and pressure. The distinct sound you hear from the exhaust of an engine is the discharge of high pressure sonic pulses. These pulses bounce and resonate against the manifold walls and each other, which shapes the manner in which the exhaust gases exit the combustion chambers. The saying that a vehicle needs backpressure in order to make peak power isn't exactly correct. A typical engine is built and optimized for a certain range of RPMs, in which the exhaust discharge momentum (a function of velocity) actually helps pull air out of the combustion chamber during the exhaust stroke, and sometimes, part of the intake stroke as well. How well this works is controlled by the actuation of the valves and how the engine was designed, as most road cars are designed to keep a portion of the exhaust gases in the combustion chamber at low RPM to optimize for fuel efficiency.

In order to benefit from open headers on a modular 4.6, you'd just need a custom set of cams and a tune to optimize for the RPM range of your choice, that's about it. No need to do it on a road car since it'd smell bad, get you beaten by the people you piss off, and you'd probably lose a small bit of fuel efficiency and low RPM power. I haven't studied Ford engines enough to know whether you'd gain any noticeable power at higher RPM from open headers on a stock motor, but I'm sure there's some potential there if the camshafts were fabricated with that in mind.
 

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Proud American
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Sadly very few people really understand compressible flow in terms of automotive exhaust discharge, so my humble appeal to all of you is please don't just post random info you've heard or read on the internet somewhere, since it's probably incorrect. By acoustically tuning the manifolds, the major players in exhaust flow are port discharge velocity and pressure. The distinct sound you hear from the exhaust of an engine is the discharge of high pressure sonic pulses. These pulses bounce and resonate against the manifold walls and each other, which shapes the manner in which the exhaust gases exit the combustion chambers. The saying that a vehicle needs backpressure in order to make peak power isn't exactly correct. A typical engine is built and optimized for a certain range of RPMs, in which the exhaust discharge momentum (a function of velocity) actually helps pull air out of the combustion chamber during the exhaust stroke, and sometimes, part of the intake stroke as well. How well this works is controlled by the actuation of the valves and how the engine was designed, as most road cars are designed to keep a portion of the exhaust gases in the combustion chamber at low RPM to optimize for fuel efficiency.

In order to benefit from open headers on a modular 4.6, you'd just need a custom set of cams and a tune to optimize for the RPM range of your choice, that's about it. No need to do it on a road car since it'd smell bad, get you beaten by the people you piss off, and you'd probably lose a small bit of fuel efficiency and low RPM power. I haven't studied Ford engines enough to know whether you'd gain any noticeable power at higher RPM from open headers on a stock motor, but I'm sure there's some potential there if the camshafts were fabricated with that in mind.
isnt it shitty being an engineer sometimes? LOL
 

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Too Soon, Junior!
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Haha I've heard that the worst thing about going into automotive engineering is spending thousands of hours designing and optimizing a vehicle system from conception to production, then having it ruined because the consumer thinks he knows better :lol
 

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sorry bro, but thats a myth. a lot of hot rods have open headers and even top fuel dragsters... use some common sense.

I ran open LT's for a minute and when i revved it up it made people jump... :cool:
only because they thought their local garbage truck was about to hit them, open headers sounds stupid on our cars
 

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only because they thought their local garbage truck was about to hit them, open headers sounds stupid on our cars
I have to agree, and that garbage truck bit was hilarious. :eek:

Every time I see an open header video of a close to stock 4.6, I'm just like, what are you doing? I mean it's cool to see what it sounds like when doing the exhaust like 0949er's video shows, but otherwise it's dumb as hell.

The backpressure argument is also dumb. It's not a matter of the backpressure, it's the exhaust gas velocity. Let's imagine something as simple as a garden hose. For a little hose, they spray pretty far on certain settings of the little gun majigger sprayer. Take that off, and it's just a limp flow of water that just falls to the ground. Rip the mid pipe off of a 4.6, and that exhaust flow just becomes a limp ball of gasses that is lost in this huge world, doesn't know where to go, and flows slow as **** on a high dairy diet.

Techno’s “Know your car” Series #4 –

Exhaust Theory

Plenty of write ups on it that can explain it better than I can at 5:20 something A.M. But anyhow it almost annoys me that someone wants to run open headers on these cars. I hate that gargly sound I get for a couple hundred RPM above idle just from the O/R X pipe. Almost sounds like an exhaust leak. It's horrible even with a cammed car with long tubes, let alone a stock internal 4.6 with open manifolds.
 

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!FACEPLATED!
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but dont you have open headers f8l?
only had them for a day

I haven't studied Ford engines enough to know whether you'd gain any noticeable power at higher RPM from open headers on a stock motor, but I'm sure there's some potential there if the camshafts were fabricated with that in mind.
on a stock engine 4.6, you will lose power with open LTs and run slower 1320 times. I have done testing at the track back to back runs open LTs compared to midpipe w/ dumped mufflers, and back to open LTs, then back to the exhaust again. Every time I put the exhaust back on, the car ran quicker times
 
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