Quote:
Originally Posted by
oldskool
Maybe I misunderstand your plan, but aren't the LNF and LE5 heads different because of the provisions for direct injection? Are you just developing on the LE5 and then moving over to the LNF once you can get the castings?
I must admit my general ignorance on the theory here. I know the idea on n/a applications is to get more airflow through the engine and increase high rpm power. Is it the same on t/c applications? Wouldn't a higher flowing head directly affect the boost threshold? Enlighten me, please!
Yea, they are two totally different heads and will therefore have different ports.
I havent gotten to the point yet where I have 2 heads next to one another to compare.
When it comes to forced induction,all things being equal, NA theory applies.
However all things are NOT equal so there are a few specific needs for forced induction.
A well designed port will have no more cross sectional area than is nessicary for maximum power.
That is calculated using a max velocity in the port at power peak. The idea situation is near equal velocity throught the cross sectional area( great port utilization), so drag losses are at a minimum and the entire column of air has as much INERTIA as possible. This is the real key to great overall power.
Enter the forced induction into the equation and our inertia increases dramtically as boost pressure rises. This somewhat changes the way our fluid (air) behaves.
To make a long story short, forced induction ports tend to be a little smaller than their NA counterparts to mix on/off boost performance.
Max performance FI ports will be very similar to their NA counterparts because off boost performance is of little concern.
The biggest differnce in NA vs FI setups is in the camshaft selection,specifically the lobe separation. A non-issue in our fully variable cams.
