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

[usbseawolf2000]

I found juicy information in Lexus press release for the RX 450h. We have heard of these advancements to be in the 2010 Prius. It was a pleasure to read about them.

The highlight summary is the 10% better fuel economy AND 20% more horsepower.

These new technologies may explain the mysterious pipes under the 2010 Prius in the BossDowner leaked video and the under the hood sneak peek #10.

Exhaust Gas Recirculation

The cooled EGR system allows precisely metered and spent exhaust gas to enter the intake system, lowering exhaust gas temperature while also reducing engine pumping losses via decreased intake vacuum. An EGR delivery manifold ensures even distribution of the exhaust gasses to all cylinders. The high-capacity EGR cooling system can reduce the gas temperatures from about 880˚ C to 150˚ C, improving volumetric efficiency. The cooled EGR also eliminated the need for exhaust VVT-i.

Exhaust Heat Recovery System

Another key to improvements in fuel economy comes from the Exhaust Heat Recovery System. An important part of the hybrid control strategy is to stop the engine when it’s not needed, for example in low power demand conditions in city driving. But in winter driving, engine heat is needed to warm the interior cabin and demand on the electric drive motors will be naturally higher in these conditions, especially during warm-up. When temperatures drop below 0˚ C, battery output is also reduced and drive motor performance suffers accordingly.

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.

Exhaust heat is recaptured from the exhaust pipe just downstream of the catalyst where a recovery unit is mounted directly on the exhaust system. A thermostatically controlled valve forces part of the exhaust gas to re-circulate in a chamber, heating the surrounding coolant quickly. A spring in the valve allows it to open during full acceleration. When engine coolant warms sufficiently, the valve opens to allow exhaust gas to bypass the heat recovery system.

Source

[jprates]

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...

[SageBrush]

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.

[drees]

Originally Posted by usbseawolf2000

The highlight summary is the 10% better fuel economy AND 20% more horsepower.

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.

Originally Posted by jprates

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

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.

[spwolf]

Originally Posted by drees

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.

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 :-).

[nyty-nyt]

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.

[ruby]

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

[jprates]

Originally Posted by nyty-nyt

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.

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?

[kinghuang]

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

[Tech_Guy]

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