Toyota to release 2 different Prius-es to US & Europe

Bob,

I am not an engineer but the way I vision the 1.8l could be utilized to generate more power without the partial power or pumping loss is described below:

To make the point across easier, I am going to make up some numbers. Let's say the current 1.5l Atkinson cycle ICE use the whole 1.5l displacement when the gasoline ignites and expands as the pistons move. However, during the compression cycle, some of the gas goes back into the manifold (say 0.5l) and when it is closed, only 1.0l of air and fuel got compressed. This is why Prius has much higher compression ratio (13:1) than a non-hybrid car with an Otto cycle. Remember, Prius ICE is not turbo/supercharged and it runs on 87 Octane regular gas without knocking. Toyota has a better explanation with pics and graphs.

Now, going to 1.8l ICE.... If we use the whole 1.8l during the expansion cycle and compress only 1.0l (hence 0.8l back in the manifold), you are extracting more energy by allowing the piston to travel further upon the ignition. In that explanation, I see the 1.8l ICE making 15kW almost efficient as the current 1.5l ICE. The benefit of having 1.8l ICE is to make more power and less noise at the output people normally use.

In summary, 1.8l can be used to further increase the ratio of the expansion cycle.

 

This is my point about the type of driving done in NA vs Japan or Europe. In the latter two locations with larger populations and relatively shorter distances much if not most of the driving is done in slow-and-go traffic.

In NA with greater distances and less traffic density the speeds are relatively higher for longer distances. It's nothing to go on a trip here for 1000 miles at 75-80 mi.

I don't have a scanguage to monitor the data but if the Prius pulls 15 kW at steady state cruising at 60 which in my view is the sweet spot for this Gen 2, then what is the demand at 75 or 80 mph?

 

But since you are only consuming the same amount of Air/Fuel as the 1.5l ICE your maximum indicated power will be about the same but with larger friction losses/weight etc. I would expect the additional expansion ratio would only give a very small increase in power and not enough to outweigh the other losses. Currently the compression ratio is fixed by design - if it could be variable then there might be some opportunity for getting the best of both worlds.

If the 1.8L has a similar expansion ratio to the 1.5L then at low power outputs it will be less efficient (even the 1.5L efficiency drops below about 12-15KW output that is needed for low to moderate speeds).


kevin

 

OK guys, I was asked secrecy from the local Press Officer here in Portugal about this but I was just informed that at least one of our dealers is already spreading the word among its customers so no more reasons for keeping it under cover:

EUROPE WILL GET EXACTLY THE SAME 1.8 LITRE ENGINE AS THE USA MARKET

According to this salesperson the presentation in Portugal is scheduled for June 11th, and a selected group of customers should have a gathering shortly after to do some test driving.

So there you go, Toyota changed its mind and decided to go for one single engine all over the world.
The equipment and accessories will differ from market to market as usual, but the engines and MGs will be the same all over.

 

am i the only one to notice that the new prius looks more like a honda, and the new honda looks more like a prius?

ill probably wait until 2012 to get another one, just because that is how much i have left on my financing however if i can get nav and the sunroof and the touring for less then say 26,000 i might trade in.

 

Looking at the patents, the computer controlled, variable intake and exhaust valves should have both duration and phase control and eliminate the throttle plate while optimizing efficiency across a broader range of speeds and power settings. But it is a fair question to ask why not just put this technology in the 1.5 L. It comes down to a question of thermodynamic efficiency fall-off at higher power settings.

The 1.5L engine seems to lose efficiency above 2,600 rpm and really tanks above 4,100 rpm (NHW11 testing.) If the 1.8 L. engine can avoid excursions into these areas, producing diesel-like efficiencies at higher power levels, it will shine on the high speed benchmarks and acceleration loads. Remember the mileage tests involve dictated speed changes and excursions into higher rpms drives the engine into worse thermodynamic efficiency regions. A slower turning, larger displacement engine can produce enough power and minimize excursion into inefficient regions.

