Prius Performance On Hills?

[Surv1v0r]

Hi, I hope someone can help here.

I am considering buying a new Prius. However, looking at the specs when compared to the alternative I have in mind (Skoda Octavia) I get the feeling that whilst the Prius wins hands down around town and perhaps also wins on long motorway runs it may lack power and might struggle when fully loaded with four adults and luggage and on hilly / mountain roads due to lower power (129 -vs- 150) and MUCH lower torque (181 -vs- 320).

Based on practical experience, would you agree or disagree with this assessment?

[Cyker]

As long as there is charge in the Battery it's fine, but if you use up the Battery just before hitting a long uphill section it can struggle. It will get a lot of charge back through regeneration going back down the hill tho' so if it's undulating rather than a steady uphill then it'll be okay.

[Chris Dance]

My son uses his prius fully laden in the French Alps and has no problems in the mountains.

I have never had any problems with my Prius on hills in the UK.

[Surv1v0r]

My son uses his prius fully laden in the French Alps and has no problems in the mountains.

I have never had any problems with my Prius on hills in the UK.

As long as there is charge in the battery it's fine, but if you use up the battery just before hitting a long uphill section it can struggle. It will get a lot of charge back through regeneration going back down the hill tho' so if it's undulating rather than a steady uphill then it'll be okay.

Hhhmm, I hadn't thought of the Battery charge aspect, I had expected to be running on the engine.

As I understand it, the Prius only relies on Battery power when travelling at 31 mph or less. My approach to the French Alps would typically be on a motorway so I guess that I would expect to have a fully charged Battery. However, the long ascent to a resort is quite likely to be at speeds less than 31mph. Presumably when the battery gets low, you do revert to using just the engine?

My other destination is the Lake District and so there would typically be a fair bit of up and down hill as well as braking on twisty lanes. This ignores the long gentle ascent on the M6.

All of this stems from past experiences with four adults, skis, walking gear, etc. on board where I have felt that my current car (ancient 2L Auto Picnic) tended to struggle. Sadly it has been time for a replacement for quite a while now,

[jonesbach]

Be careful when you compare the hybrid with normal cars. Engine power may be less, but it will be supplemented by the electric motors and torque is less, but the electric motors have it in abundance.

It's not just ICE or electric, on a steep hill you may have ICE direct, part Battery, and part ICE converted to electricity by motor/generator to run second electric motor(This provides the torque).

The negative, I think it is like the Auris, you cannot tow.

[Cyker]

The Prius and, in fact, all HSD-powered cars can use either or both the electric and petrol engine depending on the situation; It's not just a speed related.

If you're going quite slow, the car will try to run on just the electric engine.
If you are cruising at a constant speed, the petrol engine tends to do most of the work.
Under hard acceleration or hill climbing, both engines will be providing power to the wheels.
If the Battery is low, the petrol engine will rev harder to charge it and still provide drive.
If you're braking, the electric motor will charge the Battery and if you're rolling down a hill the petrol engine may feed power into the Battery as well or shut off completely!

The petrol engine is designed for diesel-level efficiency but the sacrifice is that it has sod-all torque (It's in the same ballpark as a 1.0 or 1.3 VVTi IIRC); What it provides is the baseline cruising power to keep the car rolling at constant speeds as this just requires enough torque to overcome air resistance.

The acceleration torque is mostly provided by the electric motor which, like all electric motors, provides maximum torque from a standstill all the way to max revs which is why the HSD can have surprisingly good acceleration.

The way they work together is the 'synergy' Toyota likes to talk about (Weak but efficient petrol motor to keep the car rolling combined with powerful but limited charge electric motor to give grunt when it's needed).

The car can take you up a hill on the petrol engine alone, but it has to drop the gear ratio to do this which means it'll be revving like crazy if it's steep and you're heavily loaded.

Because most of the grunt is provided by the electric motor, you do have to be a bit more mindful of the charge level if you know you'll need that grunt. Generally this isn't a problem, but we have had a few people get caught out.

