In Reply to: Plse tell me why b4 I mod mine! posted by moots on July 31, 2001 at 22:10:03:
I must warn you that some people think that the K&N type filters do not filter the air as good as the stock filter and might harm your engine.
Rob Levinson from UUC Motorwerks says that "it is really doing every E34 owner a disservice for three reasons:
• First, conclusive tests from independent labs show that K&N filters, no matter how well-oiled and cleaned, let through huge amounts of large particulate that damages engines. Oil analysis shows 5x as much silicate contamination. Additionally, the oil from these filters tends to muck up the MAF and cause an engine-damaging lean-run condition.
• Second, an open element filter like that sucks in hot underhood air and subjects the filter to "fan wash", the swirl that creates a vacuum effect. On the E36 M3, we measure a 15hp loss from open cone filters.
• Third, the E34 airbox is designed with an integral velocity-stack style venturi at the opening. Running one of these engines on a dyno, you can cause a 5hp drop just from putting your finger on the stack lip. Removing that airbox undoes a lot of good BMW engineering. Yes, these filters make a "really cool" noise... but noise does not equal power. Stick with a stock paper element in the factory airbox, you're not getting any more power with a K&N garbage-filter, just damaging your motor."