Prius Noob - Any Tips

[Sagitar]

Dear cbcdesign

I cannot morally let your comment “The idea that it is unsafe doesn't stand up to scrutiny” regarding my comments “safety considerations” go unchallenged.

Please refer to the following :--

http://www.drivertrainingtoday.co.uk/forum/index.php?action=printpage;topic=2664.0

http://www.iam-bristol.org.uk/index.php?option=com_content&task=view&id=225&Itemid=58

and the attachment dazzle lifted from the Highway Code.

Now I will expand on my reasoning.

Holding a vehicle stationary by only the footbrake is unsafe for several important reasons.

1. The dazzle situation you appreciate, but did you also know that according to the Road Vehicle Lighting

Regulations - regulation No. 27 it the law not to dazzle?

2. Consider the mechanics of getting hit up the rear whilst in this unsafe situation.

Vehicle runs into your rear - Your body is subjected to the ‘whiplash effect’

A. Head thrust back into the headrest [hopefully correctly adjusted] but still could sustain

Injury.

B. Your torso [supported by the seat and backrest] is pretty well protected, but

due to the softness of the seat construction, your torso will be pulled further into

it.

As your legs are attached they also will be pulled back and as you feet are

attached to your legs they will also be pulled back and as one of them is holding the

footbrake on, the pressure will be diminished or even released completely.

To exacerbate the problem, the feet and lower legs don’t have any support, so will

also be whiplashed back [pivoting from the knees] further diminishing the

braking pressure. Result NO BRAKES.

C. Your car will now be thrust forward unrestrained either into the vehicle in front or

Into the traffic stream, be you on a roundabout or at a road junction.

This will put you into the potential situation of further damage to your car and

further damage to you. Overall Result Increased DAMAGE risk to everything.

Risk all this because you can’t be bothered to apply the parking brake, which I believe on the Prius is foot operated so you don’t even have to take your hands off the steering wheel !!!

Oh Come On !! - You’ve got another foot [hopefully, if not I apologise] use that to effect the parking function. I am presuming the Prius parking pedal is left foot operated ,not that it makes any difference.

Terry

Interesting, but I would hesitate to be as certain as you are, not only because the physics and physiology of leg extension are not fully described by your note, but also because the braking force available from the parking brake is much less than the braking force available from the firmly applied foot brake.

Your note about dazzle and the law gives the impression that you are claiming that dazzle from brake lights is, of itself, illegal. If that is the impression that you intended to give, then you are wrong. The section of the Highway Code (paragraph 114) that deals with the use of brakes in stationary queues uses the word "should" i.e. it is advisory, and not a legal requirement. If it was a legal requirement it would use the word "must". My guess is that it is advisory because of the complexity of the situation that it covers. If you read it in detail, it advises the application of the footbrake as long as there is moving traffic behind you. It advises removal of the foot from the footbrake to reduce glare, only when the following traffic has stopped. i.e. it is saying, quite sensibly in my view, that having your brake lights showing is a good thing if you are being approached from the rear by another vehicle.

[kithmo]

1. The dazzle situation you appreciate, but did you also know that according to the Road Vehicle Lighting

Regulations - regulation No. 27 it the law not to dazzle?

3.

C. Your car will now be thrust forward unrestrained either into the vehicle in front or

Into the traffic stream, be you on a roundabout or at a road junction.

This will put you into the potential situation of further damage to your car and

further damage to you. Overall Result Increased DAMAGE risk to everything.

Terry

1. There is a difference between "Must" and "Should" in regulation 27 of the highway code, "Must" for headlights foglight etc and "Should" for brake lights, so it is not against the law to hold your foot on the brake when stood, although it is a bit inconsiderate.

3. c. LOL, I don't think the Prius is capable of thrusting forward especially when both your feet are being pulled off the pedals, it will if you let go of the brake and press the accellerator.

Re: the creep function, If the Auris uses the same Hybrid system as the Prius why would the creep be disabled when pressing the brake pedal on the Prius and not on the Auris ? it doesn't make sense.

Re: Using the foot operated parking brake, I stand corrected, it is the same with the Prius, you don't have to apply the footbrake if you have put the gear selector in "N" then go to "D" it's only if you have selected "P" that you have to press the brake pedal. You have a convert, I may adopt the foot operated parking brake and "N" technique when stood in traffic and my traction Battery is well charged, if I can get used to it.

[cbcdesign]

Risk all this because you cant be bothered to apply the parking brake, which I believe on the Prius is foot operated so you dont even have to take your hands off the steering wheel !!!

