backpressure and nitrous?
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From: reading, pa, usa
backpressure and nitrous?
when running nitrous does the same theory as a turbo apply? less back pressure the better or no? because i saw on the zex site they eliminated the cat on thier d16z6 hatch and just used a test pipe. i know with all motor u want some backpressure but what about with the use of nitrous?
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From: Simi Valley, CA, USA
Re: backpressure and nitrous? (97grnrs)
No, you will not lose power, you will gain power.
You never need any backpressure ever ever EVER EVER!!!!!!!!!!!!!! It doesn't matter what kind of setup you have. All a motor wants to do is breathe in as easily as possible and exhale as easily as possible. Backpressure is a no-no.
I wonder how that myth ever got started.
You never need any backpressure ever ever EVER EVER!!!!!!!!!!!!!! It doesn't matter what kind of setup you have. All a motor wants to do is breathe in as easily as possible and exhale as easily as possible. Backpressure is a no-no.
I wonder how that myth ever got started.
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From: St.Charles, MO, USA
Re: backpressure and nitrous? (EnzoSpeed)
It's a proven fact that on any car, some back pressure is important no matter what. If you have absolutely no back pressure, you gain high-end power, but at the sacrifice of low-end torque. Think about it, if what you say is true, what would happen if you say, completely eliminated all backpressure and removed your entire exhaust and your header? Even after tuning, to adapt to having 0 backpressure of course, any motor would run like complete ***. Don't you ever read HCi? They had an article explaining this in one of their mags a while back.
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From: Simi Valley, CA, USA
Re: backpressure and nitrous? (1990DA)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1990DA »</TD></TR><TR><TD CLASS="quote"> It's a proven fact that on any car, some back pressure is important no matter what. If you have absolutely no back pressure, you gain high-end power, but at the sacrifice of low-end torque. Think about it, if what you say is true, what would happen if you say, completely eliminated all backpressure and removed your entire exhaust and your header? Even after tuning, to adapt to having 0 backpressure of course, any motor would run like complete ***. Don't you ever read HCi? They had an article explaining this in one of their mags a while back.</TD></TR></TABLE>
Oh, so THAT'S how the myths get perpetuated
.
You are incorrect Mr. 3-posts. I've seen a car tuned without a header at all and it does in fact make more power than running open header. Bottom line - a motor is just a pump - it wants air IN and exhaust OUT. Don't buy into the bullshit.
Oh, so THAT'S how the myths get perpetuated
.You are incorrect Mr. 3-posts. I've seen a car tuned without a header at all and it does in fact make more power than running open header. Bottom line - a motor is just a pump - it wants air IN and exhaust OUT. Don't buy into the bullshit.
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From: tallafizzy, FL state
Re: backpressure and nitrous? (1990DA)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1990DA »</TD></TR><TR><TD CLASS="quote"> It's a proven fact that on any car, some back pressure is important no matter what. If you have absolutely no back pressure, you gain high-end power, but at the sacrifice of low-end torque. Think about it, if what you say is true, what would happen if you say, completely eliminated all backpressure and removed your entire exhaust and your header? Even after tuning, to adapt to having 0 backpressure of course, any motor would run like complete ***. Don't you ever read HCi? They had an article explaining this in one of their mags a while back.</TD></TR></TABLE>
as enzo is saying, back pressure is a pretty stupid myth; its about keeping velocity in the fluid not that backpressure nonsense
noobie
as enzo is saying, back pressure is a pretty stupid myth; its about keeping velocity in the fluid not that backpressure nonsense
noobie
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From: sd north county, CA, USA
Re: backpressure and nitrous? (97grnrs)
"backpressure is a myth" "you never need any backpressure ever ever ever"
You guys are totally wrong. There are tons of variables when it comes to tuning
an engine, not just Hondas, any engine. One of those variables is.. yep, exhaust system backpressure.
A particular engine setup may very well make more "peak" power and torque
with very little backpressure, but Ive seen more than a couple cars dyno'd that make much better power throughout the entire rpm band with a certain amount of exhaust backpressure. Why is this? It all has to do with the timing and velocity of the exhaust gases. Yes, an engine is an air pump, and the pulsing of the exhaust gases can actually help "pull" gases from other cylinders, letting the engine breathe better or worse depending on, yes, the amount of exhaust system backpressure.
