Different air filters for different 940 models?

[Laird Scooby]

Well between us we should both have enough air filters to see us into our cars' respective 34th years.

I'm surprised just how little of the actual filter is used compared to the actual size of it. A bit annoying considering the ignition advance is derived from the airflow and engine speed measurements (from MAF and coil respectively) so if there's not enough airflow for the rpm, the logical idea the ECU would get is that the timing is over-advanced so it may well retard the timing for safetys sake.
Not only would that result in a loss of economy but power as well and could in severe cases, cause overheating. Having seen my air filter, it explains why mine has felt a bit "asthmatic" recently, especially at the top end and if my theory about the timing is right, why it's also a bit thirsty at the moment as well!

I might have a look to see if the filter housing can be opened up to use more of the actual filter, mine has gone that black in 2 years or about 7-8k miles.

Not impressed with that!

[haymitch]

The correct air filter have been delivered and I fit it to my car earlier today. Thanks for the help!

Strangely the eBay seller sent me one correct filter and another completely random filter as the second of the 2:1 offer, so now I have to contact them. Life is never easy

[bob12]

You have to weep don't you!!

Assuming it's the same website; Daniel has told me my smaller ones will be dispatched on Monday. I shall wait with baited breath!

Personally, I would claim a refund off Laird Scooby

Bob.

[bob12]

Originally Posted by Laird Scooby

Well between us we should both have enough air filters to see us into our cars' respective 34th years.

I'm surprised just how little of the actual filter is used compared to the actual size of it. A bit annoying considering the ignition advance is derived from the airflow and engine speed measurements (from MAF and coil respectively) so if there's not enough airflow for the rpm, the logical idea the ECU would get is that the timing is over-advanced so it may well retard the timing for safetys sake.
Not only would that result in a loss of economy but power as well and could in severe cases, cause overheating. Having seen my air filter, it explains why mine has felt a bit "asthmatic" recently, especially at the top end and if my theory about the timing is right, why it's also a bit thirsty at the moment as well!

I might have a look to see if the filter housing can be opened up to use more of the actual filter, mine has gone that black in 2 years or about 7-8k miles.

Not impressed with that!

Assuming they are the right ones ^^^^^^, he,he!!

To your main comment about the apparent main volume of air passing through only part of the filter.

My filters seem to be used more or less through/across the whole of the filter going by the dirt collected by the filter. Although that's not much on only 3K a year.

I was just wondering if your air box/intake is fitted with a Wahler air thermostat that automatically controls the intake air flap between hot air off the manifold or direct via the front grill?

If that has never been changed it will be 'dead' and will be stuck in one place. This will affect or restrict air flow into the underside of the air box, and that may possibly mean only part of the filter receives a direct flow or partial flow of air.

If you get what I mean!

Bob.

P.S. Thinking about it I replaced the air thermostat a couple of years ago .... and maybe, just maybe, I can recall a definite 'drift' of contaminant on only part of the filter before the change ... but my mind dulls with time!

[Laird Scooby]

Originally Posted by bob12

You have to weep don't you!!

Assuming it's the same website; Daniel has told me my smaller ones will be dispatched on Monday. I shall wait with baited breath!

Personally, I would claim a refund off Laird Scooby

Bob.

Mine (same size as yours Bob) were despatched on Friday so it will be interesting to see who gets there's first - you probably!

As for claiming a refund off me, there's two hopes - no hope and antelope!

Originally Posted by bob12

Assuming they are the right ones ^^^^^^, he,he!!

To your main comment about the apparent main volume of air passing through only part of the filter.

My filters seem to be used more or less through/across the whole of the filter going by the dirt collected by the filter. Although that's not much on only 3K a year.

I was just wondering if your air box/intake is fitted with a Wahler air thermostat that automatically controls the intake air flap between hot air off the manifold or direct via the front grill?

If that has never been changed it will be 'dead' and will be stuck in one place. This will affect or restrict air flow into the underside of the air box, and that may possibly mean only part of the filter receives a direct flow or partial flow of air.

