Air Cleaner mod?

[binarycortex]

After talking with a friend of my I decided to do something about my air cleaner. I should have replaced it a long time ago but economically times are tough right now and my engine was still running so it doesn't need to be replaced. My friend said he just "hoovers" his after a while, so then I thought "well it couldn't hurt". Now I have read several places that have said that a new air cleaner (or cleaned out in my case) wont help MPG, but it will help acceleration.

Originally Posted by http://www.fueleconomy.gov/feg/maintain.shtml

A new study shows that replacing a clogged air filter on cars with fuel-injected, computer-controlled gasoline engines does not improve fuel economy but it can improve acceleration time by around 6 to 11 percent.

I believe this conclusion is partially incorrect. It's true that newer FI vehicles will maintain a correct air/fuel ratio but if you still use a lot of throttle you wont get any MPG increase. The reason for the acceleration increase is that the engine can breathe easier which eliminates pumping losses. When you eliminate pumping losses you get more HP which means you can use less throttle to accelerate which means more MPG.

The method to my madness:
I took the top off of my stock air cleaner box. Pulled out the air cleaner. There was some loose dirt on it but it didn't look too bad other than being slightly yellowish. So I took out the shop vac and vacuumed it clean. I tossed it on top of the trashcan so I could start to pack up the shop vac. But then I noticed a lot of dirt around the air cleaner. -=light bulb=- Ok at this point I realized I needed to beat the dirt out of it so that's what I did. I kept beating it and vacuuming up the dirt until no more dirt came out. Then I put everything back together.

Now for the results:
Driving in to work I have struggled to get over 34 mpg (SGII) for the morning trip in. Bad days its around 30 and average days its 32-33. On good days its in the 35's. Lately I have been using the TPS sensor on my SGII, which I believe is the Throttle Position Sensor, to monitor how deep I have my right foot in it. What feels like a 1cm foot movement is 2 or 3 on the TPS. Prior to the cleaning I was at 16 or so to accelerate, sometimes as low as 15 on the TPS but never lower. I noticed at one point I was at 14 and accelerating still, and interestingly enough at 14TPS and 40mph my instant FE was over 40mpg and going up. For the past week or so I have been able to consistently achieve 38 or better MPG every morning. Granted I rarely actually achieve the speed limit because it takes so long to accelerate up to the speed limit and I have a short drive, around 8.5 miles.

I hope this helps someone else out there who doesn't want to spend the money on a new air cleaner, especially when the current one is just fine.

[tasdrouille]

Cleaning the air filter is popular in south american countries. I have read a SAE paper testing simple methods to clean air filters. The most effective simple way to do it is tapping the filter a couple times on a flat surface so the dirt fall off, then blow air through the filter from the inside out with an air compressor. You have to be careful not to contaminate the clean side though.

[binarycortex]

Originally Posted by tasdrouille

Cleaning the air filter is popular in south american countries. I have read a SAE paper testing simple methods to clean air filters. The most effective simple way to do it is tapping the filter a couple times on a flat surface so the dirt fall off, then blow air through the filter from the inside out with an air compressor. You have to be careful not to contaminate the clean side though.

That's why I had a shop vac, to just suck the dirt up rather than blow it around. Also something I left out, since I live in the desert I had a layer of sand in the bottom of my air cleaner box which makes me think I should have cleaned this a while ago. I think this filter is the original, 113000+ miles on it. At the very least its got 103k on it since we got the beetle with about 10k miles on it.

[Piwoslaw]

I wish it was that easy for me: My air filter is way behind the engine. To get to it from the top, you have to take apart almost everything in the engine. You can get at it from below, but that requires removing the engine
I'm planning to move it up front, giving better access and a shorter intake air route with less bends. This will let me clean the filter more often.
I wonder what car companies say about vacuuming your filter?

[guudasitgets]

I used a K&N copy (chineese but it works better)

[binarycortex]

Originally Posted by Piwoslaw

I wish it was that easy for me: My air filter is way behind the engine. To get to it from the top, you have to take apart almost everything in the engine. You can get at it from below, but that requires removing the engine
I'm planning to move it up front, giving better access and a shorter intake air route with less bends. This will let me clean the filter more often.
I wonder what car companies say about vacuuming your filter?

Sounds like a Volkswagen New Beetle except for the getting at it from below part. Its the box connected to the tube in the upper right corner, and yes its under the body work. Also on the 1998 model you cant get a screwdriver straight down on to some of the screws that hold the top on because they are under the body work that is towards the rear of the car. Im not sure what year this beetle is but its close.

[tasdrouille]

Oh, haven't noticed you have a NB!

If the filter for the 2.0 is anything like the TDI, you CANNOT reuse the filter. Those have one time compressible seals. Once you open the airbox you have to change the filter. That's why filters on those are inspected by lifting the airbox to look from under.

[binarycortex]

Originally Posted by tasdrouille

Oh, haven't noticed you have a NB!

If the filter for the 2.0 is anything like the TDI, you CANNOT reuse the filter. Those have one time compressible seals. Once you open the airbox you have to change the filter. That's why filters on those are inspected by lifting the airbox to look from under.

Thats interesting, on the 2.0 gas engine in my NB the airbox is completely enclosed, there is a tube with a conical flare at the end coming in from the side that points to the wheel well. The edges of the air filter were orange, and either polyurethane or rubber.