tempestv8

Not sure if this is common knowledge, but possibly it might be documented in the owner's manual somewhere.

In my city driving, there are lots of instances when the engine is started and stopped every few seconds. This is especially true when I'm driving up the ramps of a multi-storey car park. Step on the accelerator, engine kicks in, release the accelerator to go around a bend, engine stops. Step on the accelerator on the straight part of the carpark, engine kicks in, turn around a ramp, engine stops.

My thinking is that perhaps all this incredibly frequent starting and stopping can't be all that good to the engine.

That's when I found a way of keeping the engine running till I know I'm not constantly prodding and releasing the accelerator pedal.

By shifting the gear lever to the S position, the engine keeps running constantly. Yippie, the annoying constant starting and stopping ceases and the engine just idles like a regular ICE when not required.

Anyone else do this when driving in some conditions where there's significant starting and stopping of the engine?

The one downside of this is that having the engine running all the time doesn't mean that it's charging the traction battery. That's still controlled by a computer which doesn't take into account that the engine is running, so it might not actually use the idling engine to generate charge for the battery. Missed opportunity there.

riredale

The hybrid engine is designed to be started and stopped millions of times; MG1 is the big electric motor that spins up the engine in a fraction of a second. It's bolted on to the back of the engine's flywheel, not at all like a conventional starter motor that has to engage a gear on the perimeter of the flywheel. If you don't like the idea of the engine starting up and stopping every few seconds, that's your call, but it is designed to do just that.

tus

Your thinking would be correct if the 450h was not a hybrid. The MG1 and traction battery enable the thing to instantly start and stop frequently, without the normal wear of a "standard" starter system.

In fact, if you look at a hybrid car more like a boat or aircraft, where maintenance schedules are determined by running times instead of miles traveled, you're actually putting more wear on your engine by forcing it to run all the time.

tempestv8

Interesting video, thanks for sharing.

I'm keeping the engine running mainly to keep the vehicle feeling smooth, as there is a discernable sensation when the engine kicks in every time. It's super subtle but there, and I can feel it.

I only keep the engine running whilst ascending the multi storey car park situation. In most other driving conditions I leave the gear shift in the "D" position and try to minimise engine starts and stops by careful application of the accelerator pedal, whilst watching the power gauge.

salimshah

But that is the design philosophy of hybrid.

Another option would be to go easy on the gas pedal and drive slowly in the parking garage so that there is no need of the gas engine to kick in. Sports mode in the garage is an overkill.

The down side of the electric motor drive is that you can sneak up on unsuspecting pedestrians in the garage.

Service mode also lets the gas engine run without the shutdown,

Salim

tempestv8

How does the hybrid engine develop it's oil pressure? If the oil pump is mechanically driven like it is on the RX350, then I think all that stop starting vs an engine left idling can't be a good thing for the engine. The most wear and tear occurs in the short time when the engine is started/running but oil pressure has not built up.

Begs the question - how does Toyota hybrid engines deal with this issue of engine wear when oil pressure is not fully up. If the oil pump isn't any different to the contentional RX350, then this can't be a good thing to have the engine stop and start all the time. Anyone know how engine oil pressure is managed on a hybrid engine?

ukrkoz

Well, what oil pressure does the engine need, if it is not running? When you drive a conventional car and turn engine off, does it require oil pressure management?

tus

The oil pump is a mechanical one. What makes the hybrid system different is the MG1 motor spins the system up to ~1k rpm almost instantly which pressurizes the oil system before the fuel injectors and ignition system are enabled.

HKPolice

The constant start/stopping probably won't increase engine wear once it's warmed up. The annoyance factor is more of an issue to you so keep it in sport mode in the parking lot if you want.

HKPolice

Do you have any proof of that? If it were true, why do hybrid engines last over 400k miles easily? Surely all that start/stopping would limit the lifespan to half that.

https://priuschat.com/threads/400k-m...-owner.152294/

http://www.hybridcars.com/toyota-pri...ginal-battery/

https://jalopnik.com/this-is-what-a-...s-l-1717745908

tempestv8

I have a ScanGauge II plugged in and I can see that whenever the engine fires up, it is typically at around 1200 RPM when taking off at the traffic lights.

It doesn't feel like the MG1 is revving up the motor before the internal combustion process starts - it actually feels like the engine is firing on all cylinders immediately.

Nonetheless, I don't mind the stop and start process when at traffic lights, but it's the shunting between stopping and starting at rapid fire succession in some conditions that really irks me.

Anyhow, to resolve the possible low oil pressure situation, I'm using engine oil formulated for "stop start engines". Maybe it's just a marketing gimmick but it makes me feel a bit happier.

See this marketing blurb: https://www.castrol.com/en_au/austra...tart-wear.html

salimshah

One of the things I had to retrain my self with Hybrid was starts and stops. By feathering the gasped on starts (from stopped position) I let the electric motor pull the vehicle and if I have to stop (in stop and go traffic) the ICE never needs to fire up. The other thing I tried [and could not stand] was the ECO mode. This is opposite of the Sport mode. In this mode the electric motor is used for longer and one can prevent the ICE firing up, but in this mode the computer takes over instead of the driver and feathering of the gas pedal.

Question about the oil pump and pressure is still interesting and would be enlightening. The pressure helps get the oil up, but most of the lube is one by gravity as the oil flows down. Since some one mentioned that part of the braking is done by the engine dead (with no active firing) cycles, so an oil pump that works all the time would make sense.

Salim

NateJG

tempestv8

Just on that last point re the water pump, the GS 450h has an electric water pump, so no external belt whatsoever. Why Lexus chose to keep the belt driven water pump on the RX450h, I don't know but would love to find out the logic or reasoning behind that.

HKPolice

The GS450h costs more than the RX450h and is more performance oriented, therefore it's much more likely that the GS450h will be driven hard.
If the engine is turned off immediately after being driven hard, the coolant will heat soak with a mechanical waterpump that isn't turning. The electric waterpump can be left on after the engine is turned off to prevent heat soaking.

I wouldn't be surprised that after being driven hard, the RX450h will force the engine to idle just to cool it down. At least the idling will charge the battery though.