2010 Prius 2ZR-FXE engine efficiency map

90mph is just 144kmph
even that this is above the 120 here in the netherlands lots of people drive 140 here
and when you go to germany 140 is slow
you drive 150 to 180 there with a normal car.

so its not really going to try to compete

on the other hand
in germany lots of highways are going down from NO limit to 130kmph
so in that case ( and its growing ) its a nice thing for the new prius

battle the diesels

 

Even so TP. By pulse & glide one is effectively removing one lane from the road for practical purposes. Which right does one have to limit the traffic on a 2 lane road to 1 lane only? It just does not feel right.

I hate it when people in front of me can't keep a steady speed. Anyhow, I doubt that p&g from 65-45km/h can get you much better results than cruising with CC at 60 km/h for example. At 65 km/h the efficiency of both the inverter and MG2 is maximum (~93.7% combined). On top of that, this is just bellow limit speed you can go without the ICE turning, which is beautiful.

In practical terms, the Prius will pulse with ICE on to charge the HV battery about half the time, and stealth with ICE off the rest of time. I can always get around 2.5 L/100km (94 US MPG) with this very straight forward "technique" and I don't have to bother the other drivers with annoying pulse & glide speed variations.

 

Allow me to disagree here.

We also have 120 km/h high-way speed limit here, and just like in NL most drive at 140 km/h .

By being a lot more efficient at around 90 mph the new Prius is in fact attacking the diesels strong since this is the most commonly used high-way cruising speed.

This is excellent.

 

it was about the german autobahn
thats wath i was replying to

when you look at normal driving EU speeds then yes this new prius will do a lot better on the highway

but not when competing to a diesel when driving 180-200kpmh i think on the german autobahn:fear:

 

Still not convinced here

At 180 km/h what do you think is the efficiency of a BMW 525d? Or a VW Passat TDi? What do you reckon is their consumption?

I would not bet either way!

 

Could someone rent a diesel for a day and possibly run it up and down the highway at different speeds to measure the mileage?

Bob Wilson

 

I live too far away from Germany to test this, and anyway I refuse to drive diesels, I don't drive those pollution manufacturing plants!

I always find myself amazed when I read some American folks asking for diesel cars in the US. If they only knew how terrible the emissions on those cars are... but that's a different topic.

 

Allow me to agree here.

 

[scratching head]where are the BSFC circles below 220 ?[/scratching head]

btw, and I hope someone will correct me if I am wrong, a bsfc of 220 equals 36% engine efficiency. My read of this new engine is that it *extends* the efficient range, but maximum efficiency is little improved over the Prius G2 engine. This reinforces my earlier opinion that P&G at low speeds and avoiding high speeds puts a G2 driver in the same fuel economy ballpark as the G3. Speeds of 43 to low 50's mph might be a G3 strength though, since P&G in that speed range in the G2 is at best a pain, and often not practical.

I also get the impression that petrol engine efficiency over 40% is quite a barrier.

 

BSFC - how to go down the garden path!

If you are interested in the BSFC and how it relates to our vehicle, I would recommend reading this synopsis:

Brake Specific Fuel Consumption

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The key quote:

I asked the question about what rpm folks are using knowing full well they would report numbers significantly lower than the BSFC charts show as optimum. There is a method to my madness but we can discuss that another day.

Bob Wilson

 

Yet another stupid question --

Ken's charts have torque on the Y axis. Is that not equivalent to load (and the reason the bsfc is on the z axis ? I've been under the impression (for years now) that the Prius pseudo-cvt does a pretty good job all by itself in setting load, particularly if the gas pedal is not jerked around too badly.

Which brings me to my question: why are Ken's charts not useful for actual driving or engine comparisons, or are you trying to hint at something else ? Your teaser regarding lower rpms than the graph suggests is interesting. Perhaps related to air flow on the road, which is not present on a dyno ?

 

The product of the the engine rpm and torque is the power produced by the engine. So as you look at the chart, notice initially the engine rpm does not increase but the torque does. That is MG1 increasing the torque and keeping the ICE rpm constant. This leads to your next question:

It is brilliant!

The trick is to realize that in 'real life', our engines often work at partial throttle. This means the actual BSFC graph needs to come from operational data. The chart is nice but the published charts are offset to the right.

Good Prius friend, Hobbit, had done some investigation of variable intake valve timing. In theory, the variable intake valve timing should serve as a secondary throttle mechanism. However, I don't think anyone has completed this analysis.

It is my belief that increasing the delay of the intake valve is equivalent to partially closing the throttle plate but without the throttle plate, pumping loss.

You are nibbling around the area. We need fuel flow, engine or MG1 torque with ICE rpm, throttle plate position and intake valve timing offset. Collecting enough data, we can plot the BSFC for different throttle and intake valve settings and get a more accurate map.

