Confused about PHEV, Hybrids, etc...

[edy]

One of my colleagues recently leased an Acura 350h NX 2023. She was told by the sales rep that it will use all electric up to 60 km per hour. I said, "do you mean up to 60 km distance", and she said "no until driving 60 km per hour". I asked "what is the range, does it do all electric, is it a plug-in" and got a blank stare.

My point is, I'm getting very confused about the mix of technologies now available in hybrid vehicles. It seems that we have a huge mix of modes and much of it seems to be minimally controlled by the user (which I guess is a good thing?).

On the one extreme, you have your typical internal combustion engine (ICE), and on the other is EV all-battery vehicle. In between I thought there were essentially only 2 different hybrids... "HEV" and "PHEV". The HEV doesn't plug-in and essentially just figures out the best mix of power from the ICE and Battery and charges itself, and the PHEV actually lets you drive for a certain distance using all-battery and when it depletes it switches on the ICE to charge it and falls back to more of an HEV mode.

What confuses me about the Acura 350h is that it does not seem to be a PHEV, but up to a certain speed it will operate only from the battery and if you drive slowly and not accelerate too much it will stay on battery only? I guess they didn't bother giving a range spec as it doesn't apply in this case, as it is not truly a PHEV. I don't know what kind of algorithms they are using so I was hoping someone in here can shed some more light on this.

The PHEV is simpler to understand. It seems that if a user wants to travel under a certain range per day they could simply use their car almost like a full EV, and never rely on the ICE. However if they decide to go beyond the range and battery depletes, they can rely on the ICE to get them around (eliminating range anxiety).

HEV mode is more confusing as there seems to be more going on regarding how the car actually balances between the two. Does it use the EV motors to accelerate only, to assist torque during acceleration, to keep it rolling at a constant speed? When are those motors active and do you really have any control over it? Can you actually drive the car so that you never use the ICE, or is going to be running no matter what as it needs to recharge the battery?

[sokoloff]

I'm not familiar with that specific car (I wonder if it's actually a Lexus rather than an Acura), but I am shopping for and have done a lot of research on a different brand's PHEV.

There's a limit of both capacity and power that would limit the distance you could go on battery (capacity) as well as the maximum speed (where power matches aerodynamic drag), so having a maximum speed limit spec makes sense.

Integration between the ICE and electric motors is automated and relatively seamless in the current hybrids (and has been for years).

The Lexus 350h is not a plug-in hybrid, but uses the ICE to charge the electric battery. Where the electric battery gets its charge is somewhat irrelevant to the hybrid driving experience. You have to run the ICE engine at some point to charge the battery, but while the battery is charged, you can drive it in electric-only mode. Some amount of people buy a PHEV and then rarely plug it in. This car works the same way as those cars, just with a smaller battery and no capability to plug it in.

https://www.drivingelectric.com/lexus/nx-350h has more info on this specific car.

[ejeffrey]

The NX 350h is a Lexus, not an Acura, and it is a regular hybrid.  The NX 450h is a PHEV.

I'm not familiar with the newer hybrid systems, but if it is like the older Prius models it can can travel at low speeds (like in a parking lot) on battery alone but with no significant battery only range.  Also, sometimes the sales staff will quote a number that doesn't mean much of anything: the maximum vehicle speed at which the ICE engine can be at zero RPM.  This is given by the gear ratios and the maximum RPM of the electric motor.  On the Prius this is in the 40 mph / 60 kph range.  Again, this number is not terribly relevant -- the electric motor doesn't have enough power to maintain this speed on level ground.  When coasting or going downhill at above 40 mph, the engine still must rotate but will do complete cylinder deactivation.  The exhaust and intake valves are closed and fuel delivery is shut off.  This eliminates pumping losses and overall the drag is pretty low.

[tom66]

Toyota only makes a few PHEVs;  the majority of their hybrid line up is the so-called "self-charging hybrid" which is a stupid, loaded marketing term that makes people think the car is better than one which needs to charge, but I suppose that's the awful genius of marketing terms.

