Hybrid Engines when cold | Motoring discussion | Back Room Forum

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Thu 4 May 2023 20:36

Hybrid Engines when cold - Dingle232

I was having a conversation with a friend of mine a couple of days ago. Both of us are old enough to remember the advice never to rev a car too hard until it was warmed up. I have always stuck to this and tend to treat my cars very well.

However, with a hybrid there's sometimes very little control over the engine revs whether it's warm or not, and we were discussing whether this would actually do damage in the long run. For example, as I leave home I have to go up a hill and the engine operates at high revs without being warmed up because the battery/motor alone won't propel the car up the hill.

There are a million high mileage hybrids out there so I suspect it's something that's possibly catered for by modern oils or more regular maintainence but I thought it was an interesting discussion point.

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Thu 4 May 2023 20:50

Hybrid Engines when cold - gordonbennet

If you take Toyota as being without question the leader in sucsessful proven over time hybrid technology then the proof is there that running hard from cold isn't doing them much harm, though arguably the thousands of Toyota hybrids covering the hightes mileage on taxi or similar work will invariably have warm engines for most of the day.

The ultra thin oils must help in this regard.

There's a top Toyota tech with his own channel on Youtube (the car care nut) and he was talking about how to get the best out of hybrids, he recommends giving it some beans from cold to get the engine warm and running efficiently, never once mentioned being gentle with the engine to allow things to expand etc, presumably all this was designed in from scratch.

Maybe some of us are too kind to our engines and cars in general, we all know of vans and cars that live locally that seldom see any TLC and once started from below freezing point are thrashed mercilessly making enough noise to have you cringing in sympathy with the vehicle, they never seem to break down.

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Thu 4 May 2023 20:59

Hybrid Engines when cold - badbusdriver

with a hybrid there's sometimes very little control over the engine revs whether it's warm or not

I disagree.

As with any powertrain involving an ICE (including hybrid), how many revs the engine pulls is directly related to how far down the accelerator pedal is pressed. If you don't want to over-rev it when cold, don't press the pedal down too hard.

Also, some engines are designed to rev higher than others. For example, the Honda Jazz we used to have produced peak power and peak torque at 6k and 5k rpm respectively. Avoiding over-revving that engine when cold is not going to be the same as avoiding over-revving an engine which produces peak power and torque at much lower revs.

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Sat 6 May 2023 12:44

Hybrid Engines when cold - Dingle232

with a hybrid there's sometimes very little control over the engine revs whether it's warm or not

I disagree.

As with any powertrain involving an ICE (including hybrid), how many revs the engine pulls is directly related to how far down the accelerator pedal is pressed. If you don't want to over-rev it when cold, don't press the pedal down too hard.

Also, some engines are designed to rev higher than others. For example, the Honda Jazz we used to have produced peak power and peak torque at 6k and 5k rpm respectively. Avoiding over-revving that engine when cold is not going to be the same as avoiding over-revving an engine which produces peak power and torque at much lower revs.

I woud half disagree back :-). When driving the car I agree with you but I find the throttle slightly harder to control. Maybe that's me.

However, with my car from cold, I don't even have to touch the accelerator and the engine can kick in at around 2.5 - 3000 RPM for some minutes without the car even moving. Presumably this is to put some juice back in the battery but the only way to control that is to turn it off. I am not in any way concerned that it's an issue, just thought it was an interesting discussion.

As gordonbennet pointed out earlier, there are just too many of these things, particularly Toyotas, on the road for it to be a problem.

Maybe I am just getting old :-)

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Thu 4 May 2023 21:08

Hybrid Engines when cold - craig-pd130

For example, as I leave home I have to go up a hill and the engine operates at high revs without being warmed up because the battery/motor alone won't propel the car up the hill.

Yes, my BMW 225XE's ICE used to kick in at 4,000rpm from stone cold if I was a little heavy-footed in the car's 'normal' drive mode. Didn't seem to cause to any problems though.

According to BMW technical literature I found, the ICEs used in the plug-in hybrids have plated cylinder walls and coated pistons to minimise friction/wear, and the ECU also used the starter / generator to turn the engine over without firing it up to circulate oil occasionally, presumably so that the risk of starting 'dry' is minimised.

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Thu 4 May 2023 22:32

Hybrid Engines when cold - bathtub tom

As some of these hybrids use the Atkinson cycle (Toyota and Kia at least), then perhaps asking lots from cold isn't too much?

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Fri 5 May 2023 00:44

Hybrid Engines when cold - Terry W

Oil chemistry and viscosity varies with temperature. This is probably optimised to deliver best performance (minimum friction and wear) when hot which is the normal operating condition.

Traditional advice was to avoid high rpm until the engine got to normal working temperature which may take 3-5 miles.

Engines are now manufactured to much finer tolerances and oil chemistry has improved.

