Bringing this up again. Must mean I've been back home for over twelve hours and have switched back to boat-think.
I was looking at the Accuski documentation and got the servo type from a picture listed there. A good servo, but there's better ones out there - faster, stronger, and most importantly, digital. Digital servos (never owned one myself) basically do two things: 1) allow better resolution and power by greatly reducing the pulsewidth of the power pulses (gets more power to the servomotor quicker, and allows changes in servomotor power to be effected quicker), and 2) some allow programming to vary the endpoints, travel rate, width of so-called deadband, and center point. Most of the latter points can be done mechanically, just by adjusting the length and mounting angle of the servo arm on the servo. We did that on ailerons to provide twice the up-travel than down travel and called it 'differential'. With the right amount of differential, there's little adverse yaw and little need for rudder inputs.
Obviously, I'm back to thinking of ways to improve Accuski's control response. The feedback loop (venturi/paddlewheel issue) is different altogether, and there might be a way around that (change the tach output of the Lexus into the same signal the domestic boats provide, then beg and plead with Accuski to make the firmware change to allow both tach and paddlewheel inputs to be used by the MDDC). BUT...like Pete said before, if the dash speedo is good enough for you to manually control speed, then the venturi should be good enough for speed control too (maybe marginally).
However, we're pretty sure that the control side is lacking as well, and that might be fixed easier (without having to rely on Accuski) by playing with linkage and servo. Unfortunately, I only know of one local Epic and it's not equipped, so I don't have any hardware to look at/play with.
I doubt the servo really needs to be stronger, but if you were going to upgrade the servo, you might as well upgrade the servo. Speed might be a good thing, and there are several analog servos that would offer both better speed, torque and resolution. When a digital servo sees a delta, the finer pulse widths allow more power to get to the servo quicker (reportedly). Combine a torque/speed upgrade with a digital upgrade, and we'd probably cut a decent chunk out of the lag. Not enough though.
Digital servos with programmable endpoints would allow the 'differential' I was referring to earlier. That also involves buying a programmer ($150) or finding someone with one, and I'd rather just do it mechanically. By playing with servo arms and possibly changing the servo, I can get more throw in the important part of the throttle travel.
THE MAIN QUESTION FOR YOU.....is how would you envision we would need to change the 'map'. If it's as simple as 'amplifying' what the current system asks for in the critical wakeboard speed range, I can do it mechanically. I'm not so concerned with the single-button pull-up - just want it to track better once at speed.
I've forgotten most of what I learned about damping and transfer functions, but what I'm trying to say is that a mechanical solution would change both sides of the ramp (apply more throttle to reduce a speed deficiency and cutting throttle harder to reduce an overspeed) equally. I can rig it to ask for much more throttle, but it will also chop the throttle harder than stock when needing to bleed speed. Would this just worsen things by making an oscillation bigger?
Do you think the fix is to change the map so that there is sort of a decay, like it not only puts its foot down harder, but also lets off the throttle slower. Not sure of an easy way to that mechanically.
How would you change control response?