Motorway runs are a bit of a weakness for the HSD as, although the electric motor isn't taking much power from the battery, the petrol engine is using all its power to drive the car so the battery gets very little opportunity to get charge from it, esp. if you're driving quite fast. If the charge is very low, the engine will run harder to charge the battery to a certain level, but this uses more fuel.
I've never driven one in such a use-case so I'm not sure how it would be in the real world, but I'd be a bit wary of tackling a hill in a HSD after a long motorway run...!
I'm sure actual HSD owners will have more useful real-world evidence than me for this!

That said, if you're going to do lots of long-distance driving and up hills, a diesel-powered estate of some sort may be a better fit as they love that kind of work :)

Edit: Put all the linefeeds back in. Why you keep eating them forum!?

[ian rooke]

Hi I have had 3 Prius's and now have a Lexus CT200h (same gear train) and haven't yet found a hill it cannot tackle with ease when going up hill it cannot drop a gear as it is a constant velocity box so never rev's like mad.

[Aceshigh84]

My Auris manages to get itself up the Rhuallt hill on the A55 in North Wales without missing a beat. When using cruise control it doesn't even slow down.

Yes, the "rev" counter (can't remember the proper name right now) goes into the power zone and stays there til I reach the top, but I certainly wouldn't say it struggles.

[Surv1v0r]

<snip>

That said, if you're going to do lots of long-distance driving and up hills, a diesel-powered estate of some sort may be a better fit as they love that kind of work :)

<snip>

That is pretty much the conclusion I had come to which is why I am considering the Octavia despite being hugely impressed with the Prius.

I have just been told that a recent report in the Economist magazine found that 19 of the top 20 most fuel efficient cars were "clean diesels". The VW Polo was the best at 3.8 litres/100km - the Prius with 4.2 litres/100km came 20th - LINK.

[Cyker]

Yeah, I'd not read much into that Economist article as it has quite a lot of factual errors which make me think the author has done very little research. Urea injection!? I think maybe one manufacturer used that as an experiment and nixed it pretty quickly.

It's like ford and their special super-expensive oil that was used to regenerate DPFs, but nobody ever changed which would eventually cause the DPF to fail, so they stopped doing that.

The normal compression ratio for diesels was 20:1, which has dropped for some of the newer lighter engines. Toyota were one of the first I know of to do that, with 17.5:1 in their first 1.4D4D (Which AFAIK has one of the largest rev ranges of diesel engines even now!)

One of the reasons that the HSD has a large (And slightly rabid :P) following here is that they tend to be a lot more reliable than modern diesel engines; Old diesel engines are virtually indestructible, but modern ones are a lot more fragile and temperamental due to all the emissions control junk they bolt on.

For your use-case, that shouldn't be an issue; The biggest problems are caused when the car is used extensively in the city and/or for short journeys - This leads to things like the injectors, EGR and DPF crudding up which is why I take my ickle Yaris out for a nice run now and then and occasionally dump some V-Power through it (Even then I still need to clean out the EGR system now and then; Thankfully mine was made before euro-regs made DPFs mandatory!)

[Ten Ninety]

Don't buy a Prius if you think it's going to be the most economical car in the world. It isn't, and it will be even less so if you spend a lot of time going up and down hills. It won't 'struggle' but it will make a lot of noise and burn a lot more fuel than it does on a flat road. Like most cars, really, but the difference is almost certainly more noticeable in the hybrid.

Many modern diesels will make less fuss going up hills and can, as the posted article suggests, deliver better 'economy' if you consider purely miles-per-gallon. However, you also have to live with all the usual negatives of diesel driving and ownership which may or may not bother you. Presumably they don't, as if they did you wouldn't be considering a diesel alternative in the first place.

The hybrid rationale can perhaps best be illustrated by *****ising the old petrolhead phrase used to justify a choice of 'inferior' car; It's not about how fast economical you go, it's about how you go fast economical. The driving characteristics of the HSD are uniquely tuned to relaxing and de-stressing modern, traffic-choked driving. That's a huge part of why owners are often so devoted; possibly rather more so than on the basis of fuel economy alone. Only you will know how important that may be to you.

