May 19th 2006.
Some of
my customers are using these K&N add-on air filters.
They're supposed to give you more horsepower by
allowing more air into the engine. Allowing
the engine to breathe more freely. This may be OK for ten
laps in a club race, but for long term use on the highway?
NOT a good
idea.
Apart from
the messy job of cleaning then, these filters actually
let more fine particles of dirt through into the engine.
Our experience
is that the inlet manifold, known as a throttle
body in technical terms, needs cleaning at least three
times more often
than normal.
Here's
why:
|
Paper |
|
Oiled Gauze
(K&N) |
| Large particle
efficiency |
very good |
|
very good |
|
| Small particle
efficiency |
very good |
|
very poor |
|
| Airflow capacity
|
very good
|
|
above average |
|
| Dust holding capacity
|
superior
|
|
very good |
|
| Load up characteristic
|
superior
|
|
very good
|
| Backfire characteristic
|
above average
|
|
very good |
|
| Cleanability
|
superior
|
|
poor
|
|
The Desert Research Institute
DoD #0200 WMTC BMWRA DIOC
Reno, Nevada (702) 673-7380
What this table shows is
that in order for the K&N filter to allow more air flow, it needs
to also allow more fine particles to
enter
the engine as well. Which is OK for a racing car, which
will have an oil change every 150 kilometres or so, anyway.
A General
Motors technical service bulletin (04-07-30-013A0),
issued in January 2005 says as follows:
"The use
of an excessively/over oiled aftermarket, reusable
air filter may result in:
Service
Engine Soon (SES) light on;
Transmission shift concerns,
slipping and damaged clutch(es) or bands.);
Engine driveability concerns,
poor acceleration from a stop, limited engine r.p.m.
range.
"The oil
that is used on these air filter elements may be transferred
on to the Mass Air Flow sensor, causing contamination
of the
sensor.
As a result,
the grams per second signal from the MAF may be
low and any or all of the concerns listed may occur.
The TSB
goes on to say:
"The use
of an aftermarket reusable air filter does not
void the vehicle's warranty."
However,
rest assured that any damage caused by the use of an
improperly oiled aftermarket air filter will void the
warranty on
related
failures.
An air
filter that fails to filter out fine particles as it
should may result in MAF sensor contamination, which will
produce symptoms
similar
to those caused by an over-oiled air filter.
There are
people who have modified their motorcycle fuel and
exhaust systems to use K&N filters, with good results.
However,
they have modified their bikes to cancel out the lean
running conditions normally required to meet emission
standards.
The air
filter is part of the package of opening restrictive
intake and exhaust systems and increasing fuel flow
to take
advantage
of added air flow. The filter is not a stand-alone
fix. A fuel-injected car engine that's finely tuned by
an on-board engine
management
system cannot be easily modified.
Installing
an aftermarket oiled air filter isn't worth the risk
of driveability issues that may result.
There are
serious doubts in my mind about the claims of increased
power and fuel economy gained solely through the use
of this
product.
Who wants
to admit they got taken when they've bought an expensive
product like this?
So, it
MUST be working. Right?