Bigger TB: Is it time?
04-02-2003, 11:50 PM
#16
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Originally posted by turbo_Z
you said the torque curve would be more usable at 5k rpm which it not accurate.. maybe hp curve but everyone knows you dont have torque up high. have you ever seen a dyno graph?
ok i misunderstood you about the programming. i thought you were saying the tb would rob him of hp because of this stock tune.
you said the torque curve would be more usable at 5k rpm which it not accurate.. maybe hp curve but everyone knows you dont have torque up high. have you ever seen a dyno graph?
ok i misunderstood you about the programming. i thought you were saying the tb would rob him of hp because of this stock tune.
Horsepower IS NOT FREAKING POWER!
It is a measure of Torque at a specific RPM!
All Horsepower is torque in ft./lbs. times rpm, divided by 5,252.
THAT IS IT. Have you ever seen an LS1's dyno graph? Ever notice how that torque curve is so flat up high? That is why they have higher "peak" HP ratings than us...It is because we suck at high RPM's, and they don't! All we have to do is concentrate on high RPM tuning to equal an LS1's stock HP rating. **** people this is as easy as 10*10/5.
The only use I have for horsepower is bitchslap "modded" Honda's.
I want Torque. I want Torque at EVERY RPM! If I have 300 lbs feet of torque at 4500RPMs, and 270 at 5000, that means I have a peak of 257.044HP at 4500 RPM and 257.044at 5000RPMs... Wow, the same...
Figure it out...10 more lbs feet at 5000RPMs means 266.56HP at 5000RPMS. More torque at high RPMs is why LS1's are consistantly kicking our asses stock for stock. What all the fancy heads and cams that cost major bucks and make the top end so great really do is put our torque peak at a higher RPM than stock, peaking higher than the stock peak around 3-4K, whereas an LS1 will peak more like 4500RPM's.
Why do you think the Honda S2000 makes 240HP? Is it powerful? Hell no...It revs to 9000 RPMS, with the same torque as a damn Civic. That "massive" amount of HP/Liter is irrelevant.
Take Physics 101 then question me.
04-02-2003, 11:53 PM
#17
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Originally posted by 96z
This was posted a WHILE back by injuneer when I had asked why Craig at GTP said a 58mm TB was costing me power on my head cam A4 car....take it for whats its worth.
"I can tell you why an oversize TB won't help. Just because a TB can flow more air at a given pressure drop doesn't mean it will cause more air to flow into your specific engine. Air flow is determined largely by the heads and cam. The TB is simply there to act as a "valve".... allowing the engine to run at less than 100%.
Yes, if you had a severely undersized TB to start with, you would choke off the amount of air that can flow into the engine, but put a grossly oversize TB in place of a correctly sized TB, and it isn't going to magically make the engine demand/flow more air.
A measurement of flow means nothing if it isn't accompanied by a pressure drop. Pressure drop is roughly proportional to the diameter raised to the 2.5 power. Once you reach a certain point, the reduction in pressure drop is negligible. And the only thing that is going to change the amount of air filling the pistons is the pressure drop in the air inlet track. A fraction of an inch of water isn't going to alter volumetric efficiency any appreciable amount.
As a point of reference, when we first set up my engine, we used N-alpha programming, where fuel is essentially determined by throttle position and rpm. At 77% open, the 58mm TB was flowing about as much air as the engine needed. In effect, the engine could have made the same amount of power on a 52mm TB. Going larger did not cause the engine to flow more air, or make more power.
I can't tell you why Craig is saying the 58mm is costing you power because you have an A4. I doubt that the velocity of the air through the TB bores is of major significance, since the volume of the plenum relative to the volume of the runners should effectively decouple the TB from the runners. I "think" that's the case... can't prove it for the specifics of the LT1 plenum.
But the idea that putting a larger TB or a larger MAF sensor or a larger CAI magically makes your engine flow significantly more air is a popular misconception. The increase in flow is proportional to the reduction in pressure loss, relative to full atmospheric pressure.... a few 1/10th's of an inch H2O from an oversize component means virtually nothing."
This was posted a WHILE back by injuneer when I had asked why Craig at GTP said a 58mm TB was costing me power on my head cam A4 car....take it for whats its worth.
