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tdi owners K&N reviews


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Power benefit? No I didn't see one. The Tdi filter is massive anyways. Cost benefit due to being able to wash it is what I went for.

Shocked. Didn't think you'd go for an aftermarket filter.

I personally won't go anywhere near aftermarket filters. Oiled properly, they have a filtration efficiency between 60% - 92% (directly from the K&N website) whereas a paper filter has an efficiency of 99% at all times. For me, that's enough to put me off, but there's the other issues with aftermarket filters as well. Improperly oiled filters can have even less filtration and an unoiled aftermarket filter is basically filtering nothing. You'd be better putting a net curtain over your air intake. If you get onto the MX5 forum, someone fitted a K&N and took a sample of oil after a few thousand miles. There was 6x engine particles found in the oil when a K&N was fitted or something ridiculous. Now granted, he said hadn't been oiled, but still why take the risk? It just isn't worth it.

I'm also not convinced by the power gains whatsoever. As Dblock says, he hasn't seen any and almost every GTI owner I've spoken to has commented to say they've seen no improvement in performance when a K&N installed.

You've also got the issue of heat soak. Unless you fit a CIA, you will probably suck in hot air which a diesel doesn't like. Yet, when you filter a CIA, unless you do it correctly, you run the risk of sucking in water. A factory airbox has a CIA as standard.

If it's the sound you want, just drill your airbox.

Edited by Skezza
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On diesels it can make a difference. On most of my cars I run panel or CIA. E.g. on a 2.9 bmw or 2.7merc engine I could 110% feel the benefit on them. Plus 2 services and it's paid for itself. I should maybe swap it with the paper one now that I'm remapped so I can see if there is a difference.

Of course paper has 99%. That's why it's so restrictive.

As for not oiling a filter that's like me saying I got 100 x the amount of debris with a paper filter. Granted I didn't fit it to the car...

You say engine particles so is that from scoring the bore? I'm dubious of that do you have a link?

Also I think your confused, the one for the diesel is a direct replacement that sits in the airbox. You have to be trying hard to hydrolock your engine with an induction kit lol!!

Here is the filter here

417K46FMYPL._SX300_.jpg As you can see it's several times larger than the petrol model so I don't think drilling the box would work due to the design.

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On diesels it can make a difference. On most of my cars I run panel or CIA. E.g. on a 2.9 bmw or 2.7merc engine I could 110% feel the benefit on them. Plus 2 services and it's paid for itself. I should maybe swap it with the paper one now that I'm remapped so I can see if there is a difference.

Of course paper has 99%. That's why it's so restrictive.

As for not oiling a filter that's like me saying I got 100 x the amount of debris with a paper filter. Granted I didn't fit it to the car...

You say engine particles so is that from scoring the bore? I'm dubious of that do you have a link?

Also I think your confused, the one for the diesel is a direct replacement that sits in the airbox. You have to be trying hard to hydrolock your engine with an induction kit lol!!

Here is the filter here

417K46FMYPL._SX300_.jpg As you can see it's several times larger than the petrol model so I don't think drilling the box would work due to the design.

Not convinced by the restrictive argument. MCM Mythbusted them and pretty much proved the gains are negligible. Now that test wasn't scientific but I would say it's fair to say without extra work to benefit from the increased air flow, the benefits will be pretty non-existent.

The particles was a thread on the Mazda MX5 forum. I'll have a look for it pal.

I didn't realize you were using a conical filter replacement. I wrongly assumed you were using a cone filter.

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Not convinced by the restrictive argument. MCM Mythbusted them and pretty much proved the gains are negligible. Now that test wasn't scientific but I would say it's fair to say without extra work to benefit from the increased air flow, the benefits will be pretty non-existent.

The particles was a thread on the Mazda MX5 forum. I'll have a look for it pal.

I didn't realize you were using a conical filter replacement. I wrongly assumed you were using a cone filter.

Turbo diesels unless going for silly power don't need any tweaks really. The cylinder is filled with air every cycle. You got a turbo compressing it. I do like MCM but their mythbusting has been mythbusted many times. E.g. leaf blowers can make boost and painting your intercooler black isn't always better.

Also thats the rule. More filtration means less flow. More flow means less filtration. It's not that paper is a better medium it's got smaller gaps. Try to breathe through your sleeve if wearing a t shirt. Now try to do it with a piece of paper.

Edited by Dblock
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The paper one has a much bigger surface area though.

If you pull the plastic end caps off the paper filter and stretch it out, you would see what I mean. The surface area is massive.

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it's very interesting isnt it, I have been reading that if the tdi breathes better it gets better mpg and runs a bit smoother.

don't know what to believe haha

hmmm. No idea about smoother, but can't see how a k and n would help mpg. You'd be better getting a remap.
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The paper one has a much bigger surface area though.

If you pull the plastic end caps off the paper filter and stretch it out, you would see what I mean. The surface area is massive.

I don't really get you? The caps that kinda locate it in the box?

I thought the whole point in those little zig zags on the k&n where for more surface area. I can't remember seeing them on the oem one.

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The standard paper one looks like this:

http://www.partsmonster.co.uk/ekmps/shops/stephenlawes/images/genuine-seat-arosa-6h-1.7sdi-1.4tdi-97-04-air-filter-14807-p.jpg

As you can see it's pleated, and has a lot more pleats. And therefore a much bigger surface area.

I have seen a photo before where someone stretched a paper one out and compared it with a K&N type one; the paper one was about 5 times bigger.

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This would be a really good experiment and probably kill the restrictive argument once and for all.

There is a possibility that the filter is over sized. It's not an argument. Panel filters are less restrictive. Speak to people who tune cars on dynos etc. it's physics more filtration = less flow. But again I don't know if the filter is the limiting factor.

I had a 106 1.5diesel I ran on veggie oil. It took 22ish seconds to 60. Wouldn't get there if it was pretty windy lol. But I changed the small filter and complicated airbox (I blame the airbox tbh) for a cheapy cone filter. The 0-60 dropped to about 18ish seconds. Now that was in summer vs winter and no compensation for wind as it made a massive difference in that car but it was peppier.

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  • 2 weeks later...

I've ran a K&N filter (same as the TDI) in my SDI for the past five years, and it doesn't make any difference to the MPG -still regularly get 60+ normal use -although it does make the car that bit more responsive, especially from the off and the SDI's weak spot of between 40-50mph.

Avoid the knock off renewal kits on eBay though, as some have the consistency and usability of strawberry sauce.

Edited by Hazy
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