42MM ITB's equal to what size throttle body......
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From: SC
42MM ITB's equal to what size throttle body......
I was just going off surface area and came up with 4-42mm ITB's being equal to 1-84ish mm TB....Is this correct and if so then how could some people say that 42mm ITB's would choke in the upper RPM range on a 1.8-2.0L motor.Most people only run like 64-70mm TB on highly modded settups.
I have seem that most of the aftermarket ITB manufacturers really have short overall lengths (from valve face to velocity stack face). Why do they seem to focus on really high RPM's and they (TWM) seem to overkill the 1.8L settup with 50mm ITB's. I base the last statement off the fact that they have 50mm ITB kits for 1.8L and 2.2L applications.One of these motors surely suffers from 50mm......So which is it?
I have seem that most of the aftermarket ITB manufacturers really have short overall lengths (from valve face to velocity stack face). Why do they seem to focus on really high RPM's and they (TWM) seem to overkill the 1.8L settup with 50mm ITB's. I base the last statement off the fact that they have 50mm ITB kits for 1.8L and 2.2L applications.One of these motors surely suffers from 50mm......So which is it?
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Re: 42MM ITB's equal to what size throttle body...... (blazin)
I think that what most people forget is that ITB's aren't designed for massive increases in airflow, but rather massive increases in air velocity with increased airflow just being a perk. An ITB setup is designed using the straight runner design with velocity stacks for the sole purpose of increasing the air velocity, which (according to the laws of physics) will force more air into the combustion chambers.
Lets break this down. Air moving at a higher rate of speed will force itself into the combustion chamber at a higher rate of speed and slightly compress itself under the force of more air that is moving in at the set rate of speed, thus when the intake valves close there is more air inside the combustion chamber than there would be with another setup that doesn't offer the same level of air velocity. But it doesn't stop there. When the intake valves close, the air still has momentum and compresses itself against the closed valve until the valve opens again and it all rushes in with even more velocity due to the vacuum created in the combustion chambers by the lack of air (it's all going out the exhaust valves).
With this being said, it's easy to understand why an ITB setup can be optimal in many circumstances. However it heavily depends upon the exact design of the ITB setup in question as to what it's particular flow characteristics will benefit most. It's proven that short runner, large opening designs compliment high RPM applications designed for maximum peak power. Likewise, longer runners and smaller openings will better compliment midrange power. Take a TWM setup and a DIY GSXR 1000 setup and put them on identical engines (lets say a B18C with 11.5:1 compression, Skunk2 stage 2 cams, and a stock P72 head) and then tune each one. The dyno chart for the TWM setup will show a considerable increase in peak power over the GSXR setup, however the GSXR setup (if well built) will show favorable midrange power numbers.
So thus, a 42mm setup isn't really choking the engine, it's just not flowing in a way that will best suit higher rpm power. The exact dimensions of each ITB setup depend heavily upon the flow characteristics of the cylinder head, rather than the displacement of the engine. I think a lot of people forget that.
Lets break this down. Air moving at a higher rate of speed will force itself into the combustion chamber at a higher rate of speed and slightly compress itself under the force of more air that is moving in at the set rate of speed, thus when the intake valves close there is more air inside the combustion chamber than there would be with another setup that doesn't offer the same level of air velocity. But it doesn't stop there. When the intake valves close, the air still has momentum and compresses itself against the closed valve until the valve opens again and it all rushes in with even more velocity due to the vacuum created in the combustion chambers by the lack of air (it's all going out the exhaust valves).
With this being said, it's easy to understand why an ITB setup can be optimal in many circumstances. However it heavily depends upon the exact design of the ITB setup in question as to what it's particular flow characteristics will benefit most. It's proven that short runner, large opening designs compliment high RPM applications designed for maximum peak power. Likewise, longer runners and smaller openings will better compliment midrange power. Take a TWM setup and a DIY GSXR 1000 setup and put them on identical engines (lets say a B18C with 11.5:1 compression, Skunk2 stage 2 cams, and a stock P72 head) and then tune each one. The dyno chart for the TWM setup will show a considerable increase in peak power over the GSXR setup, however the GSXR setup (if well built) will show favorable midrange power numbers.