The Toyota hybrid architecture has changed over the years but the majority of these are based on some kind of power-split device.  This allows the electric motors and engine to run simultaneously with the pairing of motors and planetary gearset acting as a variable-ratio transmission, and it gives these cars the "e-CVT" gearbox marketing name, but crucially these cars do not really have a CVT with all of its associated problems.  The hybrid synergy drive is actually a rather clever architecture and it deserves praise for its simplicity and performance (as much as I think hybrids are becoming obsoleted by pure electric vehicles for most users.)

What confuses me about the Acura 350h is that it does not seem to be a PHEV, but up to a certain speed it will operate only from the battery and if you drive slowly and not accelerate too much it will stay on battery only? I guess they didn't bother giving a range spec as it doesn't apply in this case, as it is not truly a PHEV. I don't know what kind of algorithms they are using so I was hoping someone in here can shed some more light on this.

When Toyota (not Acura/Honda) say the vehicle can run up to 60km/h on electric power alone they are in the technically correct but not really useful category of facts.  Yes, the e-CVT/HSD architecture can *probably* get the vehicle up to 60km/h without engaging the engine, but since achieving that will likely (a) exceed the nominal acceleration limit for pure-electric mode (typically more than 20-30kW) and (b) likely deplete the battery sufficiently such that the engine must run to recover charge, that fact is really not that useful.   

The battery in these vehicles is typically of the order of 1-2kWh, with peak charge/discharge of around 25-40kW.  Even in the most optimistic driving pattern you are not going more than 1-2 miles on a full charge, and the full battery cannot be utilised anyway (merely around 50% to protect its lifespan).  And, even so, that battery must be topped up by the ICE, as you note, there is no way to plug the vehicle in.  So even if it did offer pure EV mode, what would be the point?  You are still burning petrol, just a few miles earlier.  They do often offer an 'EV Mode' button in the car.   I would not recommend using this, because you are just going to get 1 mile of pure electric mode, followed by a few miles more of the engine running under higher load to recuperate that charge.  You would be better off just using the petrol-electric motor hybrid as normal, with the computer selecting the most appropriate mode given the acceleration, grade, temperature etc.

Non-plugin hybrids offer pretty good economy when you use them as they are really intended for:  stop-and-go traffic or city traffic.  There is a lot of opportunity to recuperate charge there, which can allow the pure EV modes to work longer.  However, many times they seem to be sold to people who do a lot of driving on the highway, and this might be where the 60km/h claim also comes into it.  These people would be better with diesel or pure EV, but Toyota doesn't like marketing either.

[edy]

The NX 350h is a Lexus, not an Acura, and it is a regular hybrid.  The NX 450h is a PHEV.

Thanks! Yes it's the Lexus she was talking about.

When coasting or going downhill at above 40 mph, the engine still must rotate but will do complete cylinder deactivation.  The exhaust and intake valves are closed and fuel delivery is shut off.  This eliminates pumping losses and overall the drag is pretty low.

So the ICE is still mechanically coupled to the wheels via the transmission via some gear ratio, so it is actually still rotating the crank shaft and cylinders are pumping but empty (no fuel/spark), or does the ICE get disconnected from the wheels completely (like when the transmission is put into "Neutral" or like when a clutch is pressed down?).

I wonder if some kind of "phase diagram" exists which shows the blend of ICE/electric contributing in different scenarios. Like a chart with one axis being speed/RPM, the other being torque or something like that, with areas shaded based on whether they are mostly ICE, mostly electric motor or both.

There is also "parallel" and "series" hybrid configurations, where in parallel mode both ICE and electric motor can drive the wheels (coupled to transmission).... i.e. "electric motor assist", whereas in the series mode the ICE is used to primarily produce electricity for the electric motor system and not coupled directly to the drivetrain (essentially it is an EV with a small efficient ICE that runs only to charge the battery when needed). I'm assuming the second type (series) would be more likely to be in the PHEV type of vehicle.