"I can tell you why an oversize TB won't help. Just because a TB can flow more air at a given pressure drop doesn't mean it will cause more air to flow into your specific engine. Air flow is determined largely by the heads and cam. The TB is simply there to act as a "valve".... allowing the engine to run at less than 100%.
Yes, if you had a severely undersized TB to start with, you would choke off the amount of air that can flow into the engine, but put a grossly oversize TB in place of a correctly sized TB, and it isn't going to magically make the engine demand/flow more air.
A measurement of flow means nothing if it isn't accompanied by a pressure drop. Pressure drop is roughly proportional to the diameter raised to the 2.5 power. Once you reach a certain point, the reduction in pressure drop is negligible. And the only thing that is going to change the amount of air filling the pistons is the pressure drop in the air inlet track. A fraction of an inch of water isn't going to alter volumetric efficiency any appreciable amount.
As a point of reference, when we first set up my engine, we used N-alpha programming, where fuel is essentially determined by throttle position and rpm. At 77% open, the 58mm TB was flowing about as much air as the engine needed. In effect, the engine could have made the same amount of power on a 52mm TB. Going larger did not cause the engine to flow more air, or make more power.
I can't tell you why Craig is saying the 58mm is costing you power because you have an A4. I doubt that the velocity of the air through the TB bores is of major significance, since the volume of the plenum relative to the volume of the runners should effectively decouple the TB from the runners. I "think" that's the case... can't prove it for the specifics of the LT1 plenum.
But the idea that putting a larger TB or a larger MAF sensor or a larger CAI magically makes your engine flow significantly more air is a popular misconception. The increase in flow is proportional to the reduction in pressure loss, relative to full atmospheric pressure.... a few 1/10th's of an inch H2O from an oversize component means virtually nothing."
THIS IS NOT A STOCK CAR THE THREAD POSTER HAS! It is cammed! He has higher lift and duration than stock! HE CAN FLOW MORE AIR!
04-03-2003, 12:05 AM
#18
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A second reply to that engineers statement...If the 58MM is "flooding the engine" with air, and therefore making it run lean, then logically adding more fuel would be the BEST way to go, to maitain the A/F ratio, rather than robbing the engine of air it obviously can get. Why waste that? The only damn reason the damn engine is lean is because of the stinking 48MM loving MAF, not "too much air" If too much air is a problem, get rid of the 30 pound pulley on the supercharger. All you need is a freaking MAFT to adjust the A/F while on the dyno with wideband o2.
Notice, though, he never did say the 52MM was a problem, just a 58mm, which I didn't recommend.
Notice, though, he never did say the 52MM was a problem, just a 58mm, which I didn't recommend.
04-03-2003, 12:19 AM
#19
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Originally posted by HM Murdock
A second reply to that engineers statement...If the 58MM is "flooding the engine" with air, and therefore making it run lean, then logically adding more fuel would be the BEST way to go, to maitain the A/F ratio, rather than robbing the engine of air it obviously can get. Why waste that? The only damn reason the damn engine is lean is because of the stinking 48MM loving MAF, not "too much air" If too much air is a problem, get rid of the 30 pound pulley on the supercharger. All you need is a freaking MAFT to adjust the A/F while on the dyno with wideband o2.
Notice, though, he never did say the 52MM was a problem, just a 58mm, which I didn't recommend.
A second reply to that engineers statement...If the 58MM is "flooding the engine" with air, and therefore making it run lean, then logically adding more fuel would be the BEST way to go, to maitain the A/F ratio, rather than robbing the engine of air it obviously can get. Why waste that? The only damn reason the damn engine is lean is because of the stinking 48MM loving MAF, not "too much air" If too much air is a problem, get rid of the 30 pound pulley on the supercharger. All you need is a freaking MAFT to adjust the A/F while on the dyno with wideband o2.
Notice, though, he never did say the 52MM was a problem, just a 58mm, which I didn't recommend.
04-03-2003, 12:30 AM
#20
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Uhh... IT WILL ADD POWER. Not PEAK power, remember no car but true electrics make peak power at every RPM. If you make 275 peak HP at say 5100RPMS and peak torque at 4000PMs at 325lbs ft, and correspndingly make 283 Ft lbs at 5100RPMS and 247HP at 4000RPMS.
