Air intake made my car worse...!
F4i Pilot
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From: at The BEACH,Ft. Lauderdale, FL
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when i still had all the stuff on my car, and people would ask me what i had done and id tell them. theyd always ask "oh uh what intake you got?" phh the OEM one!
i dont see myself spending $200 and something dollars for the K&N and i was rather unimpressed with the results of the others to say the least. especially with the whole AEM printing the wrong results. 20hp from an intake?! yeah sure...
i dont see myself spending $200 and something dollars for the K&N and i was rather unimpressed with the results of the others to say the least. especially with the whole AEM printing the wrong results. 20hp from an intake?! yeah sure...
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Joined: Sep 2003
Posts: 842
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From: Austin, TX
Rep Power: 0 1. Boundary Layer theory
When a flow flows through an object, it creates surface friction. All we know friction slows down the flow, but further out from the surface, the speed of flow is the same as it has no restrictions.
2. Aerodynamic of a pipe.....
If you cut the pipe into cross-section, and draw out the velocity profile, the contact sides are going to have low velocity, while the center is having high velocity. Low velocity doesn't end at a point, but it builds up, it's the boundary layer, and it will keep disturbing the center flow causing turbulence. Eventually the air flow will become laminar(fully developed low speed flow) ONLY when the pipe is LONG ENOUGH. Laminar flow is GOOD for combustion because of a stable pressure and ease of mixing air with fuel.
3. Aerodynamic of our intake runners.....
Having the low speed intake from the CAI or short ram, with the throttle body fully opened(partially opened is another story), the center flow is cut off, causing a stagnation(0 velocity) at the center flow, creates a flat plate effect, wich is another boundary layer. It is small enough that the BL can be ignored. Still, the flow is laminar, running through a 20-in intake runner, which will FURTHER SLOW DOWN the flow. Because of the BL(remember that the cornering or curves of the pipe makes the flow distribution uneven), it is what actually causing the swirl effect of OUR intake runner. The same concept also applies to the intake pipe.
3. Older intake manifolds
Older Honda has the manifold 90 deg out of plane from the intake flow direction. What it means is that, the flow comes to a zero(0) velocity, then accelerating down the engine. The flow is going to be turbulent when it reaches the valve, which is a high velocity flow charing into the engine. This helps explain why the older cars are gaining a little more hp than our car with CAI/SR.
4. 01+ Stock air box design
Here we are, from the resonator outlet. Everything placed before the resonator is going to be 0 velocity(Look at the two 90 deg turn). Now, geting into air filter box. Flow starts from buttom, passing through the filter, then reaches 0 velocity(90 deg turn). Then again, to the top of the throttle body, one more 90 deg turn. The flow accelerates from there, getting into the engine. If you can imagine, the speed from stock box is actually going to be higher than with CAI or short ram. The idea is this: The flow from the tube straight into TB is already laminar(or close to), which will be further decelerate when getting into the manifold. The stock box starts from 0, having pressure difference and accelerates down the pipe, creating high speed swirl(vs. low speed swirl from CAI/SR), which is harder to become fully developed. That's all the low end comes from.
****This reply may not be completely accurate. Everything is just from my limited knowledge. If you find errors, please let me know or discuss it. Thanks.
When a flow flows through an object, it creates surface friction. All we know friction slows down the flow, but further out from the surface, the speed of flow is the same as it has no restrictions.
2. Aerodynamic of a pipe.....
If you cut the pipe into cross-section, and draw out the velocity profile, the contact sides are going to have low velocity, while the center is having high velocity. Low velocity doesn't end at a point, but it builds up, it's the boundary layer, and it will keep disturbing the center flow causing turbulence. Eventually the air flow will become laminar(fully developed low speed flow) ONLY when the pipe is LONG ENOUGH. Laminar flow is GOOD for combustion because of a stable pressure and ease of mixing air with fuel.
3. Aerodynamic of our intake runners.....
Having the low speed intake from the CAI or short ram, with the throttle body fully opened(partially opened is another story), the center flow is cut off, causing a stagnation(0 velocity) at the center flow, creates a flat plate effect, wich is another boundary layer. It is small enough that the BL can be ignored. Still, the flow is laminar, running through a 20-in intake runner, which will FURTHER SLOW DOWN the flow. Because of the BL(remember that the cornering or curves of the pipe makes the flow distribution uneven), it is what actually causing the swirl effect of OUR intake runner. The same concept also applies to the intake pipe.