So thus, a 42mm setup isn't really choking the engine, it's just not flowing in a way that will best suit higher rpm power. The exact dimensions of each ITB setup depend heavily upon the flow characteristics of the cylinder head, rather than the displacement of the engine. I think a lot of people forget that.
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From: Biggest Little City
Re: 42MM ITB's equal to what size throttle body...... (blazin)
you are on the right track. I have some crazy idea though of one thing not to forget that is a factor is think about the actual "suface area" taken up by the butterfly of the single throttle body, and then on the itb's you are having a butterfly in each, granted they are smaller, but overal aread of that 2mm wide butterfly in one 70mm throttle body compared to the four individual 42mm's.
2mmx70mm=140mm of area by the larger throttle body.
2mmx42mmx4eaches=336mm of area total for the itb's.
I came up with the four 42mm=6000mm of surface area
while the single 70mm=3847mm
so the 42mm would equal an 88mm throttle body in surface area.
so despite the butterfly area being twice as large on the itb's they are clearly a larger passage.
2mmx70mm=140mm of area by the larger throttle body.
2mmx42mmx4eaches=336mm of area total for the itb's.
I came up with the four 42mm=6000mm of surface area
while the single 70mm=3847mm
so the 42mm would equal an 88mm throttle body in surface area.
so despite the butterfly area being twice as large on the itb's they are clearly a larger passage.
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From: SC
Re: 42MM ITB's equal to what size throttle body...... (RenoRacing)
So looking at "Air Volume" a 42mm ITB settup should far out flow say a 68-70mm TB ITR manifold settup.....I assume "Air Velocity" would go to the ITB settup for sure... 
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Re: (na200whp)
to clarify lets ask this question another way. take a built b20 vtec w/ 68mm t/body and itr manifold and dyno it . will that motor make more or less peak power w/ diy itb set up measuring 42mm each? hypothetically . should it extend or shorten the power band? make less tq down low ? you don't have to be exact just generalize?
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Re: (na200whp)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by na200whp »</TD></TR><TR><TD CLASS="quote">to clarify lets ask this question another way. take a built b20 vtec w/ 68mm t/body and itr manifold and dyno it . will that motor make more or less peak power w/ diy itb set up measuring 42mm each? hypothetically . should it extend or shorten the power band? make less tq down low ? you don't have to be exact just generalize?</TD></TR></TABLE>
you will definitely make less peak power. 42mm ITBs are a midrange modification for sure.
a 64mm TB, and skunk2 IM will definitely make higher top end since they use a ramming effect to achieve high volumetric efficiency(dependant upon runner size, length, etc). Whereas, the ITBs use passive cylinder filling.
Modified by DefiantGSR at 4:05 AM 4/21/2004
you will definitely make less peak power. 42mm ITBs are a midrange modification for sure.
a 64mm TB, and skunk2 IM will definitely make higher top end since they use a ramming effect to achieve high volumetric efficiency(dependant upon runner size, length, etc). Whereas, the ITBs use passive cylinder filling.
Modified by DefiantGSR at 4:05 AM 4/21/2004
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Re: (DefiantGSR)
maybe you guys should tell bisi that his ~8,500+ rpm engine would make more power if it had a single throttle body, instead of one individual barrel per port.
better yet, why not tell leslie durst that running twm itb's was a bad idea, lol: http://www.turbomagazine.com/f...durst/
itb's are definitely tuneable, via the intake manifold length and diameter, and the stack length and diameter... they are not just passive devices.
airflow into a port is never continuous, it pulses, and since air is compressible, it can even have a spring-like effect to it... but gas columns also have momentum... it gets pretty confusing, and i'm certainly no engineer.
the only sure thing that you can do is to use the airflow numbers thru the intake port on the head, that you got from the flow bench, plotted against the peak rpm that you intend to run, and see how much cfm the engine will consume... that part isn't rocket science, i've posted the math out here in other threads.