I'm sure at the end of the day the consumer doesn't really care what is going on under the hood as long as they see a fuel savings. Driving pattern will likely also affect efficiency. If I'm interested in purchasing a hybrid one day in the future I would also want to understand at least a bit about what is going on, but it seems there quite a number of variations now and algorithms that the vehicle uses to figure out what to use when.

The Toyota hybrid architecture has changed over the years but the majority of these are based on some kind of power-split device.  This allows the electric motors and engine to run simultaneously with the pairing of motors and planetary gearset acting as a variable-ratio transmission, and it gives these cars the "e-CVT" gearbox marketing name, but crucially these cars do not really have a CVT with all of its associated problems.  The hybrid synergy drive is actually a rather clever architecture and it deserves praise for its simplicity and performance (as much as I think hybrids are becoming obsoleted by pure electric vehicles for most users.)

Thank you for the explanation, as well about the EV mode button and the way the battery is used. Then I am to assume this is a "parallel" type configuration and that the ICE/electric motors are both coupled into the drive-train and a computer can figure out the best times to use either and even do some fancy engine shut-off or cut fuel to cylinders (cylinder deactivation/CDA) when needed?

My wife's Acura MDX is not a hybrid, but when we come to a full stop the engine will shut off completely. When you press the gas, it starts up again quickly and let's you move. it's a bit scary because there is a delay and I worry sometimes doing a left turn, if it shuts off how much lag will there be to start up again. Feels like those diesel golf carts.

[tom66]

Here's a good simulator:
http://eahart.com/prius/psd/

The ratios will vary between vehicle models but it will show the rough idea.  For cruising, the HSD system will essentially want to keep the engine at the most efficient speed, which is typically the lowest speed that will support the torque required.   Net battery charge will be zero, MG1 and MG2 will have balanced power so the only losses are a little bit of heat in the inverter/motors.  Under acceleration, the engine speed will necessarily increase (to both accommodate the increasing speed and the increased torque required) but additional torque will be input from the battery/EV system.  Once up to speed, the engine loading will be increased to recuperate this charge, again ideally maintaining that most efficient operating point for the given load requirement.

The vehicle will essentially act to keep the battery at around 50% SoC.  If you regen a lot, e.g. going down hill, it will be able to use more electric torque later on to return the battery back to 50% effectively 'recycling' that energy.   Similarly, if you drive with a lead foot and the battery goes below 50%, then it will use regen or engine charging to return it to 50%.

[YurkshireLad]

I used to have a Camry Hybrid and it could drive on electric at just under 60km/h, but only on a flat road and with constant speed. Typically I could drive on electric for, I'm guessing here from memory, almost 1km while crawling in stop/go traffic if I didn't press the accelerator pedal too much.

[tom66]

Some other notes --

So the ICE is still mechanically coupled to the wheels via the transmission via some gear ratio, so it is actually still rotating the crank shaft and cylinders are pumping but empty (no fuel/spark), or does the ICE get disconnected from the wheels completely (like when the transmission is put into "Neutral" or like when a clutch is pressed down?).

I couldn't say for sure about this Lexus but there are hybrids out there which have clutches to disconnect the engine, to improve efficiency.  An engine, oil, and valves adds a fair bit of load that can be eliminated for coasting and regen.  But how much benefit?  Harder to say.  It was enough for VW to add it to my car.

There is also "parallel" and "series" hybrid configurations, where in parallel mode both ICE and electric motor can drive the wheels (coupled to transmission).... i.e. "electric motor assist", whereas in the series mode the ICE is used to primarily produce electricity for the electric motor system and not coupled directly to the drivetrain (essentially it is an EV with a small efficient ICE that runs only to charge the battery when needed). I'm assuming the second type (series) would be more likely to be in the PHEV type of vehicle.

In my experience (owning a VW plug-in hybrid and somewhat knowledgeable about other models of PHEV) the series-hybrid configuration is very rare.  I think the reason for this is the double-conversion losses are excessive.  Most PHEVs are parallel hybrids only.  In the case of my Golf, the hybrid motor sits on the crankshaft of the engine and goes through the same gearbox as the engine's torque does.  There is a simple clutch that disengages the engine when it is not required to reduce drag.   The clutch slips as necessary to provide engine start as well, with the electric motor mapping in the extra necessary torque, without impacting the driving feel (the engine can and will start at 30 mph, and you don't notice it, it's all rather impressive in my opinion!)

