Featured 2 New Toyota Hybrids To Be Revealed May 18

I think the spare would be the same, if supplied. The OD's of the equipped tires are roughly the same, regardless of rim size.

 

I was reading the abstracts, and many refer to the cold start period of PFIs.
That says very little about the PM of fully warmed port injected engines, to properly comparing to diesels.

 

Yes, most of those show high PN emissions @cold start or off-cycle ambient conditions. However, the firsts reference ( Real driving particle number (PN) emissions from China-6 compliant PFI and GDI hybrid electrical vehicles - ScienceDirect ) shows an entire RDE/PEMS test cycle. Note in the abstract:

PFI engines have very low PN emissions except at engine start (cold or hot) and high engine load (e.g., heavy acceleration).

An older paper comparing PN emissions from various engine technologies is available at https://publications.jrc.ec.europa.eu/repository/bitstream/111111111/26204/1/physical%20characterization%20of%20exhaust%20particle%20emissions%20from%20late%20technology%20gasoline%20vehicles%20_%20online.pdf . Note especially Figure 38 on page 47 which shows graphically the comparisons between the technologies.

 

In general, particulates is a hot button issue these days, because the Obama EPA said, in so many words, particulates have extreme high death rate. Furthermore they said, many contaminants can be assumed to be associated with particulates, therefore many contaminants are deadly even at trace levels. For example, mercury in coal regulations are based on assuming particulates are associated the mercury, this then allows an alarming high death rate calculation for mercury, but of course, mercury is bad due to mercury, and not due to exaggerated claims about particulate toxicity.

This kind of logic leads to the popular US eco-conclusion that all combustion process are essentially deathly.
This basic conclusion was stated by one college demonstrator in the recent Planet of the Humans directed by Michael Moore. So I feel like we need to get a better grip on reality. Yes tires probably make a lot of particulates.

 

Figure 38: Comparison of the number emission rates of non-volatile particles measured with a PMP compliant CPC (horizontal axis) and a CPC with a d50 at 4.5 nm (vertical axis), over the NEDC. Different types of symbols correspond to different vehicle categories (cycle for G-DIs, rhombus for PFI, squares for DPFs and hexagons for CNG) with different shades corresponding to different vehicles, and different sizes to different PCRFs (the larger the size the larger the dilution). The numbers indicate the average percentage difference between the [email protected] and the PMP CPC results, followed by the minimum and maximum percentage differences in the parenthesis. The two dashed lines correspond to the 6×1011 #/km limit and are shown as a guideline.

This was the test cycle used for the tests, Emission Test Cycles: Common Artemis Driving Cycles (CADC) It is one based upon modern real world drive cycles in Europe.

The graph has results for DI with an exhaust filter(GPF), and the paper discussed a couple other methods in short of reducing particles from DI after that figure.

The numbers above show the GPF working, and they didn't see a fuel economy penalty during the testing. In fact, the was a regular reduction of 1% to 3.5% for emitted CO2 with the filter. The exhaust temperatures before the filter, with injection of oxygen during deceleration fuel cut off probably means the filter was 'self' regenerating under the test cycle.

Using E75 and E85 in a flexfuel DI showed reductions as high as 97% on the motorway(highway) portion of the test. CO2 emissions were also reduced 6% to 8%.

They also tested an older dual port and direct injected engine(the older Lexus one?). Still had the cold start spike, but emitted particles were around the diesel limit once warmed up. It was a Euro 4 model, so it didn't need to meet a particle limit. A current engine tuned to meet that limit could do better.

 

All you have to do is drive a white car after a rain and you'll see all the tire particulates kicked up onto the back of the car. Even after 4" of rain the other day which you would think would wash the particulates away, a 5 mile trip and I had to wash the rear end of the car when I got home. Black grit.

 

Here is another look at PN emissions:

https://nanoparticles.ch/archive/2019_Czerwinski_PR.pdf

 

Agree.

According to https://uk-air.defra.gov.uk/assets/documents/reports/cat09/1907101151_20190709_Non_Exhaust_Emissions_typeset_Final.pdf , Figure 2 and Figure 3 on page 25, exhaust PM emissions will continue to become a smaller and smaller portion of traffic-generated PM10 and PM2.5, in Europe at least.

 

It is also the asphalt, brake dust, and whatever else has settled onto the road. Even with complete elimination of particle emissions from every component of the car, there will be the resuspension of dirt and dust with every passing of a vehicle along the road.

 

All this particulate information makes my head spin a little.

Let's take the excellent port and direct injection 2.5L engine used in these hybrids. They could add 2 tricks - variable valve control on the exhaust valves and electric warming of the catalyst. An MIT paper showed early exhaust valve closing and late intake valve opening helps reduce pm as retaining that exhaust gas helps warm up the engine while precisely metering direct injection for the full load combination of fresh air and warm exhaust. Adding electric heating of the catalyst allows low hydrocarbon exhaust during this cold start. Being a hybrid the battery can fill in to allow best engine speed for warm up and provide power for the heating of the catalyst.

At lower rpm the engine will produce very low emissions in direct injection atkinson mode. At high loads it is likely cooled egr and port injection will be required to keep emissions low but the engine can run in multiple modes.

Of course if pm is still a problem a particulate filter may be added, but since PM is going to be low it will likely last a long time.

 

Yep, dual injection and other methods should work for the US without needing a GPF. We could a just switch the fuel supply over to all E75. But EPA Tier 3 is one of the ares where it is less strict that Europe's regulations. It does impose a particle limit on a gasoline cars, but is only concerned with particle mass(PM). Particle number(PN). that Europe also has limits on, is ignored.

 

How does Toyota manage this? Such different power figures, same engine?

 

Many(all?) auto makers manage this. Differences in intake, timing, compression, exhaust, etc. can result in changes. Just changing the tune, engine control programing, can be enough; that seems to be the only difference in the 3.5L between the F150 and Raptor, and it means another 75hp for the performance trim. With hybrids, engineers get motors and a battery in the mix of things to tinker with.

PS: The 3.5L Ecoboost got dual port and direct injection in 2017.

 

I believe the difference here is mainly electronics and perhaps battery and motor/generators but am not sure the specs of either of that last 2 items.

For this specific engine slightly higher rpm gives the siena/Highlander 186 hp @6000 rpm versus the venza/Rav4 that is tuned to give max power at lower engine speeds 176 hp @ 5700 rpm. Using lower native compression (13:1 versus 14:1) and raising peak hp rpm 207 hp @6600 rpm in the avalon. All three tunes run in atkinson mode most of the time.

 

Could they have different cam shafts, different valve lifts, duration?

 

Sure- but keep in mind that pretty much everything on the road does variable intake cam phasing these days, and you can create a lot of differences just by altering the program code regulating that cam advance even if they all have the same profile cut into the metal.

 

Our late Civic (06 Hybrid) had dual intake cams (low/high lift). Normally you'd use the low lift, but hydraulic oil pressure could shift over to the high lift cams. There was one overpass I'd always notice it kick in, like a turbo.

 

They are probably mechanically exactly the same as toyota gives the engines the same number. The venza/rav4 hybrids appear to cut off the highest rpm and probably electronically change vvt on the intake valves slightly differently versus sienna/highlander. The difference in hp is just about exactly the difference in rpm, and the higher horsepower comes at the least efficient rpm. HP is the same @ peak torque 3600-5200 rpm.