Effects of rotating the Air flow
10-12-2009, 08:05 AM
#1
Effects of rotating the Air flow I've been looking, but had no luck in finding the pros and cons to inducing a rotation to airflowing through a cylinder. I'm fabricating my own air box. I'm not happy at all with the lid design for the F-Body. Since I'm going to a 417, with a 92/92 throttle body, intake, I wanted to make sure all of the upstream plumbing was larger than the throttle body. I had a conversation with Geoff at Engine Power Systems (I got my cam from him) and he explained that 100mm Mafs are touchy at best. He was explaining how the sensors requirements from the manufacturer are x number of times the diameter of pipe before and after the sensor. Thats why factory mafs have that screen. So without the screen to straighten airflow it would make the sensor erratic at best. He encouraged me to go speed density. Being Speed density gives me more room to work with. So I'm fab up an air box that will be similiar to a volant but made out of aluminum and flow much more air.
So thats the background of the question. I was thinking I could tig small ribs into the funnel area and down through the tube section. This spiral would tighten naturally as the opening necked down and would impart a rotation to the air flow. I was thinking the benefit would be reduced turbulance which result in a more tightly packed air charge? I was also thinking GIMMICK. I've been told by knowledgable people though that polishing to a mirror finish produces more turbulance than a slightly textured surface. Something about real small vertices at the surface wall actually act like a bearing surface for the air column. Suppose it could work like that?
Looking for some thoughts and opinions. Time required to do it doesn't matter as its my hobby and its one of a Kind.
thanks ed
So thats the background of the question. I was thinking I could tig small ribs into the funnel area and down through the tube section. This spiral would tighten naturally as the opening necked down and would impart a rotation to the air flow. I was thinking the benefit would be reduced turbulance which result in a more tightly packed air charge? I was also thinking GIMMICK. I've been told by knowledgable people though that polishing to a mirror finish produces more turbulance than a slightly textured surface. Something about real small vertices at the surface wall actually act like a bearing surface for the air column. Suppose it could work like that?
Looking for some thoughts and opinions. Time required to do it doesn't matter as its my hobby and its one of a Kind.
thanks ed
10-14-2009, 12:03 PM
#4
the mirror finish thing is correct. on a highly polished surface, the airflow will try to stay laminar, causing a longer transition and more turbulence. if you look at the front edge of some airplane wings, there are rough areas on the top leading edge. this causes the transition from laminar to turbulent flow to occur in a much shorter length, overall reducing drag, or in this case loss of pressure. the MAF looks effectively like a laminar flow element, which is a measuring device that requires approximately 10 times its diameter in front of the element and 2-5 times the diameter after the element to maintain accuracy.
as for rotating the flow, think about it this was, the flow path of a single particle going straight through is going to be shorter than the path for a particle that spirals around on the way in. it would be the same effect (if the ribs actually impart any spiral to the flow path) as adding length to the intake pipe. longer pipe = more loss of pressure = less flow. i bet that ribs would only add drag anyway, and decrease the flow through the pipe.
the short answer buried in all that crap is dont bother with any polishing or anything else. the best setup will be a little length (2-5 times the diameter) straight behind the MAF with no elbows, joints, etc., and more importantly 10 times the diameter before (filter side) the MAF of straight pipe.
as for rotating the flow, think about it this was, the flow path of a single particle going straight through is going to be shorter than the path for a particle that spirals around on the way in. it would be the same effect (if the ribs actually impart any spiral to the flow path) as adding length to the intake pipe. longer pipe = more loss of pressure = less flow. i bet that ribs would only add drag anyway, and decrease the flow through the pipe.
the short answer buried in all that crap is dont bother with any polishing or anything else. the best setup will be a little length (2-5 times the diameter) straight behind the MAF with no elbows, joints, etc., and more importantly 10 times the diameter before (filter side) the MAF of straight pipe.
10-16-2009, 10:21 PM
#6
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Just like why golf ***** have a dimpled surface. They can go around 50% further than a smooth golf ball. As for spiraling the air into the intake, the air will lose energy when it is forced into a spin like flowing through that tornado as seen on tv crap. Then that spiraling air has to go through the MAF horizonal plate, throttle body plate, split into 8 different paths and pass the valve. There is no chance of that spiraling air to make it through all of that. The vortec design helps though since it is spiraling the air directly into the cylinder.
