Helix dictates the shift pattern....
A reverse angle serves two purposes, the lower(flatter) first angle keep rpms UP, which on a turbo sled makes for more spool/boost down low.
Think of riding your motorcycle and not upshifting early, but holding that gear til rpms raise.
The higher(steeper) finish angle allows the top speed rpms to remain in check, meaning the top speed rpms will be lower or NOT keep rising too far. This can come in very handy on a turbo, as they make so much power the top rpms typically need a TON more weight in tips of flyweights. Adding alot of tip weight into the primary, may help to keep top rpms down, but then they become so heavy the sled can feel laggy corner to corner, as the weights are too heavy to swing quickly. Lots more can be done with weights, but the reverse angle helix can aid the top end RPMS.
Typically reverse angle may ET slower, as it stalls the shift which stalls the forward motion of sled, however on a turbo, the additional spool/boost can be much higher to counteract this, so this is where good testing comes in back to back.
The Hurricane tunes, which are ALL early spool tunes, allow for progressive helix's to be run, while stock tunes or NON early spool tunes, truly need a reverse angle for best corner to corner snap.
Dan
