Drivetrain Oversize TBs with stock inlet tube...
#1
Oversize TBs with stock inlet tube...
Well upon taking apart my engine today for some cools mods i decided to cut the stock throttle body to supercharger inlet tube at its most restrictive point. After a few mesurements I figured out that the area of that part of the tube is about half the area of the stock throttle body.
So my question is, how can a larger throttle body increase to power of the car is the bottle nech is not the TB, but the tube right after it?
I'm going to make one out of aluminum tubing to get rid of this god aweful thing. If anybody had made a new one post up some pics.
PS: i know about M7s air gain thing, i just don't like the idea of pulling in air from directly behind the radiator.
So my question is, how can a larger throttle body increase to power of the car is the bottle nech is not the TB, but the tube right after it?
I'm going to make one out of aluminum tubing to get rid of this god aweful thing. If anybody had made a new one post up some pics.
PS: i know about M7s air gain thing, i just don't like the idea of pulling in air from directly behind the radiator.
#2
#5
My measurement was taken four inches away from the supercharger inlet. The port has an upsidedown L shape to it.
I'm picking up materials tomorrow to finish my turbo setup that i'm putting together, and while i'm getting that i'm going to pick up some alum stock so i can start to make a new pipe.
I'm picking up materials tomorrow to finish my turbo setup that i'm putting together, and while i'm getting that i'm going to pick up some alum stock so i can start to make a new pipe.
#6
The benefit is that, assuming air can flow nicely into the larger TB and through the tube, it will gain velocity roughly proportional to the change in the cross area of the SC duct. If the cross sectional area is cut in half, the air moves roughly twice as fast. It's the same idea as a "velocity stack." The faster the air moves through a given cross-sectional area, the more mass you flow, and the more air will pass through the valves per unit time. The faster the air, the theory goes, the more power.
#7
OK, i see what you're saying. I have a question though. Have you ever seen the inside of the SC inlet tube? It is far from being a velocity stack. Not only that, but it is so deformed and not straight that it HAS to hurt the volume and velocity of the air traveling though this peice.
If what you're saying at trully be applied to this inlet tube, then i'll make a new tube that is made of 1" pipe. It'll act as a velocity stack right? Botum line, i think a straight 2.5" or 62mm ID pipe would work MUCH better that the stock peice.
In fact, i want to try this so badly that i've already started to make a new peice. I just finished making the part that holds the gasket for the SC inlet. tomorrow i'll make a merge for this peice to a 2.5" ID alum pipe. I'll then snake that pipe towards the original location of the TB.
I think i'm going to test the vacume at the SC inlet with the stock tube and the new one too, so i have some hard facts.
If what you're saying at trully be applied to this inlet tube, then i'll make a new tube that is made of 1" pipe. It'll act as a velocity stack right? Botum line, i think a straight 2.5" or 62mm ID pipe would work MUCH better that the stock peice.
In fact, i want to try this so badly that i've already started to make a new peice. I just finished making the part that holds the gasket for the SC inlet. tomorrow i'll make a merge for this peice to a 2.5" ID alum pipe. I'll then snake that pipe towards the original location of the TB.
I think i'm going to test the vacume at the SC inlet with the stock tube and the new one too, so i have some hard facts.
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#8
Originally Posted by autoxguy305
OK, i see what you're saying. I have a question though. Have you ever seen the inside of the SC inlet tube? It is far from being a velocity stack. Not only that, but it is so deformed and not straight that it HAS to hurt the volume and velocity of the air traveling though this peice.
If what you're saying at trully be applied to this inlet tube, then i'll make a new tube that is made of 1" pipe. It'll act as a velocity stack right? Botum line, i think a straight 2.5" or 62mm ID pipe would work MUCH better that the stock peice.
In fact, i want to try this so badly that i've already started to make a new peice. I just finished making the part that holds the gasket for the SC inlet. tomorrow i'll make a merge for this peice to a 2.5" ID alum pipe. I'll then snake that pipe towards the original location of the TB.
I think i'm going to test the vacume at the SC inlet with the stock tube and the new one too, so i have some hard facts.
If what you're saying at trully be applied to this inlet tube, then i'll make a new tube that is made of 1" pipe. It'll act as a velocity stack right? Botum line, i think a straight 2.5" or 62mm ID pipe would work MUCH better that the stock peice.
In fact, i want to try this so badly that i've already started to make a new peice. I just finished making the part that holds the gasket for the SC inlet. tomorrow i'll make a merge for this peice to a 2.5" ID alum pipe. I'll then snake that pipe towards the original location of the TB.