Call me Mr. 2-posts, yes, Im a noobie when it comes to Honda-tech although Ive been on Hybrids.jp off and on since '97. Not that it matters since real world experience is more important than reading about it. Im not trying to step on anyone's toes here, just trying to back up 1990DA's post. Im just here waiting the two weeks so I can post some stuff for sale.
Anyways, If you think we're wrong, Id encourage you to do some research on it. Real research, not internet heresay message board stuff.
Back to the original post, yes, a stock D16Z will make better power minus a cat converter, especially on the bottle.
You guys are totally wrong. There are tons of variables when it comes to tuning
an engine, not just Hondas, any engine. One of those variables is.. yep, exhaust system backpressure.
A particular engine setup may very well make more "peak" power and torque
with very little backpressure, but Ive seen more than a couple cars dyno'd that make much better power throughout the entire rpm band with a certain amount of exhaust backpressure. Why is this? It all has to do with the timing and velocity of the exhaust gases. Yes, an engine is an air pump, and the pulsing of the exhaust gases can actually help "pull" gases from other cylinders, letting the engine breathe better or worse depending on, yes, the amount of exhaust system backpressure.
Call me Mr. 2-posts, yes, Im a noobie when it comes to Honda-tech although Ive been on Hybrids.jp off and on since '97. Not that it matters since real world experience is more important than reading about it. Im not trying to step on anyone's toes here, just trying to back up 1990DA's post. Im just here waiting the two weeks so I can post some stuff for sale.
Anyways, If you think we're wrong, Id encourage you to do some research on it. Real research, not internet heresay message board stuff.
Back to the original post, yes, a stock D16Z will make better power minus a cat converter, especially on the bottle.
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From: Simi Valley, CA, USA
Re: backpressure and nitrous? (Twinkies)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Twinkies »</TD></TR><TR><TD CLASS="quote">You guys are totally wrong. There are tons of variables when it comes to tuning. Furthermore, I'm a douchebag blah blah blah </TD></TR></TABLE>
You know, I've personally built and tuned enough race cars that I feel I shouldn't have to fight with idiots, but I just can't help myself. If you're talking about venturis, then it's true that the *appropriate* exhaust sizing must be used. But that's not backpressure, that's actually creating negative pressure. Backpressure, such as that created by a muffler, cat, or resonator, is positive. Therefore, BACKPRESSURE IS NEVER GOOD.
You know, I've personally built and tuned enough race cars that I feel I shouldn't have to fight with idiots, but I just can't help myself. If you're talking about venturis, then it's true that the *appropriate* exhaust sizing must be used. But that's not backpressure, that's actually creating negative pressure. Backpressure, such as that created by a muffler, cat, or resonator, is positive. Therefore, BACKPRESSURE IS NEVER GOOD.
Joined: May 2005
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From: Simi Valley, CA, USA
Re: backpressure and nitrous? (Twinkies)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Twinkies »</TD></TR><TR><TD CLASS="quote"> Why is this? It all has to do with the timing and velocity of the exhaust gases. Yes, an engine is an air pump, and the pulsing of the exhaust gases can actually help "pull" gases from other cylinders, letting the engine breathe better or worse depending on, yes, the amount of exhaust system backpressure.</TD></TR></TABLE>
The Venturi Effect is NOT created by backpressure
The Venturi Effect is NOT created by backpressure
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From: Saint Joseph, MO, USA
Re: backpressure and nitrous? (Twinkies)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Twinkies »</TD></TR><TR><TD CLASS="quote">
A particular engine setup may very well make more "peak" power and torque
with very little backpressure, but Ive seen more than a couple cars dyno'd that make much better power throughout the entire rpm band with a certain amount of exhaust backpressure. Why is this? It all has to do with the timing and velocity of the exhaust gases. Yes, an engine is an air pump, and the pulsing of the exhaust gases can actually help "pull" gases from other cylinders, letting the engine breathe better or worse depending on, yes, the amount of exhaust system backpressure.
</TD></TR></TABLE>
what you just described is exhaust gas velocity and exhaust scavenging, neither of which are caused by, or multiplied by the backpressure variable.
blow through a straw. now cover the end of the straw almost completely and blow through it. wow, its now harder to push air through the tube. that, my friend, is backpressure, which engines "never ever ever need"
moron.