[Chris Dance]

If you use the Prius in the Alps in Winter it is essential you have winter tyres fitted. As for a diesel UGH!!

[jonesbach]

You will notice many people on this site with 'Fuelly' links. I recommend you search there for real life economy. Most magazine experts seem to be living in another universe, certainly the characteristics of the car I bought turned out to be nothing like the one they used for a test drive.

[Joseph D]

Motorway runs are a bit of a weakness for the HSD as, although the electric motor isn't taking much power from the battery, the petrol engine is using all its power to drive the car so the battery gets very little opportunity to get charge from it, esp. if you're driving quite fast. If the charge is very low, the engine will run harder to charge the battery to a certain level, but this uses more fuel.

I've never driven one in such a use-case so I'm not sure how it would be in the real world, but I'd be a bit wary of tackling a hill in a HSD after a long motorway run...!

I'm sure actual HSD owners will have more useful real-world evidence than me for this!

As an actual HSD owner, I feel qualified to rebut this and feel that this particular paragraph cannot go unchallenged.

First off, I think your armchair theoretics are challenged when coming to terms with how an HSD works in practice and it maybe an idea to let actual owners with real life knowledge comment.

Motorways are not a weakness for the HSD. I have had my Prius pushing along motorways at 70mph on just the electric motor and certainly not had any such problems as you espouse at any speed on "a motorway run". The way the computer juggles the combination of the two MG's and the ICE is complex and constantly changing second by second as you drive and in no way is the ICE using all its power to drive the car. (The reality is, the whole HSD can only work because of the computer control unit it is that complex!) The HSD is always using a varying combination of the ICE and MG's to provide power to the wheels and charge to the HV Battery such that I often have my HV Battery in the green range doing "motorway runs".

This whole concept pushed that, on a climb up hill, the Battery will eventually become spent and you will be left like a dead duck struggling to go further is just rubbish. Nothing could be further from the truth. If the battery is low and torque is required, the ICE will spin up and generate electricity to supply power to the electric motor and also charge the HV. Compared to regular cars (petrol and diesel) this does seem strange when it happens but you just need to go with the flow and let the HSD do it's thing. I have never had a problem going up any hill, including climbing up into the German alps for well over half an hour at 100km/h (60 mph). Sure the MPG's dropped significantly, but the beauty is that what goes up must come down and you will recoup a significant amount of the cost of going up, when you come back down (as I did on that occasion).

Any prospective HSD driver need not fear tackling a hill after a long motorway run as, I can assure you, it will get the job done.

[Cyker]

Oooh I was afraid I'd get this

Just to clarify, I was NOT saying that the HSD is *bad* on a motorway, just that it is the weakest part of its repertoire. It's well known that the HSD works best when it's able to leverage the regeneration features rather than using the petrol engine to generate electricity. This means towns, A-roads etc. are where it is strongest.

I didn't know you could run at motorway speeds on just the electric motor alone; That is pretty cool! I assume this is a new feature as the last HSD I drove would mostly use the petrol engine at as low rpm as it could get away with when on a constant cruise.

As for the hills thing, if you read back I also never said that the car would 'be a dead duck' as you put it. In fact, I wrote exactly what you did - That in a low Battery situation, the petrol engine revs up higher (Which can be a bit disconcerting if you aren't expecting it!) to take the load so the car will not get 'stuck'. If the car is heavily loaded and the hill is steep, there WILL be a noticeable performance drop vs. with a fully charged Battery, but in the sense that you can't plant your foot and expect the car to leap forward, not that it won't go up said hill (Which it should be fine with)!

As I said tho', that would be an unusual (and hopefully rare!) worst-case scenario situation for most people.

[johalareewi]

As I understand it, the Prius only relies on battery power when travelling at 31 mph or less.

