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TDI Fuel Economy Discussions about increasing the fuel economy of your TDI engine. Non TDI related postings will be moved or removed.

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Old February 19th, 2018, 01:18   #1
pastduebill
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Default K & N air filter

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
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Old February 19th, 2018, 03:27   #2
oilhammer
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Oh geez.....



Look here please:

http://forums.tdiclub.com/showthread.php?t=290373
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Old February 19th, 2018, 03:50   #3
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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 !!!
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Old February 19th, 2018, 13:06   #4
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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
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Old February 19th, 2018, 17:00   #5
pastduebill
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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.
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Old February 19th, 2018, 17:50   #6
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Quote:
Originally Posted by pastduebill View Post
Too much disrespect and personal opinion from people who think they are experts here.
Same goes for all the K&N Zombies that just can't believe that those hyped up air filters are no good..

Last edited by MichaelB; February 19th, 2018 at 20:25.
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Old February 20th, 2018, 09:15   #7
crazyrunner33
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Quote:
Originally Posted by pastduebill View Post
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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Last edited by crazyrunner33; February 20th, 2018 at 09:17.
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Old February 20th, 2018, 09:58   #8
Vince Waldon
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Quote:
Originally Posted by pastduebill View Post
still don't understand why It would reduce the mpg.
Hmmm. Are you talking about mpg calculated by hand over multiple tanks of fuel, or what a dashboard display reads?
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Old February 20th, 2018, 12:31   #9
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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.
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Old February 21st, 2018, 07:31   #10
pastduebill
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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.
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Old February 22nd, 2018, 14:10   #11
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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.
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Old February 22nd, 2018, 14:52   #12
Vince Waldon
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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?
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Old February 22nd, 2018, 15:28   #13
PD Rig
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Quote:
Originally Posted by Vince Waldon View Post
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...

Last edited by PD Rig; February 22nd, 2018 at 15:31.
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Old February 22nd, 2018, 15:30   #14
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Quote:
Originally Posted by PD Rig View Post
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?
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Old February 22nd, 2018, 15:39   #15
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Quote:
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What does an R32 have to do with a 2015 Jetta TDI?
Laughing! Other than it being a vw, nothing at all. Thread jacked by a random thought while reading the above...
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