A particular engine setup may very well make more "peak" power and torque
with very little backpressure, but Ive seen more than a couple cars dyno'd that make much better power throughout the entire rpm band with a certain amount of exhaust backpressure. Why is this? It all has to do with the timing and velocity of the exhaust gases. Yes, an engine is an air pump, and the pulsing of the exhaust gases can actually help "pull" gases from other cylinders, letting the engine breathe better or worse depending on, yes, the amount of exhaust system backpressure.
</TD></TR></TABLE>
what you just described is exhaust gas velocity and exhaust scavenging, neither of which are caused by, or multiplied by the backpressure variable.
blow through a straw. now cover the end of the straw almost completely and blow through it. wow, its now harder to push air through the tube. that, my friend, is backpressure, which engines "never ever ever need"
moron.
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From: Charlotte, NC
Re: backpressure and nitrous? (Twinkies)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Twinkies »</TD></TR><TR><TD CLASS="quote">"backpressure is a myth" "you never need any backpressure ever ever ever"
You guys are totally wrong. There are tons of variables when it comes to tuning
an engine, not just Hondas, any engine. One of those variables is.. yep, exhaust system backpressure.
A particular engine setup may very well make more "peak" power and torque
with very little backpressure, but Ive seen more than a couple cars dyno'd that make much better power throughout the entire rpm band with a certain amount of exhaust backpressure. Why is this? It all has to do with the timing and velocity of the exhaust gases. Yes, an engine is an air pump, and the pulsing of the exhaust gases can actually help "pull" gases from other cylinders, letting the engine breathe better or worse depending on, yes, the amount of exhaust system backpressure.
Call me Mr. 2-posts, yes, Im a noobie when it comes to Honda-tech although Ive been on Hybrids.jp off and on since '97. Not that it matters since real world experience is more important than reading about it. Im not trying to step on anyone's toes here, just trying to back up 1990DA's post. Im just here waiting the two weeks so I can post some stuff for sale.
Anyways, If you think we're wrong, Id encourage you to do some research on it. Real research, not internet heresay message board stuff.
</TD></TR></TABLE>
Your cause and effect is terribly flawed. It sounds like you're the one with lots of internet research (E-Search?).
Ask yourself: why would you ever want to keep air from getting out of an engine?
You guys are totally wrong. There are tons of variables when it comes to tuning
an engine, not just Hondas, any engine. One of those variables is.. yep, exhaust system backpressure.
A particular engine setup may very well make more "peak" power and torque
with very little backpressure, but Ive seen more than a couple cars dyno'd that make much better power throughout the entire rpm band with a certain amount of exhaust backpressure. Why is this? It all has to do with the timing and velocity of the exhaust gases. Yes, an engine is an air pump, and the pulsing of the exhaust gases can actually help "pull" gases from other cylinders, letting the engine breathe better or worse depending on, yes, the amount of exhaust system backpressure.
Call me Mr. 2-posts, yes, Im a noobie when it comes to Honda-tech although Ive been on Hybrids.jp off and on since '97. Not that it matters since real world experience is more important than reading about it. Im not trying to step on anyone's toes here, just trying to back up 1990DA's post. Im just here waiting the two weeks so I can post some stuff for sale.
Anyways, If you think we're wrong, Id encourage you to do some research on it. Real research, not internet heresay message board stuff.
</TD></TR></TABLE>
Your cause and effect is terribly flawed. It sounds like you're the one with lots of internet research (E-Search?).
Ask yourself: why would you ever want to keep air from getting out of an engine?
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From: sd north county, CA, USA
Re: backpressure and nitrous? (EnzoSpeed)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnzoSpeed »</TD></TR><TR><TD CLASS="quote">
Oh, so THAT'S how the myths get perpetuated .
You are incorrect Mr. 3-posts. I've seen a car tuned without a header at all and it does in fact make more power than running open header. Bottom line - a motor is just a pump - it wants air IN and exhaust OUT. Don't buy into the bullshit.</TD></TR></TABLE>
I think the disagreement here is in the terminology of backpressure.
To put it very simply, backpressure is an amount of restriction that alters the exit of exhaust gases from the combustion chamber which is what the original post was about. I dont know what your definition of it is, but anytime you change the amount of exhaust restriction, whether it be piping diameter, length, bends, or system components, etc you're going to effect exhaust system "scavenging".