Wrong. Toyota HSDs blend electric and petrol power as necessary at all speeds.

The Prius and, in fact, all HSD-powered cars can use either or both the electric and petrol engine depending on the situation; It's not just a speed related.

What he said.

If you are cruising at a constant speed, the petrol engine tends to do most of the work.

Err. No it doesn't.

as you just said "all HSD-powered cars can use either or both the electric and petrol engine depending on the situation; It's not just a speed related."

The car can take you up a hill on the petrol engine alone, but it has to drop the gear ratio to do this which means it'll be revving like crazy if it's steep and you're heavily loaded.

ROFL (Rolling on the floor laughing)

Drop a gear ratio in a Toyota hybrid?????

Because most of the grunt is provided by the electric motor, you do have to be a bit more mindful of the charge level if you know you'll need that grunt. Generally this isn't a problem, but we have had a few people get caught out.

WTF???

Motorway runs are a bit of a weakness for the HSD as

Rubbish

I've never driven one in such a use-case so I'm not sure how it would be in the real world, but I'd be a bit wary of tackling a hill in a HSD after a long motorway run...!

I can believe that.

I'm sure actual HSD owners will have more useful real-world evidence than me for this!

Of course we will ;)

Yeah, I'd not read much into that Economist article as it has quite a lot of factual errors which make me think the author has done very little research.

Lots of people comment on hybrids without doing research.

In fact lots of people comment on lots of things they know very little about.

There is a lot of bad science around. :(

One of the reasons that the HSD has a large (And slightly rabid :P) following here...

is because this is the hybrid forum.

Be careful you don't get bitten.

[Parts-King]

What a sensible post, best ive read for ages

Kingo

2 x Prius, 1 x Auris HSD and 1 x Yaris HSD driver and ocassional Prius Plug in driver ;)

[Glyyde]

Having driven past Haldon hill in Exeter A38 numerous times with both Prius and Prius+, I wouldn't say that it has any problem going up hills even when I have 4 adults, 2 kids, and plenty of luggages. we start the climb with the Battery at 6 bars and end it at 6 bars. Most of the climb are powered by the petrol engine and little is needed of the electric Battery. If I needed extra boost to overtake crawling truck or other smaller engine cars, I can do it with ease. The best thing about this kinda steep hill is when you come back down. The EV Battery gets fully charge and for the next few climb, the EV produces much of the torque which provides the car with a pretty good MPG.

60-65MPG up and down A38 from Plymouth to Exeter is what I consider as good mileage. There are a fair amount of hills along this. I am not sure what a diesel will gives, but my friend drive a Mercedes A class diesel (obviously much smaller) at around the same speed as I do are getting mileage worst than mine. So there you go.

[Joseph D]

Just to clarify, I was NOT saying that the HSD is *bad* on a motorway, just that it is the weakest part of its repertoire.

So is this like saying, "I didn't say Claudia Schiffer is ugly, just that the weakest part of her repertoire is her ears. They are too big."?

It's well known that the HSD works best when it's able to leverage the regeneration features rather than using the petrol engine to generate electricity.

This is true to a point, but is a very limited and simplistic summary. It does leverage regeneration, but equally, will use the petrol engine to generate electricity as and when required. As I said, it is a very complex system, but luckily, as a driver you do not need to know anything, as Mr T has wrapped up all the complexity and knowledge into the system controlling computers to take care of everything for you. The driver just needs to drive as normal.

This means towns, A-roads etc. are where it is strongest.

Not exactly, its optimal state is doing 44 mph on the flat. But it does love 30 mph with a full Battery too.

I didn't know you could run at motorway speeds on just the electric motor alone; That is pretty cool!

My point exactly and yes it is.

I assume this is a new feature as the last HSD I drove would mostly use the petrol engine at as low rpm as it could get away with when on a constant cruise.

You know what they say about assuming. And for future reference it may be an idea to state what are assumptions and what are known for a fact.

No, this is not especially new, as I drive a '06 Gen 2 Prius and I understand that the Gen 3 only does it better.

