HSI details

Haven't tested mine enough to help you out with the XXX facts, but one thing I've noticed that you don't mention is that the center line is "sticky"...there is a little bit of play in the accelerator once the center line is hit before the bar moves to the right and the engine lights.

 

From Hobbit's page:

Coming from a guzzling Subaru, it is very pleasant to see ScanGauge showing low RPM and high manifold pressure while operating in this green zone, indicating much reduced pumping loss.

I've been dropping into the lower Red zone too much and seeing the manifold pressure fall, indicating the return of pumping losses. At least RPM is very low. This seems to be a hint that I should be breaking into Pulse & Glide, at least at speeds where Stealth is available. More practice is needed.

Will try to test and report back at the end of the week, if no one else has done so by then. But if it gets significantly higher than Gen2, I'll wimp out.

I wasn't able to confirm this, at least while sitting in the driveway. More detail in my next report.

My foot has adapted to leaving this mode engaged permanently. I leave it on partly to cover the rough spots in my style, partly to gain the more efficient AC mode, partly to make cruise control (when I'm lazy) less aggressive. Most full time Gen3 drivers are likely to similarly adapt, though it should be turned off for test drives by folks accustomed to "vroom vroom".

For shorter and shallower hills, where the 'fake engine drag' regeneration is not enough to prevent undesired acceleration but B is too much, I've taken to temporarily setting Cruise Control to increase regeneration to hold the car at a constant speed. This is very effective, until the traction battery fills, at which point the ICE starts whining as a high powered vacuum cleaner (high RPM and strong manifold vacuum) for real engine braking.

The thread that first mentioned this suggested that it is a new feature in Gen3.

 

Will this help?

Near as I can tell, the HSI is a simple power requested indicator. One of the interesting but seldom used data points the Graham Mini-scanner reports is 'requested power.' My testing suggests the HSI behaves like a 'requested power meter.'

Bob Wilson

 

I was able to test a few things on a road trip the past few days.

From Hobbit's "Tao of Hsi":

Confirmed. It worked fine for me this afternoon, on each of several tries.

Regarding HSI display ECO area:

Unfortunately, the nearly ideal road section for this test, a known level section along a reservoir, had potential witnesses, so no go. I did try it in twice on other stretches, aborting both runs at 79 mph without having reached a steady speed. Unfortunately the GPS betrayed 25-30 foot descents.

Max RPM while still in this ECO area varies with speed -- 1660 rpm at slow street speed of about 20-25 mph, about 2400 rpm at 60 mph, and a solid 3200 rpm at 79 mph.

This trip included descending 6 mountain grades long enough to completely fill the traction battery on regeneration (CC and B modes) and automatically revert to pure compression braking, spinning up as high as 4700 rpm. If doing it again, I'd keep track of how much elevation loss was thrown away without regeneration, but it was almost certainly more than 5000 feet. That represents about a half gallon of gas spent climbing that could not be recovered by later downhill glides or regenerations. Despite this loss, mpg was 58.8 (displayed) or 57.2 (simple pump calculation) or 56.0 (pump including slight overfill on previous refill).

 

Hobbit,

I don't have my Prius yet, 20 days and counting, but I found your Tao of HSI to be very informative.

Could you please clarify your statement "As always, working engine-run times into upcoming road elevation changes generally gives the best results"? I think I have a general idea of what you are talking about, but some more specifics would help.

I am sure that you are right that pressing the ECO mode button brings up the HSI scree. When we did a test drive, I engaged ECO mode and the HSI screen popped up. The salesman was completely surprised.

Thanks.

 

I'd agree with the "sticky" concept at the center line (when it exists) on the HSI. This was one of the first things I noticed after driving my new 2010, and I commented on it through this thread: Got the "Feel" of the HV/ICE Line!.

One benefit of the HSI is that you can see whether your demand/draw on or from the HV battery/electric motor(s) is too high to justify keeping the car in EV.

 

Definitely leave this open, as I found only the neighborhood of the answer, not the actual answer. Though it is probably in the low 80s, I did have the bar well into the triangle, almost to the point where the ECO label turns off, and the road was providing a slightly gravity assist. The descent was visible only on the GPS, not visually from the terrain, but Prius certainly makes good use of gravity when it is available.

No wind was seen, but the very low vegetation was not good for displaying it.

 

Hobbit,

Please see a post I made in another thread.

This comes only from observation and I cannot confirm this with technical information.

If it can be of any use, although it brings more questions than answers!

 

Using the following display points:

The 75% point is marked with the right-most yellow tape. The camera parallax error is due to the cover being displaced from the active display. The right-most yellow tape looks to be at the 75% point from the driver seat.

The values I get for energy on a hill climb using a Garmin nuvi GPS to record velocity and altitude are:

Notes:

• at 100% Eco, the speed was ~35 mph, 72F
• at 75% Eco, the speed was ~25 mph, 72F
• holding a constant power setting while driving is distracting

Bob Wilson

 

(Image courtesy of Hobbitt)
Don't know if this helps - on what I believe is windless flat and anyway same result in both directions - by holding the HSI actually very slightly below what the image indicates I ran out of road at 90 and had to back off. It may have been my imagination but from just over 80 the rate of acceleration seemed to increase noticeably - could the aerodynamics be working better over 80?
(My car is a base UK model T3 with 15" wheels)

 

Do you have a portable GPS, like a Garmin nuvi? If you have a Garmin, I can share a Perl program to convert the trace data into an Excel compatible spreadsheet and then we can analyze the data. But to answer your question.

Yes, there are non-linear, aerodynamic effects including a local peak drag that then falls off. It is possible to reach a 'terminal velocity' and then descend a small hill and emerge 'on the other side.' You'd be able to sustain that speed unless you went too slow and then the local drag spike would decellerate to the 'slow speed.'

I have on stretch that I've reached 100 mph before in my NHW11 (2003 Prius.) I may try a maximum acceleration test with the GPS and we'll see what happens:


Bob Wilson

 

If I may: what is "spark" in the graph?

 

Regret no, not yet.

It did feel like that I think, but I'll need to try it some more times and on different roads to be sure.
Will be interesting to see too if anybody else notices it.

I found it anyway when googling for garmin nuvi's!

I can see this leading me to wind the Linux up again.

 

That is the spark advance. Back then, there was a lot of buzz about using spark advance as a way to detect efficient engine operating regions. It was easy enough to record it and the dip was curious but nothing that really 'sparked' my interest.

In this test, I had force-charged the traction battery and then pulled out on the test area. The engine was off until I floored the accelerator and held it there until the end of the test.

The spark advance change was curious but of brief duration. I didn't see anything worth pursuing in that line. The reason is I soon began to look at energy flows, the power consumed by drag and inertia versus the power provided by the ICE augmented by the traction battery.

To make any use of the spark or valve or throttle advance, I would be building a model of a very sophisticated engine, the 1.6L. As interesting as that might be, I'm more interested in systems, the total vehicle performance. It is the way my mind works.

Bob Wilson

 

I've now got a Garmin and that's showing that my speedo is about 4mph optimistic so for 90 read 86.
When I get the chance will try again and check the road is level.