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

[usbseawolf2000]

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.

[DeadPhish]

Originally Posted by bob_ninja

Thanks for the info.
Hmmm, now I am confused.



Doesn't sound like it works too hard.



So it only needs 15 kW of ICE's 57 kW, again light load, no?

According to this 1.5L engine seems to have an easy life and doesn't work hard. So again, why is 1.8L needed?

15 / 57 = 26%
Bigger 1.8L would be utilized even lower, guessing around 20%, so what is gained? The present engine seems to have nice 40ish kW for passing or going faster, right?

I just don't see what is bigger ICE going to do that the present engine doesn't????

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?

[kevinwhite]

Originally Posted by usbseawolf2000

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.

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

[jprates]

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.

[rigormortis]

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.

[bwilson4web]

Originally Posted by bob_ninja

. . .
I just don't see what is bigger ICE going to do that the present engine doesn't????

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

[jprates]

Originally Posted by bwilson4web

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.

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?

[jprates]

Originally Posted by jprates

Take a look at post #24 on this thread.

Sorry Bob, post #24 is from another thread, here: Leaked document reveals Honda Insight mpg & CO2

[donee]

Originally Posted by nyty-nyt

The only problem with the smaller engine is the long time it takes to warm in winter, and the rapid cooling during pulse and glide in cold weather. I don't know if a 1.8 solves that. Otherwise it has plenty of power. The world needs to get off the power addiction and learn to conserve momentum to save fuel.

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.

[spwolf]

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

To counter this challenge, Lexus developed an efficient system that recovers exhaust heat to quickly raise coolant temperature during warm-up. This allows the engine to stop sooner, helping to improve fuel economy during this phase. For example, testing at -5˚ C on a typical driving pattern (below) showed that the engine could be stopped a full 1,000 seconds (over 15 minutes) earlier than the previous model.

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.