Also, just because the ICE is spinning does not mean it is consuming any fuel or indeed driving the wheels. It may just be spinning at minimum revs to drive one of the MG's to provide power to charge the HV and/or power the other MG. One has to interpret the HSI properly. How else do you get 90 - 100+ mpg going 70 or 80 mph?

As for the hills thing, if you read back I also never said that the car would 'be a dead duck' as you put it. In fact, I wrote exactly what you did - That in a low battery situation, the petrol engine revs up higher (Which can be a bit disconcerting if you aren't expecting it!) to take the load so the car will not get 'stuck'. If the car is heavily loaded and the hill is steep, there WILL be a noticeable performance drop vs. with a fully charged battery, but in the sense that you can't plant your foot and expect the car to leap forward, not that it won't go up said hill (Which it should be fine with)!

I agree you might not have said that explicitly, but the implication is there. As an owner I'm in no doubt, it is a view held having read other posts on the subject, but most of the time I just say "Whatever!" in my mind and move on as I and other actual longterm drivers know it to be CRAP (complete rubbish and piffle), however others coming to this forum seeking authoritative information take it on board and somehow it becomes fact. This is evident when people who don't know keep regurgitating the same rubbish post after post.

As I said tho', that would be an unusual (and hopefully rare!) worst-case scenario situation for most people.

So why focus on it?

I do know that people come to this forum to hear from owners and drivers of hybrids to get real world answers to their questions - I know I certainly do. I find that some of the posts from posters that lack this real life (and long term) experience to be particularly annoying in the respect of regurgitating the various urban legends that go around. Fortunately, they sometimes start "It is well known that ..." or "I understand that ..." so can be recognised. For me personally, I just wish that people stick to commenting on, and in, the area of their expertise, I find it very frustrating sifting through the dross.

In the words of the famous Forrest Gump, that is all ah got t' say abou' that.

[Cyker]

Well discussion and education is what the forum is for ;)

Although I have driven a few of the HSDs, I don't own one so I can only say what I've come across in my more limited experience, esp. since so few people seemed to want to put forth any useful info to begin with!

I know you seem to think I'm attacking your car, but honestly that is not my intention. I didn't think everything I was writing would be 100% correct (I was shooting for at least 80!) and was relying on you 'actual' owners to fill in the blanks and corrections as I do in other forums.

I hoped for less of the snark, but I can understand if you feel some knobhead is trying to put down your car you're going to get a bit ****** about it; Just let me say again that is not my intention at all

Of course, if I have offended you all that much, I shall not to step foot in this part of the forum again (At least until such time that I forget I said this :P :D)

But to counter some of the snark with some of my own:

@johalareewi - The ROFLing at the gear ratio comment suggests you don't know how the HSD works - It is not a 1-ratio box like most of the all-electric cars - It incorporates a continuously variable gearbox! This means the gear ratio of the ICE to the wheels can be varied from a low ratio ('1st gear') to a high gear ('top gear') with a virtually infinite number of steps in between.

This is why if you floor the accelerator in, e.g. a Prius, the engine note doesn't gradually rise like in a normal car but heads straight for the redline and stays there until you back off - The engine is running at its most powerful level while the CVT adjusts to the speed (Effectively 'climbing the gears')

So yeah, you can drop the gear ratio in a HSD!

@Joseph D - Yeah I didn't mean to focus on the whole worst case hill scenario but that specific scenario was what the OP was concerned about so the discussion just kept heading towards that. To be fair, people are going to want reassurance on the weakest aspect of a car so that is usually where the focus is. Frankly, I was putting more effort in playing it down than I do with the weaknesses of my beloved diesel Yaris! ("I want to get a diesel Yaris but I am only going to drive it around town!" "Don't. It'll explode. Get a petrol or HSD one instead." )

As for the snide Claudia comment you made, that is actually a very good analogy; I always find it funny when people say the HSD is bad on the motorway when actually the mpg is generally 50-60s which is not far off a good diesel, and that same diesel would not get anywhere near the in-city mpg of a HSD!

