Identical wheels, a billet wheel will be heavier then a cast.
Less weight does mean faster spool up, if they are identical wheels.
Billet refers to being made out of "one piece" which can be steel, aluminum, etc...
Billet wheels are typically made to be stronger then cast wheels and come in different designs. That's the main benefit.
I beg to differ.... The billet wheels I am using are made from a Lightweight A2000 Alcoa Aluminum.
I have weighed bullseye billet wheels in the past that Are heavier than the cast version, which will hinder spool time.
The billet version of the WWG2 for the Stock SD turbos is MUCH lighter than the cast version.
This is my point. YOUR billet wheel weighing less then the cast version of the wheel is a nice benefit that was not outlined by YOU (that I saw). The NORM as your stated experience supports is that identical wheels (as in design) is that the cast wheels are lighter then the billet wheels. The internet hooplah about billet wheels is that "they're so much lighter, they're shiney, they flow so much more air" is kind of annoying. In this case, your product minimally is lighter then it's cast counterpart, which is the exception and good news. Changing nothing else, the wheel should be stronger and spool faster. I don't know your product enough to comment about its other benefits/negatives but I personally shake my head when people smack the "it's billet so it'll spool faster" comment out there.
Everyone will say something different... The turbo builder i have talked to ALL say the Billet aluminum wheel size for size is lighter and flows more air the the stranded cast wheel... A lot has to do with the design of the wheel... Hence i said this...
Sorry for the derail NRHX2009!! I will stop here now.... I like what you are doing... Keep it up!!!
Once again, it comes down to identical wheels so we are comparing apples to apples then to what actually constitutes the word "billet". IE: a billet wheel could be made out of steel, aluminum, whatever (metal) for all I care...
Without a wheel re-design (ie: identical wheels) the flow should be more or less the same, spool up will be determined by the weight (ie: identical wheels), the main benefit as I stated in my original post is the fact the billet wheel should be stronger (no matter the *common* materials used) vs cast.
PS, I like what you're doing, and I've bought a few chargers off of you prior to you becoming a sponsor. Would be nice to run a 66mm in the stock classes so we are finally closer to the 65mm stock dmax turbos....