i've even thrown out some carb airflow numbers, so you'll generally know if that itb will flow enuf... most likely it will, because one barrel of an itb only has to flow what the entire engine will use... check the archives.
better yet, why not tell leslie durst that running twm itb's was a bad idea, lol: http://www.turbomagazine.com/f...durst/
itb's are definitely tuneable, via the intake manifold length and diameter, and the stack length and diameter... they are not just passive devices.
airflow into a port is never continuous, it pulses, and since air is compressible, it can even have a spring-like effect to it... but gas columns also have momentum... it gets pretty confusing, and i'm certainly no engineer.
the only sure thing that you can do is to use the airflow numbers thru the intake port on the head, that you got from the flow bench, plotted against the peak rpm that you intend to run, and see how much cfm the engine will consume... that part isn't rocket science, i've posted the math out here in other threads.
i've even thrown out some carb airflow numbers, so you'll generally know if that itb will flow enuf... most likely it will, because one barrel of an itb only has to flow what the entire engine will use... check the archives.
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From: puyallup, or, usa
WOWOWOW!
I can tell its HT...
The crucial thing no one mentioned is that the Single TB only gets one pulse at a time passing through it....
In a common plenum design, the TB there to regualte the pressure level in the plenum which all cylinders feed off.
In a seprate apature feed ITB setup, the atmosphere is regulated, and the choke in the runner (throttle) is what controls flow, and output.
Before i see anymore of you making really dumb comments like, 4x42mm is small, you may want to keep in mind that the JGTC NA NSX breathes from 1x41mm TB and makes more power then anyother NA on this board.
Now, something that you guys might want to put just about 5% of you brain into before talking about what is the "good" ITB size. What happens if your ITB size is smaller then port opening? Venturi effect rapidly drops air speed as it aproches the port from the needed expansion in the manifold to mate with the port opening.
And visa versa...
HT.... why do i still post...
PS, ITBs are only underestimated by fools. They are a very powerful tool when done properly. I have never seen just nice tq curves with a plenum as i have with ITBs
I can tell its HT...
The crucial thing no one mentioned is that the Single TB only gets one pulse at a time passing through it....
In a common plenum design, the TB there to regualte the pressure level in the plenum which all cylinders feed off.
In a seprate apature feed ITB setup, the atmosphere is regulated, and the choke in the runner (throttle) is what controls flow, and output.
Before i see anymore of you making really dumb comments like, 4x42mm is small, you may want to keep in mind that the JGTC NA NSX breathes from 1x41mm TB and makes more power then anyother NA on this board.
Now, something that you guys might want to put just about 5% of you brain into before talking about what is the "good" ITB size. What happens if your ITB size is smaller then port opening? Venturi effect rapidly drops air speed as it aproches the port from the needed expansion in the manifold to mate with the port opening.
And visa versa...
HT.... why do i still post...
PS, ITBs are only underestimated by fools. They are a very powerful tool when done properly. I have never seen just nice tq curves with a plenum as i have with ITBs
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Re: (liveforphysics)
http://www.team-integra.net/fo...ion=1
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by liveforphysics »</TD></TR><TR><TD CLASS="quote">WOWOWOW!
I can tell its HT...
The crucial thing no one mentioned is that the Single TB only gets one pulse at a time passing through it....
In a common plenum design, the TB there to regualte the pressure level in the plenum which all cylinders feed off.
In a seprate apature feed ITB setup, the atmosphere is regulated, and the choke in the runner (throttle) is what controls flow, and output.
Before i see anymore of you making really dumb comments like, 4x42mm is small, you may want to keep in mind that the JGTC NA NSX breathes from 1x41mm TB and makes more power then anyother NA on this board.
Now, something that you guys might want to put just about 5% of you brain into before talking about what is the "good" ITB size. What happens if your ITB size is smaller then port opening? Venturi effect rapidly drops air speed as it aproches the port from the needed expansion in the manifold to mate with the port opening.
And visa versa...