The Volt and BMW i3 REx are two examples of series-hybrid vehicles.  For the Volt the architecture is much the same as the Prius but the engine *can* run in parallel with the motor in some cases - I am not an expert on the Volt so defer to others here.  For the BMW i3 REx, there is only an electrical connection between the 25 hp engine/generator and the battery pack, so the vehicle cannot be powered by the petrol engine alone.  This simplified the design at the expense of efficiency, but the REx was only ever offered as 'training wheels' for long distance trips, in case you needed to reach the next charger.    It's no longer manufactured anyway.

[edpalmer42]

I own a 2020 Prius Prime Plug-In Hybrid.

I accelerate to highway speed on battery alone.  Acceleration is adequate, but not impressive.  I drive at highway speed on battery alone.  The battery is rated for 40 Km (~25 mi.) range, but that's more for around town driving.  I think battery range on the highway would be less.  Battery range will also be reduced if the battery is too hot, too cold, if you use air conditioning or heat, etc.

The connection between the two electric motors, the gas engine, and the tires is pure gears.  There are no belts, chains, etc. that you'd typically see in a regular CVT.  By controlling the speed and direction of the two electric motors the computer gives you the equivalent of a CVT.  The gas engine doesn't spin unless it's actually running and providing power.  The hand-off between the gas engine and the electric motors is invisible.  Unless I'm watching the display that shows energy flows around the system, I can't tell the difference.  If I'm watching the display, I can see changes on a second-to-second basis.  Sometimes the engine drives the wheels, sometimes it charges the battery, sometimes both, sometimes the engine shuts off and the battery handles everything.  Sometimes the engine drives the wheels by itself, sometimes the electric motors handle everything, sometimes both the gas engine and the electric motors drive the wheels at the same time.  The car decides what is most efficient at that moment.

There's a Youtube video that explains the transaxle on the Prius and the Prius Prime.

Overview - 25 min.: 
Deep Dive - 113 min.: 

Ed

[nctnico]

However, many times they seem to be sold to people who do a lot of driving on the highway, and this might be where the 60km/h claim also comes into it.  These people would be better with diesel or pure EV, but Toyota doesn't like marketing either.

No. Diesel is expensive to run & repair (been there, done that) and emits a lot of pollution. An EV takes long to charge (with expensive electricity from fast chargers on top of that). I already ran the numbers and a Toyota hybrid offers the best economy for doing long highway journeys plus having very low emissions.

[YurkshireLad]

Hybrids are better around town than they are on the highway. If you're doing mostly highway driving, I don't think a hybrid is the best option. It's not bad, but I don't think you'll get the best mileage out of it. You're not doing enough braking to put energy back into the battery. I think I got my best economy on a single journey while driving up and down the hills in Vermont. I think it was something like 4.6l/100kms.

[nctnico]

That depends on the type of hybrid; the only hybrids to consider need to have a true Atkinson cycle engine. Such engines are much more efficient so even on highways, you'll get a much better mileage compared to a conventional ICE based car. Unfortunately there are only a few manufacturers that make such hybrids (typically with a drive train from Toyota).

[Cerebus]

Just for completeness, there's one category missing, the mild hybrid.

These have thrown away the alternator and starter motor, and replaced them with a motor capable of moving the vehicle and being used as a generator. This is combined with a relatively small lithium chemistry battery - 1 kWh or less. So to start moving you use the electric motor, then the ICE is "bump started" once you're moving. They will have a small, low speed all electric range, but we're talking 10s, perhaps 100s of metres, not kilometres. Typically there's a small amount of regenerative braking as well, and the motor is obviously used in generator mode to recharge the battery. At the end of the day it's more of a re-working of the standard ICE engine's ancillaries than a true hybrid.

