Less restriction = more flow

[Smokescreen]

Engines are air pumps. Most OEM air filters and housing are designed to flow more air than the engine can use in its stock form following the stock map. It has to be to accomodate the various temperatures, barometric pressures and altitudes for correct operation over much of the globe.

You will not see any gains from increased flow unless the fuel maps are designed and the plumbing is equally modified to take advantage of it.

 

[Tony10s]

Originally Posted By: 901Memphis
Do yourself a favor and toss the K&N in the trash. Keep using the paper filter and don't disturb it until it reaches the manufacturers filter interval.


I use paper air filters too ... I don't plan on using a K&N air filter or any air filter that needs to be oiled.

 

[badtlc]

Originally Posted By: Shannow
Originally Posted By: badtlc
any time you can reduce restriction, even in the air filter, it reduces the force required to pump air into the engine. It is simple physics. Whether or not those gains in efficiency are perceptible at low RPMs/throttle is a different story, but it is there regardless.


It's not...reduce the restriction in the air filter, you have the throttle plate more closed, to control engine load speed...it's simple physics.


Unless the throttle plate is completely closed, you'd be incorrect.

 

[Shannow]

Originally Posted By: badtlc
Originally Posted By: Shannow
It's not...reduce the restriction in the air filter, you have the throttle plate more closed, to control engine load speed...it's simple physics.


Unless the throttle plate is completely closed, you'd be incorrect.


OK, how do you control engine speed/load ?

By controlling the manifold absolute pressure...by controlling the throttle plate position.

Manifold absolute pressure is what it is due to (ignoring altitude for a second) the air filter and assembly DP, and the throttle plate position.

More restriction in the air filter means you open the throttle more...for the same manifold absolute pressure, and therefore power output around town and the highway...f

Only time the filter DP plays any part is at W.O.T....at anything part throttle, it's meaningless.

Unless physics is different in your world, at which point I'm happy to hear how they work there...'splain away.

 

[badtlc]

you also control the fuel.

and the restrictions of the plate and filter are in series. They add together. You reduce the filter restriction and you are reducing the force required to pump air through the intake. You can dance around it all you want, but again it is simple physics. It isn't as complicated as you want to make it.

 

[OVERKILL]

Originally Posted By: badtlc
you also control the fuel.


In most modern cars the fuel is controlled by the MAF, which also extrapolates load from airflow. Which ties back into Shannow's point.

On other cars, it is controlled by a MAP sensor, which measures directly what Shannow mentioned.

Of course the load tables also account for temperature, RPM and factor spark advance into it as well but generally the biggest restriction in the intake tract is the throttle blade unless we are at WOT and then often it is a silencer of some sort either before or after the filter.

 

[badtlc]

Originally Posted By: OVERKILL
Originally Posted By: badtlc
you also control the fuel.


In most modern cars the fuel is controlled by the MAF, which also extrapolates load from airflow. Which ties back into Shannow's point.

On other cars, it is controlled by a MAP sensor, which measures directly what Shannow mentioned.

Of course the load tables also account for temperature, RPM and factor spark advance into it as well but generally the biggest restriction in the intake tract is the throttle blade unless we are at WOT and then often it is a silencer of some sort either before or after the filter.


Again, restriction isn't limited to the throttle plate. Is it the most significant? Yes. The air filter is in series with the throttle plate. Any restriction, no matter how small "adds" to the throttle plate restriction along with any bends and drag within the intake itself. The statement that the throttle plate is the only restriction is patently false.

 

[OVERKILL]

Originally Posted By: badtlc

Again, restriction isn't limited to the throttle plate. Is it the most significant? Yes. The air filter is in series with the throttle plate. Any restriction, no matter how small "adds" to the throttle plate restriction along with any bends and drag within the intake itself. The statement that the throttle plate is the only restriction is patently false.


Shannow stated:

Originally Posted By: Shannow
Manifold absolute pressure is what it is due to (ignoring altitude for a second) the air filter and assembly DP, and the throttle plate position.

More restriction in the air filter means you open the throttle more...for the same manifold absolute pressure


He didn't state the throttle plate was the ONLY restriction.

