Fuel Consumption

[Dave R.]

Is there any engineering reason why a CVT box is employed in preference to a standard auto? I'm sure the answer will be weight/size or the technology associated with the blend of power sources but I have to say for me it seems the weak point of the car. The interior is pretty pleasant now I've found a comfortable seating position and the trim doesnt seem too bad. The ride is very good but the inability of the CVT box to transmit the power at a sensible rev/noise level seems to be a let down. I'm sure the Atkinson cycle engine doesnt help but I do worry how much motorway hammer that engine can handle!

Re your question about why CVT box is used... actually it isn't a CVT box.... it's a power-split device that allows the drive to come from a mix of petrol engine and electric motors in various combinations. Take a look at the explanation here Power Split Device Animation and you will see what I mean. It just wouldn't work with a conventional gearbox.

I must agree with you that for motorway cruising, a conventional diesel is likely to be just as economical (if not more so).... but then you just have to make the most of the relaxed driving style of the Prius. Also, try easing off the accelerator slightly once you are up to speed... you may find your consumption improves. Also, as GrumpyCabbie says, the cold weather knocks your consumption back quite noticeably. Take a look at data on fuelly.com and you will see that mpg dips during the winter.

[atraindriver]

I've seen my mpg on the trip drop this week from around 58 mpg to 45 mpg driving my 3 mile commute. It's colder so I have the heater on, it's damp so I need to demist the screen every morning, it's darker so I have the lights on more and there's more traffic so I have to go with the flow on the short dual carriageway stretch and drive a little faster than I normally did. Not much chance to use EV as the engine cuts in as soon as I put the demisters on. But hey, it's still better than the my previous car a Mondeo 20 TDCi Auto, that did 28 mpg in winter and 30 mpg in summer, although in this weather I do miss the electric front screen and supplementary air heater, an electric element in the heater that gave me warm air within 30 seconds of starting the car.

I think your problem is the three mile commute. It takes at least that to warm up the car, so the engine is going to be running the whole time. You lose the benefit of the motor taking over at low loads. Also, as the engine is cold, it's going to run at its least efficient.

Just be grateful you're getting 45 mpg. You won't get anywhere that on a conventional car, petrol or diesel, as you found with the Mondeo.

I got my used Gen2 T4 this summer and have also been really surprised by the effects of temperature, demisting, heating etc...typical return run to Paddington (33 miles) in Sept was 63.5 mpg (MFD, probably about 58 in reality), now with fog, frost, etc etc down to about 55.7 (MFD, prob about 51 in reality). That's a loss in economy of about 14%. Still pretty damn good, though...

[kithmo]

Try pressing ev when you first start up (assuming you have enough battery left from the night before). This, i beleive, bypasses the initial engine warm up stage.

Not when you put the screen demister on, the engine comes on immediately.

[timberwolf]

Try pressing ev when you first start up (assuming you have enough battery left from the night before). This, i beleive, bypasses the initial engine warm up stage.

Not when you put the screen demister on, the engine comes on immediately.

It would probably have been better to say it delays rather than bypasses the initial warm up stage. Put on the defogger and the delay would be much shorter. :D

[flow]

Try pressing ev when you first start up (assuming you have enough battery left from the night before). This, i beleive, bypasses the initial engine warm up stage.

Not when you put the screen demister on, the engine comes on immediately.

It would probably have been better to say it delays rather than bypasses the initial warm up stage. Put on the defogger and the delay would be much shorter. :D

Abit heavy going but, you might find this thread over on Prius Chat useful...

http://priuschat.com/forums/gen-iii-2010-prius-technical-discussion/76501-gen3-warming-up-stages.html

[Terry953]

Abit heavy going but, you might find this thread over on Priuschat useful...

http://priuschat.com/forums/gen-iii-2010-prius-technical-discussion/76501-gen3-warming-up-stages.html

As you say a bit heavy going and do we need to know? I think not.

I consider the easiest way to review this situation is to remember that all car services [lights - wipers - heaters - demisters - etc - etc] are run off the engine or it's 12v Battery, if the engine didn't start soon after switching on all these items on a cold start, this Battery would soon discharge and the car will not run if this Battery is U/S.

I'm glad to hear the engine start on these cold mornings to run the heaters - demisters - whilst I scrape the frost off the side windows.

The 'traction' battery does only that provides traction either alone [EV mode] or with the engine and has no job in running car services.

Personally I would have liked an engine charging light just to reassure me that the 12v battery is being charged, but Toyota have decreed otherwise. :ffs:

Oh! sorry the thread was originally about consumption - You are bound to increase petrol consumption at this time of year - the shorter the journey the more noticeable this will be and conversely the longer the journey the less noticeable it will be.

EX. I did a 132 mile journey in the cold last week after having to scrape off the frost and ice, I got a 60.1 mpg for that, compare that to my normal Fuelly average, I'm not complaining. ;) Cheers TerryB

[FourFourTwo]

Well, I finally get to pick up my brand new Auris HSD tomorrow!!

