K & N air filter

pastduebill

Member
Joined
Oct 19, 2017
Location
Arkansas
TDI
2015 Jetta TDI (man)
2015 Jetta TDI manual trans.
My question is about a slight MPG reduction after dropping in a K & N air filter. Can anyone technically explain how a filter with LESS restriction would reduce MPG?
Have used K&N for decades on vehicles (motorcycles, pickups, cars - gas and diesel) with improved MPG/performance on all of them. With no codes or MAF sensor problems ever. I don't understand why anyone would slop enough oil on it to drown the MAF sensor anyway, but that's a different topic.
Is the ECM 'programmed' for the exact restriction of the OEM filter?
Would appreciate a technical answer for this.
Thanks,
Bill
 

scooperhsd

Top Post Dawg
Joined
Aug 19, 2003
Location
Kansas City KS
TDI
NB, 2000, RED(5 Speed conversion) 2015 Golf SE
We don't care what your previous experiance with K&N air filters is - they DON'T work on TDI's , and in fact are determental to the life of your MAF !!!
 

crazyrunner33

Veteran Member
Joined
Jul 11, 2006
Location
NC
TDI
'10 Golf(bought back)
I had great luck with the K&N that came in my truck when I picked it up 10 years ago! The K&N kept the Cummins alive for a full 230k miles before the engine was dusted. I'd like to see a Cummins go for longer than 200k with a paper filter.

/sarcasm
 

pastduebill

Member
Joined
Oct 19, 2017
Location
Arkansas
TDI
2015 Jetta TDI (man)
Thank you oilhammer for linking some actual research & facts.
I see the OEM filter is about as efficient in flow as the K&N but still don't understand why It would reduce the mpg.

Too much disrespect and personal opinion from people who think they are experts here.
 

crazyrunner33

Veteran Member
Joined
Jul 11, 2006
Location
NC
TDI
'10 Golf(bought back)
Thank you oilhammer for linking some actual research & facts.
I see the OEM filter is about as efficient in flow as the K&N but still don't understand why It would reduce the mpg.

Too much disrespect and personal opinion from people who think they are experts here.
It kills the MAF and causes the compressor wheel to erode. The former will reduce mileage before the latter. When servicing EGR free ISB Cummins engines in industrial applications, the compressor wheel looks squeaky clean and almost brand new even with 10,000 hours. The engines with the K&N or even the AFE will have in consumer trucks usually have worn out looking compressor wheels. An ISB in an industrial application lasts around 10,000 hours when following the Cummins service schedule, the ones that die early are the ones with aftermarket filters, or operators that overide the derate when a minor issue occurs and turns a 100 dollar sensor problem into a 5,000 dollar service call.

The worst K&N eroded compressor wheel on a Cummins equipped with an HT3B ended up having a going away party by sucking a piece of metal out of the K&N cone filter and lodged it between the compressor wheel and housing. On the note of collapsing filters, avoid Baldwin, even their paper ones. One was on a well serviced ISB and was sucked right in and killed a 2,000 dollar HE351VE.
 
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Nevada_TDI

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Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
When a rotating part that spins in excess of 100,000 RPM--sometimes up to 160,000 RPM-- the smallest amount of compressor erosion will create an out-of-balance scenario and cause a catastrophic turbo failure.
 

pastduebill

Member
Joined
Oct 19, 2017
Location
Arkansas
TDI
2015 Jetta TDI (man)
I've never seen a air filter company state their micron filtration rating.
Also, an EGR causes soot to be ingested into the top end. How much more erosion is that?
I blocked the EGR on a Series 60 Detroit engine. At the 15,000 mi. service the oil was so clean you could still read the writing on the dipstick through the oil. Before, the oil was black in a week.
 

PD Rig

Veteran Member
Joined
Oct 25, 2014
Location
Pennsylvania
TDI
2004, 2015 Golf TDI
So say someone bought a cold air intake and has an oil cone filter on the end of the long cool looking metal tube that goes down into the bumper. What would be suggested. Revert to stock ( stock air box) or get a dry type cone filter. I bought my r32 with a cold air intake already installed. Always kind of shake my head when I am washing the filter... any experience with the dry type cone filters? I would have to buy the air box, dam and Intake flex hose to revert back to stock.
 

Vince Waldon

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Joined
Apr 25, 2009
Location
Edmonton AB Canada
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2001 ALH Jetta, 2003 ALH Wagon, 2005 BEW Wagon
One way to think about the answer to your question: do you want the engine to be drawing in hot air from inside the engine compartment, or cool air from outside the engine compartment?

Or does the cone filter setup your car currently has also draw from outside?
 

PD Rig

Veteran Member
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Oct 25, 2014
Location
Pennsylvania
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2004, 2015 Golf TDI
One way to think about the answer to your question: do you want the engine to be drawing in hot air from inside the engine compartment, or cool air from outside the engine compartment?

Or does the cone filter setup your car currently has also draw from outside?
Technically both. It's in the bumper behind one of the bumper cover cutouts. there is nothing that creates a separate compartment for the filter. Your question just helped me answered my question. Go with what works well. Stock...
 
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MichaelB

Veteran Member
Joined
Aug 11, 2009
Location
SE Wisconsin
TDI
2014 Passat SE DSG
So say someone bought a cold air intake and has an oil cone filter on the end of the long cool looking metal tube that goes down into the bumper. What would be suggested. Revert to stock ( stock air box) or get a dry type cone filter. I bought my r32 with a cold air intake already installed. Always kind of shake my head when I am washing the filter... any experience with the dry type cone filters? I would have to buy the air box, dam and Intake flex hose to revert back to stock.
What does an R32 have to do with a 2015 Jetta TDI? :confused:
 

SilverGhost

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Joined
Mar 25, 2005
Location
Back in So Flo - St Lucie
TDI
'05 Golf - totaled :(, wife's '13 Beetle - buy back, TDIless
I have the flow and particle size tests for K&N stored around here somewhere. Some truck guys got together and bought time on a flow tester. I think its on my old laptop I'll have to dig out.

Jason
 

Mongler98

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Mar 23, 2011
Location
COLORADO (SE of Denver)
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98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
toss that POS away and go with a Swiss cheese mod on the air box with a MANN filter.
 

Midwesthick

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Oct 26, 2011
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Denver
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A3, GSW, 02-Golf
I rock an AFE dry flow filter with the stock setup. No complaints here but I would 100% stay away from an oiled element.
 

SilverGhost

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Joined
Mar 25, 2005
Location
Back in So Flo - St Lucie
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'05 Golf - totaled :(, wife's '13 Beetle - buy back, TDIless
HA! Found the air filter test. It was posted over at Diesel Bombers truck forum. Test is an ISO 5011 and uses machine Testand Corp of Rhode Island.

Here is the link

Jason
 

[486]

Top Post Dawg
Joined
Mar 1, 2014
Location
MN
TDI
02 golf ALH
When a rotating part that spins in excess of 100,000 RPM--sometimes up to 160,000 RPM-- the smallest amount of compressor erosion will create an out-of-balance scenario and cause a catastrophic turbo failure.
ehh, fine dust doesn't affect balance, large chunks do

same reason axial turbine engines can ingest quite a bit of fine dust, it erodes the compressor blades pretty evenly
Ever see an air filter on an aircraft? Some helicopters run oiled cloth filters that only really stop the large bits, but for the most part it's just considered and written off as normal wear.
They don't have cylinder walls and piston rings, however.
 
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