Im using the term here loosely as the original post did. You can certainly say that increasing or decreasing the scavenging effect of an exhaust system at a certain rpm will increase or decrease power output . When youre saying “backpressure is a myth” that phrase by itself, out of context, is completely untrue. Every exhaust system has some kind of backpressure.
I never said that the venturi effect is CREATED by backpressure.
You posted this comment, saying that you saw A (one) car making more power without a header. So we're supposed to think that all engines are better off without any type of exhaust system? Thats totally rediculous. If that’s true, then somebody is doing a good job marketing $300+ headers and $500+ exhaust systems for all the Honda kids because obviously, they should just be taking off their hoods, investing in heat shielding material and taking off their factory exhaust manifolds to race.
Idiot douchebag moron huh? Whats there to be butt hurt about? Its just a discussion.
Say whatever you want, Im done with this topic.
Oh, so THAT'S how the myths get perpetuated .
You are incorrect Mr. 3-posts. I've seen a car tuned without a header at all and it does in fact make more power than running open header. Bottom line - a motor is just a pump - it wants air IN and exhaust OUT. Don't buy into the bullshit.</TD></TR></TABLE>
I think the disagreement here is in the terminology of backpressure.
To put it very simply, backpressure is an amount of restriction that alters the exit of exhaust gases from the combustion chamber which is what the original post was about. I dont know what your definition of it is, but anytime you change the amount of exhaust restriction, whether it be piping diameter, length, bends, or system components, etc you're going to effect exhaust system "scavenging".
Im using the term here loosely as the original post did. You can certainly say that increasing or decreasing the scavenging effect of an exhaust system at a certain rpm will increase or decrease power output . When youre saying “backpressure is a myth” that phrase by itself, out of context, is completely untrue. Every exhaust system has some kind of backpressure.
I never said that the venturi effect is CREATED by backpressure.
You posted this comment, saying that you saw A (one) car making more power without a header. So we're supposed to think that all engines are better off without any type of exhaust system? Thats totally rediculous. If that’s true, then somebody is doing a good job marketing $300+ headers and $500+ exhaust systems for all the Honda kids because obviously, they should just be taking off their hoods, investing in heat shielding material and taking off their factory exhaust manifolds to race.
Idiot douchebag moron huh? Whats there to be butt hurt about? Its just a discussion.
Say whatever you want, Im done with this topic.
Joined: May 2005
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From: Simi Valley, CA, USA
Re: backpressure and nitrous? (Twinkies)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Twinkies »</TD></TR><TR><TD CLASS="quote">
You posted this comment, saying that you saw A (one) car making more power without a header. So we're supposed to think that all engines are better off without any type of exhaust system? Thats totally rediculous.</TD></TR></TABLE>
Yes we are. All engines operate the same - air IN, exhaust OUT. NO engine is going to want a header instead of nothing.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote"> If that’s true, then somebody is doing a good job marketing $300+ headers and $500+ exhaust systems for all the Honda kids because obviously, they should just be taking off their hoods, investing in heat shielding material and taking off their factory exhaust manifolds to race.</TD></TR></TABLE>
Except the whole damn point of an exhaust system is to expel the exhaust away from your car, not up under the hood. Aside from that, you can't realistically run without a header because it ruins the exhaust valves.
You posted this comment, saying that you saw A (one) car making more power without a header. So we're supposed to think that all engines are better off without any type of exhaust system? Thats totally rediculous.</TD></TR></TABLE>
Yes we are. All engines operate the same - air IN, exhaust OUT. NO engine is going to want a header instead of nothing.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote"> If that’s true, then somebody is doing a good job marketing $300+ headers and $500+ exhaust systems for all the Honda kids because obviously, they should just be taking off their hoods, investing in heat shielding material and taking off their factory exhaust manifolds to race.</TD></TR></TABLE>
Except the whole damn point of an exhaust system is to expel the exhaust away from your car, not up under the hood. Aside from that, you can't realistically run without a header because it ruins the exhaust valves.
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Joined: May 2003
Posts: 1,543
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From: Ben Lomond, Ca, USA
Re: backpressure and nitrous? (97grnrs)
I think backpressure is being used here as a generic term.