I think i'm going to test the vacume at the SC inlet with the stock tube and the new one too, so i have some hard facts.
Anyways, before mocking up a design, you must remember that you're gonna need to drill holes to add all of the lines that intersect the stock tube. You're also gonna need to mold a new SC-mating interface. The SC mating surface is NOT circular. Overall, the project is not gonna be easy, especially considering you must measure to make sure your tube fits! Test fit with the radiator and fan assembly replaced BEFORE you get too far. It's close, from personal experience .
#9
Originally Posted by ingsoc
You're basically re-inventing the AGS, which is a worthwhile mod given some recent but as yet unreleased data [it's coming soon!] data. Even the stock tube DOES give a functional velocity increase- the only limiting factor to velocity is how smooth you make the flow path.
Anyways, before mocking up a design, you must remember that you're gonna need to drill holes to add all of the lines that intersect the stock tube. You're also gonna need to mold a new SC-mating interface. The SC mating surface is NOT circular. Overall, the project is not gonna be easy, especially considering you must measure to make sure your tube fits! Test fit with the radiator and fan assembly replaced BEFORE you get too far. It's close, from personal experience .
Anyways, before mocking up a design, you must remember that you're gonna need to drill holes to add all of the lines that intersect the stock tube. You're also gonna need to mold a new SC-mating interface. The SC mating surface is NOT circular. Overall, the project is not gonna be easy, especially considering you must measure to make sure your tube fits! Test fit with the radiator and fan assembly replaced BEFORE you get too far. It's close, from personal experience .
#10
Originally Posted by autoxguy305
Already finished with the peice that connects to the SC The ID of one side is 2.5 (roughly) and the ID of the other side is 2.25 (roughly). I cut a 1/2 inch strip of 1/4" alum that was just over a foot long then bent it around pipes (2.5" and 2.25") to get the shape i needed.
Please post a picture, if you can!
#11
Originally Posted by ingsoc
The benefit is that, assuming air can flow nicely into the larger TB and through the tube, it will gain velocity roughly proportional to the change in the cross area of the SC duct. If the cross sectional area is cut in half, the air moves roughly twice as fast. It's the same idea as a "velocity stack." The faster the air moves through a given cross-sectional area, the more mass you flow, and the more air will pass through the valves per unit time. The faster the air, the theory goes, the more power.
Great idea on the new SC tube, BTW. Don't bother with any "velocity stack" flow restriction, though. Make the flow area as large as possible!
#14
Originally Posted by inimmini
Not sure I buy into this velocity stack idea. If the cross sectional area is cut in half, sure the average velocity of the flow would double, but the mass flow rate wouldn't change. No air mass flow increase, no more power. But, even this description is optimistic. As the flow velocity increases, viscous losses increase proportionally to the shear rate (at least for a Newtonian fluid in laminar flow, which is a reasonable assumption for the flow in the SC tube, although admittedly I haven't tried to calculate a Reynolds number). Therefore, if the flow area were cut in half, in actuality the flow velocity would increase somewhat less than 2x, and therefore mass flow would be reduced.
Great idea on the new SC tube, BTW. Don't bother with any "velocity stack" flow restriction, though. Make the flow area as large as possible!
Great idea on the new SC tube, BTW. Don't bother with any "velocity stack" flow restriction, though. Make the flow area as large as possible!
Therefore, I must respectfully disagree about the velocity stack bringing no benefit. I'm positive you'll agree:
When the path area decreases, the air velocity WILL increase [not perfectly, but nonetheless]. Also, you'll likely agree that the cam lobes keep the valves open for a set and predictable amount of time. The faster the air flows through them, the more air you're passing in.
Now, I'll agree that the air mass does not change in a given tube during the acceleration (air is not created ). BUT, there is a functional increase in the amount of air that can pass through when you widen the intake end, because of the reduction in resistance in the larger tube. So, when you widen the intake end, you take more air in, and when you take more air in and the area of the path narrows, you get a net gain in air velocity.
The path keeps narrowing down, all the way down to our tiny intake valves. The velocity increases quite a bit, especially after the supercharger.
#15
Originally Posted by ingsoc
Agreed on making the area as large as possible. The wider the intake tube, the more volume of air you can flow per unit surface area. The wider the cross-section, the less resistance there is along the tube, hence the "faster" the air will travel. People always imagine flowing water through a narrow hose versus through a wider hose.
Therefore, I must respectfully disagree about the velocity stack bringing no benefit. I'm positive you'll agree:
When the path area decreases, the air velocity WILL increase [not perfectly, but nonetheless]. Also, you'll likely agree that the cam lobes keep the valves open for a set and predictable amount of time. The faster the air flows through them, the more air you're passing in.
