I am from the UK I am currently researching within the area of hybrid electric vehicles and have been trying to improve the way in which refinement of these vehicles is assessed during the early design stages. I have driven a Toyota Prius on a number of occasions. I have also had some subjective assessors stating that the feedback through the steering wheel is quite heavy, and the brake sounds are very squeaking when applying the brake pedal very hard, for example.



Just a question to anyone who has any feelings on any of the refinement issues with regards to the Toyota Prius you own, or have driven? What would you specify as both the positive and negative points Toyota have managed to achieve with the Toyota Prius? Who knows with your help, we may be able to improve something that is already a fine piece of manufacturing.




Thanks,

John ;-)

 

I'm not sure what you mean by refinement issues, but I'll tell you if you're pressing the brake pedal that hard, you're not driving the car efficiently. You should only ever stomp on the brake in emergency situtations. Using the brakes kills your fuel economy.

/a guy goes into the doctor's office and says, "it hurts when I do this..."

 

Hi John,

First welcome and I understand you currently have no hybrid. Are you 'kicking the tires' stage or something else?

You might start with reading our FAQ to get some idea of how we find the Prius to work. But I have a little problem with "subjective" assessments:

- "steering wheel is quite heavy"
- "squeaking when applying the brake pedal very hard"

Having driven farm equipment and a 1929 Model A Ford, I find the Prius steering to be quite easy. Can you give some indication of the test environment and compared to what?

As for "squeaking", the rod actuated Model A Ford brakes sang a Wagner Opera . . . sometimes accompanied by a driver and passenger chorus. Again, we need some understanding of the test envrionment.

I have braked my NHW11 03 Prius hard enough to feel the Anti-Lock Brakes (ABS) kick in. I don't remember any unusual noises because the incident was exciting in other ways.

Frankly, I wish the horn were tied to the ABS system, which would mask any brake noises and take one last burden off of the driver. I think hard braking should be vividly remembered by all parties involved with flashing lights and horns.

Bob Wilson

 

There is a distinct electric motor whine that the Prius emits when braking normally or moderately, that may be what you're talking about. Personally I rather like that sound. The other possibility is that the friction brakes hadn't seen much action due to electric braking being used 99% of the time on the test vehicle and this hard braking test made them squeak, but I've never heard of that before.

Steering can be a little weird, but I think it's more of a suspension issue, if anything. My friend upgraded his suspension (TRD) and his Prius drives like a whole new car, no more over-steering! I don't find it too stiff, but I haven't exactly compared it to luxury cars either.

 

The environment in which I have been running subjective experiments is within an NVH (noise, vibration and harshness) simulator. We captured sounds and vibrations from a Toyota Prius under a number of tests which covered the full spectrum of HEV specific driving conditions.



Once we had captured the appropriate data (sounds, vibrations, component switching), we needed to make sure that the correct HEV control strategy was in place to be able to reproduce exactly what was being heard, felt and used whilst driving the vehicle in the real world. By being able to reproduce the Toyota Prius operations within a virtual world we are able to change the configurations of the standard model, increase/decrease the initial Battery SOC, change the control strategy (e.g. EV only mode lengthening), for example. Then get subjects to drive the vehicle and assess how they perceive the refinement of the vehicle. Once you test a number of different configurations and control strategies it is then possible to find out some of the more objective measures for these by feeding in the actual drive cycles used by the subjects into a performance model to see what the emissions, fuel economy, etc. would have been.



It was felt that not enough subjective assessment of customers was being considered early on before in the design loop in conjunction with the more objective side. Once we understand what customers like to feel and hear, it is then easier to see whether a particular vehicle design is feasible in terms of costs, manufacturing, performance, etc. Whereas before, the first real input a customer can have is when they see the vehicle for the first time in a showroom, when it is too late to have any real significant input into the vehicle they want, apart from air conditioning yes/no or car colour for example.



So trying to find out some of your views may help with the kind of important questions I’d need to ask, and what kind of experiments are worthwhile involving potential customers in.

 

John,

Thank you for the complete explanation. Without context, I tend to assume a neophite posting. Please take my real Model A Ford comments with wry grin.