It is correct to say that a restriction in your exhaust system is always a bad thing as far as producing maximum horsepower (i.e.: a catalytic converter, potato in the exhaust, etc.).
Accoustic tuning of the exhaust header is what enables it to help the engine to make power.
If you hook a pressure gauge up to your exhaust system before the cat you will always see a few PSI registering on the gauge because the cat is a restriction (I'm talking factory cat, not high flow). If you hook a pressure gauge up to an engine that has an exhaust header, muffler, etc that has been properly accoustically tuned you may also see a few PSI register on the gauge. This does not mean that there is a restriction or a problem with the exhaust. A cheap mechanical gauge with a needle, even a high quality one, such as those made by Snap-On, is not fast enough to register each individual exhaust pulse and even if it were your eyes wouldn't be able to take it all in. Using high speed pressure transducers in multiple locations and software that is able to sample thousands of times per second you would be able to get an idea of what is going on in the exhaust but that is not available to the average guy. As a matter of fact, tuners like DC Sports or Comptech or whoever your header is made by don't even use that method, their headers are made by educated trial and error and many dyno pulls.
Accoustic tuning is the science of harnessing the energy of the outgoing exhaust 'pulse' to 'pull' in fresh air/fuel charge during camshaft overlap. It is quite complicated. A book that covers it in some depth is <u>Performance Tuning in Theory and Practice</u> by A. Graham Bell.
Removing your cat may or may not make any difference on your car. It depends a lot on how extensively it is modified. The more air that you are trying to move through the engine the more of a restriction that cat is going to be. In the end, the only way to test this theory is to install a test pipe and do before and after dyno pulls (with that being the <u>only</u> modification).
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnzoSpeed »</TD></TR><TR><TD CLASS="quote">Yes we are. All engines operate the same - air IN, exhaust OUT. NO engine is going to want a header instead of nothing. </TD></TR></TABLE>
This quote is untrue. A properly tuned header will produce more power than open exhaust ports (correct me if that is not what you meant). If you uncork them like that the most likey effect you will get is to kill torque at lower RPM while making no additional power than you would with a properly tuned header at high RPM, the engine would be very 'peaky'.
-Scott Tucker
It is correct to say that a restriction in your exhaust system is always a bad thing as far as producing maximum horsepower (i.e.: a catalytic converter, potato in the exhaust, etc.).
Accoustic tuning of the exhaust header is what enables it to help the engine to make power.
If you hook a pressure gauge up to your exhaust system before the cat you will always see a few PSI registering on the gauge because the cat is a restriction (I'm talking factory cat, not high flow). If you hook a pressure gauge up to an engine that has an exhaust header, muffler, etc that has been properly accoustically tuned you may also see a few PSI register on the gauge. This does not mean that there is a restriction or a problem with the exhaust. A cheap mechanical gauge with a needle, even a high quality one, such as those made by Snap-On, is not fast enough to register each individual exhaust pulse and even if it were your eyes wouldn't be able to take it all in. Using high speed pressure transducers in multiple locations and software that is able to sample thousands of times per second you would be able to get an idea of what is going on in the exhaust but that is not available to the average guy. As a matter of fact, tuners like DC Sports or Comptech or whoever your header is made by don't even use that method, their headers are made by educated trial and error and many dyno pulls.
Accoustic tuning is the science of harnessing the energy of the outgoing exhaust 'pulse' to 'pull' in fresh air/fuel charge during camshaft overlap. It is quite complicated. A book that covers it in some depth is <u>Performance Tuning in Theory and Practice</u> by A. Graham Bell.
Removing your cat may or may not make any difference on your car. It depends a lot on how extensively it is modified. The more air that you are trying to move through the engine the more of a restriction that cat is going to be. In the end, the only way to test this theory is to install a test pipe and do before and after dyno pulls (with that being the <u>only</u> modification).
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnzoSpeed »</TD></TR><TR><TD CLASS="quote">Yes we are. All engines operate the same - air IN, exhaust OUT. NO engine is going to want a header instead of nothing. </TD></TR></TABLE>
This quote is untrue. A properly tuned header will produce more power than open exhaust ports (correct me if that is not what you meant). If you uncork them like that the most likey effect you will get is to kill torque at lower RPM while making no additional power than you would with a properly tuned header at high RPM, the engine would be very 'peaky'.
