Yep, you are absolutely correct about the Rostra's response being non-linear but it does not really matter. The useful range of throttle movement on a CC is so small that it does not change appreciably over that travel. As the cable attaches at approx. 90 degrees on the throttle arm, and the throttle's movement is only a few degrees, we can disregard any non- linearity in the loop closure behavior and treat it as if it were linear- really it will be close enough. Besides all of that, even if the CC's attachment were rotary, the response of the engine to throttle movement itself in non- linear anyway; opening the throttle 1/8 of the way allows more than 1/8 of the total airflow or total power, at least at low engine RPM, so whichever way you want to measure linearity.... it isn't linear. Further, as the throttle bodies and throttle plates are round, the entire system becomes even more non- linear and is less and less sensitive to throttle movement (in degrees) as the throttle is opened further and further. Put another way, the last 1/8 of the throttle travel has very little impact on power output compared with the first 1/8 throttle travel.
The MC Cruise is considerably different than a Rostra or Audiovox but only in execution, the principle is the same. The other major difference is that the Rostra is a displacement system (based on position) while the MC Cruise and Audiovox are force based systems (based on force applied- the displacement of the throttle is a secondary function of that force). The MC Cruise actually uses an Audiovox or Audiovox copy actuator and creates a new end point for the throttle cables on the motorcycle. So instead of the throttle cables attaching to the throttle plate shaft, they are moved to attach to the MC Cruise actuator and in turn the actuator has a pair of cables that go to the throttle plate shaft. Functionally it is identical to the Audiovox system- as the vehicle speed pulses decrease per unit time, there is more and more force applied to the throttle to increase the pulse rate. As to if the MC Cruise system is rotary or linear, it is rotary in nature although because of the above stated reasons I do not believe that matters.
Brian
Well, as usual Brian, that all makes sense and I most likely should just forget about it and save me some work. However I just have got to try my theory out, eventually.
Let me make sure that I have got the main facts correct. The McCruise and the Audiovox both have the same or same type of actuator, however the Audiovox is attached linearly (like the Rostra usually is). The McCruise actuator is actually hooked up directly to the throttle pulley (throttle plate shaft) and acts rotationally? If I've got that right
then I guess what I'm saying is, of the three only one is hooked up to act rotationally, and it is the only one of the three that I haven't
heard complaints about (except when they cough up the money to buy it
) I think what I just typed is known as an anecdotal argument and doesn't really hold water to your well thought out response. However it's enough for me to cling to.
Now about the non-linear response of the engine to throttle movement, since that would apply to an auto as well, would it be out of the question to think that the designers have an algorithm in there to compensate for that?
Anyway, it may all have to do with cable slack like you said, since in my situation it seems to only happen just after I have opened the throttle a lot more than what the Rostra was doing. Maybe after I hook up my "Engaged" LED I'll be better informed as to just when it gives up trying.
Overall I still gotta say, I love my Rostra. It's made some long (for me) trips much easier and no doubt saved me from some speeding tickets.
When I called Rostra (last summer) they were helpful, however I didn't volunteer the vehicle information until I was asked. The response was a very audible Al Gore like sigh followed by continued help but with less enthusiasm. I think it's time to tell them that we're installing them in manual transmission Honda Civics. (
Pinocchio emoticon goes here)