Now, I'll agree that the air mass does not change in a given tube during the acceleration (air is not created ). BUT, there is a functional increase in the amount of air that can pass through when you widen the intake end, because of the reduction in resistance in the larger tube. So, when you widen the intake end, you take more air in, and when you take more air in and the area of the path narrows, you get a net gain in air velocity.
The path keeps narrowing down, all the way down to our tiny intake valves. The velocity increases quite a bit, especially after the supercharger.
Therefore, I must respectfully disagree about the velocity stack bringing no benefit. I'm positive you'll agree:
When the path area decreases, the air velocity WILL increase [not perfectly, but nonetheless]. Also, you'll likely agree that the cam lobes keep the valves open for a set and predictable amount of time. The faster the air flows through them, the more air you're passing in.
Now, I'll agree that the air mass does not change in a given tube during the acceleration (air is not created ). BUT, there is a functional increase in the amount of air that can pass through when you widen the intake end, because of the reduction in resistance in the larger tube. So, when you widen the intake end, you take more air in, and when you take more air in and the area of the path narrows, you get a net gain in air velocity.
The path keeps narrowing down, all the way down to our tiny intake valves. The velocity increases quite a bit, especially after the supercharger.
I'm FAR from an intake runner design expert but I'm pretty sure that cross sectional area isnt where its at, especially when dealing with turns. You want the short turn wider because the air naturally wants to follow the shortest path. You'll have a higher velocity around the inside turn and the air slows down as the turn get wider.
Bigger duct means the larger surface area of creates more friction.
Its not simple and not always intuitive (atleast to me). Bigger isnt always better.....yeah i said it.
#16
Originally Posted by macncheese
Bigger isnt always better.....yeah i said it.
Put another way, it is much harder to drink through a thin straw.
As far as density, density will only change with temperature as it passes through a simple tube, I do believe. Increase the temp, decrease the density. But, since temp would not appreciably change if you swap tubes, it's a non-factor, I think...
#17
Originally Posted by Ingsoc
As far as density, density will only change with temperature as it passes through a simple tube, I do believe. Increase the temp, decrease the density. But, since temp would not appreciably change if you swap tubes, it's a non-factor, I think...
#18
#19
Originally Posted by macncheese
Bernoulli's Principle says otherwise!
Anyways, though, I was trying to keep it sort of simple, and I'm pretty sure that the density won't change too much. If it does decrease, then that will be at the product of creating even higher velocities per given decrease in tube size, since, if pressure fell and the number of particles remained the same, volume would have to increase.
#20
I do agree that when the flow gets to the valves, which open a fixed amount determined by the cam, that a higher flow velocity should = greater mass flow. However, the SC tube is so far upstream from the valves that any change in velocity there will be inconsequential. For example, even if the flow were to speed up thru the SC tube, it can't penetrate thru the vanes of the SC, so the inertia of the gasses upstream of the SC will be wasted as heat.
Originally Posted by ingsoc
Agreed on making the area as large as possible. The wider the intake tube, the more volume of air you can flow per unit surface area. The wider the cross-section, the less resistance there is along the tube, hence the "faster" the air will travel. People always imagine flowing water through a narrow hose versus through a wider hose.
Therefore, I must respectfully disagree about the velocity stack bringing no benefit. I'm positive you'll agree:
When the path area decreases, the air velocity WILL increase [not perfectly, but nonetheless]. Also, you'll likely agree that the cam lobes keep the valves open for a set and predictable amount of time. The faster the air flows through them, the more air you're passing in.
Now, I'll agree that the air mass does not change in a given tube during the acceleration (air is not created ). BUT, there is a functional increase in the amount of air that can pass through when you widen the intake end, because of the reduction in resistance in the larger tube. So, when you widen the intake end, you take more air in, and when you take more air in and the area of the path narrows, you get a net gain in air velocity.
The path keeps narrowing down, all the way down to our tiny intake valves. The velocity increases quite a bit, especially after the supercharger.
Therefore, I must respectfully disagree about the velocity stack bringing no benefit. I'm positive you'll agree:
When the path area decreases, the air velocity WILL increase [not perfectly, but nonetheless]. Also, you'll likely agree that the cam lobes keep the valves open for a set and predictable amount of time. The faster the air flows through them, the more air you're passing in.