Oh Come On !! - Youve got another foot [hopefully, if not I apologise] use that to effect the parking function. I am presuming the Prius parking pedal is left foot operated ,not that it makes any difference.

Terry

If you think a handbrake is more effective that the application of all four brakes on all four wheels you are sadly mistaken. Many handbrakes are nothing more than crude drum brakes and have nothing like the force four hydraulically operated disk brakes will apply. That somewhat negates your argument about being hit from behind in my opinion. Being hit with a hand brake on is far more likely to result in a bigger jolt and more forward movement in fact, not less as you would have people believe.

You don't even bother to consider all the extra wear and tear on the gearbox and hand break that your "method" inflicts on the vehicle either or the fact that break lights are off as sagitar mentioned which is even more unsafe if nothing is stopped behind you but traffic is approaching from the rear.

Sorry but your arguments do not stand up to scrutiny in my opinion.

As I said, the only point you make that has merit in my opinion is regarding dazzle at night. I too find it annoying and then and only then use the handbrake. As a matter of safety however it most certainly is not safer at all. Foot brakes are far more powerfull than hand brakes as any decent mechanic will confirm.

[Terry953]

3. c. LOL, I don't think the Prius is capable of thrusting forward especially when both your feet are being pulled off the pedals, it will if you let go of the brake and press the accellerator.

Re: the creep function, If the Auris uses the same Hybrid system as the Prius why would the creep be disabled when pressing the brake pedal on the Prius and not on the Auris ? it doesn't make sense.

Hey kitmo !

Your Prius will be thrust forward with considerable force if, as I described in my exposition, some monkey runs into your boot !!

Regarding the 'creep function' It was you that said this function was disabled - not me.

[Refer to your post 06 May 2011 - 03:13 PM = In option 3, I believe holding the footbrake disengages the creep, so no stress on the transmission/battery AFAIK, ]

That's why I gave instructions to look at your 'Energy Monitor' to prove it is discharging your Battery.

Another thing I only noticed this afternoon, I had been driving around a car park in EVO, then stopped [the Energy Monitor was registering a discharge as normal].

When I moved off in 'D' the engine started, and I moved to another place to embark my wife, as is my normal practice when stopped, I applied the parking brake and selected 'N' the engine revs increased slightly indicating removal of the load - the car sunk down as the attempted driving stresses were removed and the 'Energy Monitor' charging indication disappeared as normal.

I concede the "dazzle" statement but that doesn't make it excusable.

Cheers Terry

[kithmo]

Regarding the 'creep function' It was you that said this function was disabled - not me.

[Refer to your post 06 May 2011 - 03:13 PM = In option 3, I believe holding the footbrake disengages the creep, so no stress on the transmission/battery AFAIK, ]

That's why I gave instructions to look at your 'Energy Monitor' to prove it is discharging your battery.

Cheers Terry

But you were saying it is still in creep mode with the footbrake on in "D"

My energy monitor on the Prius doesn't show any discharge when holding the car on the footbrake in "D".

[Sagitar]

But you were saying it is still in creep mode with the footbrake on in "D"

My energy monitor on the Prius doesn't show any discharge when holding the car on the footbrake in "D".

I think this is just a misunderstanding. First of all, can we assume that the ICE is warmed up, so it is not running and charging the traction Battery?

In order to create gentle forward motion with no accelerator applied, a small emf is applied to the traction motor to create torque. With the brakes applied, the traction motor cannot rotate and therefore it uses no energy (other than a tiny amount of waste heat). Lifting the foot from the brake allows the traction motor to rotate, some energy is used to create acceleration and the vehicle rolls forward gently. Pressing the accelerator pedal increases the torque at the traction motor and increases the rotational speed up to the point where the ICE joins in - etc.

Putting a voltage across the motor will create torque, but will not use energy if there is no motion. Think of a tank of water with a tap low down on one side. The water height above the tap creates pressure at the tap, but no water flows unless you open the tap. Applying and releasing the brake is like closing and opening the tap.

[GreenJuice]

Re: the creep function, If the Auris uses the same Hybrid system as the Prius why would the creep be disabled when pressing the brake pedal on the Prius and not on the Auris ? it doesn't make sense.

You have a convert, I may adopt the foot operated parking brake and "N" technique when stood in traffic and my traction battery is well charged, if I can get used to it.