10-24-2009, 09:52 PM
#7
regarding the maf screen, it's purpose is to straighten airflow prior to the MAF sensor providing a laminar airflow which will result in accurate and consistent readings by the MAF sensor because it's a heated element and the measurement is based on how much it is cooled- the cooling affect changes the resistance of the element which the computer sees and correlates it to a mass air flow as in grams per second of air which it then bases fuel injection off of. Without the screen, turbulent air flow can happen in the throttle body. With airflow being laminar a given mass flow would always result in the same cooling affect but with turbulent air flow that same mass air flow can cool the sensor more or less making for inconsistent inaccurate measurements. So that's the scoop behind the MAF screen, the purpose of which is to provide power and economy and performance under all driving conditions. here's a good read on it explaining in more detail:
http://www.gmtips.com/3rd-degree/dox...maf-screen.htm
if you don't need economy, low emissions, and optimal light load low throttle performance then the speed density model is the way to go- just base everything off engine rpm, manifold absolute pressure, and air temp. And i think under full throttle conditions the computer stops reading the MAF anyway so at that point it's a restriction in the intake, so if your goal is power then you don't want a MAF sensor in there.
regarding rotating the airflow, that is all a ******* gimmick created by those tornado ******** to take advantage of people's ignorance to sell a bullshit product. for max power, you need maximum air passing thru the intake (which you refer as a cylinder, not the combustion chamber above the piston correct? ). the way to get max airflow, which is mass air flow- the most air molecules from one point to another- is in the least amount of distance moving as fast as possible. the least amount of distance is a straight line or parallel to the surface containing the airflow. If you rotate the airflow, each air molecule as to travel farther (which would also increase drag) so then to get the same mass air flow in a given time when the flow is rotating you have to increase the velocity of the air flow. So you do NOT want to rotate the airflow.
regarding laminar vs turbulent air flow, and golf *****,
http://www.howstuffworks.com/question37.htm
the way it works in the nutshell is this, to get maximum mass air flow (most molecules moving as fast as possible) you need maximum air pressure and minimum surface drag since the air flow is contained in this case the intake piping, or cylinder as you called it. well air pressure doesn't change, you're stuck with atmospheric unless we start talking about forced induction. and your stuck with whatever air density is for the given environmental conditions. for minimum drag, the flow over a highly polished smooth surface would be more laminar and actually has more drag than a scenario where the surface is rough which creates a very small turbulent layer above the surface which reduces drag. This is the golf ball theory, and the golf ball also spins when flying through the air which is why the dimples work. in the scenario of airflow in your intake and through your cylinder head ports, there is some roughness which creates a very small if not microscopic turbulent layer which would reduce drag and increase overall airflow. But that roughness (how you polish it) to get minimal drag and optimal airflow all depends on the size of the port, the shape of the port, and the temperature (density) of the air which changes as it gets closer to combustion chamber. All this is insignificant to the shape and sizing of the port which has the most affect on airflow velocity. And to the extent you would have to control surface roughness to get better airflow would be down on the order of the texture of the ports between a cast iron cylinder head versus and aluminum cnc head. having something as large as ribs is a restriction and while it may increase velocity because the diameter is now smaller there would also be less mass so it nulls out any benefit. if your goal is max airflow to make max power, I would look at redesigning the shape or the intake manifold rather than changing surface roughnesses, but don't forget an intake design that results in max airflow (such as single plane vs dual plane intakes) generally sacrifices low speed low load performance.
my question is, if there was no hood and no space restriction, would 8 individual intake ports coming straight off each intake port on the head be the way to go? each would be going towards the other cylinder head, and you'd probably have to bend them upward a little so they don't run into the opposite head because it's a V engine. And you would need a throttle body on each one so 8 throttle bodies total, all somehow connected to operate simultaneously which probably wouldn't be too hard these days with drive by wire electronics and throttle position sensors. And for a car driving down the road at speed you'd want a 90 deg. bend in each to point them forward to take advantage of ram air affect.
http://www.gmtips.com/3rd-degree/dox...maf-screen.htm
if you don't need economy, low emissions, and optimal light load low throttle performance then the speed density model is the way to go- just base everything off engine rpm, manifold absolute pressure, and air temp. And i think under full throttle conditions the computer stops reading the MAF anyway so at that point it's a restriction in the intake, so if your goal is power then you don't want a MAF sensor in there.
