K&N air filter
08-06-2011, 11:53 AM
#12
I fried my MAF in my Turbo Diesel Ford Excursion in less than 36k miles. Fixed under warranty. Running an Air-Raid (K&N like) re-chargable filter. Still using it just not oiling it up as much. Haven't had a problem since and it's been 4 or so years.
This being said, I did use MSDS filters in my 08 S6 with no problems on the MAF or in any other area, but I am sticking to factory filters on my 08 S8.
YMMV.
This being said, I did use MSDS filters in my 08 S6 with no problems on the MAF or in any other area, but I am sticking to factory filters on my 08 S8.
YMMV.
08-06-2011, 02:57 PM
#13
AudiWorld Super User
One thing while deciding about K&N anyone should do: take stopwatch and measure 0-60 time, take filter out and measure it again (won`t hurt engine for that short time). No difference and so crispy response. Unfortunately it is just sound. Don`t forget to`put filter back. OEM one, by all means. 
08-06-2011, 09:17 PM
#14
AudiWorld Super User
Several things I didn't mention before relevant to air filters:
1. I have never seen hard data--meaning dyno--showing the non stock filters do anything meaningful. Some folks use them for sound, but that's more the cone stuff and often another performance subtract if it doesn't draw cold air from up front rather than hot under hood air.
2. To not just be rain clouds on the whole subject, on what do I do to help the air intake side.
a. Well, since swearing off the K&N's for MAF motors, any time I have the airbox open for some reason, or otherwise usually at oil change cycles in between the major (filters and plugs) service intervals, I just pull out the filter and blow it clean (gently) with an air hose. The cars do build up a fair mount of stuff. The basic free air hose treatment probably cleans up 90% of it. The W12's and S8's have the dual boxes, and though the flow through each should be less than the single box 4.2 type set up (either 3.0 or 2.6 liters per filter for the other motors), certainly I find a good amount of stuff in the dual boxes if I let it go to the mid point in the normal filter change cycle. On my C5 4.2, definitely some dirt and grit (and a few leaves and such) by 10-15K miles.
b. From my panel filter experience with the A6 4.2, there is a lot of variance in filter quality out there, particularly the number of pleats and sometimes the quality of the glue at the sides. Bottom line, consistently the name brand German filters (Mann, etc.) have shown better in construction and pleat count. Higher pleat count gives you more filtering surface area and at least in theory a bit more flow capacity. By contrast, some of the other car OEM filters I have dealt with (like Toyota) may not even have pleats, but rather just some occasional waves in the surface area for reinforcement; that's a definite recipe for faster clogging/less effective surface area.
3. For you guys still on the air intake performance improvement path, the old 4.2 S6 and S8 are relevant data points. So how did they up the horsepower on those as far as the intake side tweaking (putting aside things like exhaust, cams, engine map, etc.)? First, basically all the added power was way up in the revs, above the normal 4.2 redline. Then as they moved up the redline, on the intake side what they did NOT do was switch to a bigger filter or air box. That's always been a real clue for me of where the 4.2 bottlenecks are and aren't. What they did do is use a modified intake with two phases instead of three, and add an auxiliary hose intake to the air box itself with a flap that only opened at higher RPMs. The last one to me is the interesting part--it suggests there was a flow restriction coming into the air box from the ducting. I own a C5 4.2 and can definitely sense that--kind of a tortured path down to the box with a molded tube that was bent in suboptimal ways to get it to fit underhood with the V8. Don't know the D3 4.2 air box set up, but might be something to look at as a mod. On the W12 and presumably the S8, it's literally a straight shot to the twin air boxes and they sit relatively far forward so the air path is short.
4. The no bones about it, "do not try this one at home" mod--some of the 2.7T S4 (or C5) guys would take the screens out of the MAF to improve the flow. (At least on the C5), the MAF has a plastic grid type screen that I guess is used to improve the directionality of the airflow passing the sensor, plus a fine mesh screen. The two together do gum up the airflow. If you have the MAF out of the car, the screens are very obvious right in the main bore. BUT, having played with it on the C5, first the screens are not easily removed, especially without damage. It's possible, but takes some time with an Exacto knife. More importantly the change was indeed pretty radical. The motor became very rev happy actually. Problem was at least in that car the tranny TCU just couldn't keep with it or couldn't process the reading (the MAF reading is processed by the TCU too) and thus the car could be overrev'ed way too easily before the tranny could make the shift. I never VAG COM'ed the flow, but the butt dyno said the change was obvious. If you had a manual tranny (as you might on an old 2.7T S4) the shift issue wouldn't matter, but it was a clear no go on the 4.2 to avoid over rev damage risk. Indirectly though, it was suggesting things other than the filter--in this case the core of the plumbing after the air box on the way to the intake--were more critical.
Coming back around to the filter, I pass all this along to say that I have played with the 4.2 intake system a fair amount and looked at what has been done in things like the prior S 4.2's. The filter was actually a relative constant in design and general size for a long time, and the factory tweaks were instead in other parts of the overall intake system.
