Sounds like a fairly innocuous task, but changing the air filter on your Porsche 911 is vital for maintaining performance and the longevity of your car. The air filter catches dust and debris and prevents it from entering the engine. So every 10,000 miles you should replace the filter for a new one. If your Porsche only comes out for the summer months and you don't register 10,000 a year, it is still wise to change the filter. After all, the cost of a new filter is insignificant compared to repairing a damaged Porsche engine.
This article covers the variations of air filters over the period 1965 to 1989.
One the earliest of the 911s the air filter in found on top of the carburettors, or if your 911 has it, the Mechanical Fuel Injection unit or the MFI as it is often referred to. To replace the air filter first just remove the long nose assembly from the air filter housing and replace it with new one. While your in there check the housing for dirt and give it a clean before putting the new filter in. Make sure you align the filter properly so the long nose cover fits back on properly.
The air filter assembly changed in design in 1973 when Porsche introduced for 911s, the Continuous Injection System (CIS). The air filter case is made of plastic and held in place with two rubber straps. Changing the air filter on these 911s couldn't easier. Simply detach the straps from the air filter box, and list out the old air filter. Wipe the inner surfaces of the air filter box to make sure they are clean and free from dust, and then place the new air filter in position. Now is a good time to check the condition of the original rubber straps and checks for signs of cracking or vulcanisation. Finally re-attach the rubber straps to complete the job.
In 1984 Porsche launched the 911 3.2 Carreras. The Carrera has a Motronic Fuel Injection system, which incorporates a square air filter that is mounted to the right side of the engine compartment in a black plastic air box assembly. The filter is to be found in the air box which is held on with steel spring clips. To replace the filter simply remove the spring clips, remove the old filter, clean the inside surfaces of the air box and then insert the new filter. Re-attach the spring clips and your done.
We can't discuss air filter replacement for your Porsche without giving mention to the availability of after market filters. There are a few things to consider when thinking about using an aftermarket air filter. First of all make sure they fit as snugly as the original. Make sure the filter material is of sufficient quality to filter our the dust and debris. You also need to ensure that the filter is not overly restrictive on air flow which will detrimentally effect power. There are many claims about increased horsepower from after market filters. Don't believe everything you read, many claims of increased horsepower are over stated to say the least. As a parting thought it's worth considering that the guys at Porsche spend a lot of money on R&D and engine development and you can't help thinking if there was a better design they would have adopted it.
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