3. Older intake manifolds
Older Honda has the manifold 90 deg out of plane from the intake flow direction. What it means is that, the flow comes to a zero(0) velocity, then accelerating down the engine. The flow is going to be turbulent when it reaches the valve, which is a high velocity flow charing into the engine. This helps explain why the older cars are gaining a little more hp than our car with CAI/SR.
4. 01+ Stock air box design
Here we are, from the resonator outlet. Everything placed before the resonator is going to be 0 velocity(Look at the two 90 deg turn). Now, geting into air filter box. Flow starts from buttom, passing through the filter, then reaches 0 velocity(90 deg turn). Then again, to the top of the throttle body, one more 90 deg turn. The flow accelerates from there, getting into the engine. If you can imagine, the speed from stock box is actually going to be higher than with CAI or short ram. The idea is this: The flow from the tube straight into TB is already laminar(or close to), which will be further decelerate when getting into the manifold. The stock box starts from 0, having pressure difference and accelerates down the pipe, creating high speed swirl(vs. low speed swirl from CAI/SR), which is harder to become fully developed. That's all the low end comes from.
****This reply may not be completely accurate. Everything is just from my limited knowledge. If you find errors, please let me know or discuss it. Thanks.
Joined: Sep 2002
Posts: 51,241
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From: NV
Rep Power: 812 
Good points. But there is also a place where more air volume at the expense of air velocity will increase power to a point. The way K&N designed their intake, the pipe is no larger in diameter than the throttle body. So it keeps air moving fairly fast, while still providing more air due to the filter element. I think that's why there is no low end loss with this intake. You do lose a bit of power from 3.5-4.5k rpms tho.
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Joined: Sep 2003
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From: Austin, TX
Rep Power: 0 Volume helps combustion, velocity helps to produce work, while horsepower is the change of work* in a particular RPM for a given time.....
There is actually 4 works in a 4-cycle engines: intake work, governed by W=m/2(v^2)-Q1; compression work, W=-m(h2-h1); combustion work, W=Q2; and exhaust work, W=-m(h4-h3).....
The reason of heaving the upward works negative is because they rely on the work produced on another cylinder, which means work is taken away from the system....
Adding up all terms will give a net work produced in ONE cylinder, which should be equilvalent to net TORQUE.....It can be seen that both velocity and volume is important, and why turbo-charge can raise TORQUE(in differential form, HORSEPOWER) significantly...
*Work and torque in SCALAR form is the same thing except they are in different direction.....Torque is used in rotation(such as flywheel), and work is non-directional, can be everywhere....
There is actually 4 works in a 4-cycle engines: intake work, governed by W=m/2(v^2)-Q1; compression work, W=-m(h2-h1); combustion work, W=Q2; and exhaust work, W=-m(h4-h3).....
The reason of heaving the upward works negative is because they rely on the work produced on another cylinder, which means work is taken away from the system....
Adding up all terms will give a net work produced in ONE cylinder, which should be equilvalent to net TORQUE.....It can be seen that both velocity and volume is important, and why turbo-charge can raise TORQUE(in differential form, HORSEPOWER) significantly...
*Work and torque in SCALAR form is the same thing except they are in different direction.....Torque is used in rotation(such as flywheel), and work is non-directional, can be everywhere....
Last edited by 82801BA; Sep 7, 2004 at 04:19 PM.
Joined: Sep 2002
Posts: 51,241
Likes: 20
From: NV
Rep Power: 812 Ha about which intake to get? Honestly K&N fipk is gonna give you a few horses up high without losing low end power. I just ordered one and will be getting a new S&B high quality filter with it.
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Joined: Jul 2004
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From: Sacramento
Rep Power: 0 I just installed an AEM short ram and i've had no problems what so ever. The only draaw back that i've seen so far is the normal one, more air means bigger bang, so more fuel is needed (hence) you go through gas a little quicker. A big thing to look at is what model you have (i.e) if you have an EX rather than a DX. My buddy Tom got a Intake for an EX and it looked the exact same as mine but there was one big difference. The airflow going through the chabmer is designed to hit a certain speed and draw. The EX one was demanding to much for his DX, so we traded it over for a DX-LX short ram. You could notice the difference from the get go after that.
Eitehr you got a crappy intake or, even though you say you did it right, it never hurts to check your work again. Make sure your air sensor is nice and snug in the inlet. That is a big factor that could lead to the misfire. Oh, and I don't know why, but running supreme helps a bit after you install the intake. Don't know why, but it does.
If you don't have an AEM, get one....they are top quality.
Eitehr you got a crappy intake or, even though you say you did it right, it never hurts to check your work again. Make sure your air sensor is nice and snug in the inlet. That is a big factor that could lead to the misfire. Oh, and I don't know why, but running supreme helps a bit after you install the intake. Don't know why, but it does.
