I changed the pollen filter on my Skoda Fabia yesterday. Lots of leaves fell out and the difference is like night and day. OK, it just effects how blowy my air con is which isn’t too amazing.

It got me thinking about what else I can change easily that might make a difference.

I think a high performance air filter looks easy to do. Will it make a noticeable difference to performance? Are there any side effects (eg more muck likely to get into engine etc?)

Replacing is a copy and paste affair. The performance difference is like night and day. I did it and it never misses a beat.

Do you have a petrol or a diesel? If diesel no point as you won’t gain any performance. Diesels need more fuel for more performance not air like petrol engines. If you have a petrol go for a induction kit like a K&N 57i as this will produce more bhp over a normal panel filter.

Also a cotton gauze or foam filter filters more dust etc than an oem paper filter so no engine damage.

Note how may “performance” air filter supplier are able to give rolling road graphs to back up their claims of increased performance!
In my experience they simply make more noise.

What Mr Mojo said. Assuming its petrol, better breathing (either in or out) will make a big difference.

I have some snake oil whcich will add 100bhp…. Interested?

One problem with non-sealed performance filters is that they sit in a hot engine bay sucking in hot air which isn’t as good for performance as cold air which would come from through the standard air filter and housing.

On some engines they do produce an awesome induction roar when gunning it 8)

Will it hell as like make a difference!

Go on, show me an independent dyno graph showing before and after, for an air filter. I double dare you!!!

**waits to be proved wrong** 🙂

Mr Mojo, you seem confused. Are you the man who couldn’t light his coal fire? Petrol and diesel both require air to combust.

Yes, but you need to flow more fuel as well as air or all that happens is you get a weaker mixture….

P.s. An induction filter will do f-all.

It won’t make a weaker mixture, because the MAF/AFM sensor is after the filter (obviously) and will still measure the flow of air correctly. So the mixture of fuel will not be effected.

Fadda – better breathing in or out will make a big difference.

If by big difference you mean a completely unnoticeable in comparison to a new OE filter. Then yes. It will make a HUGE difference.

So the mixture of fuel will not be effected.

Unless the airflow is outside the parameters of the ECU or the capabilities of the injection system.

The chances are a filter on it’s own will do diddly squat. But it could make the car worse before it makes it better

PeterPoddy – That’s just not going to happen by fitting an aftermarket air filter.

you need to buy the air filter with the power balance on the box…

if you replace the original filter with one that flows more air then maybe you’ll get more power. If the original filter isnt restricting the flow then you wont . On lots of cars its the throtle body causing the restriction.

Still got that snake oil for you…….

You will flow more air, but it will be hotter air from inside the engine bay which gives you less performance. Unless you go for a sealed performance filter with a cold air feed from outside of the engine bay.

The trouble is, you really need to be drawing in cold air, from outside the car, not sucking in warm air from the engine bay. Its even worse in turbo’d cars due to the extra heat generally in the engine bay.
I did read that a decent oil whetted gauze type filter can be as effective as a std paper filter with a better airflow, but they need regular cleaning. The cheaper paper / cotton filters tend to let me air through, as well as more dust, so in the longer term you can end up with wear in the engine.

ok just a little more to the combustion. Air does not help the combustion. The oxygen in the air does. Most “chav kit” are basically sucking up the warm air from above the engine. Most standard air boxes suck up colder air from the outside. However the density of hot air is lower than the density of fresh air and thus with a chav kit you get less oxygen in your combustion chamber to burn.
I very much like the idea of the 20£ box working better than a system designed by a team of qualified people…

Mine help…

An aftermarket air filter will still need cleaning and re-oiling and some people have had problems after re-oiling them as they put too much on which then contaminated the MAF.

h4muf – Member
Mine help…

Yes, our race car helps from this type but it draws air from outside and it’s very highly tuned.

For regular road cars, no gain. But it sounds good. That is all….

Sorry sales hype imho

It is all well and good getting more air in but everything has to be balanced and you need to get the gasses out

Then have you got too lean a mixture???? etc

EDIT oops I had this thread on for 30 minutes while eating my tea ( bunny and pheasant casserole) before I replied

Now about that snake oil???????

SD
Modern engine management system will cope with a small increase in extra airflow. On vxr astra its best to remove the cat below the turbo before messing with the intake . It will still pass the mot emmissions test ok too. After that increase the size of the intercooler(cooler charge/denser air) all before changing the airfilter type.

Knottie

now about my picasso 😆

Will it hell as like make a difference!

I had my 4 cylinder kit car on a rolling road. With the standard k&n paper air filter it produced 127bhp. With no filter 132bhp. Both tests were done within 10mins of each other and after the car was nice and warm.

Although I’d never recommend driving without a filter, it shows that a poor filter will reduce the horsepower of a car. Not by much admittedly! The foam ITG one now fitted is somewhere in-between.

Mr Mojo, you seem confused. Are you the man who couldn’t light his coal fire? Petrol and diesel both require air to combust.

