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ChazInMT · 03-15-2014, 02:15 AM

Not Trolls, really. (Well, maybe Frank is a bit of a troll Frank Lee Selfie) Just maybe a bit wiser to how things function in automobiles and not really wanting to put up with claims that are unsubstantiated and to be sure, challenge the laws of physics.

If you came in here and said you were able to drive across a lake now because you just installed new tires, you'd get the same reaction.

In the intake for most gasoline engines, the throttle plate controls how much air the engine receives. This is set based on how much power you need, and the air required to mix with the amount of fuel being used. So, the variable here is power required to go a certain speed. The amount of power requires an exact amount of air.

Lets look at the 2 extremes for an air filter. If a filter is highly restrictive, then the throttle will open more for a given power setting than it normally would to draw more air through the filter, same amount of air enters the engine, same amount of fuel since the fuel injection operates somewhat independently of the throttle position. Thus fuel economy is the same.

If you remove the filter and have no restriction, then the throttle will close a bit, the same amount of air and fuel will burn for a given power requirement and again, no change in fuel economy.

Now if you want the most power you can get out of your engine for the greatest amount of acceleration possible, then without a doubt, a lower restriction on the air filter will maximize power output. But this does not mean it is more fuel efficient, it's a common misconception that more efficient an engine is at creating horsepower, then the more fuel efficient it is as well. If this were the case, then a Bugatti Veyron should get around 95mpg. They don't.

As some have tried to point out, the KN filter is awful at actually filtering the air going into your engine, somewhat large microscopic particles can pass through it such as tiny sand particles, these will act like sand paper on the wear surfaces of your engine and cause it to wear out much sooner than it would if you had a filter that stopped these bits. This is why the wiser among us will give up a few extra 1/10ths of a second in our 0-60 MPH acceleration in order to get a few extra 10's (100's) of thousands of miles out of our engines.

So there it is, the basic physics of why a 8% gain in fuel efficiency was not caused by an air filter change. If you look at my Honda fuel efficiency, it jumps from 28 mpg to 43 mpg depending on a whole crapload of variables, air intake restriction is not one of the variables. So, nobody is saying you didn't see a 8% change, they are saying it was certainly caused by something else besides the air filter swap, ie, driving speed, wind direction, traffic patterns, driving habits, and air temperature. Any of these could easily impact your mpg readings by 8%.

03-15-2014, 02:15 AM	#25 (permalink)
ChazInMT Aero Deshi Join Date: Jan 2010 Location: Vero Beach, FL Posts: 1,065 MagMetalCivic - '04 Honda Civic Sedan EX Last 3: 34.25 mpg (US) Thanks: 430 Thanked 669 Times in 358 Posts	Not Trolls, really. (Well, maybe Frank is a bit of a troll Frank Lee Selfie) Just maybe a bit wiser to how things function in automobiles and not really wanting to put up with claims that are unsubstantiated and to be sure, challenge the laws of physics. If you came in here and said you were able to drive across a lake now because you just installed new tires, you'd get the same reaction. In the intake for most gasoline engines, the throttle plate controls how much air the engine receives. This is set based on how much power you need, and the air required to mix with the amount of fuel being used. So, the variable here is power required to go a certain speed. The amount of power requires an exact amount of air. Lets look at the 2 extremes for an air filter. If a filter is highly restrictive, then the throttle will open more for a given power setting than it normally would to draw more air through the filter, same amount of air enters the engine, same amount of fuel since the fuel injection operates somewhat independently of the throttle position. Thus fuel economy is the same. If you remove the filter and have no restriction, then the throttle will close a bit, the same amount of air and fuel will burn for a given power requirement and again, no change in fuel economy. Now if you want the most power you can get out of your engine for the greatest amount of acceleration possible, then without a doubt, a lower restriction on the air filter will maximize power output. But this does not mean it is more fuel efficient, it's a common misconception that more efficient an engine is at creating horsepower, then the more fuel efficient it is as well. If this were the case, then a Bugatti Veyron should get around 95mpg. They don't. As some have tried to point out, the KN filter is awful at actually filtering the air going into your engine, somewhat large microscopic particles can pass through it such as tiny sand particles, these will act like sand paper on the wear surfaces of your engine and cause it to wear out much sooner than it would if you had a filter that stopped these bits. This is why the wiser among us will give up a few extra 1/10ths of a second in our 0-60 MPH acceleration in order to get a few extra 10's (100's) of thousands of miles out of our engines. So there it is, the basic physics of why a 8% gain in fuel efficiency was not caused by an air filter change. If you look at my Honda fuel efficiency, it jumps from 28 mpg to 43 mpg depending on a whole crapload of variables, air intake restriction is not one of the variables. So, nobody is saying you didn't see a 8% change, they are saying it was certainly caused by something else besides the air filter swap, ie, driving speed, wind direction, traffic patterns, driving habits, and air temperature. Any of these could easily impact your mpg readings by 8%.