Hi all

I picked up a (used) 2013 RX450H a few months ago and I'm really loving the smoothness of the vehicle so far. However, I've noticed that when coasting downhill, and when the brakes are not applied, the engine doesn't switch off - the fuel consumption figures are about 3-4L/100km when coasting, and when I come to a complete stop at the bottom of the hill, the readout is infinityL/100km as the engine is running. This is also when I can actually feel the engine running as the car is now stationary. The engine then switches off after a few seconds. Is this normal? Not sure if I've only just noticed now or if this is a new development indicating an issue. Thoughts / comments much appreciated!

 

I think it may be some other things running - not just the engine. number of things are at play here:

1) engine could run to dump extra energy generated by the regen motor
2) AC compressor could be running - separate system. it can run on its own without the engine running.

 

I have two hybrids. RX450h and CT200h.

​​​​​Maybe when you go above around 40 mph, the ICE kicks in? Maybe to make sure you can slow down going downhill with engine braking and to generate even more electricity to recharge the hybrid batteries quicker/run your AC if it's on and other applications that is on?

The ICE shuts down usually after a few seconds after you come to a complete stop and not moving anymore. Then as soon as you step on it the ICE kicks in (you can have this delayed ICE kicking in by having the feather touch with your foot).

It's all good. No worries.

 

With my 2010 rx450h...
Got the scanguage2 recently and I noticed the same results... in coasting down hill...the center console power display showed, engine shut down, power from wheels to the generator, then to the batteries...
while the scanguage2 showed RPM of 895... speed of 30... ( instant) MPG of 9999 and avg (mpg) of 28
... and it sounded like the engine , or generator was running... which eventually shut down.
The rpm's, and the power display of the engine off, do not always match up.
Could be as others mentioned of the generator or compressor running... since I am told the compressor runs off electricity..

 

Ahh good point on that first bullet point! Yes this usually happens when the battery is full or near full. Also there was another poster who mentioned engine braking, which I think could be the case as well!

 

The engine MUST physically spin starting just above 40mph / 65kph, even if the vehicle is not using fuel and either coasting or being powered electrically (otherwise it would force the generator motor to overspin as a result of the CVT gear ratios). However, it often will use fuel to maintain an idle (at high speeds, cold temps being common reasons). It sounds like to date you've only had your RXh during colder months. The engine is far likelier to remain running / consuming fuel during this time because it will try to maintain engine temperatures for heating and efficient combustion. Engine and outside air temp together is the largest factor in determining how often the engine will shut down. When both engine and air temps are nice and warm, and there isn't too much draw from A/C, you'll often find the engine will stop consuming fuel during coasting, and will physically stop spinning as your speed drops below the magic speed boundary previously mentioned. Once outdoor temps get past 15C / 60F its a whole new experience driving a hybrid.

 

As mentioned, the engine is spun with the fuel off to dissipate energy so the battery pack is not overcharged. An ICE with a closed throttle is essentially a very big vacuum pump, and requires a great deal of energy to be spun. It's essentially a very quiet version of a "Jake brake" as used on big trucks.