It may not increase PEAK power(which is for dyno queens) but it will increase torque at high RPM's, which increases horsepower there too. It will mean better times in the 1/4
It may not increase PEAK power(which is for dyno queens) but it will increase torque at high RPM's, which increases horsepower there too. It will mean better times in the 1/4
04-03-2003, 01:20 AM
#21
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Originally posted by 95TA8280
some people think these bigger TBs are too big and messes up the airflow.....
some people think these bigger TBs are too big and messes up the airflow.....
04-03-2003, 02:06 AM
#22
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Lets make this simple..he is not maxing out his 48mm TB, if he was he would get a gain...he is not so he wont!! That is a simple as it gets.
The motor can only bring in as much air as it needs and as injuneer explains it acts like a gate. It doesnt matter if you have a 52 mm TB or a 520mm TB the same amount of air will be brought in by each cyliner on the intake stroke....Try this for example...say you had to inhale as much air as you could through a 48mm tube, than you had to do the same with a 52mm tube...will you automatically be able to inhale more air because the opening is 4mm larger?....no....because your lung volume stays the same. Unless you increase your lung volume internally you will inhale the same amount through both. If there was a point where the 48mm was restriciting your ability to inhale than you will benefit from a larger tube...
Unless you can prove that a car with his mods is being choked by the 48mm TB, no matter what RPM you have no point to your arguement and it is wrong.
The motor can only bring in as much air as it needs and as injuneer explains it acts like a gate. It doesnt matter if you have a 52 mm TB or a 520mm TB the same amount of air will be brought in by each cyliner on the intake stroke....Try this for example...say you had to inhale as much air as you could through a 48mm tube, than you had to do the same with a 52mm tube...will you automatically be able to inhale more air because the opening is 4mm larger?....no....because your lung volume stays the same. Unless you increase your lung volume internally you will inhale the same amount through both. If there was a point where the 48mm was restriciting your ability to inhale than you will benefit from a larger tube...
Unless you can prove that a car with his mods is being choked by the 48mm TB, no matter what RPM you have no point to your arguement and it is wrong.
Last edited by 96z; 04-03-2003 at 02:21 AM.
04-03-2003, 02:50 AM
#24
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If he's not maxing out his 48MM, then whay does the power fall off? Hmm?
I don't give a hoot what some engineer says. Engineers can, and are frequently wrong. They sure as hell couldn't design a distributor for the LT1.
And just how do you know how much his 48mm TB is flowing?
Do you know the percent, because i'm all ears.
This is simple physics people.
It isn't about how much the cylinder can hold, that is not a constant. It is about how fast can the engine, and therefore the throttle body, replenish? I sincerly doubt that the ambient [ressure in the Intake manifold is at its max with the 48MM TB. If it was, then forced induction is irrelevant. The bigger the openeing, the more air gets in the manifold. The more in the manifold, the more the heads can flow. Higher pressure is like that...It flows better into places where pressure is lower, IE a cylinder after it pumps the air back out the exhaust valve. This is how wind works. This is how vacuum works. This is why we are alive. This is how our own damn hearts work. He already has more duration, lift, and a better lobe seperation degree than stock, therefore there is a greater need for air. At high RPM's that need becomes very frequent. Remeber, with new springs,a nd an updated valve train, he can rev higher than the engineers ever inteded for the LT1 to rev. The greater the air flow, the higher the pressure, the faster the air will move from one spot(where the air is under high pressure) to the other (where the air is under low pressure, or vacuum, in the case of a cylinder.) Why most people don't see any gain is because the stock programming will NEVER, not ONCE take into account higher pressure on 94 and up LT series, MAF driven vehicles, because th MAF reading is the same regardless of size of throttle body. I absolutely gurantee he would have more power after proper tuning with a 52 or even 58mm TB. If the damn MAF and PCM still thinks the TB is is stock, it will never take into account higher volumeteric flow and ambient pressure when sending the injector pulses. Ever wonder why 93's seem to respond pretty well to 52mm TB's? THe run in speed density, or MAP, Manifold Ablsolute Pressue. to edit the injector pulses, therefore the PCM DOES see more air in the manifold.
This principle is why windspeed is not constant, and we have weather on this doomed planet.
A simple example.
Take a bottle of Nitrous Oxide. It delivers a very high pressure gaseous substance into the Manifold. Right? Can we all agree on the basic workings of a dry setup? OK, thanks.
If the heads cannot handle the additional flow, how does a dry system work without direct injection into a cylinder?