If you get what I mean!

Bob.

P.S. Thinking about it I replaced the air thermostat a couple of years ago .... and maybe, just maybe, I can recall a definite 'drift' of contaminant on only part of the filter before the change ... but my mind dulls with time!

All the air goes into the underside of the air box Bob - it has to or it would be unfiltered if it went straight in the top!

The purpose of the thermostatic flap valve is to direct warm air from the exhaust during warm-up and in colder weather to improve drivability. Under full throttle conditions it's meant to swing to the colder air inlet and i've come across some cars that actually have a vacuum controlled thermostatic flap so when you bury the loud pedal, it swings to the colder air side automatically as cold air is denser than warm, moist air so provides more power.

However, that is largely irrelevant as the air filter box only has one inlet which is fed from the thermostatic valve.

Having seen the tiny trumpet for the cold air inlet (between the headlamp and radiator) i wonder if that is restricting power and/or increasing the air velocity so more air/dirt is forced into the filter box than the engine would normally use.

Maybe i'm over-thinking this, i'll look at opening up the top of the filter box so it does actually use all of the air filter element. If that doesn't improve the life of the filter and performance/economy then i don't know!

[Laird Scooby]

Well my filters arrived today :



Mixed bunch of brands and exact sizes, one even had the pre-filter foam on it.
There were two Mahle filters, a Delco and a UFI - i went with one of the Mahles for todays change.





The old filter and the lid - no obvious reason why it should only be pulling through that particular square though! I'll keep an eye on this one and see what happens!

On the road it feels more urgent and doesn't sound flat anymore. I had planned on checking the CO reading on the old filter against the new one but no chance of that now. I'll check it soon anyway as i'm hoping to get it in for an early MoT.


*** EDIT *** Just seen why it has the black square - look at the picture of the airbox lid and the bottom of the housing below it! It's the housing causing it!

[bob12]

Ha, ha, ... you beat me!!

As long as they are the right size I guess no worries at the price! They must have a big box of random filters that conform to the spec and they just grab whatever!

You got a pic of the air box (looking down into it?). I tried in my mind to flip the old filter over into the air box by gave up as your box isn't like mine ... yours seems more streamlined!

I have been trying to find the pics I have of mine over the past couple of days to comment on your previous posts, but can't!!

At least you have no found out the reason for the shape of your contaminated filter which is a problem I don't have. Bob.

[Laird Scooby]

Must be some sort of miracle Bob - i did see a bright light in the sky over to the east last night, thought it was just one of the local UFOs so ignored it!

I haven't got a pic of the airbox looking down into it, if i feel up to it tomorrow i'll try and get one but you can just see the square shape or at least the edge of it in my pic above. If i do get a pic that should show the square shape reflected in dirt on the filter!

The top of it is a pretty good shape, even has an intake trumpet on the inlet that becomes the outlet to the MAF!

All that said, the airbox itself isn't a great design, not sure i'd be able to make what i think would work better.

[bob12]

The inside of the top of your air box looks slightly different to mine. I attach a selection of photos.

Still no news of the filters .... yet.

Bob

[Laird Scooby]

Your air filter box is very different to mine Bob! I wonder if mine was broken at some point and replaced with one from a scrapyard with a "that'll do" attitude.

Just seems odd that a 2.8 V6 has a more restrictive airbox than a 2.3 4 cylinder. Also the longer trumpet on mine doesn't add up either, the individual cylinder volume in mine is less so a tuned length would be shorter than yours - the approximate volume of each of my cylinders is 475cc so smaller even than a 2.0 individual cylinder at 500cc and the 2.3 at 575cc roughly.

I'll go and get some pics of my airbox soon, in particular the bottom half internally and if i can find a part number on it, all the better as i can then (hopefully) cross reference it.

With a bit of luck, your filters will turn up soon, the messenger of doom (postie) has just passed my front window with nothing for me so maybe yours will land soon!