HT.... why do i still post...
PS, ITBs are only underestimated by fools. They are a very powerful tool when done properly. I have never seen just nice tq curves with a plenum as i have with ITBs</TD></TR></TABLE>
maybe you can comment on this site/thread(note page 9)...
Modified by DefiantGSR at 8:40 AM 4/21/2004
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by liveforphysics »</TD></TR><TR><TD CLASS="quote">WOWOWOW!
I can tell its HT...
The crucial thing no one mentioned is that the Single TB only gets one pulse at a time passing through it....
In a common plenum design, the TB there to regualte the pressure level in the plenum which all cylinders feed off.
In a seprate apature feed ITB setup, the atmosphere is regulated, and the choke in the runner (throttle) is what controls flow, and output.
Before i see anymore of you making really dumb comments like, 4x42mm is small, you may want to keep in mind that the JGTC NA NSX breathes from 1x41mm TB and makes more power then anyother NA on this board.
Now, something that you guys might want to put just about 5% of you brain into before talking about what is the "good" ITB size. What happens if your ITB size is smaller then port opening? Venturi effect rapidly drops air speed as it aproches the port from the needed expansion in the manifold to mate with the port opening.
And visa versa...
HT.... why do i still post...
PS, ITBs are only underestimated by fools. They are a very powerful tool when done properly. I have never seen just nice tq curves with a plenum as i have with ITBs</TD></TR></TABLE>
maybe you can comment on this site/thread(note page 9)...
Modified by DefiantGSR at 8:40 AM 4/21/2004
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Re: (DefiantGSR)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DefiantGSR »</TD></TR><TR><TD CLASS="quote">
a 64mm TB, and skunk2 IM will definitely make higher top end since they use a ramming effect to achieve high volumetric efficiency(dependant upon runner size, length, etc). Whereas, the ITBs use passive cylinder filling.</TD></TR></TABLE>
defiantgsr, you aren't getting the big picture on the so-called "ramming effect"... which is really helmholtz resonance.
the claim that "itbs use passive cylinder filling" is totally wrong... the reason i said that itbs are "tuneable" is because each itb barrel is it's own seperate helmholtz resonator.
you can see a clear explanation of itb barrel resonance in this link, they are referring to blowing air over the top of a bottle neck, but the effect is the same when the air is being drawn thru an itb barrel, with the intake valve opening and closing against a gas column that has momentum: http://www.phys.unsw.edu.au/~jw/Helmholtz.html
so, itb's DO have a solid "ramming effect".
on page 9 of the link you posted, DaBoyNBlu explained it perfectly, but mb talked it down, because it appears that he doesn't understand the simple physics of itb's.
the references by both mb and liveforphysics to pressure within the common plenum of a single tb setup is largely insignificant to making h.p... if fact, the main thing that common plenum volume does is slow down throttle response, and allow all the pressure waves from the other intake ports to muddy the signal going into the port that is drawing air.
EXCEPT for the brief rpm point where the common plenum is carefully designed to take advantage of the other pressure wave(s)... that is the ONLY time you will see a "ramming effect" with a common plenum, period... but it is significant to making h.p.! the potential is there to achieve slightly better v.e. than with the itb "ramming effect"... but it's very difficult to accurately engineer everything correctly, i don't think that internet posts are sophisticated enuf to make it happen... you need some serious engine design software.
so the disadvantage that both itb's and a single tb/common plenum share is that their helmholz resonance (aka "ramming effect") can only happen for a brief instance of the rpm band... but the itb has all the advantages thruout the rest of the rpm band, because the itb pressure wave moving in and out of the itb barrel is clean and un-muddied by the conflicting pulses of a common plenum.
a 64mm TB, and skunk2 IM will definitely make higher top end since they use a ramming effect to achieve high volumetric efficiency(dependant upon runner size, length, etc). Whereas, the ITBs use passive cylinder filling.</TD></TR></TABLE>
defiantgsr, you aren't getting the big picture on the so-called "ramming effect"... which is really helmholtz resonance.