I can offer a possible explanation to explain the observations by others on the 'creep function'. I use ScanGauge to monitor current flow in (regeneration) and out (energy use) of the traction Battery.

a) When stationary in D, it is possible to hold the car still whilst only lightly applying the footbrake. On the Prius Gen 2 energy display, a yellow arrow shows up between the electric motor and the wheels. Scangauge shows several amps of current drain.

b ) Remaining stationary in D, then pressing more firmly on the footbrake, the yellow arrow on the display disappears and Scangauge shows a drop in current drain to a just over a couple of amps.

c) In Neutral, foot off the brake, the Scangauge value is lowest, below one amp.

From these observations, you can see that 'timberwolf' is correct that the creep is reduced or cancelled by holding with the footbrake, if you hold it firmly enough. It also shows that the lowest energy use state is in Neutral.

A few years ago on Prischat, I exchanged the same discussion currently being shared on this thread, with Ken a well known Japanese hypermiler. Serious hypermilers apparently use Terry's option 2. It does take some getting used to as it involves a 'dance' of both feet and a hand on the gearstick. I do it without thinking now. It is possible to hold the car stil with your left foot on the parking brake with full load on an incline and without engaging that first parking 'click'.

I have owned a variety of automatic cars over the last 20+ years and 'always' used to selfishly and lazily sit on the footbrake at traffic lights. This Prius is the one car that has given me the incentive to rethink my driving habits.

On a separate issue in this thread, measurable and significant MPG gains have been reported by many, including myself, who overpressure their tyres. Ultimately I see it as an issue of personal choice and personal responsibility. However, the evidence that I have seen does appear to show such gains do continue to rise with pressures well above the maximum side-wall pressure from the manufacturer (and these have been tested and used by some crazy hypermilers out there!). So at the pressures that we are discussing here, there is plenty of scope for individual preference and safety. My advice is to research the topic thoroughly and take personal responsibilty for your actions.

[Terry953]

But you were saying it is still in creep mode with the footbrake on in "D"

My energy monitor on the Prius doesn't show any discharge when holding the car on the footbrake in "D".

Well 'kithmo' my Auris one does, check out 'green juices' post Yesterday, 09:50 PM his Prius does as well.

Maybe you have a problem - time to visit the dealer ?? It seems a bit of a mystery to me.

Cheers Terry

[Terry953]

I think this is just a misunderstanding. First of all, can we assume that the ICE is warmed up, so it is not running and charging the traction battery?

Putting a voltage across the motor will create torque, but will not use energy if there is no motion. Think of a tank of water with a tap low down on one side. The water height above the tap creates pressure at the tap, but no water flows unless you open the tap. Applying and releasing the brake is like closing and opening the tap.

Dear Sagitar

I disagree with your theory for the following reasons:---

Emf [Electro Motive Force - Pressure] is Voltage not current flow [Amps]

Your water analogy is flawed in this case and should never be used in other than very simple electrical circuit explanations - I would therefore modify it as follows :---

Think of a tank of water with a tap low down on one side.

The water height above the tap creates pressure [VOLTAGE or EMF] at the tap [sWITCH],

but no water [CURRENT] flows unless you open the tap [CLOSE the SWITCH - select ‘D‘ say against the resistance of the vehicle weight and the brake].

Applying and releasing the brake is like VARYING THE RESISTANCE or varying the flow rate of the water by closing and opening the tap.

It is current flow [Amps] in our case that drives a transmission motor.

This is what is indicated on our Energy Monitors not EMF, however if the resistance to move the motor is greater than the force of the current supplied, then the energy will be converted into heat [with all its detrimental implications] including draining the transmission Battery. In other words the motor is in a stalled situation and generating only heat.

{This is why the manual states not to have ‘D’ engaged for extended periods when stationary}

You can modify this situation depending on your needs by :---

1. Disengaging the ‘D’ [ie closing the tap] thereby removing the rcurrentnce, the attempted curentbatterynd drain from the bettery.

[The Energy Monitor stops registering current flow from the battery]

2. Deliverthrottleower by pressing the thottle [ ie opening the tap]

[The Energy Monitor registers current flow from the battery]

3. Reduce the resistance by releasing a brake then the vehicle will move.

[The Energy Monitor registers current flow from the battery]

Green Juice’s explanation basically backs me up by supplying rough current measurements at various situations where I only have the graphic Energy Monitor.

However I still maintain being stationary and in ‘D’ is bad driving practice [as per IAM & Highway Code to name just two sources] and detrimental to the hybrid system [as noted in the drivers manual]

Oh! By the way ‘Green Juice’ us Auris owners don’t have to do a dance to set the parking brake as it is the conventional hand lever type, so after applying it you select ‘N’ with just the left hand.