-Scott Tucker
Joined: May 2005
Posts: 1,789
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From: Simi Valley, CA, USA
Re: backpressure and nitrous? (AutoEng2002Si)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AutoEng2002Si »</TD></TR><TR><TD CLASS="quote"> A properly tuned header will produce more power than open exhaust ports (correct me if that is not what you meant). </TD></TR></TABLE>
No, that's what I meant. I saw the dyno myself on a B18. The "open port" dyno was definitely more favorable than the open header dyno. Both setups were tuned.
No, that's what I meant. I saw the dyno myself on a B18. The "open port" dyno was definitely more favorable than the open header dyno. Both setups were tuned.
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From: Ben Lomond, Ca, USA
Re: backpressure and nitrous? (EnzoSpeed)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnzoSpeed »</TD></TR><TR><TD CLASS="quote">
No, that's what I meant. I saw the dyno myself on a B18. The "open port" dyno was definitely more favorable than the open header dyno. Both setups were tuned.</TD></TR></TABLE>
So you're saying you saw this on one engine? Is your point that in some cases more power will be made with open ports or are you trying to generalize and say this is true for all engines? What exactly does 'more favorable' mean and what is your idea of the setups being 'tuned'?
-Scott
No, that's what I meant. I saw the dyno myself on a B18. The "open port" dyno was definitely more favorable than the open header dyno. Both setups were tuned.</TD></TR></TABLE>
So you're saying you saw this on one engine? Is your point that in some cases more power will be made with open ports or are you trying to generalize and say this is true for all engines? What exactly does 'more favorable' mean and what is your idea of the setups being 'tuned'?
-Scott
Joined: May 2005
Posts: 1,789
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From: Simi Valley, CA, USA
Re: backpressure and nitrous? (AutoEng2002Si)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AutoEng2002Si »</TD></TR><TR><TD CLASS="quote">
So you're saying you saw this on one engine? Is your point that in some cases more power will be made with open ports or are you trying to generalize and say this is true for all engines? </TD></TR></TABLE>
All
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote"> What exactly does 'more favorable' mean and what is your idea of the setups being 'tuned'?</TD></TR></TABLE>
Favorable meaning more hp without a loss in tq. Tuned meaning dyno tuned for peak hp.
Idea being:
With header - scavenging creates vacuum to evacuate cylinders at the expense of slight backpressure
Without header - no scavenging, no backpressure.
Seems like a wash. I doubt that it will always make more power, but more realistically it would make the same amount of power.
Doesn't matter though. Can't run open ports because it warps exhaust valves. Plus you'd be inhaling carbon monoxide.
Bottom line - backpressure never good. Mufflers, cats, bends, resonators: all backpressure and therefore bad. Undersized piping: creates backpressure = bad. Oversized piping: creates backpressure = bad.
A proper exhaust has least amount of backpressure possible - this includes piping size which seems to be overlooked.
So you're saying you saw this on one engine? Is your point that in some cases more power will be made with open ports or are you trying to generalize and say this is true for all engines? </TD></TR></TABLE>
All
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote »</TD></TR><TR><TD CLASS="quote"> What exactly does 'more favorable' mean and what is your idea of the setups being 'tuned'?</TD></TR></TABLE>
Favorable meaning more hp without a loss in tq. Tuned meaning dyno tuned for peak hp.
Idea being:
With header - scavenging creates vacuum to evacuate cylinders at the expense of slight backpressure
Without header - no scavenging, no backpressure.
Seems like a wash. I doubt that it will always make more power, but more realistically it would make the same amount of power.
Doesn't matter though. Can't run open ports because it warps exhaust valves. Plus you'd be inhaling carbon monoxide.
Bottom line - backpressure never good. Mufflers, cats, bends, resonators: all backpressure and therefore bad. Undersized piping: creates backpressure = bad. Oversized piping: creates backpressure = bad.
A proper exhaust has least amount of backpressure possible - this includes piping size which seems to be overlooked.