the claim that "itbs use passive cylinder filling" is totally wrong... the reason i said that itbs are "tuneable" is because each itb barrel is it's own seperate helmholtz resonator.
you can see a clear explanation of itb barrel resonance in this link, they are referring to blowing air over the top of a bottle neck, but the effect is the same when the air is being drawn thru an itb barrel, with the intake valve opening and closing against a gas column that has momentum: http://www.phys.unsw.edu.au/~jw/Helmholtz.html
so, itb's DO have a solid "ramming effect".
on page 9 of the link you posted, DaBoyNBlu explained it perfectly, but mb talked it down, because it appears that he doesn't understand the simple physics of itb's.
the references by both mb and liveforphysics to pressure within the common plenum of a single tb setup is largely insignificant to making h.p... if fact, the main thing that common plenum volume does is slow down throttle response, and allow all the pressure waves from the other intake ports to muddy the signal going into the port that is drawing air.
EXCEPT for the brief rpm point where the common plenum is carefully designed to take advantage of the other pressure wave(s)... that is the ONLY time you will see a "ramming effect" with a common plenum, period... but it is significant to making h.p.! the potential is there to achieve slightly better v.e. than with the itb "ramming effect"... but it's very difficult to accurately engineer everything correctly, i don't think that internet posts are sophisticated enuf to make it happen... you need some serious engine design software.
so the disadvantage that both itb's and a single tb/common plenum share is that their helmholz resonance (aka "ramming effect") can only happen for a brief instance of the rpm band... but the itb has all the advantages thruout the rest of the rpm band, because the itb pressure wave moving in and out of the itb barrel is clean and un-muddied by the conflicting pulses of a common plenum.
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Re: (danimal)
thanks for the explanation danimal. I do realize that IMs only have this one 'peak' jump over a couple hundred rpms(maybe more?) in power b/c you tune the frequencies. I was under the impression that if you tune these frequencies perfectly, you can acheive greater power than ITBs.(greater than 100% volumetric efficiency). From the calculations earlier in the thread, it seems that skunk2 sized their IM length from flange to plenum to get a 'peak' at 6500 or so.
All the fastest hondas use intake/TB/IM..no?
skunk2 was the first in 12s with ITBs(i believe), but only made it into the 10s with the traditional IM...
thoughts? explanations?
All the fastest hondas use intake/TB/IM..no?
skunk2 was the first in 12s with ITBs(i believe), but only made it into the 10s with the traditional IM...
thoughts? explanations?
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From: puyallup, or, usa
First off, if you are dealing with 1/3 or 1/4 wave resonates, you have many differnt harmonincs that you engine will also be tuned for. This also means, for every harmonic, you will also have a node point that will drop you.
The resonate freq tuning of an intake runner is somthing mainly done by people who understand what to look for in a manifold. Does runner legnth matter? YES Does volume matter? YES Taper? yes, but resonate freq of the tube is for people to talk about who dont understand that engines can not make any performance bennift from all the resonate freq tuning in the world. Unless they have a CVT, but thats another story...
Things can only resonate at 1 freq (rpm) as a base freq, and they will also constructively resonate at all even harmonics, and deconstructively resonate at all odd harmonics. These things balence eachother perfectly, and it why resonate freq tuning is not a reasonable factor in manifold design.
Something else to note, when people think they are slick plugging in there constants for the speed of sound to tune there tubes, they forget that pressure effects the speed of sound. I am yet to find a program that intigrates the pressure wave change in the port to compensate for speed of sound changes in the port.
SO, why do we get this effect of longer runners making more lowend? and shorter making more top end?
Energy stored in inertia of the collum of air balences. Higher RPM, faster moving air, and its mass of the cololum may be reduced and it will still carry the same superchargeing force behind it. Like wise, longer tube, with a lower air speed from lower rpm will also have the same energy to super charge it. This is why longer runners are better for low end, and shorter are better for top end. Dont listen to this highschool IM design talk about resonate freqs. Its just not capable of being effective for any engine that needs a change in RPM to accelerate the car. Not to mention, when you factor in the pressure change effecting the speed of sound, your runners would need to be tuned to an 8th wave, or be about 4ft long. Either way, its not able to help you.
