mandala
Active Member
I was needing to change my air filter and i am considering going with a K&N. What pros and cons are there?
Anyone use K&N air filters in their coupe?
- Thread starter mandala
- Start date
Not using a K&N in the e9, but have one in my e12.
Pros -- lasts virtually forever with proper care, rumored to flow more air than the stock filter, which may provide a couple extra ponies.
Cons -- takes some work to clean and maintain, rumored to allow larger particles of dirt to pass than the stock paper filter, which may cause accelerated engine wear.
Pros -- lasts virtually forever with proper care, rumored to flow more air than the stock filter, which may provide a couple extra ponies.
Cons -- takes some work to clean and maintain, rumored to allow larger particles of dirt to pass than the stock paper filter, which may cause accelerated engine wear.
steve in reno
Well-Known Member
k&n air filters
I have 2 on my 2800 cs(250K miles), one on my work truck(150k), and one in the wife's sub(80k).
Have used k&n since motorcycle days, 1970's.
Purchase a cleaning kit also, and clean @30k, not 70k.
Easy to clean and work very good. Not cheap for initial cost, but search around for the better deals.
RECOMMENDED
steve
I have 2 on my 2800 cs(250K miles), one on my work truck(150k), and one in the wife's sub(80k).
Have used k&n since motorcycle days, 1970's.
Purchase a cleaning kit also, and clean @30k, not 70k.
Easy to clean and work very good. Not cheap for initial cost, but search around for the better deals.
RECOMMENDED
steve
I did back-to-back test runs with K&Ns vs similar filters I got from JCWhitney, and the K&N had 60-80mph acceleration times that were 0.2 sec slower, This was an average for 10 runs.
Visually the filters were quite similar, but I have no data on their relative particulate filtering. As I maintain the car regularly and generally don't drive on dusty roads I did not consider this an issue.
I've since put Redline filters on the car, along with new 38/38s. Time to redo the test runs and compare the new carbs against the old 32/36s.
IMHO, K&Ns are over-hyped and over-priced.
Visually the filters were quite similar, but I have no data on their relative particulate filtering. As I maintain the car regularly and generally don't drive on dusty roads I did not consider this an issue.
I've since put Redline filters on the car, along with new 38/38s. Time to redo the test runs and compare the new carbs against the old 32/36s.
IMHO, K&Ns are over-hyped and over-priced.
jhjacobs
Well-Known Member
I have them on my '71 E9. Also on my '01 Harley. I can't tell much about performance improvement on the E9 but they clearly help the hog.
gazzol
Well-Known Member
Here's my tuppence worth, "Performance" air filters will only give you a gain in performance if the old filter was causing a restricton to the induction system, that said if you choose to try one my advice would be to buy a cotton+gauze type (like K+N) of any make as opposed to a foam type. Foam filters may cost less to buy but they don't last as long. I bought a PiperX (pronounced pipercross) which are the leading competitor to K+N here in the UK, over a period of time I can only assume that oil fumes from the engine bay have attacked the foam and its gone hard and if you rub it (stop sniggering at the back) it disintegrates.
coupe74
Well-Known Member
K&N
Someone did quite an extensive dyno test with their coupe and posted the results (to the Registry I think) a few years ago. They found worse results with K&Ns, especially if a dedicated cold air flow was not provided. You might be able to find the report in their archives. If you do, it might be worth linking-to from the E9 Tech section.
Someone did quite an extensive dyno test with their coupe and posted the results (to the Registry I think) a few years ago. They found worse results with K&Ns, especially if a dedicated cold air flow was not provided. You might be able to find the report in their archives. If you do, it might be worth linking-to from the E9 Tech section.
Mario L.
Well-Known Member
Don't do it!
K&N style filters will allow more dirt into your engine.
This includes any other filter using oil and cotton cloth in between nicely folded window screen.
Some foam filters are very effective, but oiling them and cleaning them properly is messy.