[ejeffrey]

That depends on the type of hybrid; the only hybrids to consider need to have a true Atkinson cycle engine. Such engines are much more efficient so even on highways, you'll get a much better mileage compared to a conventional ICE based car. Unfortunately there are only a few manufacturers that make such hybrids (typically with a drive train from Toyota).

This.  The biggest efficiency improvement on traditional hybrids comes from using a more efficient engine and keeping it running in the most efficient operating range as much as possible.  The battery and electric motor work to provide a torque boost to get more acceptable performance out of an Atkinson cycle engine and also to average out load a bit so that the engine can stay operating at peak efficiency more of the time.  Regenerative braking definitely helps around town, but the car will also charge the battery from the engine while cruising if doing so keeps the overall system operating higher efficiency.

As for mild hybrids: they are more like an improved stop-start system with a 48 volt electrical system so they can use an electric AC compressor.  They hardly count as a hybrid -- while the motor can technically move the car it is a negligible fraction of overall traction power.

[Someone]

Just for completeness, there's one category missing, the mild hybrid.

These have thrown away the alternator and starter motor, and replaced them with a motor capable of moving the vehicle and being used as a generator. This is combined with a relatively small lithium chemistry battery - 1 kWh or less.

As for mild hybrids: they are more like an improved stop-start system with a 48 volt electrical system so they can use an electric AC compressor.  They hardly count as a hybrid -- while the motor can technically move the car it is a negligible fraction of overall traction power.

They might be stretching the term "hybrid" but a battery of roughly 1kWh is close to the optimum overall energy efficiency for interurban driving (not carting around more weight than required, it is unusual to have conditions where a car can use more than that from regenerative braking.

Around town with lots of start stop and low speeds, pure electric makes sense.

[Someone]

However, many times they seem to be sold to people who do a lot of driving on the highway, and this might be where the 60km/h claim also comes into it.  These people would be better with diesel or pure EV, but Toyota doesn't like marketing either.

No. Diesel is expensive to run & repair (been there, done that) and emits a lot of pollution. An EV takes long to charge (with expensive electricity from fast chargers on top of that). I already ran the numbers and a Toyota hybrid offers the best economy for doing long highway journeys plus having very low emissions.

Yes, you have extremely strong and blinkered opinions about what works for you, but dont mention all the constraints/conditions which make that true.

Here in Australia (where diesel and petrol are almost identically taxed, no incentive either way there) a diesel car is cheaper on running costs as the maintainence has been shown to be no higher than petrol engines, either type of engine wears out well past the other drive train parts which are common to both. That's comparing identical models available in both engines, slightly higher upfront cost, lower operating costs. Which applies to hybrids, higher upfront cost for promise of lower operating costs.

One of the auto associations here puts out a broad (but somewhat shallow) analysis:
https://rac.com.au/car-motoring/info/buying-a-car/running-costs
For the typical 15,000km/year and mixed city/highway driving that normal people do, the life-cycle cost of any engine choice petrol/diesel/hybrid ends up lost in the noise. People need to be heavily biased toward/away from long distance highway driving, or much higher/lower km use for any difference to appear.

[gnuarm]

(as much as I think hybrids are becoming obsoleted by pure electric vehicles for most users.)

Hybrids are not being obsoleted by BEVs.  They are different technologies for different purposes.  A hybrid provides a similar experience to a pure ICE vehicle, while offering higher gas mileage.  A BEV provides a total break from gasoline and the resulting potential for elimination of pollution. 

An ICE is like wearing a bullseye in a shit slinging contest.  A hybrid is like being in the same contest, but wearing a poncho.  A BEV is like sitting in the stands watching the bloody mess.

[nctnico]

However, many times they seem to be sold to people who do a lot of driving on the highway, and this might be where the 60km/h claim also comes into it.  These people would be better with diesel or pure EV, but Toyota doesn't like marketing either.

No. Diesel is expensive to run & repair (been there, done that) and emits a lot of pollution. An EV takes long to charge (with expensive electricity from fast chargers on top of that). I already ran the numbers and a Toyota hybrid offers the best economy for doing long highway journeys plus having very low emissions.