Danimal- nice to see you have taken Jr. High physics. Might want to cram a few compressible fluid dynamics courses under your belt before speaking about freq tuning a manifold however.
The resonate freq tuning of an intake runner is somthing mainly done by people who understand what to look for in a manifold. Does runner legnth matter? YES Does volume matter? YES Taper? yes, but resonate freq of the tube is for people to talk about who dont understand that engines can not make any performance bennift from all the resonate freq tuning in the world. Unless they have a CVT, but thats another story...
Things can only resonate at 1 freq (rpm) as a base freq, and they will also constructively resonate at all even harmonics, and deconstructively resonate at all odd harmonics. These things balence eachother perfectly, and it why resonate freq tuning is not a reasonable factor in manifold design.
Something else to note, when people think they are slick plugging in there constants for the speed of sound to tune there tubes, they forget that pressure effects the speed of sound. I am yet to find a program that intigrates the pressure wave change in the port to compensate for speed of sound changes in the port.
SO, why do we get this effect of longer runners making more lowend? and shorter making more top end?
Energy stored in inertia of the collum of air balences. Higher RPM, faster moving air, and its mass of the cololum may be reduced and it will still carry the same superchargeing force behind it. Like wise, longer tube, with a lower air speed from lower rpm will also have the same energy to super charge it. This is why longer runners are better for low end, and shorter are better for top end. Dont listen to this highschool IM design talk about resonate freqs. Its just not capable of being effective for any engine that needs a change in RPM to accelerate the car. Not to mention, when you factor in the pressure change effecting the speed of sound, your runners would need to be tuned to an 8th wave, or be about 4ft long. Either way, its not able to help you.
Danimal- nice to see you have taken Jr. High physics. Might want to cram a few compressible fluid dynamics courses under your belt before speaking about freq tuning a manifold however.
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Re: (liveforphysics)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by liveforphysics »</TD></TR><TR><TD CLASS="quote">
Danimal- nice to see you have taken Jr. High physics. Might want to cram a few compressible fluid dynamics courses under your belt before speaking about freq tuning a manifold however.</TD></TR></TABLE>
wow liveforphysics, no one is arguing against you. this is a forum for thoughts and explanations. dont take it personal.
I took UC Davis physics...just didn't relate any of it to engines. Starting upper division physics courses next yr =P
Modified by DefiantGSR at 9:12 PM 4/21/2004
Danimal- nice to see you have taken Jr. High physics. Might want to cram a few compressible fluid dynamics courses under your belt before speaking about freq tuning a manifold however.</TD></TR></TABLE>
wow liveforphysics, no one is arguing against you. this is a forum for thoughts and explanations. dont take it personal.
I took UC Davis physics...just didn't relate any of it to engines. Starting upper division physics courses next yr =P
Modified by DefiantGSR at 9:12 PM 4/21/2004
Re: (danimal)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by danimal »</TD></TR><TR><TD CLASS="quote">maybe you guys should tell bisi that his ~8,500+ rpm engine would make more power if it had a single throttle body, instead of one individual barrel per port.
better yet, why not tell leslie durst that running twm itb's was a bad idea, lol: http://www.turbomagazine.com/f...durst/
</TD></TR></TABLE>
What about the first car to run in the 9s all motor? Ericks Racing, i seem to remember him doing it with a ported GSR manifold
I think ITBs are great, and they have their advantages over a single TB setup
However, it is debatable whether having more air velocity is in fact better then having a single TB/Manifold setup that flows more air
better yet, why not tell leslie durst that running twm itb's was a bad idea, lol: http://www.turbomagazine.com/f...durst/
</TD></TR></TABLE>
What about the first car to run in the 9s all motor? Ericks Racing, i seem to remember him doing it with a ported GSR manifold
I think ITBs are great, and they have their advantages over a single TB setup
However, it is debatable whether having more air velocity is in fact better then having a single TB/Manifold setup that flows more air
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From: SC
So how much WHP can a set of the 42mm DIY ITB settups support?Some people are claiming like 16hp midrange over their previous TB settup on an otherwise stock engine.....Is that a fairly realistic number to look for on a more aggressive settup?