Another Can of Worms Cheers Terry

[Jan&tone]

However I still maintain being stationary and in ‘D’ is bad driving practice [as per IAM & Highway Code to name just two sources] and detrimental to the hybrid system [as noted in the drivers manual]

The IAM recommend LEAVING THE GEAR SELECTOR IN D and applying the handbrake when stopped at traffic lights or other momentary stops. The physical act of removing the vehicle from D and into N or P at short stops such as traffic lights, zebra crossings etc puts excessive wear on the gearbox. Modern automatic gearboxes are designed to be held on the handbrake for short periods of time and this therefore does not create excessive wear.

As to Hybrids, there is as yet no specific guidance. (Those lofty people at Chiswick haven't heard of Prius and Auris yet)

Unfortunately I can't quote you the exact paragraph word for word from the IAM Guidance on Automatic Gearboxes because it's at home and I'm at work, but it's the one I give all Associates should I have one that has an automatic gearbox in the vehicle they are going to take their Advanced test in.

[Terry953]

The physical act of removing the vehicle from D and into N or P at short stops such as traffic lights, zebra crossings etc puts excessive wear on the gearbox. Modern automatic gearboxes are designed to be held on the handbrake for short periods of time and this therefore does not create excessive wear.

As to Hybrids, there is as yet no specific guidance.

Unfortunately I can't quote you the exact paragraph word for word from the IAM Guidance on Automatic Gearboxes because it's at home and I'm at work, but it's the one I give all Associates should I have one that has an automatic gearbox in the vehicle they are going to take their Advanced test in.

Please explain to me in technical detail how excessive or even any wear takes place, and to what components in your auto-gearboxes does this wear effect when the vehicle is stationary out of gear as compared to in gear.

When you have to hand your IAM book on auto gearboxes please copy me their guidance on Toyota Hybrids, Hey! but you say there is "no specific guidance", so what do you give your Associates that have a Prius or Auris car prior to their Advanced test?

Perhaps it is time to refer the matter to your IAM for their "specific guidance" and quote us their reply. This is getting very woolly

[capnbirdseye]

I tried the trick with the foot parking brake when I first had the car & it does indeed hold before the first click (altho it makes no difference if it does click & lock as it releases so easily) but seeing the yellow arrow lit the whole time ( gen2) put me off doing it because as far as I know electric motors don't like being fed with current whilst being unable to turn.

[Jan&tone]

Please explain to me in technical detail how excessive or even any wear takes place, and to what components in your auto-gearboxes does this wear effect when the vehicle is stationary out of gear as compared to in gear.

[/unquote]

No idea! I'm not technical, only going by what I've been told by people who have far more experience of this!

You will note that as I said above, I have no specific guidance on Hybrids, other than to treat them as normal auto boxes.

It's only getting wooly because people are trying to get too technical.

Hybrids are technically different to a normal automatic, in that they have an ecvt box rather than a torque converter, but they have an engine, 4 road wheels and go when you push the go button like any other motor vehicle!

I checked mine today, sitting outside the garage with the car in D and my foot on the footbrake, there was no repeat no flow from the ice or the battery to the wheels shown on the display.

I can only assume from that, that there is no drag taking place rherefore no wear.

Aa others have said on other threads, how you treat the Prius and Auris, and no doubt the ct200 and 450h is for the owner to decide after reading the book and taking their pick from this forum. We all have our own method and sequence at 'stop' points, some are safer than others but most are functional.

The OP asked for 'any tips' not lectures on the technical aspects of hybrids. Let us keep to the original thread and give 'tips' not overly serious lectures

[kithmo]

I checked mine today, sitting outside the garage with the car in D and my foot on the footbrake, there was no repeat no flow from the ice or the battery to the wheels shown on the display.

I can only assume from that, that there is no drag taking place rherefore no wear.

+1

[cbcdesign]

In a conventional Auto gearbox, particularly in older cars, the linkage is entirely mechanical and moving it into and out of drive every time you stop at lights or junctions is going to increase the likelihood of premature failure. Like any mechanical joint, it has a finite life and extending that by minimising unnecessary shifting is common sense in my opinion.

I found this in the North East London and Essex Group of Advanced Motorists:- When stationary in traffic, even for many minutes, it is not necessary to move the gear lever into neutral because the torque converter absorbs the engine propulsion force but does not transmit it all to the gearbox as the engine revs are too low. No wear is taking place. In fact, more wear will take place if the driver engages neutral and then engages a gear when he is able to move off.

