Originally Posted by
Hemituna
The dodge system is still a push rod, cam under head setup with ONE camshaft with both intake and exhaust "cams" on one stick, you cant move the intake side without the exhaust side moving too, its one hunk of metal. So if you tell the ECU advance the intake side 14 degrees, the exhaust side gets RETARDED by the same exact amount.
^^
300c is correct in that there is 1 cam...both intake and exhaust lobes are attached to this 1 stick...however if you advance the intake 5 degs, logic dictates that the exhaust advances 5 degs too.
The confusing part is that the cam lobe centreline NUMBERS which go in opposite directions. This is because of the way this is measured relative to TDC.
Take for example a stock 6.4L or Hellcat cam. Both have 120.5 LSA. When at 120.5 ICL, this cam is "straight up"...neither advanced or retarded, both lobes are at 120.5 CL
Advance the cam 5 degrees, and Intake CL is now 115.5 degs, while exhaust is 125.5 degs...seems strange and takes a while to get your head around it.
That is why at idle when it is fully advanced it will show exhaust 134ish (120.5 +14) and intake 106.5ish (120.5 -14)
Try playing around with a cam calculator and you will see what I mean.
When you change cams, change LSA, and change the advance ground into the cam all these numbers change.
BUT, the PCM doesnt know that a change has been made.
So you need to work out where the cam lobes actually ARE while being forced to retain the PCM's original number system.
Just a matter of working backwards really...but you need to understand where both lobes are to get a good result.
Advance down low and retard up top are kinda the principles, but it is not always as easy as that tho.
Many other factors come into play like boost level, LSA and where you really want the intake/exhaust lobe to be.
If you look at hellcat/demon tables, the cam is most retarded at low rpm/high load and actually is slightly more advanced as rpm increases etc...