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From: Ben Lomond, Ca, USA
Re: backpressure and nitrous? (EnzoSpeed)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnzoSpeed »</TD></TR><TR><TD CLASS="quote">
All
</TD></TR></TABLE>
That is not true, this is like having a 3" primary. You'd have to spin the engine to some amazing speed for that to be usefull. You need to have some primary exhaust tube length to time the accoustic pulses correctly for the RPM range you are tuning for so that the rarefaction (the 'vacuum' traveling at the speed of sound) reaches the exhaust port right as the exhaust valve is begining to close and the intake is beginning to open (overlap) so that the higher pressure of the intake charge moves towards the lower pressure of the rarefaction. This draws out burnt combustion gases from the previous cycle that would otherwise dilute the incoming charge and reduce volumetric efficiency - that is what this is all about, increasing volumetric efficiency. I seriously doubt that the higher HP number you saw on that engine when it had the header removed had anything to do with the fact that the ports were open. I would think it was more likely a design flaw in the header or some other fluke. How much difference in HP was there anyway? Was there any other changes at all made to the engine? Obviously the fuel mixture would have had to have been recalibrated if the engine was flowing so much more freely so if that was done that may have something to do with it.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnzoSpeed »</TD></TR><TR><TD CLASS="quote">
Favorable meaning more hp without a loss in tq. Tuned meaning dyno tuned for peak hp.
Idea being:
With header - scavenging creates vacuum to evacuate cylinders at the expense of slight backpressure
Without header - no scavenging, no backpressure.
Seems like a wash. I doubt that it will always make more power, but more realistically it would make the same amount of power.
Doesn't matter though. Can't run open ports because it warps exhaust valves. Plus you'd be inhaling carbon monoxide.
Bottom line - backpressure never good. Mufflers, cats, bends, resonators: all backpressure and therefore bad. Undersized piping: creates backpressure = bad. Oversized piping: creates backpressure = bad.
A proper exhaust has least amount of backpressure possible - this includes piping size which seems to be overlooked.</TD></TR></TABLE>
I totally agree with you that you risk warping the valves especially after a hard run. Of course the comment about carbon monoxide is true, it would suck to pass out at 130. Backpressure, not good. Muffler, cats, bend etc. = gases have mass and don't like to turn corners. Proper tubing size is very important. I agree with you on all those points.
All
</TD></TR></TABLE>
That is not true, this is like having a 3" primary. You'd have to spin the engine to some amazing speed for that to be usefull. You need to have some primary exhaust tube length to time the accoustic pulses correctly for the RPM range you are tuning for so that the rarefaction (the 'vacuum' traveling at the speed of sound) reaches the exhaust port right as the exhaust valve is begining to close and the intake is beginning to open (overlap) so that the higher pressure of the intake charge moves towards the lower pressure of the rarefaction. This draws out burnt combustion gases from the previous cycle that would otherwise dilute the incoming charge and reduce volumetric efficiency - that is what this is all about, increasing volumetric efficiency. I seriously doubt that the higher HP number you saw on that engine when it had the header removed had anything to do with the fact that the ports were open. I would think it was more likely a design flaw in the header or some other fluke. How much difference in HP was there anyway? Was there any other changes at all made to the engine? Obviously the fuel mixture would have had to have been recalibrated if the engine was flowing so much more freely so if that was done that may have something to do with it.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EnzoSpeed »</TD></TR><TR><TD CLASS="quote">
Favorable meaning more hp without a loss in tq. Tuned meaning dyno tuned for peak hp.
Idea being:
With header - scavenging creates vacuum to evacuate cylinders at the expense of slight backpressure
Without header - no scavenging, no backpressure.
Seems like a wash. I doubt that it will always make more power, but more realistically it would make the same amount of power.
Doesn't matter though. Can't run open ports because it warps exhaust valves. Plus you'd be inhaling carbon monoxide.
Bottom line - backpressure never good. Mufflers, cats, bends, resonators: all backpressure and therefore bad. Undersized piping: creates backpressure = bad. Oversized piping: creates backpressure = bad.
A proper exhaust has least amount of backpressure possible - this includes piping size which seems to be overlooked.</TD></TR></TABLE>
I totally agree with you that you risk warping the valves especially after a hard run. Of course the comment about carbon monoxide is true, it would suck to pass out at 130. Backpressure, not good. Muffler, cats, bend etc. = gases have mass and don't like to turn corners. Proper tubing size is very important. I agree with you on all those points.
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el_Presidente
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Apr 26, 2002 01:50 PM