Worse Fuel Economy

[Danbag]

Hello,

I have reciently installed a K&N Airfilter to my 2000 (W) Golf TDi, in a vain attempt to make the fuel efficiency better (honest!). And in theroy, it should work, if it had enough air, but it doesnt!

It comes with 2no tubes that fit next to the front off-side headlight (after you remove the cawling) and sucks a tiny bit of air from under the gap at the front of the bonnet, but it’s not enough.

Does anybody have a design for air intake that doesnt involve cutting holes and putting stupid vents in body panels, and wont frighten me everytime it rains

Or just any advice to make it better anyway....tis mighty frustrating!

Many thanks in advance!

[JohnnyBee]

Sadly there are only a couple of options open to you, Dan; one is to source the filter housing from a VR5 or VR6 and fit that as a direct substitute.
You may have to 'cut and shut' the mounting points to get it to sit down properly, but it does flow a lot more than the standard article.
The other way is to 'modify' your own airbox to accept a single 3" intake trunking hose to increase the flow into it; however off the top of my head I can't remember if you have to blank off the existing pickups and take the feed from the side of the box, or whether you can get away with opening up the holes in the existing face to get it to fit.
Looking at the fundamental problem of poor MPG, it may well be that the MAP sensor is leaking internally, thus overfuelling all the way through the range up to say 60% boost, where it won't make any appreciable difference anyway.
Certainly worth a look, as they are noted for this problem after a fair mileage.
JB.

[Danbag]

This maybe (well...probably) a stupid question but, Is a MAP sensor the same as MAF sensor ie mounted on the main air intake hose? If so I had this (MAF),replaced around 25,000 miles ago.

Do I remeber right when thinking the original box had an air intake coming from the wheel arch? Using the original box is more efficient then leaving the air filter open in the engine bay? Where would the new 3" hose draw air from?

Thanks for help....I clearly need it!Dan

[Huweth]

Just to warn you, I have heard that the oil in K&N filters damages your MAF. Not sure how long this takes, but maybe it's worth fitting a stock filter. Some people believe that it's about as good as they get. Then perhaps it would help to fit more intake options...?

[JohnnyBee]

That was quick, Dan!
The MAF sensor (Mass Air Flow) measures the total amount of air going into the engine, but the MAP sensor (Manifold Absolute Pressure) tells the ECU what load is on the engine in terms of boost pressure.
As the boost increases, the ECU widens the injector trigger pulsewidth, hence increasing the amount of fuel injected.
As the MAP sensor always relates to atmoshperic pressure, any leakage will delay the onset of that increase, which in turn effectively starves the engine of fuel relative to the demand you're putting on it.
The nett result of all this is that the donkey feels sluggish, particularly in the lower range, which leads to bigger throttle openings for longer periods to get the required performance.
Taken as a whole, the gross effect is the use of far more fuel than an equivalent motor not thus affected.
I hope I've explained it logically enough!
As for the filter side of things, I'd assumed that you're still using the original VW filter housing with a K&N element fitted?
If that's not the case, could you please explain how you've got it set up?
JB.

[Danbag]

That was quick, Dan!
The MAF sensor (Mass Air Flow) measures the total amount of air going into the engine, but the MAP sensor (Manifold Absolute Pressure) tells the ECU what load is on the engine in terms of boost pressure.
As the boost increases, the ECU widens the injector trigger pulsewidth, hence increasing the amount of fuel injected.
As the MAP sensor always relates to atmoshperic pressure, any leakage will delay the onset of that increase, which in turn effectively starves the engine of fuel relative to the demand you're putting on it.
The nett result of all this is that the donkey feels sluggish, particularly in the lower range, which leads to bigger throttle openings for longer periods to get the required performance.
Taken as a whole, the gross effect is the use of far more fuel than an equivalent motor not thus affected.
I hope I've explained it logically enough!
As for the filter side of things, I'd assumed that you're still using the original VW filter housing with a K&N element fitted?
If that's not the case, could you please explain how you've got it set up?
JB.

Well, I am keen to diagnose this....well while I’m at work anyway (nothing like getting paid to sort out other things!!)

Ok, thank you for that explanation. Is there anyway I can effectively determine it is the MAP sensor, or is it a case of changing it and see??

If so, how do I go about replacing it?

This is a picture of the inside engine bay (not my car) http://www.tuningdirekt.com/catalog/images/K&N/57-0222.jpg
Even shows the 2no shoddy tubes that they ask you to wedge next to the front offside headlight and zip tie to the battery cable. There’s got to be a way of getting a better supply of air to it.
Dan

[Danbag]

Just to warn you, I have heard that the oil in K&N filters damages your MAF. Not sure how long this takes, but maybe it's worth fitting a stock filter. Some people believe that it's about as good as they get. Then perhaps it would help to fit more intake options...?

Really??....Damn!
I have had problem in the past (with MAF), it stopped my car going above 80mph. Had it replaced and....well....I can still exceed that (not that it happens often....*cough*cough*).

Wonder if there is anyway to protect it, does the MAF sensor degrade over time (get progressively worse), or just all-of-a sudden fail? - I cant believe I took my car to a garage to get it replaced last time

Dan

[Dave Avant]

Basically the oil on the filter gets sucked towards the engine and any excess can stick to the MAF element, this in turn can reduce the MAF's sensing capabilities.

I have just fitted a K&N panel filter to my TDi, but before I fitted it I washed it in hot water first to remove any excess oil and a fair amount came out. Its a red oil. The oil is there to filtrate even more than the cotton guaze. Unless its driven in a really dusty environment then it will be OK with less oil. It will probably take a few thousand miles to affect the MAF sensor, but they can be cleaned!! You can clean them with electrical contact cleaner and either blow hard with mouth or if you have one an air compressor. Some have noticed an improvement after cleaning even with a standard filter.

[Danbag]

Basically the oil on the filter gets sucked towards the engine and any excess can stick to the MAF element, this in turn can reduce the MAF's sensing capabilities.

I have just fitted a K&N panel filter to my TDi, but before I fitted it I washed it in hot water first to remove any excess oil and a fair amount came out. Its a red oil. The oil is there to filtrate even more than the cotton guaze. Unless its driven in a really dusty environment then it will be OK with less oil. It will probably take a few thousand miles to affect the MAF sensor, but they can be cleaned!! You can clean them with electrical contact cleaner and either blow hard with mouth or if you have one an air compressor. Some have noticed an improvement after cleaning even with a standard filter.

That good to know, many thanks. You think washing it would help, the open filter I have?

Do you know any particular products. To be honest Ive had a look online (quickly), and I cant find (well...more like, know), how to clean it - got any tips?
Dan

[Dave Avant]

For the filter, I just used hot water with a very small amount of Mr.Muscle as you don't want to completley remove the oil from the filter, then leave to dry.

The leccy cleaner, I got mine from http://www.cef.co.uk/ its made by Acorn I think. I have 2 types, one cleans and the other cleans and protects, for the MAF you want the one which cleans and DOESN'T protect.