Yes, you have extremely strong and blinkered opinions about what works for you, but dont mention all the constraints/conditions which make that true.

Here in Australia (where diesel and petrol are almost identically taxed, no incentive either way there) a diesel car is cheaper on running costs as the maintainence has been shown to be no higher than petrol engines, either type of engine wears out well past the other drive train parts which are common to both. That's comparing identical models available in both engines, slightly higher upfront cost, lower operating costs. Which applies to hybrids, higher upfront cost for promise of lower operating costs.

One of the auto associations here puts out a broad (but somewhat shallow) analysis:
https://rac.com.au/car-motoring/info/buying-a-car/running-costs
For the typical 15,000km/year and mixed city/highway driving that normal people do, the life-cycle cost of any engine choice petrol/diesel/hybrid ends up lost in the noise. People need to be heavily biased toward/away from long distance highway driving, or much higher/lower km use for any difference to appear.

Where these 'running costs analysis' go wrong is by looking at the first few years only. Spending over 500 euro per month on a car? You've got to be friggin' kidding me. If you are going to look at craddle to the grave, you'll see an entirely different picture. It takes a very careful selection to find that car that has really low costs. The first step is to buy a used one which is 6 to 8 years old with around 125k km 'on the clock'; that way most of the devaluation has been eaten by the previous owner(s). The second step is to figure out whether the typical problems are simple (and thus cheap) to fix. Ofcourse it helps that I'm in a country where you can buy cars that are produced in Germany and are of decent quality to begin with.

And diesel is just dead. Just because of the pollution associated with diesel it is not a good choice. In addition to that diesel engines have become extremely fragile and expensive to repair/maintain. Look at prices for replacing the particle filter for example and problems due to internal pollution of a diesel engine. My previous car was a turbo diesel from 1999 with exhaust recirculation (EGR). The latter caused a buildup of 1cm of oil and sooth inside the air intake manifold. It was difficult to get that cleaned out. Fortunately it was possible to close the EGR to stop sooth getting into the intake but you can't do that on modern diesels. At the end the fuel injection pump (Denso, not some kind of crappy brand) started to have issues. Currently I'm driving a car on gasoline which has far exceeded the mileage of my previous 3 diesel cars and is still going strong while being very cheap to run (around 21 eurocents per km). Again: careful selection. When looking for my current car I started with looking at diesels but quickly found out that these are prone to very expensive repairs and most cars for sale needed such expensive repairs.

Currently I'm looking into a new (used ofcourse) car and I keep getting back to the hybrid Toyotas for the lowest cost per km. Downsized engines do offer a much better fuel economy compared to my current car but these are also prone to expensive failures or are just expensive to maintain (like 1200 euro for changing a timing belt which is buried deep inside the engine and needing special oil). Many cars just aren't designed to last more than 5 years and/or being maintenance friendly nowadays.

[Someone]

However, many times they seem to be sold to people who do a lot of driving on the highway, and this might be where the 60km/h claim also comes into it.  These people would be better with diesel or pure EV, but Toyota doesn't like marketing either.

No. Diesel is expensive to run & repair (been there, done that) and emits a lot of pollution. An EV takes long to charge (with expensive electricity from fast chargers on top of that). I already ran the numbers and a Toyota hybrid offers the best economy for doing long highway journeys plus having very low emissions.

Yes, you have extremely strong and blinkered opinions about what works for you, but dont mention all the constraints/conditions which make that true.

Here in Australia (where diesel and petrol are almost identically taxed, no incentive either way there) a diesel car is cheaper on running costs as the maintainence has been shown to be no higher than petrol engines, either type of engine wears out well past the other drive train parts which are common to both. That's comparing identical models available in both engines, slightly higher upfront cost, lower operating costs. Which applies to hybrids, higher upfront cost for promise of lower operating costs.