Are we all in agreement that the ITB's are going to kill the single TB settup in the usable midrange?
Are we all in agreement that the ITB's are going to kill the single TB settup in the usable midrange?
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Re: (blazin)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blazin »</TD></TR><TR><TD CLASS="quote">So how much WHP can a set of the 42mm DIY ITB settups support?Some people are claiming like 16hp midrange over their previous TB settup on an otherwise stock engine.....Is that a fairly realistic number to look for on a more aggressive settup?
Are we all in agreement that the ITB's are going to kill the single TB settup in the usable midrange?</TD></TR></TABLE>
42mm w/ what length runners? where would you place the injector?
Ex. Toda ITB's (43mm @ the plate).. bolt on b18c5 no tuning nothing. 25whp mid/15 up top, solid gains.
Toda ITB's has the injector waay out, before the plates.
Are we all in agreement that the ITB's are going to kill the single TB settup in the usable midrange?</TD></TR></TABLE>
42mm w/ what length runners? where would you place the injector?
Ex. Toda ITB's (43mm @ the plate).. bolt on b18c5 no tuning nothing. 25whp mid/15 up top, solid gains.
Toda ITB's has the injector waay out, before the plates.
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Re: (:thumbsdown:)
just an example stock itr motor 172hp127torque ..... twm itbs50mm 181hp 136torque ... the itbs had hella more midrange. i run ITBS ON MY RACE CAR AND WOULD NEVER GO BACK.
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Re: (liveforphysics)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by liveforphysics »</TD></TR><TR><TD CLASS="quote">...resonate freq of the tube is for people to talk about who dont understand that engines can not make any performance bennift from all the resonate freq tuning in the world.</TD></TR></TABLE>
"Helmholtz/quarter-wave organ pipe theory:
In an ASME (American Society
of Mechanical Engineers) paper
published in the early 1970s, Peter
C. Vorum revealed his Masters
Thesis work combining the earlier
resonant tuning characteristics
found in electrical circuits with
their acoustical counterparts in the
internal combustion engine. Pete’s
formulas provided a mathematical
means for configuring single and
multiple degrees of freedom
intake and exhaust systems, later
incorporated in selected OEM
manifold designs. His work has
formed the basis for continued
development of his "Short Pipe
Tuning" methods.
Essentially, the Vorum method
suggests the use of a quarter-wave
organ pipe analogy for the plenumrunner
(inlet port) portion of an
intake system as a "fixed" set of computed
dimensions that include the
variables mechanical compression
ratio, valve timing, rpm and piston
displacement… among others.
Then he added the effects of
cylinder volume, as it changes with
piston movement (see accompanying
illustration). Both the quarterwave
pipe and Helmholtz effects of
piston motion can be used to "tune"
the intake path, producing a
desired 240-260 ft/sec mean flow
velocity in the path at specific rpm
associated with peak torque (volumetric
efficiency).
Since the Helmholtz and quarterwave
effects can be isolated, one
from the other, "single-" and "multiple-
degree of freedom" systems can
be designed. When combined, each
can resonate at a different frequency
but at some point, become mutually
resonant and additive to the
overall cylinder filling process (see
accompanying illustration). While it
is beyond the scope of this particular
discussion to include finite
details of the Vorum method, reference
to ASME papers produced in
5 The Manifold Parts of Automotive Induction Systems
the 1970s regarding "Short Pipe
Intake Tuning" (by Peter C. Vorum)
will provide additional explanation.