One of the clever aspects of both input and output valve timing and phase management is the ability to implement a stealthy exhaust gas recirculation. What this does is help keep the engine effective expansion ratio up at variable power levels. This can be a clever way to keep emissions low while maintaining efficiency across a broad power band.

What I'm hoping to hear there is a higher speed, EV mode. The current 42 mph is just under the EU "extra urban" speed for over half of the test. If the EV mode can be higher than this limit, the vehicle should test with outstanding mileage. It will also look better on the USA tests. We might even see a return of the "real mileage is worse" claims but I won't mind.

Bob Wilson

 

I also hope for higher EV speed, 100km/h is what I expect, but don't you expect any better on the ECE15 (EU urban cycle).

Take a look at post #24 on this thread. The bigger 1.5L 2004 Prius ICE takes a lot more time to warm-up compared with the smaller 1.3L 2009 Insight ICE, and the Insight wins the ECE15 test.

This happens because the ECE15 includes the warm-up time during its execution and there is no way a Prius can warm up in only 200 seconds that the test takes. The ICE is almost always running and you never reach stage 5 of the hybrid system.

An even bigger engine will do a lot worse IMHO. I expect the 1.8L to do worse or the same at best than the present 1.5L block, but win easily on the NEDC (mixed circuit cycle).

Do you agree with this analysis?

 

Sorry Bob, post #24 is from another thread, here: http://priuschat.com/forums/prius-h...veals-honda-insight-mpg-co2-3.html#post772916

 

The 1.8 liter engine, having more engine mass, will heat up slower and cool down longer. So the fuel economy on short trips, and in cold weather will be worse, because the temp of the big engine will never be up to a good heat transfer range before the trip is over. The 1.8 liter engine may be a nicer day-trip winter car, but it will be worse for the day-to-day purpose most of us use the Prius for, commuting to work at minimum fuel consumption.

I do not seem to have the cool down issue in pulse and glide in cold weather with the grill block I am using. I have one 9 inch long grill slot opening in front of the transmission. The rest are blocked off. Temps here have been in the teens to mid twenties during commute time. Even with this configuration, I only pulse the heater on briefly as it pulls the engine temp below 80 C if I were to run it continuously.

The real solution to winter heat is not to use the engine as a furnace, as its inefficeint at that. But to make an actual furnace and run it off gasoline.

 

you guys need to read about gas recirculation in new RX450h, where they managed to cut off warm up by 15 minutes in -5C

And thats with pretty huge 3.5l V6 engine .

Also, I am pretty sure that ECE tests do not test vehicle in cold conditions? I believe the difference in city mileage should come from increased engine shut-off, same as in Ford Fusion, which is more aggresive than in previous hybrids, of course as well as with having smaller engine and smaller vehicle.

 

Ahhh, I assumed max 8K RPM ... although red section starts around 7K RPM, at least in my conventional cars. So Prius has a smaller RPM range and 3K RPM is already more than half way to max. Now I see why a bigger ICE is needed. You are saying that already after 3K RPM efficiency has peaked whereas in my mind I always picture peak efficiency in the 4K-5K range.

I'll have to reconsider this .. looking forward to actual real data once it comes out.

Oh I missed this one.Thanks.

In fact thanks to all for the great info and patience. I am happy to learn about new developments and adjust my thinking accordingly.

 

Indeed, thanks for the hint, I will search the net for more info!

You would be wrong here. Since 2000 the test cycle has a cold start. Well, to be honest the first 10 seconds are idle time, not that it makes much of a diference. You can find hundreds of references to this on the internet.

 

I think the two of you are talking about different things.

I suspect spwolf is taking about ambient temperature. (Air temperature)
jprates is talking about engine temperature. (The engine is not warmed up to full operating temperature = cold start)

Here is a link to the entire ECE procedure: Emission Test Cycles: ECE 15 + EUDC / NEDC

Ambient temperature is not cold: 20C to 30 C (68F - 86F)
However the engine is not allowed to warm up to operating temperature before the test. (Operating temperature is ~ 190F or 88C)

 

Since Bob mentioned the Valvematic patents, here's a link for serious students to study prior to the Monday 2010 Prius announcement.
http://paultan.org/valvematic.htm

Elimination of the throttle plate would be a big improvement.