2. To not just be rain clouds on the whole subject, on what do I do to help the air intake side.
a. Well, since swearing off the K&N's for MAF motors, any time I have the airbox open for some reason, or otherwise usually at oil change cycles in between the major (filters and plugs) service intervals, I just pull out the filter and blow it clean (gently) with an air hose. The cars do build up a fair mount of stuff. The basic free air hose treatment probably cleans up 90% of it. The W12's and S8's have the dual boxes, and though the flow through each should be less than the single box 4.2 type set up (either 3.0 or 2.6 liters per filter for the other motors), certainly I find a good amount of stuff in the dual boxes if I let it go to the mid point in the normal filter change cycle. On my C5 4.2, definitely some dirt and grit (and a few leaves and such) by 10-15K miles.
b. From my panel filter experience with the A6 4.2, there is a lot of variance in filter quality out there, particularly the number of pleats and sometimes the quality of the glue at the sides. Bottom line, consistently the name brand German filters (Mann, etc.) have shown better in construction and pleat count. Higher pleat count gives you more filtering surface area and at least in theory a bit more flow capacity. By contrast, some of the other car OEM filters I have dealt with (like Toyota) may not even have pleats, but rather just some occasional waves in the surface area for reinforcement; that's a definite recipe for faster clogging/less effective surface area.
3. For you guys still on the air intake performance improvement path, the old 4.2 S6 and S8 are relevant data points. So how did they up the horsepower on those as far as the intake side tweaking (putting aside things like exhaust, cams, engine map, etc.)? First, basically all the added power was way up in the revs, above the normal 4.2 redline. Then as they moved up the redline, on the intake side what they did NOT do was switch to a bigger filter or air box. That's always been a real clue for me of where the 4.2 bottlenecks are and aren't. What they did do is use a modified intake with two phases instead of three, and add an auxiliary hose intake to the air box itself with a flap that only opened at higher RPMs. The last one to me is the interesting part--it suggests there was a flow restriction coming into the air box from the ducting. I own a C5 4.2 and can definitely sense that--kind of a tortured path down to the box with a molded tube that was bent in suboptimal ways to get it to fit underhood with the V8. Don't know the D3 4.2 air box set up, but might be something to look at as a mod. On the W12 and presumably the S8, it's literally a straight shot to the twin air boxes and they sit relatively far forward so the air path is short.
4. The no bones about it, "do not try this one at home" mod--some of the 2.7T S4 (or C5) guys would take the screens out of the MAF to improve the flow. (At least on the C5), the MAF has a plastic grid type screen that I guess is used to improve the directionality of the airflow passing the sensor, plus a fine mesh screen. The two together do gum up the airflow. If you have the MAF out of the car, the screens are very obvious right in the main bore. BUT, having played with it on the C5, first the screens are not easily removed, especially without damage. It's possible, but takes some time with an Exacto knife. More importantly the change was indeed pretty radical. The motor became very rev happy actually. Problem was at least in that car the tranny TCU just couldn't keep with it or couldn't process the reading (the MAF reading is processed by the TCU too) and thus the car could be overrev'ed way too easily before the tranny could make the shift. I never VAG COM'ed the flow, but the butt dyno said the change was obvious. If you had a manual tranny (as you might on an old 2.7T S4) the shift issue wouldn't matter, but it was a clear no go on the 4.2 to avoid over rev damage risk. Indirectly though, it was suggesting things other than the filter--in this case the core of the plumbing after the air box on the way to the intake--were more critical.
Coming back around to the filter, I pass all this along to say that I have played with the 4.2 intake system a fair amount and looked at what has been done in things like the prior S 4.2's. The filter was actually a relative constant in design and general size for a long time, and the factory tweaks were instead in other parts of the overall intake system.
Last edited by MP4.2+6.0; 08-06-2011 at 09:36 PM.
08-07-2011, 11:28 AM
#16
AudiWorld Member
Does anyone know the purpose of the air pump or its functional operation? I have not had a car that had one of these before. Is it always on creating a back pressure in the air intake, or does it come on under acceleration to add more air? Is it like a mini supercharger? Does it have a variable speed?
08-07-2011, 12:37 PM
#17
AudiWorld Super User
Emissions control, not performance
Push some air into the exhaust system in front of the catalytic converters to cause them to light off earlier. Light off meaning reach operating temps. so the intended catalytic process can function. Emissions standards have tightened again, particularly in the last 5-7 years, and cold start emissions were among the biggest areas left to squeeze out improvements. Moving the converters in closer in to the engine and accelerating the process by providing some free air (and perhaps richening the mixture) are basics of how it's commonly done. Also intentionally stepping up the cold idle speed and delaying the shift from first to second. The air pump stuff, stepped up idle, delayed shift and delayed cold shift from first are actually all in my 2000 4.2, but the converters have moved closer in and become more numerous.
Air pumps have actually been around since at least the early 70's (particularly on Calif. smogged cars) , but they were clunky, heavy and accessory belt driven. Often found on old American iron smog choked V8's from the mid 70's. Back then they were seen as a HP and gas mileage subtract. No longer so, but they aren't a performance booster in typical configurations AFAIK.
Air pumps have actually been around since at least the early 70's (particularly on Calif. smogged cars) , but they were clunky, heavy and accessory belt driven. Often found on old American iron smog choked V8's from the mid 70's. Back then they were seen as a HP and gas mileage subtract. No longer so, but they aren't a performance booster in typical configurations AFAIK.
Last edited by MP4.2+6.0; 08-07-2011 at 12:45 PM.
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