TheMadReason

I am now the proud owner of a 1.8 4000s with mechanical fuel injection. Recently I changed the oil, and I realized that I must dismantle the fuel system to change the air filter! My father came up with a cunning plan; we will get a cone filter and put it on the end of the hose leading from the air box, and I will only need to change the main air filter if the fuel system is being tuned up. Will this mod affect the mechanical fuel injection system? Will I throw off my fuel mixtures or anything like that?

Rogviler

I would think you'll be okay if the regular filter is still in place as far as air metering. It may or may not cause more restriction in the system, but you'll just have to see how it feels.

Where you get into trouble is trying to put a cone filter instead of the stock one; the MAF does not like the way the air behaves with those. Many have gone that way and quickly switched back because the car will not run right. You need the air going straight in with no turbulance or swirling.

I personally like this mod (cut on the red line):



Not everyone is comfortable cutting a piece off their car, but the fact that I can change the air filter in seconds means that I'll actually do it and that's worth more to the engine than that little piece is to the car. Plus I'm convinced that Audi designed that little rounded corner just to be funny.

Either way, let us know how it works out.

-Rog

socalclimber

When I was wrenching on thse cars, I always thought it was a bitch to get at the air filter. But never went so far as to make the mod Rog is talking about (I'm a stock factory sort of guy when it comes to my own cars).

I never had to disasemble the fuel components, but I think it's easier if you disconnect black rubber intake boot from air flow sensor housing, so you can move whole air flow sensor housing assembly a bit to make it easier to "snake" new filter in place. It's definitely a contortionist manuever!

I vote for keeping stock paper element and taking your time when you need to change it.

TheMadReason

Thanks for the advice. I really hate to cut on the sheet metal. I think that I will try to put a second cone filter on the car. I live in West Texas on the fringes of the Chihuahuan Desert, and the sand can blow in sometimes. I really need to change the filter at every oil change during dirt season. I don't mind loosing a few horsepower. I am hopeing that one of those really nice cones will not restrict any more than the long stock intake hose, which snakes into the right front fender.

TheMadReason

Here is a neat solution. Thanks for the advice. The fuel lines are very flexible, and I found a way to change the air filter without removing the rubber intake boot. I took out the passanger side headlight, and I switched to a WIX filter (42170). The WIX was only 1 1/4" tall. The thin little Wix filter slipped right through the headlight hole and into the narrow airbox opening. FYI, the big fat FRAMs are more like 2 1/4" tall. There is no way that the big fram filters can do this trick. You need a really short filter. Changing the filter this way was a breeze, but when I do need to really open up the airbox to clean it, what is the best way to get the boot off? I had a really hard time removing it, and I gave up because I did not want to break anything.

TheMadReason

Also, I noticed that the old filter was stained with oil. I peered up into the MAF, and I noticed some fluid dripping down the control arm of the air flow sensor. Should I freak out about this? Is this normal?

socalclimber

BTW, it's not a MAF (mass air flow sensor), but a fuel distributor. Sometimes, they can seep a bit of fuel past the o-ring at the base, and that's what you're seeing.

Don't worry about it. If it gets worse, system pressure can drop because of the leak when engine is off. If you aren't having any hard starting issues, it's not a problem.

Glad you got a thin air filter to work for you.