Regarding the discussion about 1.5 liter vs. 1.8 liter, its not necessarily a given that a new 1.8L engine has greater mass compared to the old 1.5L. We'll have to compare the specs of the two engines to see.

 

thats true too - i dont think that new 1.8l ZR engine will be significantly heavier than old NZ engine... BUT, it will still be heavier than 1.5l NR that will be in Prius (if that happens). Still, i dont think that we are talking about more than 10-15kg.

 

No problem since many of us had to pass through the same learning experience. If you'll ignore the 'outlier' data below the zero line, you'll notice how the ICE shaft power begins to fall off around 2,600 rpm really falls off above 4,000 rpm. But in a traditional Otto engine, peak brake specific fuel efficiency occurs at a higher rpm:

Speculation on my part but I believe the variable valve timing and other engine controls in our current engines moves towards an Otto cycle to get a larger charge in and thus moves away from Atkinson cycle efficiencies. To get peak power out of the 1.5L engine, I suspect Toyota engineering had to sacrifice thermodynamic efficiency. My hope is the larger displacement will allow the new 1.8L engine to preserve thermodynamic efficiency across a broader power range.

I'd also like to see an electric water pump with elimination of the belt and coolant thermostat. If some of the exhaust gas can be used for engine block warm-up to eliminate the North American coolant thermos and use exhaust heat for cabin heating.

Bob Wilson

 

I am very happy that the new Prius will have a more powerful engine. I have always thought my 2005 Prius was underpowered off the line, and when I got a Camry the difference in power was striking. I like to get excellent mileage, but you have to like the way the car feels too. I hope the new Prius will have softer seats. My 1995 Tercel has more comfortable seats and this is not acceptable. I have also had issues with traction control. I could not climb a snowy hill a few weeks ago - the traction control just shuts off the power as soon as the wheels start slipping. Aside from these issues, I love my Prius and hope for a better one.

By the way, does the sun roof have any advantages or is it just for show?

 

thing is that in Europe, Prius will cost same money as Avensis.... For it to have only smaller engine, it makes no sense, because it is in price range of more powerful vehicle.

If Prius was priced as Auris/Corolla, it would be different... but it is not (although i do expect cheaper base version, even significantly cheaper than before).

So I fully expect 1.8l version in Europe as well, even if optional. It would let Prius compete well with vehicles that are in its price class (Avensis, Passat, Mondeo, etc).

 

How do you know that?

It's not optional, it's the only one you'll ever get.
Just like today, the future Prius will use the same ICE worldwide, I've got full confirmation from Toyota here.

I had already said it in this very same thread: http://priuschat.com/forums/prius-h...ifferent-prius-es-us-europe-9.html#post772931

 

I would be perfectly happy with the larger engine, and more power, as long as the total fuel economy is also measurably better than my Gen 2. As long as it's better in every way, I won't be upset that it wasn't optimized just for fuel economy.

For the past few years I've driven from the Bay Area to Tucson over the holiday break. It's about 14 hours of total driving time, with two or three minor mountain passes. It's mostly Interstate highways, speed limit 70 in California, 75 in Arizona.

My current Prius is happy to zoom along with the bulk of the traffic at 70-80 mph, while giving me between 42-46 mpg. I focus on driving, not on maximizing my mileage - I don't pulse and glide or do any other hypermiling techniques. I'm not criticizing them, but I don't choose to do them.

There are a few places, like heading up the Grapevine into LA, where I reach the limits of what the current car can give me. I'd like to have a bit more power in reserve. I'd like larger battery capacity, so I can store more regenerated power on the long downhill sections. I would enjoy a slightly larger passenger compartment. And I really would like better seats, with more lumbar support, more adjustments. My dog is okay with the passenger seat, since I lay it flat and put her bed onto it, so she doesn't sit on the stock seat anyway.