You'll notice there is some variability in the recommended power rpm. I suspect that if we can benchmark the data, we can identify the optimum power demand. Then we'll have something.

Bob Wilson

 

Thanks for taking the time to answer Bob. Yet I remain uncertain from your answer and so ask again: Is load and torque (viewed as fraction of the engine's maximum) the same ?

This is a very interesting discussion, but apart from just enjoying trying to understand the mechanics, I must admit that I consider the discussion academic, in the sense that my Prius comes close in actual driving to dyno tested minimum BSFC.

Incidentally, it is exactly pumping losses that prompted me in another thread to question the correctness of ascribing better mpg on the highway with the newer 1.8L compared to the G2 Prius engine to lower rpm without a discussion of how the partial power problem had been attenuated (or even, as the BSFC charts hint, improved on). I don't think it was your intent to dismiss my question as irrelevant, but that is how I read it. Yet here we are.

Looking forward to more education, and less shades of pomposity.

 

I assume 2ZR-FXE was mapped with EGR. 230 g/kWh is achieved at below 1,000 RPM! To overcome partial power problem, EGR must have been used to get that kind of efficiency.

The engine is very impressive! I wonder how it compares to the Otto cycle version (2ZR-FE).

 

To the extent that "load" is a force and "torque" is a turning force, OK.

This combination of the data gathered from my NHW11 in 'on the road' driving and part of Figure 3 from "Development of New 1.8-Liter Engine for Hybrid Vehicles" Kawamoto, Naiki, Kawai, Shikida, and Tomatsuri, Toyota Motor Company, SAE 2009-01-1061, may help:

The chart from the SAE paper was trimmed and stretched to align the engine rpm scales. In the upper chart, the small red dots are measurements of highest relative BSFC that corresponds to the 230 gm/kWh purple oval. Notice the small red dots don't quite line up with the full-throttle BSFC region of peak BSFC. In fact, some of the rpms that have been volunteered, many of the 'pulse' maximum rpms, fit nicely in the higher part of the field measured, peak BSFC. There is a practical use for this information.

Knowing the highest rpm that still exhibits peak BSFC allows drivers to achieve more traffic compliant acceleration without a loss of efficiency. Knowing the region of highest peak BSFC at lower power setting allow easier maintenance of vehicle kinetic energy (aka., the speed.) The benefit is we can start using precise engineering terms.

Hobbit has done early work on intake valve timing but I didn't realize the importance until I went to the Detroit auto show in January and in April read another paper (1.) on adjustable valves. In my minds eye, I suddenly realized where the intake valve closes relative to the piston stroke becomes another throttle mechanism ... without the pumping loss of a throttle plate!

Actually the term 'pumping loss' that is found in engine papers and discussions describes an increase in entropy when a gas passes through a constriction or orifice. It takes work to move the gas but that isn't the case if the intake valve closing on the compression stroke changes angle and goes from OPEN to CLOSE without having a constrictor, an orifice, like the throttle plate.

Hopefully this has given a clue.

Bob Wilson

1. "Newly Developed Inline 4 AR Series SI Engine," Tsuchiya, Hosoi, Hoshi, Shimamura, Hagiwara, Ito, Arai, Toyota Motor Corporation, SAE 2009-01-10048.

 

Pulse and Glide:

I've found that driving a little below the limit in the "slow" lane is very good for FE and it is more relaxing as you don't get bunched up in traffic. Seldom do I catch anyone and as long as I'm relatively close to the limit I'm not impeding traffic on 4 lane roads.

Ideally if we want to save fuel across America we need more people to drive their ICE only cars in a responsible manner and traffic will move better and people will have better FE. Just imagine though how irritating it is to someone trying to drive responsibly to meet up with a P&G Prius?

Just think how irritated you will be when the whole country is driving hybrids and you are following someone who is gliding when you want to pulse.

Just a thought, you need to try to understand the nonbelievers.

 

If we want to save fuel, period, wherever you are.

 

Hi Ken,
Wow, 45 km/h is only 28 mph. Just would not be practical here without driving the car for an hour before hand. Without the EV switch, the car would never turn off the engine during the first 2/3s of my commutes. Going from 15.5 mph to 28 mph would be just a quick little burst at 2000 rpm.

I did 77 mpg today on the 23 mile drive home. Most of it was pulse to 35 or 40 mph, then holding the glide as long as traffic would bear. Got lucky , in that in a few spots I glided an extended period into a red light down to 10 mph, just in time for the light to go green.

Bob et al,

While that statement from the BSFC article for standard cars, remember the black line in that first chart is the line the Prius computer runs the engine at. Its not a human foot controling the torque load and throttle opening. So the BSFC is charts of the Prius are very useful.

In a manual transmission car, you can run the car full throttle, by undershifting. It takes a little practice with a smooth clutch entry at very low RPM, but once the clutch is out, you can go full throttle and the engine will just slowly accellerate the car.