While we are on the topic of speed limiters, let me explain
HOW THESE GADGETS WORK AND WHY YOU CAN STILL GOVE ABOVE THE
SPEED LIMIT EVEN WHEN THESE GADGETS ARE WORKING IN PERFECT
CONDITION.
Sorry for the caps, I'm just super irritated by somebody.
As explained to The_Bus_Guide on our Hougang Central outing, speed
limiters simply cut off fuel supply when it reaches a set limit, in
this case 60km/h. There is no physical/mechanical limiter that, die
die, disallows a vehicle to go above 60km/h.
When the fuel is cut off, there are still remaining fuel in the
engine and the bus can continue accelerating. Eventually, the the
bus will slow down to approximately 60km/h and the fuel supply will
be returned. And if I'm not wrong, the 60km/h is measured by the
RPM of the engine and not by the actual rotation of the driving
axle.
In the case of automatic vehicles, the engine is not "physically"
connected to the driving axle, but instead does through a torque
converter, which is a chamber of oils linking the engine axle and
the wheel axle. This means, the wheel axle (before gear box,
connected to torque converter) can still be RPMing higher than the
engine, so when engine "slows down to 60km/h", the bus still moves
at "70km/h" or so - even higher if the bus is moving
downhill.
This means, fuel can still be supplied to the engine even if the
bus is moving higher than 60km/h (as long engine is running at
below "60km/h"). This accounts for the reason why buses and other
limited vehicles can still go higher than 60km/h even when the
speed limiter is set at 60km/h. I would say this would result in a
discrepancy of about 5 - 10km/h. So buses could be travelling at a
max of 70km/h or so.
Hope this clears the topic on speed limiters. Please note that this
information is from what I have gathered so far and not from a
horses' mouth (eg. Siemens or other speed limiter equipment
manufacters).
Others with more technical/engineering knowledge, please feel free
to contribute. I'm just a computer science undergrad who happens to
be interested in mechanical engineering.