How good is KNN Air filter?
- Thread starter Leean
- Start date
calvin said:Remus325 said:
Just added Info: Valvetronic no need to do CAI, it's already CONE filter by default. Just buy n change it, no modification required.
how do u guys channell extra cold air intake from the bumper area? can it be done at BVO?
calvin
Well-Known Member
Derektvy said:So Calvin you DIY the cold air intake from the bumper? I've just installed the K&N into my 2004 318 and lost the low end torque as Remus mentioned
Got it done by PiggyBoy, then enhanced it with cliff. U can give me a buzz whenever u wanna take a look. no worries...can always share with it... i staying east.
yendor
Well-Known Member
When changing to a cone filter, you alter the fluid dynamics of the intake system. It is important to maintain the relative length and diameter of the intact tract to maintain the factory torque peak. Changing to a larger dia but shorter tube brings the torque peak higher up the rev range while using a narrower and longer tube brings the peak lower down the range. As to the absolute figures, higher torque figures are usually easier to achieve in the lower rev range. With the short fat intakes, the torque curve may be slightly fatter at the upper rev ranges which gives you that higher power figure.
The original intake tract is designed for all round drivability i.e. city to highway. Hence there is always a compromise.
IMO, i would recommend the following depending on your desires.
Street driving: Panel Filter replacement keeping all original plumbing intact.
High speed expressway: Cone filter with original intake tract after air mass sensor.
Race: Large Cone filter with intact tract changed to a large diameter tubing and of course larger air mass meter.
All the filters should be fed with lots of cool air. And if you study the orginal system, the mouth of the intake is right in front above the grill and radiator. For the other 2 systems, you need to think of a solution.
Cheers
Yendor
The original intake tract is designed for all round drivability i.e. city to highway. Hence there is always a compromise.
IMO, i would recommend the following depending on your desires.
Street driving: Panel Filter replacement keeping all original plumbing intact.
High speed expressway: Cone filter with original intake tract after air mass sensor.
Race: Large Cone filter with intact tract changed to a large diameter tubing and of course larger air mass meter.
All the filters should be fed with lots of cool air. And if you study the orginal system, the mouth of the intake is right in front above the grill and radiator. For the other 2 systems, you need to think of a solution.
Cheers
Yendor
Whisky_Tango
Core Group Members
Rodney,
Interesting and good info
Can I say that if the Net Positve Suction Head Required(NPSHR) at the inlet manifold area is LOW, the lesser engine loading is created and thus more free reving?
Is there a method to determine the sizes of intake track for a required power and torque value?
Thinking of DIY now...
Cheers!
Interesting and good info
Can I say that if the Net Positve Suction Head Required(NPSHR) at the inlet manifold area is LOW, the lesser engine loading is created and thus more free reving?
Is there a method to determine the sizes of intake track for a required power and torque value?
Thinking of DIY now...
Cheers!
calvin said:Derektvy said:So Calvin you DIY the cold air intake from the bumper? I've just installed the K&N into my 2004 318 and lost the low end torque as Remus mentioned
Got it done by PiggyBoy, then enhanced it with cliff. U can give me a buzz whenever u wanna take a look. no worries...can always share with it... i staying east.
I'm in the east as well.... Are there any kopi session I can join in? Heard that a bunch of you guys gather at Simpang bedok regularly... Mebbe I could join in and take a look at how to DIY?
yendor
Well-Known Member
Wiskey Tango
in theory the lower the pressure(i.e. closer to atmospheric pressure) the lesser the engine sucks and the greater the amount of air each cycle of piston stroke can take in. Like exhaust theory, the thing that most people forget is that air too has mass. And it is this mass that screws up the whole show. In the study of fluid dynamics, every pipe flow a certain amount of matter given a certain mass and drag. (that is why parachutist achieve different terminal velocities in different positions) Increasing the relative pressure between the start and end points speeds things up a bit. Thus forced induction can achieve greater power.
In street engines, the rev ranges from 600-7000rpm which equates to roughly 11 times the difference in air requirements assuming WOT. The engine designer will want to move in as much air as possible within the duration of valve opening. If you plot the position of the piston versus crankshaft rotation, you will get a cosine curve. At the top and bottom, the suction effects are not present (evident from the flat gradient). Now, to get more air in at the start of the intake cycle, engineers open the valves earlier (but this gives esome exhaust gases chance to push the intake gases back into the manifold , thereby losing power, or some air/fuel mixture to go into the exhaust and hence raising enissions) The other way to to keep the air moving in on its own momentum at the bottom of the stroke which does not have any drawbacks if the valves close in time for the compression to take place.