It's because they can handle denser air.
Air can be compressed. It's volume is only determined by the size of the container.
Higher pressure means more dense air means more oxygen for the combustion part of Internal Combustion to work
This is also why cold air is better for performance.
Ever wonder why LS1's seem to respond to a ported TB when stock LT1's don't?
Their PCMs use MAF and MAP together to determine fuel delivery.
He will see a gain above 4800, he will see a better gain with PCM tuning. Engineers don't study quantum physics as a hobby. I do.
I don't care how fast you think you are, you can't violate the laws of how matter works in my universe.
Until you can, there is no way to defeat what I ahave said.
And if you can, then you are singly responsible for eliminating in one fell swoop everything we know about how everything works and interacts. In that case, you would have no recourse but to wipe me from existance for my insolence.
Just because it says junior member under my name doesn't mean I don't know the laws of thermodynamics. One of very few sets of unbreakable laws. Now Newtonian Physics, that I can help you debunk. In fact, I am not the only one working on it.
I don't give a hoot what some engineer says. Engineers can, and are frequently wrong. They sure as hell couldn't design a distributor for the LT1.
And just how do you know how much his 48mm TB is flowing?
Do you know the percent, because i'm all ears.
This is simple physics people.
It isn't about how much the cylinder can hold, that is not a constant. It is about how fast can the engine, and therefore the throttle body, replenish? I sincerly doubt that the ambient [ressure in the Intake manifold is at its max with the 48MM TB. If it was, then forced induction is irrelevant. The bigger the openeing, the more air gets in the manifold. The more in the manifold, the more the heads can flow. Higher pressure is like that...It flows better into places where pressure is lower, IE a cylinder after it pumps the air back out the exhaust valve. This is how wind works. This is how vacuum works. This is why we are alive. This is how our own damn hearts work. He already has more duration, lift, and a better lobe seperation degree than stock, therefore there is a greater need for air. At high RPM's that need becomes very frequent. Remeber, with new springs,a nd an updated valve train, he can rev higher than the engineers ever inteded for the LT1 to rev. The greater the air flow, the higher the pressure, the faster the air will move from one spot(where the air is under high pressure) to the other (where the air is under low pressure, or vacuum, in the case of a cylinder.) Why most people don't see any gain is because the stock programming will NEVER, not ONCE take into account higher pressure on 94 and up LT series, MAF driven vehicles, because th MAF reading is the same regardless of size of throttle body. I absolutely gurantee he would have more power after proper tuning with a 52 or even 58mm TB. If the damn MAF and PCM still thinks the TB is is stock, it will never take into account higher volumeteric flow and ambient pressure when sending the injector pulses. Ever wonder why 93's seem to respond pretty well to 52mm TB's? THe run in speed density, or MAP, Manifold Ablsolute Pressue. to edit the injector pulses, therefore the PCM DOES see more air in the manifold.
This principle is why windspeed is not constant, and we have weather on this doomed planet.
A simple example.
Take a bottle of Nitrous Oxide. It delivers a very high pressure gaseous substance into the Manifold. Right? Can we all agree on the basic workings of a dry setup? OK, thanks.
If the heads cannot handle the additional flow, how does a dry system work without direct injection into a cylinder?
It's because they can handle denser air.
Air can be compressed. It's volume is only determined by the size of the container.
Higher pressure means more dense air means more oxygen for the combustion part of Internal Combustion to work
This is also why cold air is better for performance.
Ever wonder why LS1's seem to respond to a ported TB when stock LT1's don't?
Their PCMs use MAF and MAP together to determine fuel delivery.
He will see a gain above 4800, he will see a better gain with PCM tuning. Engineers don't study quantum physics as a hobby. I do.
I don't care how fast you think you are, you can't violate the laws of how matter works in my universe.
Until you can, there is no way to defeat what I ahave said.
And if you can, then you are singly responsible for eliminating in one fell swoop everything we know about how everything works and interacts. In that case, you would have no recourse but to wipe me from existance for my insolence.
Just because it says junior member under my name doesn't mean I don't know the laws of thermodynamics. One of very few sets of unbreakable laws. Now Newtonian Physics, that I can help you debunk. In fact, I am not the only one working on it.
Last edited by HM Murdock; 04-03-2003 at 03:26 AM.