regarding rotating the airflow, that is all a ******* gimmick created by those tornado ******** to take advantage of people's ignorance to sell a bullshit product. for max power, you need maximum air passing thru the intake (which you refer as a cylinder, not the combustion chamber above the piston correct? ). the way to get max airflow, which is mass air flow- the most air molecules from one point to another- is in the least amount of distance moving as fast as possible. the least amount of distance is a straight line or parallel to the surface containing the airflow. If you rotate the airflow, each air molecule as to travel farther (which would also increase drag) so then to get the same mass air flow in a given time when the flow is rotating you have to increase the velocity of the air flow. So you do NOT want to rotate the airflow.
regarding laminar vs turbulent air flow, and golf *****,
http://www.howstuffworks.com/question37.htm
the way it works in the nutshell is this, to get maximum mass air flow (most molecules moving as fast as possible) you need maximum air pressure and minimum surface drag since the air flow is contained in this case the intake piping, or cylinder as you called it. well air pressure doesn't change, you're stuck with atmospheric unless we start talking about forced induction. and your stuck with whatever air density is for the given environmental conditions. for minimum drag, the flow over a highly polished smooth surface would be more laminar and actually has more drag than a scenario where the surface is rough which creates a very small turbulent layer above the surface which reduces drag. This is the golf ball theory, and the golf ball also spins when flying through the air which is why the dimples work. in the scenario of airflow in your intake and through your cylinder head ports, there is some roughness which creates a very small if not microscopic turbulent layer which would reduce drag and increase overall airflow. But that roughness (how you polish it) to get minimal drag and optimal airflow all depends on the size of the port, the shape of the port, and the temperature (density) of the air which changes as it gets closer to combustion chamber. All this is insignificant to the shape and sizing of the port which has the most affect on airflow velocity. And to the extent you would have to control surface roughness to get better airflow would be down on the order of the texture of the ports between a cast iron cylinder head versus and aluminum cnc head. having something as large as ribs is a restriction and while it may increase velocity because the diameter is now smaller there would also be less mass so it nulls out any benefit. if your goal is max airflow to make max power, I would look at redesigning the shape or the intake manifold rather than changing surface roughnesses, but don't forget an intake design that results in max airflow (such as single plane vs dual plane intakes) generally sacrifices low speed low load performance.
my question is, if there was no hood and no space restriction, would 8 individual intake ports coming straight off each intake port on the head be the way to go? each would be going towards the other cylinder head, and you'd probably have to bend them upward a little so they don't run into the opposite head because it's a V engine. And you would need a throttle body on each one so 8 throttle bodies total, all somehow connected to operate simultaneously which probably wouldn't be too hard these days with drive by wire electronics and throttle position sensors. And for a car driving down the road at speed you'd want a 90 deg. bend in each to point them forward to take advantage of ram air affect.
Last edited by 1 FMF; 10-24-2009 at 10:04 PM.
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02-13-2010, 12:53 PM
#10
would 8 individual intake ports coming straight off each intake port on the head be the way to go? each would be going towards the other cylinder head, and you'd probably have to bend them upward a little so they don't run into the opposite head because it's a V engine. And you would need a throttle body on each one so 8 throttle bodies total, all somehow connected to operate simultaneously which probably wouldn't be too hard these days with drive by wire electronics and throttle position sensors. And for a car driving down the road at speed you'd want a 90 deg. bend in each to point them forward to take advantage of ram air affect.
Look at the Harrop Hurricane, it is basicly what you just described, 8 stacks that cross over eachother with 8 throttle bodies
Look at the Harrop Hurricane, it is basicly what you just described, 8 stacks that cross over eachother with 8 throttle bodies
02-13-2010, 01:31 PM
#11
In my 04 GTO I'm running a 404 stroker with the Edelbrock proflow xt intake. I hogged the runners out with a long aluminum bit to port match to my ported heads then used 80 grit sanding cylinders to knock down the roughness the cutting bit left... The finished product looks like the texture of an orange peel and I hogged out the intake sides of the heads the same way. I then hogged and polished the exhaust side to a true mirror finish, then hand scuffed it back out with 220 grit.
Now I'm almost ready to test fire it and see just how well my port job works.
I have no MAF, running in SD mode, also no intake tube. The 4" cone filter mounts right on the Fast 90 tb feed by a ram air scoop (intake stuck out of the stock hood about an inch and a half)
Now I'm almost ready to test fire it and see just how well my port job works.
I have no MAF, running in SD mode, also no intake tube. The 4" cone filter mounts right on the Fast 90 tb feed by a ram air scoop (intake stuck out of the stock hood about an inch and a half)
