Quote:
Originally Posted by wparsons
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.
|
I think you may be confused on how AVCS works. The cams are advanced and retarded based on load levels and the reason you see the same dips on everyone's dyno is because they are all essentially recreating a constant rather than a variable. The constant is WOT on a dyno (100% load). Yes the cams can advance and retard variably through the RPM based on load but if load is the constant @ 100% on a dyno while pulling WOT the curves will look the same and essentially in the same spot because the cams have to transition through phasing at some point. Tuning advance and retard in the variable cam timing only shifts the same flow characteristics because without a true variable cam lobe profile there is no way to change the way a cam physically opens a valve, only when it opens and closes it. The only true way to get rid of this would be to disable the cam timing and put another set of cams in with a profile that will achieve whatever goals you may have. Cam timing can be tuned for sure but really all you are doing is shifting the same exact flow characteristics around not physically changing them via lift and duration. This is great for tuning emissions and power based on load which in normal driving circumstances is in fact variable but not so much on a dyno @ WOT. Either way I agree with you that this is only part of what is happening and that is why we see a smoothing after a header install. Its still there its just not as apparent.