04-03-2003, 03:01 AM
#25
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Originally posted by turbo_Z
the point we are all making here is that the car does not require the MAX CFM that the stock tb can flow. therefore going to a larger tb will not gain any more power. also a tb wont cause the engine to run lean. a MAF combined with O2 sensors will maintain the appropriate A/F ratio.
the point we are all making here is that the car does not require the MAX CFM that the stock tb can flow. therefore going to a larger tb will not gain any more power. also a tb wont cause the engine to run lean. a MAF combined with O2 sensors will maintain the appropriate A/F ratio.
CFM is never a constant, however ther more you got, the more molecules of air you have to use... Density and pressure matter. I can contain 14.7PSI worth of air(1 atmosphere) in a container the size if a pinhead. At that velocity, the 52mm tb is capable of so much more performance wise over the 48mm.
And you guys are the same people who razz me for saying that a cat back is not the first priority. A 3" intermediate is perfectly adequate for up to 600HP and more.
Who the hell wants to be adequate? I want ever last damn lbs ft out of my engine at every useable RPM.
If the TB sounded better and louder than stock, I bet you would be the first in line. It is what is called groundwork.
Do some. Then I will accept bitching about how my car makes less than his car with X mods.
04-03-2003, 03:06 AM
#26
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Hey Hey Hey, don't confuzel us common folk with your big hootinfalootin words....
Its 4AM and ma head hurts now.
In all seriousness, though, this is a great post.
HM MURDOCK, I don't get why you have a sig in only certain posts here, just seems weird.
Its 4AM and ma head hurts now.In all seriousness, though, this is a great post.
HM MURDOCK, I don't get why you have a sig in only certain posts here, just seems weird.
Last edited by scoobysnax83; 04-03-2003 at 03:12 AM.
04-03-2003, 03:21 AM
#27
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I only try to post it once per thread.
Sorry for all the big words, but they decided to consult an engineer, when they should have consulted a physicist.
Quantum Dynamics is the shiznit, yo.
It basically is the laws that govern everything, and the ones you can't ever break.
Sorry for all the big words, but they decided to consult an engineer, when they should have consulted a physicist.
Quantum Dynamics is the shiznit, yo.
It basically is the laws that govern everything, and the ones you can't ever break.
04-03-2003, 04:42 AM
#28
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Basically, what it breaks down to is this:
First of all.... you're far too arrogant for your own good. I'm really very impressed, you know how to read. So do I. Fantastic, maybe we can debate quantum chromodynamics or general relativity someday, but for now, I'll stick to the topic at hand.
The problem is, you have just enough sense as far as physics is concerned to think you're right 100% of the time, but in reality, there are other variables you haven't even begun to consider.
First. Please, go read about exhaust tuned length and diameter. Don't try to pass off this "more is always better" stuff to us because you are some huge fan of Max Planck or whatever the hell it is you read that has you convinced you're the smartest armchair 'physicist' on the block. More is NOT always better when it comes to exhaust systems.
Second. How do YOU know that the 48mm throttle body is not sufficient for a mild cammed car? (HOTcam is mild, for your information) Surely, you read enough books on physics to know that the burden of proof is on the person making the assertion. You are asserting that 48mm is too small for his motor. Why don't you tell us why this is? Back up your statements with facts, not general physics principles that may (or may not) apply to the particular situation we are discussing. Most people here have many years of experience with engines and the 'engineer' you have such a problem with, is our very own Injuneer Fred, who I am fairly certain has more technical AND practical knowledge than you have gained from whatever amount of books you have read. We all know theories. We all understand physics. So, back to the point in general. Answer me this, Neils Bohr: if the area of greatest restriction in an engine is the heads, or in the duration/lift/lsa of the particular cam (remember, the HOTcam is not big) then how is changing the size of the throttle body going to add torque magically? Where is all this 'extra' air that you will be inducting going to go, when the biggest restriction is still the plenum or the runners or the intake or the exhaust ports or the cam itself? You have convinced yourself that your knowledge of physics makes you superior to everyone on this board, and that a larger opening will ALWAYS make more torque. GM uses a 48mm throttle body on 500hp crate motors. Now, in these cases, I'm sure a 52mm throttle body would help, since the area of greatest restriction MAY WELL BE the throttle body. But on his HOTcammed car, which is probably making no more than 335rwhp, do you have any reason to believe this is his area of greatest resistance?
