Performance Air Filters - Harmful?

[Ian]

I was reading up on tuning the Z20 LET engine (Astra Mk 4 Turbo motor) and found a few sites saying to keep well away from perfromance air filters. Basically, to sum up what the sites said, you may get 1-3bhp from a filter, but depending on how you view the figures, you are 10 times more likely to harm your turbo / engine.

To explain:-

OEM filter - 99.8% filtration
K&N filter - 98% filtration.

now as K&N state, only 1.8% filtration is lost for the more free flowing filter. But look at it a different way, for every 1000 bits of dust, only 2 are let in by the OEM filter, but the K&N lets in 20. expand that to 10,000 particles:-

OEM = 20 particles let thro
K&N = 200 particles let thro.

Different way of looking at it, but when you consider that all it takes is one bit of muck to destroy your engine, you are ten times more likely to do this with a performance filter.

Tests have been done with engines examined before and after the use of a performance filter, and show that greater wear occurs with such a filter.

Food for thought, what do you guys think.

P.S. I qouted K&N cos thats the one I got the figures for, but I'm sure it could be any manufacturer.

[The Doc]

To be fair Ian, due to your in-cylinder temparatures it would burn them off the actual size of the particles so wouldn't harm your engine.

Now when I ran without and airfilter on my older car and it sucked a stone into the turbo, NOW you have problems lol!

[SCOTTEX]

As someone who makes filters I could ramble all day about this. To make it brief:
more (pure) air into the cylinders = better combustion, especially when the engine is working hard. However, if part of that extra air is dirty then the combustion will be reduced because dirty air doesn't burn as well as clean air. The key to getting more air through, is to get more pure air through and stop the dirty particles from getting in.
It is possible but it costs 000s, a Vx basic filter costs say £15, so your not going to get the height of technology.
Ramble over.

[Ian]

I was "surfin the net" and found a Porshe owners forum - a little reading came up with a guy who raced 944s. He found on a brand new engine using a performance filter that at the start of the race the engine leaked 3% pressure - rings needing bedding in. At the end of the race he found in had 29% pressure leak. Coulnt figure out why, apart from slight scoring in the bores, so he put some grease just after the air filter. At the next race with a rebuilt engine the same happened, with the car geting slower, and he found vsmall (needed a magnifying glass) bits of grit in the grease. Rebuilt the engine and at the next race ran with a stock filter - 3% pressure leak to 1%. The rings had bedded in.

He also went on to state that when doing his day job - porshe mechanic - cars that have performance filters always have noticably more wear over those with stock filters. Apparently over time (10kish) the K&Ns cotton guazes widen. Clean and refit doesnt rectify this, whilst a stock filters would be replaced with a brand new one - food for thought?

[The Doc]

See your point mate.

I personally don't use them, I change the standard paper items every 3000 miles and my oil every 4000 miles...... The 1.9 engine gets clogged up quite quickly.

[joules2.0t]

I ordered mine last week (before reading this) fitted it at the weekend along with air box mod and was a tad concerned about the amount of naked light visible through by the K+N filter element!!..
to the extent that I did not want to fit it, I literally sat there for 15 minutes weighing it up!

Well having spent £46.00 on it I thought sod it in it goes to try it out!
Not a big difference - not one that warrants shafting the engine early, this thread has just clarified my original concerns on seeing the K+N filter,....
I think it will be coming out again fairly soon!

Not sure if I Will be looking for a replacement..........

[nutron]

Took mine back out and It's still complaining that the Mass air flow sensor must be broken because it gets so much air.

[joules2.0t]

Have you tried cleaning the sensor with Isopropanol cleaning fluid (in a squirty can) Can work wonders mate. The stuff I have is called Isoclene. Use it at work to clean electrical components and other odd jobs...

Hope it sorts out ya problem.

You may just have a build up of retention oil on MAF sensor.

Will be ordering a ITG filter soon - also been onto Abbott re bigger Turbo!! (will keep for another thread)

[SCOTTEX]

Will be ordering a ITG filter soon -

If you think the K&N lets more air in, then "IF" you buy the ITG, you'll be shocked, as this is made of foam (large cavities), although it is 3 different densities, sandwiched together. Foam is a poor filter media, only stopping the large micron size particles (ie, visible to the naked eye). If you blow through one you'll understand. Small particles will flow straight through and although some will be burnt off in the combustion chamber, over time the rest will line the valves and combustion chamber.

Sorry, to put a dampner on it, but I've yet to come across a automotive air filter that I'am happy with. I could probably do to get my finger out and develop one.

[joules2.0t]

So basically it is no better than the K+N?
I suppose whatever aftermarket filter is used there will be some risk of engine contamination........bit of a tricky one that!!
No probs - All input most welcome mate!

Small particles will flow straight through and although some will be burnt off in the combustion chamber, over time the rest will line the valves and combustion chamber.

What about a good drop of Reddex now and again? That should keep the coke at bay......

What brand of filter have you tried Scottex? Currently running a stock filter then?