One of the auto associations here puts out a broad (but somewhat shallow) analysis:
https://rac.com.au/car-motoring/info/buying-a-car/running-costs
For the typical 15,000km/year and mixed city/highway driving that normal people do, the life-cycle cost of any engine choice petrol/diesel/hybrid ends up lost in the noise. People need to be heavily biased toward/away from long distance highway driving, or much higher/lower km use for any difference to appear.

Where these 'running costs analysis' go wrong is by looking at the first few years only. Spending over 500 euro per month on a car? You've got to be friggin' kidding me. If you are going to look at craddle to the grave, you'll see an entirely different picture. It takes a very careful selection to find that car that has really low costs. The first step is to buy a used one which is 6 to 8 years old with around 125k km 'on the clock'; that way most of the devaluation has been eaten by the previous owner(s). The second step is to figure out whether the typical problems are simple (and thus cheap) to fix. Ofcourse it helps that I'm in a country where you can buy cars that are produced in Germany and are of decent quality to begin with.

And diesel is just dead. Just because of the pollution associated with diesel it is not a good choice. In addition to that diesel engines have become extremely fragile and expensive to repair/maintain. Look at prices for replacing the particle filter for example and problems due to internal pollution of a diesel engine. My previous car was a turbo diesel from 1999 with exhaust recirculation (EGR). The latter caused a buildup of 1cm of oil and sooth inside the air intake manifold. It was difficult to get that cleaned out. Fortunately it was possible to close the EGR to stop sooth getting into the intake but you can't do that on modern diesels. At the end the fuel injection pump (Denso, not some kind of crappy brand) started to have issues. Currently I'm driving a car on gasoline which has far exceeded the mileage of my previous 3 diesel cars and is still going strong while being very cheap to run (around 21 eurocents per km). Again: careful selection. When looking for my current car I started with looking at diesels but quickly found out that these are prone to very expensive repairs and most cars for sale needed such expensive repairs.

Currently I'm looking into a new (used ofcourse) car and I keep getting back to the hybrid Toyotas for the lowest cost per km. Downsized engines do offer a much better fuel economy compared to my current car but these are also prone to expensive failures or are just expensive to maintain (like 1200 euro for changing a timing belt which is buried deep inside the engine and needing special oil). Many cars just aren't designed to last more than 5 years and/or being maintenance friendly nowadays.

So now you start to build out the picture of your throwaway unsubstantiated comment.... But sticking to claiming you know better than everyone else and your experience is 100% applicable to everyone else, which is isn't. Diesels are not more expensive to maintain, you found some outliers with your limited/narrow experience, that's not a universal truth and you're unable to fid any industry data to back it up. Oh and complaining about pollution while admitting you blanked an EGR? lol.

I have friends and family in the motor trade, and know what their highly experienced opinions are (that need to be correct for them to make money), as with the auto clubs not much difference in petrol/diesel/hybrid as the free/open market is pricing them all pretty fairly. The second hand market quickly picks up on any unreliable models/engines and they're priced accordingly (making motor swaps a profitable business). Modern low emission petrols are now using most of the tricks that diesels were 10-20 years ago, and surprise surprise the whole world of emissions control systems failing and particulate buildup (rather than being washed out into the air) are affecting modern petrol engines roughly equally.

Differences only appear for the outliers like: taxis spending all day in stop-start traffic (hybrids win easy), long distance travellers/commuters putting in 25,000km a year on the highway (diesel), or "grandma" going to church once a week for 1000km/year (petrol). Regular people are what the market is pricing cars for, and the open market works at levelling the lifecycle cost.

[edy]

Thanks for all the discussion, it is helpful, I've learned a lot. I also found this video that is great at explaining some of the nuances between the different types of electrification of vehicles:

[bdunham7]

That depends on the type of hybrid; the only hybrids to consider need to have a true Atkinson cycle engine. Such engines are much more efficient so even on highways, you'll get a much better mileage compared to a conventional ICE based car. Unfortunately there are only a few manufacturers that make such hybrids (typically with a drive train from Toyota).

