Give the Octavia some breathing space!

[retiredbri]

The pictures show the inlet side of the 1.4 TSI DSG Octavia III air filter. Compare the white edges with the dirtier areas to get some idea of how much dust and other particles the filter has removed.

 

 

The air filter was fitted when the car was made. The car has  just been serviced having  done 54,000 miles. I asked myself, how much air has gone through the filter?             (I really must get a life!)

 

Over a period of 3.5 years, I've travelled 54,000 miles. If all travel was at say 60 miles per hour, this has taken about 900 hours. In this time the engine has taken in about 68 million litres of air.  (Calculation below if you are interested)

An adult breathes about 3.5 million litres per year. So, in 3.5 years, my car has used the same as a human would take in about 20 years of breathing. 

 

Calculation

A 1.4TSI petrol engine at 60mph is doing about 2,000 revs per min.

Over a period of 3.5 years, I've travelled 54,000 miles. If all travel was at say 60 miles per hour, this has taken about 900 hours.

With a 1.4 TSI engine, allowing for the volume at the top of the cylinder (10.5:1 compression ratio), the real volume is closer to 1.25 litres.

I understand that for a 4 cylinder, 4 stroke engine, the flow rate of Air = Capacity  x  rpm/2  

So at 2000 rpm, this equals 1.25 times 2000 divided by 2 = 1250 litres/min

In 900 hours, the volume of air that has passed through the filter is (900 x 60 x 1250) litres of air. This is about 67.5 million litres. The actual figure will be higher because all miles were not in 7th gear. The figure above is for a normally aspirated engine. I do not know how much more air the turbo has forced through the filter.

 

Regards retiredbri

Edited 14 June, 2018 by retiredbri
To clarify that it had been serviced.

[gman1967]

Has the car not been serviced? Airfilter = service item over 3 years or 54k miles??

[pist0nbr0ke]

3 minutes ago, gman1967 said:

Has the car not been serviced? Airfilter = service item over 3 years or 54k miles??

 

+1

 

I've seen way worse filters after only 16k miles too...

[retiredbri]

9 minutes ago, gman1967 said:

Has the car not been serviced? Airfilter = service item over 3 years or 54k miles??

 

Yes, it has just been serviced (I've edited the post to state this) .

 

For the petrol 1.4 tsi, I was told that the Air filter replacement interval is 60,000 miles.

 

Regards retiredbri

[gman1967]

1 minute ago, retiredbri said:

 

Yes, it has just been serviced (I've edited the post to state this) .

 

For the petrol 1.4 tsi, I was told that the Air filter replacement interval is 60,000 miles.

 

Regards retiredbri

Well I stand corrected. In 68 cars owned/leased, never had one with paper filter that was fitted for that length of time and/or miles and not replaced either by myself, or at regular service. Wouldn't even let wifes Zafira go that long (much as i hate it!!). The Zafira, not the wife. Just to clarify

[retiredbri]

58 minutes ago, gman1967 said:

never had one with paper filter that was fitted

 

The picture was the removed one.  The box for the new one has the part number 04E 129 620 that was £20 inc vat to supply and fit.

 

Regards  retiredbri

[Gerrycan]

I reckon your guess about under estimating the volume of air passed through the filter is right.

Most owners posting pictures of  long term mileage stats show average speeds below 30 mph, sometimes well below. So the car spends more time in a lower gear than your estimates and also idling.

But yes the stats are frightening especially when you calculate the number of hours spent behind the wheel to achieve 54k miles at sub 30mph speeds.

There are only about 8760 hours in a year.

[retiredbri]

6 hours ago, Gerrycan said:

But yes the stats are frightening especially when you calculate the number of hours spent behind the wheel to achieve 54k miles at sub 30mph speeds.

 

For my retirement "speech" I worked out some "numbers". The biggest was the number of times I had changed gear while just travelling to/from work. I was over 4.7 Million.  (Also the number of times the clutch was pressed and released).

We got a Citron C3 "stop go/auto" after that before a Skoda  Fabia DSG then (a longer wheelbase and more comfortable) Octavia DSG with Cruise Control.  At 73, I need to preserve my legs for important things like going to the Doctors and shopping. 

 

[Gerrycan]

I'm guessing retired accountant....or statistician? 

[Rodge]

On 14/06/2018 at 21:34, retiredbri said:

A 1.4TSI petrol engine at 60mph is doing about 2,000 revs per min.

Over a period of 3.5 years, I've travelled 54,000 miles. If all travel was at say 60 miles per hour, this has taken about 900 hours.

With a 1.4 TSI engine, allowing for the volume at the top of the cylinder (10.5:1 compression ratio), the real volume is closer to 1.25 litres.

I understand that for a 4 cylinder, 4 stroke engine, the flow rate of Air = Capacity  x  rpm/2  

So at 2000 rpm, this equals 1.25 times 2000 divided by 2 = 1250 litres/min

In 900 hours, the volume of air that has passed through the filter is (900 x 60 x 1250) litres of air. This is about 67.5 million litres. The actual figure will be higher because all miles were not in 7th gear. The figure above is for a normally aspirated engine. I do not know how much more air the turbo has forced through the filter.

The swept volume of a 1.4 litre engine is 1.4 litres, so your calculation should be 1.4 x 2000/2 = 1400 litres/min. See https://en.wikipedia.org/wiki/Engine_displacement

 

As you point out, this is ignoring the compression from the turbo. I would suggest doubling as a starting point to compensate for the combined effects of actually being in a lower gear and the turbo.

[retiredbri]

11 hours ago, Rodge said:

The swept volume of a 1.4 litre engine is 1.4 litres, so your calculation should be 1.4 x 2000/2 = 1400 litres/min

 

Thanks - I was getting punch drunk on air at this point.

[retiredbri]

On 15/06/2018 at 06:38, Gerrycan said:

I'm guessing retired accountant....or statistician? 

 

Radar Engineer actually. Got to keep the brain active, My wife is amazed by all the useless facts I come out with 

[fabdavrav]

If its the 140/150ps engine that turbo gets to 2.2bar....

 

& the air filter is 60,000miles or 6yrs for normal conditions & EN compliant fuel & on a QI4, QI6, QI7, service... 

 

dusty or hot or other service schedules it is shorter intervals...

 

I removed mine & fitted a ITG foam replacement panel filter..as used by VWR...& I also used VW parts & blanked off the rear left engine opening & opened up the front right opening in the slam panel duct....as per the GTE (which has the same engine)....I now push out 167bhp & 267nm (up from 138bhp & 250nm)....& no remap!!!...just Shell vpower & the air filter/duct mods...