This could be a good test of a "worst case scenario" fuel consumption-wise for the following reasons:

1. The car is brand new (I understand it takes a while to achieve top fuel figures)

2. I live in Norway and it is man-size COLD here! (Currently snow everywhere and -6C, forecast to drop to -13C at the weekend and winter hasn't even started yet.)

3. It's impossible for me to drive anywhere without encountering big hills. Even the shortest trip down to my local shop involves a long, steep descent and the inevitable climb back up.

If I get even OK fuel figures out of the car over the next few months, I'll be happy. :D

I'll let you know how I get on.

[flow]

As you say a bit heavy going and do we need to know? I think not.

Well, I certainly found it useful & im sure other people will too.

By gaining even the slightest insight into exactly how the Hybrid system works, can in turn help aid Fuel economy & give a better understanding on 'why is my engine doing this, when should it do that etc'

[ashpole]

I consider the easiest way to review this situation is to remember that all car services [lights - wipers - heaters - demisters - etc - etc] are run off the engine or it's 12v battery, if the engine didn't start soon after switching on all these items on a cold start, this battery would soon discharge and the car will not run if this battery is U/S.

Doesn't the HV Battery charge the 12v one via the DC to DC converter?

[timberwolf]

I consider the easiest way to review this situation is to remember that all car services [lights - wipers - heaters - demisters - etc - etc] are run off the engine or it's 12v battery, if the engine didn't start soon after switching on all these items on a cold start, this battery would soon discharge and the car will not run if this battery is U/S.

Doesn't the HV Battery charge the 12v one via the DC to DC converter?

Correct.

Even in a conventional car it is incorrect to say that the 12v electrics are running from the 12v Battery when the engine is running because the 12v supply will actually be coming from the alternator - oh the past joys of hearing a worn out/loose alternator belt squeal when you put enough load on the 12v supply i.e. usually in winter.

[Terry953]

I consider the easiest way to review this situation is to remember that all car services [lights - wipers - heaters - demisters - etc - etc] are run off the engine or it's 12v battery, if the engine didn't start soon after switching on all these items on a cold start, this battery would soon discharge and the car will not run if this battery is U/S.

Doesn't the HV Battery charge the 12v one via the DC to DC converter?

Yes the DC - DC Converter does play a part in charging the 12v Battery from the HV Battery but that’s only half the story.

If as I stated the 12v battery drain on start up was excessive from the use of car auxiliaries and the engine not running the volt drop would be quite high and I would surmise it is this volt drop that triggers MG1 to start the engine - then charge the HV battery so that the previous drain on the HV battery is made good and the output potential of the 12v battery is raised to functional limits [possibly 13 -16 volts as in an old fashioned alternator system].

Therefore the engine starts to recharge the 12v battery [via MG1 to the HV battery and DC - DC Converter if you like.]

[ashpole]

I consider the easiest way to review this situation is to remember that all car services [lights - wipers - heaters - demisters - etc - etc] are run off the engine or it's 12v battery, if the engine didn't start soon after switching on all these items on a cold start, this battery would soon discharge and the car will not run if this battery is U/S.

Doesn't the HV Battery charge the 12v one via the DC to DC converter?

Yes the DC - DC Converter does play a part in charging the 12v Battery from the HV Battery but that's only half the story.

If as I stated the 12v battery drain on start up was excessive from the use of car auxiliaries and the engine not running the volt drop would be quite high and I would surmise it is this volt drop that triggers MG1 to start the engine - then charge the HV battery so that the previous drain on the HV battery is made good and the output potential of the 12v battery is raised to functional limits [possibly 13 -16 volts as in an old fashioned alternator system].

Therefore the engine starts to recharge the 12v battery [via MG1 to the HV battery and DC - DC Converter if you like.]

Agreed. I was merely clarifying the point as you'd said the HV battery played no part in providing car services, to me it has an important role to play.

[Terry953]

Ashpole

Agreed. I was merely clarifying the point as you'd said the HV Battery played no part in providing car services, to me it has an important role to play.

Yes I did say that, I was trying to present a simplistic explanation, but it was obviously too simplistic for our enlightened forum members.

I shall therefore retract that statement in the interests of accuracy and convivial relations within the forum.

[ashpole]

No problem! Your HV battery's going to need a hug too this weekend if the weather forecast is to be believed!

[Jan&tone]

No problem! Your HV battery's going to need a hug too this weekend if the weather forecast is to be believed!

If the weather forecast IS to be believed (which is questionable as they are never that accurate) my HV is staying firmly in the garage and it's owner will be hugging the radiator in front of the TV !!!!

[ashpole]

No problem! Your HV battery's going to need a hug too this weekend if the weather forecast is to be believed!

If the weather forecast IS to be believed (which is questionable as they are never that accurate) my HV is staying firmly in the garage and it's owner will be hugging the radiator in front of the TV !!!!

Sounds like a plan!