A 'true Atkinson cycle engine' is an entirely different animal and not something you will see in any modern car.  Modern "Atkinson' and 'Miller' cycle engines are simply marketing designations for regular Otto-cycle engines with modified valve timing and higher compression ratios (as calculated from swept volume and combustion chamber size).  Yes, these setups can be significantly more efficient at the cost of reduced power (for a given engine size) and limited operating range, but the name is just that and nothing more.  Many modern engines, including non-hybrids, use variable valve timing and lift along with mechanical compression ratios higher than would be otherwise workable to achieve similar results under the right conditions.

[gnuarm]

That depends on the type of hybrid; the only hybrids to consider need to have a true Atkinson cycle engine. Such engines are much more efficient so even on highways, you'll get a much better mileage compared to a conventional ICE based car. Unfortunately there are only a few manufacturers that make such hybrids (typically with a drive train from Toyota).

A 'true Atkinson cycle engine' is an entirely different animal and not something you will see in any modern car.  Modern "Atkinson' and 'Miller' cycle engines are simply marketing designations for regular Otto-cycle engines with modified valve timing and higher compression ratios (as calculated from swept volume and combustion chamber size).  Yes, these setups can be significantly more efficient at the cost of reduced power (for a given engine size) and limited operating range, but the name is just that and nothing more.  Many modern engines, including non-hybrids, use variable valve timing and lift along with mechanical compression ratios higher than would be otherwise workable to achieve similar results under the right conditions.

If you think modified valve timing does not produce a "true" Atkinson cycle, you aren't grasping the nature of the Atkinson cycle.  The mechanics are a trivial detail.  What is important is that the power stroke is longer than the compression stroke (or consider power and compression ratios, either way).  The compression ratio is limited by the anti-knock properties of the fuel.  So with a given compression ratio, the Atkinson cycle provides a longer power stroke, a higher power ratio, and more power from the same amount of fuel. 

The fact that the piston moves the same path for the compression and power strokes is not relevant.  The valve timing makes the compression stroke effectively shorter than the power stroke, creating an Atkinson cycle.

[bdunham7]

If you think modified valve timing does not produce a "true" Atkinson cycle, you aren't grasping the nature of the Atkinson cycle. 

I fully grasp the concept of the Atkinson cycle and I don't want to debate the details with you and I don't know what you mean by 'power ratio' anyway.  The actual result is simply that the exhaust temperature is lower, meaning more energy has been extracted than would be otherwise.  However, none of that is my point--what I was pointing out is that many engines today use this general method of increasing efficiency but only a select few market it as an 'Atkinson cycle' or 'Miller cycle'.  Therefore, IMO, making your purchasing decision based on whether the marketeers have attached this particular name to the product is not helpful.

[gnuarm]

If you think modified valve timing does not produce a "true" Atkinson cycle, you aren't grasping the nature of the Atkinson cycle. 

I fully grasp the concept of the Atkinson cycle and I don't want to debate the details with you and I don't know what you mean by 'power ratio' anyway.  The actual result is simply that the exhaust temperature is lower, meaning more energy has been extracted than would be otherwise.  However, none of that is my point--what I was pointing out is that many engines today use this general method of increasing efficiency but only a select few market it as an 'Atkinson cycle' or 'Miller cycle'.  Therefore, IMO, making your purchasing decision based on whether the marketeers have attached this particular name to the product is not helpful.

What you described (or actually didn't really describe) in other engines is not the Atkinson cycle.  The Atkinson cycle has a very specific detail, the compression ratio is lower than the power stroke (expansion) ratio.  The point of it is to allow more energy to be extracted from the expansion stroke than with a regular cycle, specifically by using different ratios on the compression stroke and the expansion stroke.  Anything else is not an Atkinson cycle.

Other methods of achieving more power extraction may achieve similar results, but it's not an Atkinson cycle if it doesn't have the same features.

[nctnico]

If you look closely at the animation in this video from Toyota, you'll notice that the length of the strokes is different:
https://sherbrooketoyota.ca/en/videos/atkinson-cycle-engine So it looks like Toyota is doing more than just having different valve timing.