So the size of the manifold, plenum capacity and intake tract up to the tip of the filter plays a part. A tapering design is best with little or no edges inside to form vortices or eddys to restrict flow. In the 6 cyl engines, the air flow is more constant as there is always 1 cylinder sucking at anytime so the air in the intake tract has a constant flow. if you have a long tract, the air momentum will continue to push some air into the cylinder at the bottom of the induction stroke. This resonance effect works best at a particular rev range. So to keep the air flow smooth, the classic bell mouths trumpets work very well. F1 engines idle at 6000rpm and rev to 18000rpm which is only 3 times the range. They do not have plenums and manifolds behind the throttle butterflies and their power delivery is easier to concentrate given the limited range.
A good way to experiment is to measure the dia of the std rubber tract and use tape to measure the length of both sides of the tract to get an average. Do this all the way to the end of the suction trumpet at the top of the radiator. keep the dia standard and play with the length. Thereafter, try experimenting with different sized tracts (harder to find) You should get some interesting results.
Factory designs are almost optimum for street driving. At most you can go 20% shorter and 10-15% wider before the engine starts to suffer from low end lethargy.
Cheers.
ps, sorry for the long reply. :wavey:
in theory the lower the pressure(i.e. closer to atmospheric pressure) the lesser the engine sucks and the greater the amount of air each cycle of piston stroke can take in. Like exhaust theory, the thing that most people forget is that air too has mass. And it is this mass that screws up the whole show. In the study of fluid dynamics, every pipe flow a certain amount of matter given a certain mass and drag. (that is why parachutist achieve different terminal velocities in different positions) Increasing the relative pressure between the start and end points speeds things up a bit. Thus forced induction can achieve greater power.
In street engines, the rev ranges from 600-7000rpm which equates to roughly 11 times the difference in air requirements assuming WOT. The engine designer will want to move in as much air as possible within the duration of valve opening. If you plot the position of the piston versus crankshaft rotation, you will get a cosine curve. At the top and bottom, the suction effects are not present (evident from the flat gradient). Now, to get more air in at the start of the intake cycle, engineers open the valves earlier (but this gives esome exhaust gases chance to push the intake gases back into the manifold , thereby losing power, or some air/fuel mixture to go into the exhaust and hence raising enissions) The other way to to keep the air moving in on its own momentum at the bottom of the stroke which does not have any drawbacks if the valves close in time for the compression to take place.
So the size of the manifold, plenum capacity and intake tract up to the tip of the filter plays a part. A tapering design is best with little or no edges inside to form vortices or eddys to restrict flow. In the 6 cyl engines, the air flow is more constant as there is always 1 cylinder sucking at anytime so the air in the intake tract has a constant flow. if you have a long tract, the air momentum will continue to push some air into the cylinder at the bottom of the induction stroke. This resonance effect works best at a particular rev range. So to keep the air flow smooth, the classic bell mouths trumpets work very well. F1 engines idle at 6000rpm and rev to 18000rpm which is only 3 times the range. They do not have plenums and manifolds behind the throttle butterflies and their power delivery is easier to concentrate given the limited range.
A good way to experiment is to measure the dia of the std rubber tract and use tape to measure the length of both sides of the tract to get an average. Do this all the way to the end of the suction trumpet at the top of the radiator. keep the dia standard and play with the length. Thereafter, try experimenting with different sized tracts (harder to find) You should get some interesting results.
Factory designs are almost optimum for street driving. At most you can go 20% shorter and 10-15% wider before the engine starts to suffer from low end lethargy.
Cheers.
ps, sorry for the long reply. :wavey:
Whisky_Tango
Core Group Members
No worries... its good to have substance information and you are willing to spend time typing it and share with all members here.
Thanx... will take these as a guideline when DIY.
Actually I have more to say and ask but since this thread is about K&N filter (which its part of the Air Intake System), I think we stop here on our discussion unless the thread owner allows.
Cheers!
yendor said:
Thanx... will take these as a guideline when DIY.
Actually I have more to say and ask but since this thread is about K&N filter (which its part of the Air Intake System), I think we stop here on our discussion unless the thread owner allows.
Cheers!
Leean, is it ok if I post some thoughts related and in addition to Rodney's? I will be happy to start a seperate thread if you wish.
Admin, if this question is not seen and answered, just delete this post and I'll start a seperate thread this weekend or next weekend. Thanks!
Admin, if this question is not seen and answered, just delete this post and I'll start a seperate thread this weekend or next weekend. Thanks!
Whisky_Tango
Core Group Members
Shaun... start new thread pls....
