Asiparks

I've seen a couple of threads here mentioning the K&N, I believe MP4.2+6.0 stated it might not be maf friendly, but I wondered how many of you have popped one in. I have had one in my D2 for around 50K with no apparent ill effects, ( but I'm careful with cleaning and re-oiling)...

so what's the concensus ?

cheers

RoninWheels

i cant say 100% if it is maf friendly or not... but many people that have tried it, at least when i was still at the dealer had maf issues. They could have used to much oil but i can't say. for the chance of having a maf issue.. skip on the k&n

bac2h

What's worse than appalling? <lol>

Asiparks

I'm sensing some discouragement, then....

MP4.2+6.0

And I've seen the oil (it's red in color and hard to miss) downstream in the intake tract. Since Audi eventually did a service action on A6 4.2 MAF's, I later got my money back for the replacement at about 40K miles.

I used them back to the C1 (on top of the Weber 32/36 two barrel), but once MAF's came in, I think it's a no go. Lots of experience oiling them too, including even overnight leaving it out to weep any extra. On the regular (not K&N) panel filters, if you buy carefully some of the good German brands have more pleats than others too, that in theory can yield more surface area. I also took to just blowing out the filter at oil changes with air to keep it cleaner and better flowing.

On my current D3 with the big canister filters, I don't think it is the arguable choke point it was with the older panel filter design. When used on a 4.2 it was really not much different in dimension than my 2.2 C3 inline 5 with 115 stock HP before mods. On the A6 body, the dual air boxes on the C5 RS6 as well as the air bypass used on the C6 S6 (another line plumbed into the air box) where both clues there was some flow restriction in that style of air box.

Net, it's an idea from a bygone era.

MP4.2+6.0

instead of the K&N, look at the air box intake. You have to be into mods and willing to cut into the air box. Older off warranty cars are more the candidates here.

I don't know the details of an early D3 4.2 set up, but look at the ducting leading into the air box. From experience that can be a choke point. It can be an awkward tight turn type molded plastic or rubber piece to deal with snaking around stuff from the front of the car back to the air box--more restrictive than the post-air box ducting typically.

The C5 S6 added bypass to flow more air to the box helped confirm the theory this was a restriction for me. I would guess the D2 S8 might have had something similar but haven't seen it up close. Don't make the mistake of just opening up the air box, punching holes to suck in underhood air or substituting a cone filter. Those options will increase the intake sound and give more sense of power, but likely will actually reduce power a fair amount with the hot underhood air.

Instead, you could look at installing an auxiliary duct from the box up to behind the grill somewhere. A few C5'ers played with that over the years. Using PVC fittings at the air box, you could get a take off point started in whatever size can be fit. Note the older S set up actually used a vacuum control valve for this. I also wouldn't route it very low to avoid water ingress risks.

One or two insulated the ducting too (typically the turbo ones), but that looked either to Jetsons or NASCAR for me--really obvious under the hood and pretty home made looking.

Asiparks

excellent stuff ! Thanks !

ernestolopez

Alright,So for someone that wants to replace the OEM air filter with a better unit,which is the best?-Without mods?

Is their a chart where all the manufacturers are listed by Carmake and performance ratings?

Thats what I want to see.Honest Numbers!? Anyone?

MP4.2+6.0

buy the filters with more folded pleats. It varies some by manufacturer, and the ones with more pleats have more effective filter surface area. From C5 experience, I've seen that difference. Have not seen any hard data on air flow though.

Or, plan B, change the filter every 10K miles. Then no worries at all except some $. Clean filters obviously run better than dirtier ones.