From a practical standpoint, this
approach enables an engine
builder or enthusiast to modify,
evaluate or design an intake manifold
targeted specifically to a piston
displacement and rpm (or range) in
which maximum torque is desired." -jim mcfarland, http://www.N2Performance.com
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by liveforphysics »</TD></TR><TR><TD CLASS="quote"> ...I am yet to find a program that intigrates the pressure wave change in the port to compensate for speed of sound changes in the port.</TD></TR></TABLE>
you haven't found that program because it appears that you are a young college student who has no experience in the real world
i believe that the major car manufacturers use engine design software costing tens of thousands of dollars, that is capable of doing just that.
based on my jr. high physics
i do agree with defiantgsr about the common plenum having a slightly greater h.p. peak potential... my problem is that no one i know of has designed a common plenum that has been 100% dyno-proven over itb's that are tuned for the same engine... you can't just slap the same plenum on every motor, and expect to see the same gains.
"Helmholtz/quarter-wave organ pipe theory:
In an ASME (American Society
of Mechanical Engineers) paper
published in the early 1970s, Peter
C. Vorum revealed his Masters
Thesis work combining the earlier
resonant tuning characteristics
found in electrical circuits with
their acoustical counterparts in the
internal combustion engine. Pete’s
formulas provided a mathematical
means for configuring single and
multiple degrees of freedom
intake and exhaust systems, later
incorporated in selected OEM
manifold designs. His work has
formed the basis for continued
development of his "Short Pipe
Tuning" methods.
Essentially, the Vorum method
suggests the use of a quarter-wave
organ pipe analogy for the plenumrunner
(inlet port) portion of an
intake system as a "fixed" set of computed
dimensions that include the
variables mechanical compression
ratio, valve timing, rpm and piston
displacement… among others.
Then he added the effects of
cylinder volume, as it changes with
piston movement (see accompanying
illustration). Both the quarterwave
pipe and Helmholtz effects of
piston motion can be used to "tune"
the intake path, producing a
desired 240-260 ft/sec mean flow
velocity in the path at specific rpm
associated with peak torque (volumetric
efficiency).
Since the Helmholtz and quarterwave
effects can be isolated, one
from the other, "single-" and "multiple-
degree of freedom" systems can
be designed. When combined, each
can resonate at a different frequency
but at some point, become mutually
resonant and additive to the
overall cylinder filling process (see
accompanying illustration). While it
is beyond the scope of this particular
discussion to include finite
details of the Vorum method, reference
to ASME papers produced in
5 The Manifold Parts of Automotive Induction Systems
the 1970s regarding "Short Pipe
Intake Tuning" (by Peter C. Vorum)
will provide additional explanation.
From a practical standpoint, this
approach enables an engine
builder or enthusiast to modify,
evaluate or design an intake manifold
targeted specifically to a piston
displacement and rpm (or range) in
which maximum torque is desired." -jim mcfarland, http://www.N2Performance.com
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by liveforphysics »</TD></TR><TR><TD CLASS="quote"> ...I am yet to find a program that intigrates the pressure wave change in the port to compensate for speed of sound changes in the port.</TD></TR></TABLE>
you haven't found that program because it appears that you are a young college student who has no experience in the real world
i believe that the major car manufacturers use engine design software costing tens of thousands of dollars, that is capable of doing just that.based on my jr. high physics
i do agree with defiantgsr about the common plenum having a slightly greater h.p. peak potential... my problem is that no one i know of has designed a common plenum that has been 100% dyno-proven over itb's that are tuned for the same engine... you can't just slap the same plenum on every motor, and expect to see the same gains.
Senior Member
Joined: Oct 2003
Posts: 10,289
Likes: 1
From: Hendersonville, NC
All of that information is good and well, however it still tell us anything we didn't already know. Resonant tuning, as stated in your post, is only beneficial for a very short part of the powerband. And as stated above, unless you operate with a CVT, which can internally modulate it's gear ratios to provide steady acceleration while holding a constant engine speed, then resonant tuning isn't really a great performance benefit. Naturally, it can be optimized by building a manifold designed to reach resonant harmony at a critical point in the powerband that will yield the maximum benefit, right after you shift for instance, however it lacks the ability to provide as solid of a torque curve as a well designed ITB setup.