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Originally Posted by edevlin
The cold air intake I got does use a N&K filter. When I was thinking about getting a cold air intake, I checked with the Porsche mechanic that has done work on my car. He warned about oil from the filters mucking up the sensors.
When I talked to the folks that installed the intake with the N & K filters, I tolk them that I was concerned about oil on the sensor. They said that was very rarely the problem (except for me?), that the only time they had seen a problem was when folks cleaned the filters, reoiled them and put way too much oil on them.
What is the role of the sensor on the intake? I am wondering how a malfunctioning sensor can mess up the operation of the car, or is it just an emissions sort of thing. I know just enough about this topic to be dangerous.
Ed
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Hi,
The MAF (Mass Air Flow Sensor) tells the ECU (
DME in Porsche Parlance) how much air is entering the engine so that the ECU can select an appropriate Fuel MAP to determine the Flow and Duration of the Fuel Injectors to get the proper A/F Mixture.
The MAF uses a thin piece of conductive film (think Mylar) which is heated by an electrical current. As more Air passes over this film, it takes away some of the heat generated by the current. The film posesses different resistance qualities at different temperatures and it is this difference in resistance which the ECU uses to determine the Mass of the Air passing over it - the resistance measure is directly proportional to the amount of Air flowing past it. If the Film becomes dirty or covered in Oil, it's ability to retain heat is increased and the resistance in the current is no longer a direct correlation to the amount of Air passing over it.
The resistance signal exceeds either the upper or lower pre-set limit and the ECU cannot get the A/F mixture right. It then goes into a pre-set default mode, sometimes referred to as
Limp Mode to both protect the engine and to keep emissions as low as possible. It cuts the amount of fuel being delivered in an attempt to establish the proper mixture. So, you're engine is being starved for fuel and this is what causes the drop in performance.
The K&N filter has been shown to be a problem on these cars. Not only that, but they're not really any better than the OEM on a stock engine. They clog in less time and they release a fine aerosol of Oil into the mix which settles on the MAF, causing the issue I described. Personally, I'd pitch it, because not only does it cause MAF problems, but it allows more dirt to pass into the engine increasing wear and necessitating a shorter Oil Change interval because much of this dirt gets retained in the Oil. Hope this helps...
Happy Motoring!... Jim'99