Quote:
Originally Posted by AZFA20
It's not incorrect per se but rather a bad choice of words to decribe what I am guessing they meant. Low speed "profile" and high speed "profile" should have probably read low speed cam "timing" and high speed cam "timing". In layman terms this would essentially result in different flow characteristics at different speeds hence them using the term "profile". I am only going out on a limb here because I dont know who wrote this but it does sound like they may have understood what they meant but just didn't convey it correctly. The headers do smooth the graphs out but the cam timing does in fact have a role in the dip we see as they transition through cam phasing. In your defence I understand how you interpreted what was written to be incorrrect because there are cam systems out there that literally ramp from one side of the lobe to the other that do essentially have different "profiles". When it comes down to it all these parts work in unison and one change affects them all in some way regardless of how small it may be. The alternative header options allow the engine to exhale a little better which translates to a smoothed out area on a graph. If everyone really wants to combat the dip just force feed it with forced induction  |
The cam timing is variable at any RPM, not set to two different "speed" bands. If the dip was purely because of the cam timing, it would've been totally tuned out by now.
What you were describing is definitely two physical cam profiles, like VVTiL or VTEC. You'll never get behavior like that from variable timing alone.