If you don't have an AEM, get one....they are top quality.
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Joined: Sep 2003
Posts: 842
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From: Austin, TX
Rep Power: 0 1. Believe or not, plastic tube with enough lubrication will give lowest drag. Also, plstic tubes do not transfer heat so well...Otherwise, build a titanium inner tube, like an airplane..... 
2. Curved tubes, with large volume at the curves will make the swirl effect minimum...Make sure that it is not a smooth curve...
3. Use intake tubes with big inlet, small outlet to create a compression in air: think of conservation of volume, mass in and mass out is the same(due to intake vaccum), but the velocity is different...Same sized tube throughout do not do any good...
4. Use intake tubes as short as you can. One thing you can try, is that by placing a small flat filter on top of the TB(similar to cabuerator), heat insulate it(important), and make a plastic intake tube to go directly on top of the radiator(of course, insulate), with wide opening and narrowing as it go closer to the TB...I think this is the idea of RAM AIR in US vehicle, but it works pretty well though...
I think non of the company builds something like this...You have to build it by yourself...
*Air compression theory
In a CLOSED system, such as inside cylinder-piston system, compression of air is due to 2 method. First, piston compression(mechanical), and second, heat(thermal).
In an OPEN system, such as the intake tube, air is compressed in another two method. First, condensing humidity(cool down), and second, charge velocity.
So make sure that the intake tube doesn't transfer heat or you will make things worse(air expands inside the tube, then more drag and lower velocity).
2. Curved tubes, with large volume at the curves will make the swirl effect minimum...Make sure that it is not a smooth curve...
3. Use intake tubes with big inlet, small outlet to create a compression in air: think of conservation of volume, mass in and mass out is the same(due to intake vaccum), but the velocity is different...Same sized tube throughout do not do any good...
4. Use intake tubes as short as you can. One thing you can try, is that by placing a small flat filter on top of the TB(similar to cabuerator), heat insulate it(important), and make a plastic intake tube to go directly on top of the radiator(of course, insulate), with wide opening and narrowing as it go closer to the TB...I think this is the idea of RAM AIR in US vehicle, but it works pretty well though...
I think non of the company builds something like this...You have to build it by yourself...
*Air compression theory
In a CLOSED system, such as inside cylinder-piston system, compression of air is due to 2 method. First, piston compression(mechanical), and second, heat(thermal).
In an OPEN system, such as the intake tube, air is compressed in another two method. First, condensing humidity(cool down), and second, charge velocity.
So make sure that the intake tube doesn't transfer heat or you will make things worse(air expands inside the tube, then more drag and lower velocity).
Thread Starter
Pimp My Ride!! Please!
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From: Midwest
Rep Power: 0 I noticed when it's hot and humid my engine really struggles with my short intake but when it's cooler outside it does seem to help. Thank goodness cooler weather is almost here! If I lived in a warm climate I'd probably go with a cold air intake but living here in Cincinnati the winters get pretty cold and I would be afraid my engine would get too much cold air. That's why I chose the short ram kind. Again, the hot/humid summer days don't work well with short rams but I don't feel like changing a cold air for a short ram just because of the season changes. The best thing to do in my case would be to keep the stock intake but I like the sound the short ram makes, plus it looks cool. 
Thread Starter
Pimp My Ride!! Please!
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Originally Posted by gearbox
Ha about which intake to get? Honestly K&N fipk is gonna give you a few horses up high without losing low end power. I just ordered one and will be getting a new S&B high quality filter with it.
So please keep us posted! Joined: Sep 2002
Posts: 51,241
Likes: 20
From: NV
Rep Power: 812 The K&N filters suck, and I bet your generic filter is even worse at keeping dirt out of the engine. I would strongly recommend getting the S&B.
http://www.intenseperformance.com/pr...e_filters.html
Reasons why:
They are in the business over 30 yrs
velocity stock design flows more air and reduces turbulence. A 5 inch S&B can flow as much air an an 8 inch standard filter.
More and deeper pleats that any other filter element
Thicker cotton gauze media (oiled) that doesn't have holes in it like the K&N does.
Better polyurethane seals around the filter and better seal
Do you need more reasons?
http://www.intenseperformance.com/pr...e_filters.html
Reasons why:
They are in the business over 30 yrs
velocity stock design flows more air and reduces turbulence. A 5 inch S&B can flow as much air an an 8 inch standard filter.
More and deeper pleats that any other filter element
Thicker cotton gauze media (oiled) that doesn't have holes in it like the K&N does.
Better polyurethane seals around the filter and better seal
Do you need more reasons?
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