Quote:
Originally Posted by AZFA20
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.
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I'm not confused about how variable timing works in the slightest... but now you've gone and contradicted yourself.
At first you said it's because there are two cam timing "profiles" (not cam profiles), one for lower engine speeds and one for higher engine speeds which have the ability to change flow characteristics. Now you're saying it's load based (as far as I know, the maps are actually speed and load based) and can't change flow characteristics.
In any case, the cam timing is not to blame for the torque dip, it's all about airflow into and out of the engine. Since Nameless actually totally reversed the dip (they got like 40wtq gain at the worst part of the stock dip) with their long tube header, it's safe to say the header is playing a big part in it.