Establish Starting Point

As with any project, the first thing you should do is establish your goals.  This is going to require a bit of math, but we’re going to determine the ideal target crank hp gain for your vehicle.  A good rule of thumb is that every 10hp you make with a gas engine requires a pound of air per minute delievered into the intake manifold. For example, to transform a 100peak horsepower (php) naturally aspirated engine into a 200php turbo engine, you’re going to need a turbocharger capable of flowing 20lbs of air per minute at a realistic boost pressure. You’ll need to compute the basic engine airflow rate in CFM as follows:

Airflow=(cubic inches displacement * rpm * 0.5 * volumetric efficiency(V.E))/1728

The *0.5 is there because a four-stroke engine only breathe every other revolution, while 1728 converts cubic inches to cubic feet per minute

If you were to insert 83 percent for V.E for a typical 2.0L Honda engine’s 122CID * 7000 * 0.5 * .83/1728=247 CFM

At 83 degrees ambient temperature at sea level 247CFM converts to pounds/minute follows: lbs/min=CFM * .07

Therefore 247CFM * .07 = 17.29 lbs of air per minute.

Using this rule of thumb this 2.0l engine should produce approximately 173 NA HP.  Now let’s see what we could do with that number using a compressor. (more…)