Whether this now means stressing the engine before it is properly warmed is debatable. My take would be that:

potential engine wear is a function of metal moving against metal. That the engine is a hybrid is irrelevant.
I feel more comfortable following traditional advice rather than unproven speculation

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Fri 5 May 2023 06:36

Hybrid Engines when cold - edlithgow

I feel more comfortable following traditional advice rather than unproven speculation

I feel more comfortable following traditional unproven advice rather than modern unproven advice, but I don't feel comfortable following any advice that doesn't seem to make sense.

There's quite a lot of it about.

"Oil chemistry and viscosity varies with temperature. This is probably optimised to deliver best performance (minimum friction and wear) when hot which is the normal operating condition."

Oil viscosity is lowest when hot. This means wear protection is inevitably lowest when hot, though this is mitigated by additive tribolayer chemistry which partially protects the metal if and when metal to metal contact occurs.

Oil viscosity is optimised to deliver best performance (fuel consumption) when hot which is the normal operating condition.

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Sat 6 May 2023 13:01

Hybrid Engines when cold - Bolt

I feel more comfortable following traditional advice rather than unproven speculation

I feel more comfortable following traditional unproven advice rather than modern unproven advice, but I don't feel comfortable following any advice that doesn't seem to make sense.

There's quite a lot of it about.

"Oil chemistry and viscosity varies with temperature. This is probably optimised to deliver best performance (minimum friction and wear) when hot which is the normal operating condition."

Oil viscosity is lowest when hot. This means wear protection is inevitably lowest when hot, though this is mitigated by additive tribolayer chemistry which partially protects the metal if and when metal to metal contact occurs.

Oil viscosity is optimised to deliver best performance (fuel consumption) when hot which is the normal operating condition.

Toyota now use a system where an electric pump feeds oil to the places that need the oil quickest to assist in warmup and reduce friction where needed.

the same applies to the cooling systems, being two, one for the engine, one for the electrics, as a pump only cools the areas needed rather than pump coolant all around the engine at the same time, clever system and said to make the engine last longer

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Fri 5 May 2023 06:48

Hybrid Engines when cold - edlithgow

...and the ECU also used the starter / generator to turn the engine over without firing it up to circulate oil occasionally, presumably so that the risk of starting 'dry' is minimised.

Nice that they are doing that, though there doesn't seem any good reason why it couldn't have been done for, say the last 20 years on all new IC engines.

Similarly but more so, it would have cost very little to build a pressurised pre-lube capability into any car produced since, say, WW2.

The fact that this has, AFAIK, never been done on a production automobile (or if it has, it must be very rare) suggests that long engine life / wear protection isn't a manufacturer priority.

Well knock me dahn wiv a fevva!

Edited by edlithgow on 05/05/2023 at 06:53

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Fri 5 May 2023 07:45

Hybrid Engines when cold - craig-pd130

Similarly but more so, it would have cost very little to build a pressurised pre-lube capability into any car produced since, say, WW2.

The fact that this has, AFAIK, never been done on a production automobile (or if it has, it must be very rare) suggests that long engine life / wear protection isn't a manufacturer priority.

Well knock me dahn wiv a fevva!

Indeed so. Back in the 90s I had MGB that had a Kenlowe electric pre-heater fitted. Great bit of kit, in winter just plug it in and let it run for 30 minutes or so, and it would warm the coolant in the block up to around 25 celsius so that when I started it, it was a 'warm' start needing just a touch of choke for a few seconds.

The engine ran sweeter and used less fuel from 'cold', and I had warm air from the heater straight away.

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Fri 5 May 2023 09:20

Hybrid Engines when cold - bathtub tom

Similarly but more so, it would have cost very little to build a pressurised pre-lube capability into any car produced since, say, WW2.

I recall seeing such a device many years ago. I can only describe it as like a small, spring loaded bike pump that sat in the oil feed. It was filled by the oil pressure that it held. When the starter was operated, a trigger released the oil back into the oilways.

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Fri 5 May 2023 10:26

Hybrid Engines when cold - edlithgow

Yes, you can buy them. MOROSO make one IIRC. They get used by racers who I understand use them as a surge chamber to protect from centrifugal forces, but, as I said, they certainly aren’t a standard fit, though they would protect against the 90% of wear in the first9 0 seconds or whatever jive which does seem to have some basis in fact.

Was your gizmo sighting OEM?

Edited by edlithgow on 05/05/2023 at 10:38

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Sat 6 May 2023 17:03

Hybrid Engines when cold - bathtub tom

Yes, you can buy them. MOROSO make one IIRC. They get used by racers who I understand use them as a surge chamber to protect from centrifugal forces,

Dry sumping and tall oil tanks can deal with that. I could never understand why british motorbikes used dry sump.

Was your gizmo sighting OEM?

I can't recall, it was a description of how the thing worked.

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