How is a larger throttle body going to in any way affect the density of the incoming air? How is it going to induct more air when the restriction is still in the heads or the cam? HOW?
Also, please, get a clue about the TORQUE vs. HORSEPOWER dichotomy. Yeah, obviously HP is a mathematical product of TQ, we all realize this. What you are failing to realize is this: Yes, peak HP DOES matter. Not AS MUCH, but it does matter. Area under the HP curve, to be specific, is more beneficial, but lets keep in mind why we even measure HP. The "pitiful" S2000 you mock is still fast because it takes advantage of something we ignorant motorheads like to call:
G E A R I N G
Yes, thats right, upper RPM torque, which gives us our HP numbers, IS STILL IMPORTANT. Remember, through GEAR REDUCTION we can still MULTIPLY our torque. Who really gives a crap how many pound feet of torque you are making at whatever RPM if you can still lay down just as much TORQUE through TORQUE MULTIPLICATION by GEARING.
Please, until you have a Ph.D in Quantum Physics, keep the arrogance to yourself. There is no need for that on THIS forum.
First of all.... you're far too arrogant for your own good. I'm really very impressed, you know how to read. So do I. Fantastic, maybe we can debate quantum chromodynamics or general relativity someday, but for now, I'll stick to the topic at hand.
The problem is, you have just enough sense as far as physics is concerned to think you're right 100% of the time, but in reality, there are other variables you haven't even begun to consider.
First. Please, go read about exhaust tuned length and diameter. Don't try to pass off this "more is always better" stuff to us because you are some huge fan of Max Planck or whatever the hell it is you read that has you convinced you're the smartest armchair 'physicist' on the block. More is NOT always better when it comes to exhaust systems.
Second. How do YOU know that the 48mm throttle body is not sufficient for a mild cammed car? (HOTcam is mild, for your information) Surely, you read enough books on physics to know that the burden of proof is on the person making the assertion. You are asserting that 48mm is too small for his motor. Why don't you tell us why this is? Back up your statements with facts, not general physics principles that may (or may not) apply to the particular situation we are discussing. Most people here have many years of experience with engines and the 'engineer' you have such a problem with, is our very own Injuneer Fred, who I am fairly certain has more technical AND practical knowledge than you have gained from whatever amount of books you have read. We all know theories. We all understand physics. So, back to the point in general. Answer me this, Neils Bohr: if the area of greatest restriction in an engine is the heads, or in the duration/lift/lsa of the particular cam (remember, the HOTcam is not big) then how is changing the size of the throttle body going to add torque magically? Where is all this 'extra' air that you will be inducting going to go, when the biggest restriction is still the plenum or the runners or the intake or the exhaust ports or the cam itself? You have convinced yourself that your knowledge of physics makes you superior to everyone on this board, and that a larger opening will ALWAYS make more torque. GM uses a 48mm throttle body on 500hp crate motors. Now, in these cases, I'm sure a 52mm throttle body would help, since the area of greatest restriction MAY WELL BE the throttle body. But on his HOTcammed car, which is probably making no more than 335rwhp, do you have any reason to believe this is his area of greatest resistance?
How is a larger throttle body going to in any way affect the density of the incoming air? How is it going to induct more air when the restriction is still in the heads or the cam? HOW?
Also, please, get a clue about the TORQUE vs. HORSEPOWER dichotomy. Yeah, obviously HP is a mathematical product of TQ, we all realize this. What you are failing to realize is this: Yes, peak HP DOES matter. Not AS MUCH, but it does matter. Area under the HP curve, to be specific, is more beneficial, but lets keep in mind why we even measure HP. The "pitiful" S2000 you mock is still fast because it takes advantage of something we ignorant motorheads like to call:
G E A R I N G
Yes, thats right, upper RPM torque, which gives us our HP numbers, IS STILL IMPORTANT. Remember, through GEAR REDUCTION we can still MULTIPLY our torque. Who really gives a crap how many pound feet of torque you are making at whatever RPM if you can still lay down just as much TORQUE through TORQUE MULTIPLICATION by GEARING.
Please, until you have a Ph.D in Quantum Physics, keep the arrogance to yourself. There is no need for that on THIS forum.
