Don't over oil it when you clean it. Too much oil will eventually get onto the tiny wire in the MAF and cook it, which will cause the MAF to fail.

 

I saw them for a BMW 325i, and the OEM German filter actually outflowed the K&N by a little, but they both were WAY better than the Fram replacement.

 

What on earth is wrong with the stock filter - it works well, its pretty cheap and it doesn't screw up your MAF no matter what... what kind of upgrade is this exactly...?

The K&N can be a bit cheaper to run - sure - as long as it doesn't eat your MAF... but is the price of filters really your biggest issue - given fuel, oil, tires, routine maintenance...

For me it wasn't a hard decision - especially after having to replace my MAF and throw away the K&N that the previous owner had been running.

Alan

 

No need to buy a K&N, anyplace that works on a lot of 928's will have one in the trash for free.

The pro K&N argument as I remember it is not that a new paper and freshly oiled K&N flow differently, but that a paper filter very quickly has the flow degraded by dirt, and the K&N reduction in flow is slower and not as much.

OTOH doesn't the factory air filter box leak like crazy?

 

a K&N filter came with the autothority chip/Hotwire MAF I installed on my 911 several years ago. seems like the last time I cleaned I may have over oiled it and contaminated the hot wire. still runs well under throttle, but irregular idle. and I could not get it to correct F/A mixture at idle. I have tried using MAF cleaner and helped some. I have sent a note to Autothority about servicing the unit, and am considering going back to my stock 'flap door' MAF depending on their reply.

 

I have used one for years, like others here have said, "just don't over oil", also I recently purchased a can of the CRC MAF cleaner.
I did the 325is first (test mule) then the 928, wow that stuff realy does clean the inside of MAF to a like new, you must follow the directions and REMOVE the MAF, don't just squrt some down the intake.

DaveK9

PS: can we talk about oil next ???

 

You must be new in these parts.
There is a basic motto when it comes to aftermarket automobile parts: "Different is Better"

 

Jeez. Not this thread again

In a previous thread Louie Ott posted dyno sheets. I have dyno sheets and may have posted them in the same thread.

Bottom line: a K&N has no statistically significant positive effect on the performance of a 928.

If I have time later, I'll see if I can dig up the threads, unless someone beats me to it.

 

Here's the post where Louie links dyno charts:

https://rennlist.com/forums/2579364-post27.html

And here's another long thread in which beating of the K&N horse starts around post #40.

https://rennlist.com/forums/928-foru...ance-mods.html

 

I won't run a K&N, because it can't filter dirt until it is clogged with dirt. I also had to replace the MAF on my 89 right after I got it. The car dynoed +10 HP with a new MAF and stock filter.

The paper filter is quite large, and has a lot of surface area. It flows well, but many like the K&N, so knock your self out. I have seen the dirt they let into the intake, and I live in an area where there can be fine dust on the roads, so I won't use them period, on any car. Nor will most of the mechanics in that I know, for the same reason. Earnest has seen the light, but I have seen the dirt.

 

I guess this has run its course (50/50 more or less).
Thanks to you all for the input, I appreciate it.
Brake pad light came on today and the exhaust started rattling, there goes the budget!
Great forum BTW.
Joe.

 

- Costs more.
- No more power.
- Lets more dirt thru.
- Can damage MAF.

We won't sell the K&N replacement for the stock filter.

 

Here are some comparative dyno runs I did years ago. Same car (90GT), same day, same dyno. Both filters were new. While the peak numbers aren't much different, notice how much rougher the dyno curves are with the K&N. The K&N may have the capability to flow more air than the stock filter, but the stock filter isn't undersized at all. A stock 928 air filter loses about 10hp on my 6.5L GT and a K&N filter loses 5 hp compared to no filter and that is at around 550 rwhp. I think the coarse screen pleats on the K&N, oriented crosswise to the air flow in from the sides, causes quite a bit of turbulence in the bottom part of the airbox. The close proximity to the MAF means turbulent air passing through the MAF and hence more variation in MAF output than with a stock filter. A rougher running engine, at least on the dyno. You probably wouldn't see this on a system where the K&N filter was located further from the MAF.
https://rennlist.com/forums/attachme...1&d=1248552972

 

If anyone has seen the stock paper filter side by side with the K&N, you'll notice that the k&N is flat, whereas the stock filter is bulged to one side.
The bulge side is installed facing up, away from the MAF. (Irrespective of which way the arrows on the stock filter points. Cause they made ones with arrows up and arrows pointing in airflow direction)

 

[QUOTE=Asiandude;6757163]Clean side facing up, dirty side facing toward MAF = not good. The workshops here are capable of this![/QUOTE

We do this all the time...it is the "self cleaning" air filter. The engine sucks all that pesky dirt out of the filter, with absolutely no work needed.

Kind of like turning your underwear inside out and wearing it again.