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barryaz1 said:
I've noticed that it 'sounds' like the ICE is running more often than is shown on the Energy display (even after accounting for the 2-second update delay). There have been times when I've been sitting at a stop -- the Energy display shows everything off, yet it sounds like the ICE is running! Maybe I'm hearing something different. But there have been times when I've seen this happening, then the ICE really does shut off, and I get the characteristic slight shudder.

Anybody have a similar experience? Is there a foolproof way to tell if the ICE is really running?
To really tell if the engine is running (burning gasoline), you can get the CoastalETech Engine Run Indicator (which tells you if the fuel pump is on).

As for the Energy Display, it doesn't tell you the whole story as to why/if the gasoline engine is running... Here is a quote from my post at: ... sage/46643

Taking message/46323 as a base, here are the reasons for the gas engine to be on:

1. You started driving after your car has been sitting for a while.
The ICE will run to bring various emissions components up to proper
operating temperatures (like the catalytic converter, oxygen sensors,
oil, etc.) so that the Prius retains its SULEV status at all times
(but will sacrifice MPG to do so). Many short trips with a cool-down
in between them will give you lowered MPG because you're always in
the warm-up period (about the first 5-10min of driving), and
unfortunately many people equate these short trips with "city"
driving, even though this isn't what the EPA considers "city"
1 - Will NOT show up on the Energy Monitor

2. Your hybrid/traction battery needs charging. Most often seen
after an extended run in stealth, or extreme stop'n'go traffic (like
when being stuck behind an accident).
2 - WILL show up on the Energy Monitor

3. Your power demands are greater than what the electric motor alone
can provide. This is often seen if you have a heavy (or even
moderate) foot on the pedal, such as when accelerating, or if you are
going up hills. Over 42MPH, the ICE will be turning for transmission
reasons, but as for running (burning fuel) it will more likely than
not be running at that speed (highway-like conditions). However,
this group has the term "warp-stealth" (known elsewhere as "fuel-cut-
mode") for when the gas engine is turning, but not receiving/ burning
any fuel (if you have the CoastalETech Engine Run Indicator you'll
see this), such as on a highway (going over 42MPG) going down a long
3 - WILL show up on the Energy Monitor

4. You have the AC on MAX or have the climate control level set to
the front windshield icon (defrost (defog?)). The AC compressor is
used in the AC MAX mode or the defrost position for dehumidifying the
air. The AC compressor is run by the gasoline engine (belts, I
4 - Will NOT show up on the Energy Monitor

5. Climate control demands. The Prius tries to keep the passengers
happy (and while doing so can keep the batteries at about room temp
for better operation, by feeding them air from the cabin (see vents
on rear package shelf)) in their climate demands. So, if the inside
of the cabin requires more heat, the engine has to run to generate
more heat, and conversely if the cabin needs more cooling, the engine
has to run the AC compressor more... If you're stuck at a LONG light
in the winter after the car has warmed up, you'll notice the engine
cycling on and off while you're sitting there, making heat, then
dissapating heat, then making heat...
5 - Will NOT show up on the Energy Monitor

6. The Prius' computers are doing some systems diagnostics. This is
the reason that following a nice electric-only drive into your
parking space and switching the Prius into the "P"/parking gear that
the engine decides that it wants to come on.
6 - Will NOT show up on the Energy Monitor

Note that the Energy Monitor will only show you power movement from
between the 4 given icons of the wheels, the electric motor, the gas
engine, and the battery. So, the gasoline engine can be running for
other reasons (usually climate control or warming emissions
components), but will not show up on the Energy Monitor because those
other reasons are not associated with either the wheels, the electric
motor, or the battery...
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