Comprehensive Improvements in New RX 450h (Most likely in 2010 Prius)

From the original page Lexus Vehicles : Lexus Advances Hybrid Drive with Comprehensive Improvements in New RX 450h / Toyota we can also see at the bottom:

A new ECO mode provides a modified throttle action and air conditioning control to support efficient driving. This mode changes the relationship between pedal movement and system output to help the driver avoid aggressive acceleration and achieve smoother operation. The A/C load on the engine is also reduced more aggressively upon acceleration. Both these factors provide improved fuel economy.

I don't think it is too far fetched to think this same mechanism is to be used for the 2010 Prius Eco mode.

Also when mentioning both main MGs, they refer that the top torque plateau has been extended further in speed. This might mean that the EV range will follow accordingly in my view:

The front motor/generator (MG2) sees a small increase (2 Nm) of maximum torque but more importantly, the range of maximum torque is extended by 15 km/h. The rear motor/generator (MGR) receives a notably larger increase of torque (9 Nm) and extends its range even further—by 35 km/h.

I can almost bet we'll have 100 km/h top speed in EV mode on the 2010 Prius... we'll see...

 

These look like real advances, improving on pumping losses and cold engine use.
I'm psyched. Too bad so many years are left in my current model. I'll just have to make do with the poor man's scan guage, radiator block, and block heater.

 

I'm pretty sure that they also switched the RX 450h to an atkinson cycle engine, too which is would be responsible for a large part of the improvement, but the exhaust-heat-recovery system is sweet.

That's a huge improvement in warmup time in cold temps that will make a huge difference in fuel economy in cold weather.

Who cares about the 100km/h top EV speed, I just want to know if they've raised the total top speed to something above ~110mph. :rockon:

 

i believe top speed is 112mph .

As to the improvements, i think by far, the biggest one is heat recirculation, especially since that is not ever measured properly by EPA...

10% better fuel consumption with larger engine, and 500 lbs heavier car is rather nice .

 

This is exciting news.
Since getting a scan gauge this year, I find that during my entire 12 mile commute, I never achieve normal engine temp, and if I use my heater I don't even hit 70 degrees C to get full hybrid mode. No wonder my winter mileage is so much worse. My block heater really doesn't help...at least the savings if any will never pay for the unit.
This solution is simple and elegant. Too bad I've only had the current car 1 1/2 years. Too soon to switch for me.

 

The engine could turn off 15 minutes earlier! And still have some heat in the cabin! Whoa. That's brilliant and phenomenal. As someone who has been using much less heat to coax out better mpg, this idea sounds very exciting to me. I really must do that grill blocking I've read about here. Maybe this weekend if I'm not snow bound.

Then, 6 years from now when I'm ready for my next Prius, who knows what other great technology they'll have in store for us

 

If you don't mind me asking, how long do you let your engine block pre-heater running before starting the Prius?

And what is the ambient temperature you have at the place where the Prius is parked with the block heater on?

And what is the ambient temperature outside in the street?

I'm asking because I'm pretty sure the heater works for me... but I would like more info, maybe I'm wrong?

I've the heater on since 4am till 8am, so 4 hours, and the ambient temperature in my garage was today 16ºC. Outside I had -4ºC. The ICE did not start when Prius was READY, and it only started when I pushed the pedal too far to enter cruise.

The ICE stopped at the first junction immediately, almost no pause, so the engine was not that cold. I have no blockers at my grill.

Unfortunately I have no gauge to check engine temperature, so I can't measure the improvements, but I find it hard to believe it won't compensate

Is your daily scenario very different from mine?

 

I park outside in -30°C weather without plugging in. This sounds like it'd make an amazing improvement!

 

The main problem with technology is that the more complex you make something, the greater propensity for something to go wrong (and resultant increased maintenance costs). For example - HID headlights improve night visibility, but the cost of repair is phenomenal compared to simply replacing a regular halogen bulb.

Keith

 

I'll say right off the bat that I have not read any of the above except for the paragraph in the original post, titled "E..G..R.." I'm busy right now and can't devote the time until later this evening. Can someone directly (cut to the chase) explain to me how heating the intake air improves efficiency? The whole point of an ICE is to take cold air and heat it; causing it to expand (also, more oxygen in cold air). So, how does this improve efficiency? I going to go out on a limb and make a guess: In [my] context, efficiency=horsepower, and in the case of the Prius, we aren't looking for max. horsepower; we are looking for max mpg. So, I'm guessing that somehow this improves mpg, yet decreases MAX horsepower. .... let me know. Thanks.

 

That's a little deep for my understanding...someone will expand on this, I'm sure.
I would add that the grill blocking (even partial blocking) really helps in cold temps. That seems to have been a "cheap" ($2.00 for one 6 foot wrap that covers about half grill) improvement overlooked by Toyota in the 2010. They could have used a variation of the temp controlled vents for controling humidity/temps under a house.

 

It's a beneficial tradeoff: warmer air is bad, less negative intake manifold pressure is good.

The efficient cooler makes it worthwhile.

 

I too was puzzled on first reading the OP's comments, for the same reasons as you state ... a hotter (=less dense) intake charge means less power output from that charge; it is the reason why we use superchargers with intercoolers to obtain maximum power from small engines.

On reading the source details however, it seems as though Toyota, with this arrangement, has managed to cleverly blend the intake charge temperature and density level with the Atkinson cycle features to optimize both the fuel efficiency and power output, enabling increases in both. While it does appear to add some complexity (and thus cost) to the overall system, I have to believe that Toyota's in-house testing has been sufficient to preserve the company's legendary reputation for reliability.

Damn clever engineering though; and I salute that.

 

thats why it mentions it lets cold air in during heavy acceleration

 

Well this perhaps explains why the total output is raised to 160hp when the engine alone only produces 100hp.

Getting very exited...at last, a larger sized fuel efficient car with the power needed to travel on motorways.

 

I need to see a shrink. I've been imagining traveling on motorways to work for months now.

 

Back in the 1910s, vehicles had "vanes"(think: vertical blinds/leuvers) in front of the radiator that were closed when the engine was cold, but opened once the engine warmed up. Early engines would never warm up without the vanes (in the winter).

Thank you.

Priceless.

Good point.

 

The Prius only has a 76 HP engine, but 110 HP system power. There is no incongruence saying the power is raised to 160 HP, with a 100 HP engine. The other 60 HP comes from the battery and is delivered to the wheels by way of Motor Generator 2.

 

Please refer to the source document cited in the OP:

"With conventional four-cycle engines, there are times when fuel enrichment becomes necessary to cool the exhaust gases to prevent degradation or destruction of the catalytic converters. With the Atkinson cycle, the expansion/power stroke is longer than the compression stroke so that combustion energy can more effectively used for production of engine power. This results in lower exhaust gas temperatures.

In the process of re-circulating exhaust gas, the cooled EGR system increases the specific heat capacity, also resulting in lower exhaust gas temperature. Regulating the amount of EGR can also control the exhaust gas temperature.

The combination of the Atkinson cycle and cooled EGR minimizes the need for fuel enrichment. The benefit is significant reduction of fuel consumption, especially during high-load driving (e.g.: hill climbs and freeway driving)."

To rephrase the above, the point of EGR in this design is to lower exhaust gas temps in order to protect the catalytic converter. When exhaust gases are recycled to the intake, this will reduce combustion chamber temps since less oxygen is available in the fuel/air mix. Therefore the fuel/air mixture burns less aggressively, and exhaust gas temp is reduced.

The traditional approach would be to enrich the fuel/air mixture to lower exhaust gas temps. However this is wasteful from an mpg perspective.