I would like to suggest another forum of Prius technologist, the Yahoogroup "Prius Technical Stuff" who would be interested in your work. Our membership has done a lot of work expanding the Prius technical envelope and maintains an extensive set of Prius technical papers and reports that now spans three groups. Everything you've posted here would be an excellent introduction:
One of the reasons why "Prius Technical Stuff" is important is our members actively engage in performance enhancements. One member whose handle is "Hobbit" recently published "Warp Stealth" on how to get optimum fuel efficiency at speeds above 41 mph. He did this using discrete electronics instrumentation versus the OBD scanning approach others have used. In short, you'll find a community of technologists who use empirical means to expand the envelope.

I'm new to the group and have my own Prius projects but they do not involve handling, yet. My first year's experiments have dealt with getting emergency power, 120 VAC power from the Prius, transaxle oil testing, some MG1/MG2 instrumentation and on-going ICE and transaxle block heater experiments. The 'low hanging fruit'.

Bob Wilson

ps. My dad thought that having us maintain and drive a 1929 Model A Ford would teach us a lot about auto mechanics. We learned . . . DON'T EVER GET A MODEL A FORD!

 

John,

Number one on my list is an energy neutral glide. When I take my foot off of the accellerator, I would like my Prius to take an energy-neutral glide. If I want to go slower, I'll use the brake. But as soon as I take my foot off, the car goes back to energy neutral, coasting without regeneration.

Number two is an indication of when my braking is transitioning from regenerative to mechanical. This would allow me to maximize my energy recovery. For example, "hard brake" to let me know I'm using the mechanical brake.

Number three on my list is a "load sensitive" cruise control, option. I would like to set my cruise control for a given "maximum" speed but allow the car to bleed off up to 5 MPH when going up a hill. Once the load goes down, the vehicle would accellerate back to the maximum cruise speed using an energy efficient ICE speed.

Number four on my list is an "air speed high" indicator that would let me know how close "to the wall" I've come. There are non-linear MPG impacts at speeds above 65 MPH. Depending upon wind direction and velocity, this point moves both ways. I would like an indication of when I can travel faster or need to travel slower to get optimum MPG.

It would be perfectly fine by me if there were a switch, button or other control that would enable or disable these four modes, called "hypermiler", to be enabled by the driver.

Bob Wilson

 

does the prius offer some way to tell when you go into an energy neutral glide? for example, on the hch, the instantaneous assist and regen gauges along with the instantaneous mpg allow you to tell when you are entering and exiting glide-neutral. it makes it pretty easy to manage the process manually.

the hch instantaneous regen gauge is useful for this. you can tell exactly how much braking is being caused by regen. it's also useful for when ima thinks it might try to sneak in a single green regen bar even though you battery charge is 7/8 full (really annoying b/c you take about 10%mpg hit when this happens) you can slightly press on the accelerator to get the single regen bar to go away.

 

Hi,
The Prius has an energy flow screen but it lacks 'units' and has a lag of a second or so. But you can adjust the throttle to 'no arrows', an energy neutral glide. The other alternative, which is illegal on a down grade, is to put the Prius in neutral. Neither approach is automatic and that is a problem our vehicles share including the HCH.

Some of the other hypermilers use an OBC scan tool to monitor energy flows with engineering units. I admire the sentiment and that is the tool I recommend to those who are serious about Pulse and Glide. But again, this adds one more burden to the driver, to distract them from situational awareness.

IMHO, the glide should be automatic, built into the vehicle.

The Prius "Consumption" display has a 5 minute average and puts up yellow-triangles for regenerative braking energy. Obviously, this is well after the actual braking event occurred but this has led to two, home-brew approaches.

An Aussi driver put an amplifier in his NHW10 so regenerative braking is more aggressive, which defers mechanical braking. Another Prius owner, Hobbit, has a circuit in his NHW20 that illuminates some LEDs when mechanical braking begins. However, my driving does not involve a lot of regenerative braking.

On my communting route, I have often gotten to work or home without even one triangle. When I do get them, it is from an alternate route that involves coasting down a hill. Even though I drive so I don't have to brake often, I would like some indication of the threshold between regen and mechanical braking.

Bob Wilson