04-03-2003, 08:01 AM
#30
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Some serious ego-tripping in this thread. Especially from a guy who does "stuff" for a living. If you venture through some of the other forums of this board you'll see that the most knowledgable people are also the most humble. Of course there are the knowledgable, egoists too but it just comes with the territory where everyone is fighting over the "I'm the smartest guy" title.
If you want to impress someone.... leave your ego behind and quantify what you're screaming is the truth. The math behind your theory is always a plus. It's what seperates the theorisist from the big boys. I'm a "static" guy so I'll just stick with what I've seen from personal experience.... either that or, thinking back on what Mark Twain said, I'll keep my mouth shut.
Sooo,
Consider the fact that so many stock eliminator LT cars are breaking into the 10's these days.... then consider the fact that they are doing that with stock 48mm throttle bodies! Restriction or no? Cause as Fred's response implied, that's all that matters. If it's a restriction then you're losing power (pumping losses). If it's not, then you're not. It's not much more complicated than that. Too large and you may have some light-throttle response problems... which can cause some drivability problems.
If you want to get technical, calculate the engine's air demand, cfm=(rpm*cid)/(2*1728) and off you go. You then need to know the throttle bore size and it's effective area (account for the shaft). From there you should be able to calculate a flow rate through the throttle. That's my basic understanding on the subject..... no quantum physics needed.
Throttle bodies are rated (cfm) at a given pressure drop (I believe 1.5" Hg.... at least that's the way they rate carburetors), so if you're "maxing" the throttle body out at it's rating, then you're probably losing power to a restriction.
In speaking to a gentlemen much more intelligent than myself, who just happens to be a memeber of this board... he stated that lowering the air velocity through the throttle from .3 "Mach" to .2, may show a gain of ~1-3%, while lowering the velocity from .2-.1 will give you absolutely nothing.
On strong ~350 ci motors (1.6hp/ci), you'll see a gain in going with an 850 carburetor vs the tried and true 750. Seen it more than a few times but it just holds true to the air demand vs restriction theory. If you correct the 750's airflow to 1" Hg, you'll see it doesn't quite have enough airflow for a small-block turning 7,000 rpm. Of course, I think it's a much more complicated thing with carbs because we have to worry about fuel shear, booster response, secondary opening rate, lotsa stuff. Throttle bodies are much simpler, until someone makes it more complicated.
-Mindgame
If you want to impress someone.... leave your ego behind and quantify what you're screaming is the truth. The math behind your theory is always a plus. It's what seperates the theorisist from the big boys. I'm a "static" guy so I'll just stick with what I've seen from personal experience.... either that or, thinking back on what Mark Twain said, I'll keep my mouth shut.
Sooo,
Consider the fact that so many stock eliminator LT cars are breaking into the 10's these days.... then consider the fact that they are doing that with stock 48mm throttle bodies! Restriction or no? Cause as Fred's response implied, that's all that matters. If it's a restriction then you're losing power (pumping losses). If it's not, then you're not. It's not much more complicated than that. Too large and you may have some light-throttle response problems... which can cause some drivability problems.
If you want to get technical, calculate the engine's air demand, cfm=(rpm*cid)/(2*1728) and off you go. You then need to know the throttle bore size and it's effective area (account for the shaft). From there you should be able to calculate a flow rate through the throttle. That's my basic understanding on the subject..... no quantum physics needed.
Throttle bodies are rated (cfm) at a given pressure drop (I believe 1.5" Hg.... at least that's the way they rate carburetors), so if you're "maxing" the throttle body out at it's rating, then you're probably losing power to a restriction.
In speaking to a gentlemen much more intelligent than myself, who just happens to be a memeber of this board... he stated that lowering the air velocity through the throttle from .3 "Mach" to .2, may show a gain of ~1-3%, while lowering the velocity from .2-.1 will give you absolutely nothing.
On strong ~350 ci motors (1.6hp/ci), you'll see a gain in going with an 850 carburetor vs the tried and true 750. Seen it more than a few times but it just holds true to the air demand vs restriction theory. If you correct the 750's airflow to 1" Hg, you'll see it doesn't quite have enough airflow for a small-block turning 7,000 rpm. Of course, I think it's a much more complicated thing with carbs because we have to worry about fuel shear, booster response, secondary opening rate, lotsa stuff. Throttle bodies are much simpler, until someone makes it more complicated.
-Mindgame