You should totally use that next time someone says the HSD is bad on the motorway :P :D

"HSD suxx0rz on motorwaiiii!"

"Yeah, sucks like claudia's ears you stupid noob!"

...

Okay, maybe that needs work

[Joseph D]

Well discussion and education is what the forum is for ;)

True

I know you seem to think I'm attacking your car, but honestly that is not my intention. I didn't think everything I was writing would be 100% correct (I was shooting for at least 80!) and was relying on you 'actual' owners to fill in the blanks and corrections as I do in other forums.

I hoped for less of the snark, but I can understand if you feel some knobhead is trying to put down your car you're going to get a bit ****** about it; Just let me say again that is not my intention at all

I don't think that you're attacking my car at all, I'm very comfortable and happy with it. I'm more trying to provide accurate information to the OP. However, I take your point about your intentions.

Of course, if I have offended you all that much, I shall not to step foot in this part of the forum again (At least until such time that I forget I said this :P :D)

No offence taken. :P :D

As for the snide Claudia comment you made, that is actually a very good analogy;

Thanks, I was quite pleased with it myself. :D :D

You should totally use that next time someone says the HSD is bad on the motorway :P :D

"HSD suxx0rz on motorwaiiii!"

"Yeah, sucks like claudia's ears you stupid noob!"

...

Okay, maybe that needs work

Yeah, maybe. :P :D

[johalareewi]

@johalareewi - The ROFLing at the gear ratio comment suggests you don't know how the HSD works - It is not a 1-ratio box like most of the all-electric cars - It incorporates a continuously variable gearbox! This means the gear ratio of the ICE to the wheels can be varied from a low ratio ('1st gear') to a high gear ('top gear') with a virtually infinite number of steps in between.

Perhaps you are not explaining how the PSD (power split device) works very well.

The ICE, MG1, MG2 and the drive shaft are inter connected via a planetary gear system (the PSD).

All have fixed gear ratios. <-- Note

By mixing the ICE, MG1 and MG2 inputs, the required power output to the wheels is produced.

When going up a hill and more 'grunt' is needed, the HSD will adjust the inputs to get the required output. This may require more grunt from the ICE, or MG1, or MG2. The HSD decides at the time.

There is no downshifting a gear.

The gear ratios are fixed and do not change.

Some reference links.

Enjoy.

http://eahart.com/prius/psd/

http://en.wikipedia.org/wiki/Hybrid_Synergy_Drive

In particular:

"HSD transmission continuously adjusts the effective gear ratio between the engine and the wheels to maintain the engine speed while the wheels increase their rotational speed during acceleration."

[jonesbach]

Thanks johalareewi, that sums it up nicely. Could you now explain that to the newspaper and magazine pundits, I'm sick of references to the CVT.

[aCactus]

Thanks johalareewi, that sums it up nicely. Could you now explain that to the newspaper and magazine pundits, I'm sick of references to the CVT.

Unfortunately the hybrid system does have a CVT although Toyota prefer to call it e-CVT. While the epicyclic (or planetary) gear train has one fixed ratio in its "normal" use eg old overdrive boxes and many automatic transmissions in the hybrids Toyota apply different input speeds to the three parts of the geartrain therby getting a Continuosly Variable Transmission if you compare the engine speed and the road speed.

[jonesbach]

You have a point aCactus. I never realised I have been driving a CVT vehicle for years. The differential has one fixed ratio with power split between output shafts providing variable output or, by your definition, CVT to each wheel in a loosely mirror image of the Toyota system. You will find reference to this on wiki where they refer to the prius as having an epicyclic differential.

While Toyota do not help by referring to e-cvt, my position is that it does not come anywhere near adequately defining the system and it leads to misunderstanding generally, not least amongst the aforementioned pundits. We do not refer to the differential as a CVT and we should not refer to this epicyclic differential as a CVT. A power split device has been used to describe it and it is a far better description.