I'd like to get a little discussion going on the importance of proper air filter sizing and force inducting a vehicle. As some of you may be aware I've toasted 3 brand new turbonetics turbos all within a week of installing them on my car. I've worked with the manager at turbonetics tryin to diagnose the problem but everything checks out ie, oil feel/drain etc etc.
One thing I came across is an engineer discussing the importance of NOT creating a vacuum on the compressor side of the turbocharger in the intake tract which can be done by not having a large enough air filter. Doing so apparently pulls oil past the seal as well as can INSTANTLY SHATTER A COMPRESSOR WHEEL (which i experienced one time and the other two time the bushing wore out so bad the wheel rubbed the housing). So i got to thinking, I beleive my air filter may be causing all my whoas. It's nothing special, just a 3" cheapy cone filter from Discount Auto.
Then I found this...this is one area I NEVER researched when i built my turbo system for my car...
Formulas provided by K&N
1. Square inches of filter required for a motor = CID x Maximum RPM / 20839
2. CFM required for a 4 stroke motor = CID x Maximum RPM / 3456
3. CFM required for a 2 stroke motor = CID x Maximum RPM / 1728
4. CFM required for a turbocharged or supercharged motor = Pounds of Boost / 14.7
Add 1.0 to this answer. This relates to #2 and #3
Example: (CID x maximum RPM x #4 ) / 3456 or 1728
5. To find circumference of a circle multiply diameter by 3.1416
6. To find diameter of a circle multiply circumference by .31831
CFM Formulas for Filters
* Round: Diameter x Height x 6 x 3.14
* Flat Panel: Length x Width x 6
* Universal Round Taper: (Base + Top) / 2 = A
Take A x Length x 6 x 3.14
* Universal Round Straight: Diameter x Length x 6 x 3.14
So according to that I need approx 600 CFM ([146.5 cid x 7000 rpm x 2.02
bars according #4 plus 1.0] / 3456) to be passed through the filter at Full boost and redline conditions which happens to be about 200CFMs MORE than what i think Im running now supposing the cheapy filters flow AS GOOD AS a K&N with the same deminsions which i highly doubt they do.
What do you guys think? Could the $20 air filter have cause me to run through $2k worth of turbochargers?
EDIT: can someone verify my calculations on a 2.4 liter at 15psi?