As a rebuilder of many BMW engines, and many Club Race engines, and performance cars I have seen extensive upper end wear from miniscule particulate that passes through these filters. Valves stems and guides and small scoring in the upper end of the cylinder bore is not unusual.
Power loss with a K&N is very possible on a dyno run, especially if the filter was just installed and is freshly oiled.
As many of us only have CS Coupes as second cars and toys, I sugges that you also be careful if using an oiled air filters on cars using MAF or HFM devices. Oils can and will carry over to these sensors and can damage them or cause running problems. They need to be cleaned only with special cleaners made for this.
K&N style filters will allow more dirt into your engine.
This includes any other filter using oil and cotton cloth in between nicely folded window screen.
Some foam filters are very effective, but oiling them and cleaning them properly is messy.
As a rebuilder of many BMW engines, and many Club Race engines, and performance cars I have seen extensive upper end wear from miniscule particulate that passes through these filters. Valves stems and guides and small scoring in the upper end of the cylinder bore is not unusual.
Power loss with a K&N is very possible on a dyno run, especially if the filter was just installed and is freshly oiled.
As many of us only have CS Coupes as second cars and toys, I sugges that you also be careful if using an oiled air filters on cars using MAF or HFM devices. Oils can and will carry over to these sensors and can damage them or cause running problems. They need to be cleaned only with special cleaners made for this.
decoupe
(deceased)
I have opened the Weber's on my engine several times this summer to change the air jets and each time have noticed a surprising amount of black crap (particles) in the float bowl which I dutifully cleaned out.
I have two fuel filters between the tank and the carbs so my guess is you are probably right that the K&N type filters do not do as good a job as paper - don't know about foam but suspect them as well.
Something else to change this winter.
I have two fuel filters between the tank and the carbs so my guess is you are probably right that the K&N type filters do not do as good a job as paper - don't know about foam but suspect them as well.
Something else to change this winter.
Honolulu
Well-Known Member
decoupe, stop and think
no way an AIR filter is gonna let crap into your CARB FLOAT BOWLS. Carb throats may show it, but if your crankcase is vented into the carb, that's where most of the black in the intake tract will be coming from.
no way an AIR filter is gonna let crap into your CARB FLOAT BOWLS. Carb throats may show it, but if your crankcase is vented into the carb, that's where most of the black in the intake tract will be coming from.
decoupe
(deceased)
You're right of course, no connection between the air filter and the float bowl. I don't have a hose from the engine breather to the carb (but will soon) so that isn't it either.
Maybe the gasket between the base and the upper assembly is deteriorating?
Maybe the gasket between the base and the upper assembly is deteriorating?
Bill Riblett
(deceased)
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Black stuff in carb bowls
This stuff is most likely your rubber fuel lines deteriorating from the inside. Make sure you replace them with hose made for fuel not vacuum, etc. The BMW stuff is expensive but reliable.
Gasoline formulations keep changing and it seems like it gets nastier and nastier! Adding ethanol doesn't help.
This stuff is most likely your rubber fuel lines deteriorating from the inside. Make sure you replace them with hose made for fuel not vacuum, etc. The BMW stuff is expensive but reliable.
Gasoline formulations keep changing and it seems like it gets nastier and nastier! Adding ethanol doesn't help.
decoupe
(deceased)
Anybody have a mass spectrometer I can borrow?
I've replaced all of the fuel lines (I used FI hose) in both the engine compartment and the trunk so assuming there is nothing coming from the metal tubing (copper?) running the length of the chassis, it isn't the lines. I think the fuel pick up in the tank is new as well.
I'll change the carb gasket in the spring and try that. I've got a pair.
I've replaced all of the fuel lines (I used FI hose) in both the engine compartment and the trunk so assuming there is nothing coming from the metal tubing (copper?) running the length of the chassis, it isn't the lines. I think the fuel pick up in the tank is new as well.
I'll change the carb gasket in the spring and try that. I've got a pair.