I stated:

Originally Posted By: OVERKILL
generally the biggest restriction in the intake tract is the throttle blade unless we are at WOT and then often it is a silencer of some sort either before or after the filter.


You'll note I also didn't state that it was the ONLY restriction, simply the biggest (unless we are WOT).

The point Shannow has made is that what you are controlling is MAP. This is done, unless we are at WOT, with the throttle blade. To obtain a given power level at a given RPM, you are targeting a specific MAP point. The ECM either measures this directly (with a MAP sensor) and fuels accordingly (factoring in blade position and everything else of course) or it extrapolates it from the data it gets from the MAF, which directly measures airflow in the intake tract BEFORE the throttle blade but AFTER the filter.

Filter restriction is only SIGNIFICANT when it affects MAP at WOT, which will in turn reduce power output. Anything below that, it is transparent because MAP is being directly manipulated by blade position.

 

[Shannow]

badtlc, painting a pinata in statements that weren't made by either myself or OVERKILL, then taking to it with a stick doesn't make you less wrong...

My statement all along has been that the restricition is the sum of those in series, and thus, at part throttle, the air cleaner restriction makes no difference, as the load is controlled by the total restriction, the throttle opens more...'cept for WOT, as previously stated.

Here, try this...

 

[Vikas]

I think a point which might be missing here is that to the driver, less restriction means better throttle response i.e. the car "feels" faster in day to day driving. Obviously, there are lots of tricks that can be done to achieve similar purposes e.g. non-linear throttle opening etc but to the driver throttle response is very real. I would go even as far as saying that it is probably the most important factor when one subconsciously evaluate the performance of a typical vehicle.

From the scientific explanation, air-filter restriction does not matter except at WOT but from practical consideration, it does make perceptible difference in day to day driving. And as they say, perception is the reality!

 

[OVERKILL]

Originally Posted By: Vikas
I think a point which might be missing here is that to the driver, less restriction means better throttle response i.e. the car "feels" faster in day to day driving. Obviously, there are lots of tricks that can be done to achieve similar purposes e.g. non-linear throttle opening etc but to the driver throttle response is very real. I would go even as far as saying that it is probably the most important factor when one subconsciously evaluate the performance of a typical vehicle.

From the scientific explanation, air-filter restriction does not matter except at WOT but from practical consideration, it does make perceptible difference in day to day driving. And as they say, perception is the reality!


My M5 has a button (sport) that changes throttle response massively (DBW). I've never noticed a difference from air filter loading

I would posit that throttle programming (DBW) or ECM tip-in parameters (cable) have a far greater effect than air filter loading unless it is at the loading point where it is a greater restriction than the TB, but then of course it should have been changed already.

 

[Garak]

Overkill, if people are worried about a little dust, go jump on an old gas powered combine next harvesting season, and let the giant 5'x2'x2' pre-filter screen clog completely with chaff. Then they'll see what restriction really is and what it will do.

 

[Evanson]

You can get better throttle response (and a better feel overall), by sitting closer to the pedals.

 

[Garak]

You get a worse throttle response if you buy an el cheapo, non OEM throttle cable for your F-150, and it snaps one week into service. Ask me how I know.

 

[hattaresguy]

Originally Posted By: Garak
Overkill, if people are worried about a little dust, go jump on an old gas powered combine next harvesting season, and let the giant 5'x2'x2' pre-filter screen clog completely with chaff. Then they'll see what restriction really is and what it will do.

Turbo charged engines typically will just about suck the air filter down the intake when it gets clogged enough. Diesels especially since they flow way more air than gas motors.

 

[Garak]

That's where the giant prefilters come in. There's a lot of stuff you don't want to be forcing.

 

[mjoekingz28]

I liken this conversation of an air filter's restriction to an exhaust. Why buy headers, high-flow cats and flowmasters when you can just cut the muffler off.

It seems having restriction to flow low at all points is better than having it stopped up then dumping at the end. Ya see?

 

[gaijinnv]

If the gauge doesn't show any restriction, you're not going to improve anything by putting in a "low restriction" filter:

HTH