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[Steve Krusich]

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Technical Theory Forum





Thread > Post #42866









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Topic:

Lab results - Restricted air filter and FE Lab results - Restricted air filter and FE





By:

Randy Bernklau







Wednesday, September 10, 2008 6:01 PM



20080924133199M42866FORUM12

























FE is fuel economy and the following air results from a

class we ran at the NCVECS lab to show the affect restricted

air filters have on fuel economy. This demonstration has

been run countless times over the years at this lab and

every time the results are the same.



This particular vehicle is a 1994 Ranger 4.0L.



The test is a mass test, IM240. For those unfamiliar with

mass testing, you can count the carbons and, given the

carbon content of the gasoline, you calculate FE. Simply

take the number of tailpipe carbons divided by the number in

a gallon of gasoline and then use the miles driven on the

test. All gas values are in grams per mile.



The restriction was done with a very rare component only

available to certified labs commonly referred to as duct

tape.



First test, new air filter, no problems.



THC = 0.099



CO = 3.967



NOx = 2.133



CO2 = 466.426



FE = 18.75 MPG



1.97 miles driven



Second test, air filter 75% restricted.



THC = 0.145



CO = 4.237



NOx = 2.002



CO2 = 451.945



FE = 19.32 MPG



1.97 miles driven.



Third test, 98% restricted, vehicle had severe driving

issues and had trouble getting through the test. Any more

restriction and it would not have completed the IM240. Only

two ribs of the air filter were visible.



THC = 0.173



CO = 8.769



NOx = 1.845



CO2 = 450.503



FE = 19.08 MPG



1.97 miles driven.



That should be the end of that myth. Any questions?



Randy Bernklau

Owner/Technician

B.C. Automotive Services

Fort Collins, Colorado, USA



Quote original text Respond privately

 

[Richard L]

What myth are you trying to prove or disprove??? You just gave us test results other thatn you state that the first test had a dirty air filter...So is there a myth going around that a dirty clogged air filter is better than a clean unrestricted air filter? If so, I have not heard that one?



...Rich

 

[Steve Krusich]

This lab's result say that greater air flow would NOT improve fuel economy. If they did performance tests I expect they would conclude that greater air flow would improve performance only but not fuel economy.



Just wondered what other thought?

 

[Richard L]

Steve,

You are correct that improved air flow only improves performanc...up to a point.



If the enging can get adequate air flow at normal driving RPMs there is not difference in MPG or performance. When you attempt to operate the engine for maximum performance, the engine requires more air and fuel to generate more HP. As long as the air filter does not restrict the air flow at higher RPM, you will get more HP at the expense of poor fuel mileage.



If the filter gets so clogged that is restricts operation of the engine at normal operating speeds, you will see a drop in MPG. The theory behind filters like K&N are that the filter material is far less restricted than the conventional paper filter which allows more air flow at higher RPM for more HP, and also runs much longer before it will restrict air flow at normal operating speed. Most paper air filters need to be replaced every 10K miles or even less. K&N is a permanent filter that only requires cleaning about every 50K miles.



...Rich