Wierd, my race car (stock engine currently installed) has very slow cranking when starting.
Ruling out things, I've tried the following:
-Newer starter vs lightweight starter: no change (both work great on my nice 928)
-1050cca battery vs 850cca battery: no change
-new 2ga battery, ground straps, even directly to starter: no change.
I wouldn't suspect that the signal wire to "start" from the ignition relay could have any effect as all I feel it does is "signal" the starter to engage: the speed of the starter is related to its power, load, and voltage: all of which are covered by my "ruling out" above.
Any thoughts??