I think because the Prius is an electrical gear stick there probably isn't any wear and tear by selecting Neutral when stationary. Its a whole new world frankly!

[Jan&tone]

I'm sure I have an electronic version of the IAM's missive on Auto boxes, If I can find it later today I'll post it somewhere

[Jan&tone]

Found it!

Attached Institute of Advanced Motorists advise on the use of Automatic Gearboxes.

Hope this helps to clear up some anomalies...

you will note that there is no mention of Hybrids, I tell my associates, when they realise what my car is, that I treat it as I would a normal Auto box - we have low gear, (B and drive (D) and P and N, otherwise it's point it and push the button!!

auto boxes.pdf

[Chris Dance]

This is getting very technical. When I got my first gen 2 prius the dealer explained that one of the advantages of the hybrid was that you did not have to move out of D when stopped for a few moments at red traffic lights etc. Just hold the car on the foot brake I was told. This is what I do. If I am stopped for some time I press P and apply the foot brake. (Hand brake). If you sat a driving test in a Prius what would you do at a traffic lights? Anybody sat a driving test in a Prius?

[Jan&tone]

This is getting very technical. When I got my first gen 2 prius the dealer explained that one of the advantages of the hybrid was that you did not have to move out of D when stopped for a few moments at red traffic lights etc. Just hold the car on the foot brake I was told. This is what I do. If I am stopped for some time I press P and apply the foot brake. (Hand brake). If you sat a driving test in a Prius what would you do at a traffic lights? Anybody sat a driving test in a Prius?

Chris, you are pretty much correct.

I went on an IAM Observers training day in mine in November last year and asked one of the examiners the same question.

The answer was that if you are stationary for traffic lights that have only just changed to red you press P. Otherwise hold it on the footbrake.

The parking brake is just that, for parking!

Bear in mind too that you have the hill start assist on the gen3, so you wouldn't need the parking brake even for a hill start!

I believe that Esther Rantzen took and passed her Advanced test in a Prius last year some time, but whether anyone has taken the DSA test in one I don't know.

[dwilson]

This is getting very technical. When I got my first gen 2 prius the dealer explained that one of the advantages of the hybrid was that you did not have to move out of D when stopped for a few moments at red traffic lights etc. Just hold the car on the foot brake I was told. This is what I do. If I am stopped for some time I press P and apply the foot brake. (Hand brake). If you sat a driving test in a Prius what would you do at a traffic lights? Anybody sat a driving test in a Prius?

Chris, you are pretty much correct.

I went on an IAM Observers training day in mine in November last year and asked one of the examiners the same question.

The answer was that if you are stationary for traffic lights that have only just changed to red you press P. Otherwise hold it on the footbrake.

The parking brake is just that, for parking!

Bear in mind too that you have the hill start assist on the gen3, so you wouldn't need the parking brake even for a hill start!

I believe that Esther Rantzen took and passed her Advanced test in a Prius last year some time, but whether anyone has taken the DSA test in one I don't know.

My previous car had a conventional automatic and I just left it in D and applied footbrake or handbrake at lights etc unless I was going to be stopped for a long, long time e.g. at temporary lights when I put it in N. (Also P when parked and R for reversing).

I've had my Prius since last August and drove it in a similar way but then after reading comments on here started to put it into P when waiting for more than a few seconds otherwise just holding it on the brake. The only time I use the foot-handbrake is when it is parked.

No hill assist on Gen2 as far as I know but it does hold on reasonable inclines. It has to be very steep not to hold. My drive is an example though!

David

[GreenJuice]

There are numerous references on the Priuschat website, cautioning against using P at lights or other stops while in traffic. A rare occurence of being shunted from behind ( which has happened to me, but not in this car) could seriously and expensively damage the gearbox. Having the parking brake strongly engaged while doing this should offer some protection.

My view is that is safer to remain in D (or N, if you don't find it too troublesome).

[dwilson]

There are numerous references on the Priuschat website, cautioning against using P at lights or other stops while in traffic. A rare occurence of being shunted from behind ( which has happened to me, but not in this car) could seriously and expensively damage the gearbox. Having the parking brake strongly engaged while doing this should offer some protection.

My view is that is safer to remain in D (or N, if you don't find it too troublesome).

Good point - I have luckily had few accidents over many years but 3 have indeed been shunted from behind whilst staionary (although in one case I was parked and out of the car!) And on the other occasions had been waiting for a time before being rammed.

Perhaps I will change my habit of using P back to just when parked....

Thanks

David