No coal fire here, must be someone else.

Petrol and diesel engines work differently with regards to producing power. With petrol the more air you can get into the engine the more power you can create. But with diesels more air doesn’t mean more power, you needs to increase the amount of fuel to increase power.

mr mojo
both petrol and diesel engines need air and fuel to produce power, Thats why they put big turbos on diesels . More air+correct amount of fuel = more power on petrol or diesel.

All engines have to draw in a given amount of air through a filter. The more free-flowing the filter, the less work will have to be done to get the air in. Regardless of what happens inside the engine. A turbo diesel will be drawing in much more air than the displacement of the engine because of the pressure increase, but then again the engine will be running at lower revs overall, so that would even things out with respect to a NA petrol… hmm…

Interestingly, drawing in warm air into a petrol engine can increase MPG significantly.

With regards the petrol/diesel argument above – both types of fuel need both more air AND more fuel to produce more power. One is useless without the other. A modern petrol will refuse to inject more fuel if there’s not enough air to burn it (which is why you lose power at altitude).

In a petrol car if there is not enough air to burn the fuel the ECU can tell because there is more of something in the exhaust.. CO perhaps? However in a diesel you just get smoke, and the ECU can’t detect that. However a turbo diesel can detect how much air is coming in so it can increase the turbo boost (assuming a modern VNT turbo) to maintain the amount of air it needs. Same is true for a turbo petrol.

HOWEVER if the air intake was restricted, then the ECU would have to make the turbo work harder, so that would in turn restrict the outflow of the engine reducing power and economy very slightly.

“Yes, but you need to flow more fuel as well as air or all that happens is you get a weaker mixture…. “
Pete – kinda true, but by actually leaning out the mixture appropriately, you can get better power gains (as standard fuel mixtures run a bit rich for safety leway..

On an RC nitro car, you can run it thin as “F”, but run the risk of the engine blowing as it gets tooo hot! Boy does it go though.
That’s how remaps (mainly on turbo cars) work in a way too.

On subject – the expensive kits (I’m talking £300) do make a difference, and I believe they are the only ones. You need a CAI (cold air induction) kit – these either have the filter out of the engine bay (wheelarch etc), or have an enclosed box with an intake pipe.

Noticable difference on our type r…

DrP

Where’s Smurf Matt when you need him? I’ll bet he could give us a definitive answer and back it up with his experiences.

I’m intrigued to know which race tracks everyone’s testing their road cars on though for it to actually matter.

Will it hell as like make a difference!

But Max Power sez it does, so it must be tru innit!!!

Foam “performance” filters work on a different principle to paper element filters.

Paper filters work like a net.
There are gaps between the paper fibres.
Anything bigger than those gaps can’t get through.
Eventually, enough of those gaps will get clogged by dirt so that the filter starts to restrict the flow of air.
Take it out, bang it on the floor upside down, refit it, carry on.

The gaps created by the bubbles in a foam filter are comparatively huge.
On there own, they would only stop very large dust particles.
They rely on being coated with a sticky oil.
The air is forced to change direction many times as it makes its way through the network of bubbles.
Each time the air changes direction, the dust particles carry straight on due to inertia.
They then stick to the sticky walls of the foam bubbles.
Eventually, all the sticky surface is covered in dust.
Any further dust will bounce off the existing dust and carry on through to the engine.
Take it out, wash it, soak it in the special oil, wring it out, refit it.

More trouble than it’s worth for a road car.

as standard fuel mixtures run a bit rich for safety

They used to with carburettors.
It’s all lean burn and knock sensors these days.

A turbo diesel will be drawing in much more air than the displacement of the engine because of the pressure increase

Volumetric efficiency.

In my experience performance filters do very little in increasing outright power on a standard car. They may increase throttle response but without a remap the ECU simply adjusts the fueling to keep the emissions within given parameters.
On mapped cars they do make a difference, still no where near the manufacturers claims.
On the subject of fueling to gain more power it’s not just down to getting as much mixture into the cylinders as possible unless you can extract it quickly too so catalytic convertors and restrictive exhausts need to be changed to get obtain the best gains.
On more and more modern cars the limiting factor is coming down to the injectors that are only able to flow a maximum amount of fuel and no amount of smooth fast flowing pipe work and mapping can over come this.

http://www.carbibles.com/fuel_engine_bible_pg5.html

webbers

[thread closed]

As for the argument about whether more power is nececary, only if you spend a lot of time with your foot nailed to the carpet (which you should have removed to save weight surely?) at the peak power RPM (~2/3-3/4 of the redline). If not you’d get more power by putting your foot down more and shifting gear later.

I have a K&N panel filter on my Focus And it makes the little 1.6 sound quite throaty when heavily accelerating. I would have got a full on cone filter for it but because of where the MAF sensor is I cant fit one.

BTW I am not a boy racer I just put the K&N on when doing a service because they filter better.