4 ms·

That sounds like a nightmare. What was the rationale for having a split control system like that? If preventing snaps of wide open throttle were the goal, then

That sounds like a nightmare. What was the rationale for having a split control system like that? If preventing snaps of wide open throttle were the goal, then having the butterflies both servo controlled would accomplish that right? Wait, when you say "downstream" do you mean the butterflies were in series on the same intake path? I'm trying to visualize what a small time delay and rate mismatch would look like here.

pengaru 5y ago
> when you say "downstream" do you mean the butterflies were in series on the same intake path? Yes, in series, literally redundant throttle plates on a common set of ITB runners: \ / \ / \ / \ / | | | | | | | | |/|-|/|-|/|-|/|-cable/rider-operated | | | | | | | | |/|-|/|-|/|-|/|-servo/ecu-operated | | | | | | | | * * * *
- function_seven 5y ago
  Top notch ASCII art there, thanks. Yeah, I'm no combustion engineer or anything, but I just can't see what would motivate a system like that. I suppose the rider has the ability to snap the throttle shut instantly, but you could achieve the same with a limit plate on the same set of butterflies that are servo-controlled. So when you open it up, you're both electonically telling the ECU what you want, and mechanically allowing the range of motion. When you snap the throttle shut, you're forcing the intakes closed. Computer gets to limit the rate of opening and coordinate the fuel, rider still gets to close it as fast as they please.
  - pengaru 5y ago
    What you're describing would still suffer from the same "catch-up" problem though, assuming the same control software. It's worth noting later versions of YCC-T are servo-actuated using a single throttle shaft. This early version was probably just something slapped on at the last minute using off-the-shelf components, and they didn't refine the control software enough to do things like at least resync the logical servo position with the cable throttle position when the rider has started closing the throttle from an overshoot position. It was just a very naive rate-limiting filter of sorts where the servo is continuously chasing the actual throttle's instantaneous position. The experience occasionally resembled a laggy high boost turbo car where tq keeps increasing despite a shrinking throttle open %. Kind of amusing in a car, Tesla FSD levels of idiotic on a ~1000hp/ton bike.

pengaru 5y ago

> when you say "downstream" do you mean the butterflies were in series on the same intake path? Yes, in series, literally redundant throttle plates on a common set of ITB runners: \ / \ / \ / \ / | | | | | | | | |/|-|/|-|/|-|/|-cable/rider-operated | | | | | | | | |/|-|/|-|/|-|/|-servo/ecu-operated | | | | | | | | * * * *

function_seven 5y ago
Top notch ASCII art there, thanks. Yeah, I'm no combustion engineer or anything, but I just can't see what would motivate a system like that. I suppose the rider has the ability to snap the throttle shut instantly, but you could achieve the same with a limit plate on the same set of butterflies that are servo-controlled. So when you open it up, you're both electonically telling the ECU what you want, and mechanically allowing the range of motion. When you snap the throttle shut, you're forcing the intakes closed. Computer gets to limit the rate of opening and coordinate the fuel, rider still gets to close it as fast as they please.
- pengaru 5y ago
  What you're describing would still suffer from the same "catch-up" problem though, assuming the same control software. It's worth noting later versions of YCC-T are servo-actuated using a single throttle shaft. This early version was probably just something slapped on at the last minute using off-the-shelf components, and they didn't refine the control software enough to do things like at least resync the logical servo position with the cable throttle position when the rider has started closing the throttle from an overshoot position. It was just a very naive rate-limiting filter of sorts where the servo is continuously chasing the actual throttle's instantaneous position. The experience occasionally resembled a laggy high boost turbo car where tq keeps increasing despite a shrinking throttle open %. Kind of amusing in a car, Tesla FSD levels of idiotic on a ~1000hp/ton bike.