Now, I'll agree that the air mass does not change in a given tube during the acceleration (air is not created ). BUT, there is a functional increase in the amount of air that can pass through when you widen the intake end, because of the reduction in resistance in the larger tube. So, when you widen the intake end, you take more air in, and when you take more air in and the area of the path narrows, you get a net gain in air velocity.
The path keeps narrowing down, all the way down to our tiny intake valves. The velocity increases quite a bit, especially after the supercharger.
#21
Originally Posted by inimmini
I do agree that when the flow gets to the valves, which open a fixed amount determined by the cam, that a higher flow velocity should = greater mass flow. However, the SC tube is so far upstream from the valves that any change in velocity there will be inconsequential. For example, even if the flow were to speed up thru the SC tube, it can't penetrate thru the vanes of the SC, so the inertia of the gasses upstream of the SC will be wasted as heat.
#22
Think of the system. The faster the air is before the SC, the more air will cram into the SC when the vanes are open to flow. More velocity upstream of the SC is essentially like having a minor boost increase, like ingsoc said.
Originally Posted by inimmini
I do agree that when the flow gets to the valves, which open a fixed amount determined by the cam, that a higher flow velocity should = greater mass flow. However, the SC tube is so far upstream from the valves that any change in velocity there will be inconsequential. For example, even if the flow were to speed up thru the SC tube, it can't penetrate thru the vanes of the SC, so the inertia of the gasses upstream of the SC will be wasted as heat.
#23
this is ain't quite right:
"The faster the air moves through a given cross-sectional area, the more mass you flow, and the more air will pass through the valves per unit time. The faster the air, the theory goes, the more power"
the first assumption in tracking flow is that that mass is conserved; it may bunch-up, but you can't get more out than what came in. One advantage I can see to higher velocity is if you have a carburettor. another is to maintain momentum right in the intake ports to aid cylinder filling.
the second assumption for flow analysis is that the total flow is a function of summing all the restrictions and pumps. Starting at the intake end, air can more easily enter your system if the entry is shaped like a velocity stack, which has the function of coupling the infinitely large exterior area gradually (over the length of the stack) down to the intake tube size.
"The faster the air moves through a given cross-sectional area, the more mass you flow, and the more air will pass through the valves per unit time. The faster the air, the theory goes, the more power"
the first assumption in tracking flow is that that mass is conserved; it may bunch-up, but you can't get more out than what came in. One advantage I can see to higher velocity is if you have a carburettor. another is to maintain momentum right in the intake ports to aid cylinder filling.
the second assumption for flow analysis is that the total flow is a function of summing all the restrictions and pumps. Starting at the intake end, air can more easily enter your system if the entry is shaped like a velocity stack, which has the function of coupling the infinitely large exterior area gradually (over the length of the stack) down to the intake tube size.
#24
Originally Posted by jlm
this is ain't quite right:
"The faster the air moves through a given cross-sectional area, the more mass you flow, and the more air will pass through the valves per unit time. The faster the air, the theory goes, the more power"
the first assumption in tracking flow is that that mass is conserved; it may bunch-up, but you can't get more out than what came in. One advantage I can see to higher velocity is if you have a carburettor. another is to maintain momentum right in the intake ports to aid cylinder filling.
the second assumption for flow analysis is that the total flow is a function of summing all the restrictions and pumps. Starting at the intake end, air can more easily enter your system if the entry is shaped like a velocity stack, which has the function of coupling the infinitely large exterior area gradually (over the length of the stack) down to the intake tube size.
"The faster the air moves through a given cross-sectional area, the more mass you flow, and the more air will pass through the valves per unit time. The faster the air, the theory goes, the more power"
the first assumption in tracking flow is that that mass is conserved; it may bunch-up, but you can't get more out than what came in. One advantage I can see to higher velocity is if you have a carburettor. another is to maintain momentum right in the intake ports to aid cylinder filling.
the second assumption for flow analysis is that the total flow is a function of summing all the restrictions and pumps. Starting at the intake end, air can more easily enter your system if the entry is shaped like a velocity stack, which has the function of coupling the infinitely large exterior area gradually (over the length of the stack) down to the intake tube size.
#25
i think your conclusion was:"The faster the air, the theory goes, the more power." By constricting parts of the system, in order to conserve mass, flow has to speed up, so yes, in that constricted arera, there is more density (and less volume), but no new mass is being developed.
my point is that velocity is irrelevant to the the total mass flowing and it is the mass that develops the power, assuming you can get it into the cylinders.
my point is that velocity is irrelevant to the the total mass flowing and it is the mass that develops the power, assuming you can get it into the cylinders.
Last edited by jlm; 11-07-2005 at 05:39 AM.