Do higher NO_x numbers explain Eco's much superior fuel efficiency?

tires are actually not the same brand.

Anyway, looking at most strict US06 tests procedures (much higher speed test) where EPA tested the vehicle, EPA's test is actually pretty close to Eco numbers when it comes to MPG at 48.1 MPG vs 42.6 and 42.9 MPG for Toyota numbers in non eco. Toyota's Eco numbers for same tests are 51 MPG. Thats pretty close.

So I guess we could possibly say that EPA's own testing shows significantly higher MPG for Prius non-ecol mode than what Toyota states.

NOx numbers are hard to understand without knowing what their "configurations" are (3 test configs for Eco model alone) and they have up to 100% variation for what should be same test. One of the test results shows same Eco model configuration achieving 60% higher Nox scores than other, which makes little sense is all results are equalized via coefficients... maybe coefficients are not perfected when it comes to NOx petrol testing? All of the numbers are around 9x-18x less than EPA NOx limits. And are generally lower than other gasoline models.

 

you keep saying 'huge'. why not tone down the hyperbole and state the actual numbers? you do sound a bit spurned by vdub. is your tdi sitting in the garage?

 

Gokhan you need to make small table of Model Year, model type, NOx to show what you are saying. I have not seen that the eco is different than other 2016 Liftbacks. Also Prius v might be of interest as one theory is the v is also tuned for better MPG...maybe eco is a v analogy.

 

I am not sure if you missed what I wrote... in the data from the link, EPA's own testing got MPG of NON-ECO model much closer to the Toyota's ECO model numbers. Data sets have EPA's own tests from some models, and for the stricter test that I checked, MPG in EPA non-eco model was 48.6 MPG vs Toyota's reported 42-45 MPG for the same test. Meaning that EPA's own test tell us that Toyota's non-eco tests might be very conservative and actually much closer in real life.

And again, when it comes to NOx testing, numbers reported there are much, much lower than EPA limits. Also numbers are not consistent, with same models tested twice getting up to 60% difference in NOx levels.

If Toyota could get mpg up and sideffect would be slightly worse NOx, they would do it for all models since numbers reported for Eco are on average at least 20x less than EPA limit and still lower by considerable amount than other gas vehicles. Thats 20x from strictest tests in the world (actual averaged EPA test is likely closer to 30x). Heck, everyone would be the same.

 

Speculation: the Prius are so much lower than the emissions standard, Toyota could do a performance tune and remain legal.

Bob Wilson

 

I think you are confusing cause and effect. If the Eco Two is 125 lbs than the Two, then the driver will be using the gas pedal less to achieve the same acceleration. Using the pedal less will effect the NOx results. It is a mystery why some believe in some 'secret sauce' when Toyota is clear on the differences between the Two and the Two Eco.

 

I am confused...
I did not know we yet had an answer for why eco is so much better +4 MPG.
Have we learned in another thread that its mostly due to a different engine control system module?

 

No. Some have resorted to fantasy to explain what they refuse. To believe

 

What we know from the Test Vehicle database:

	Represented Test Veh Model	PRIUS Eco	PRIUS	PRIUS c	PRIUS (Gen-3)
1	Test Vehicle ID	16-ZV2H	16-ZV1H	12-NP2H	10-ZW1H
2	Test Veh Displacement (L)	1.798	1.798	1.497	1.798
3	Rated Horsepower	96	96	82	98
4	Equivalent Test Weight (lbs.)	3250	3375	2750	3375
5	Axle Ratio	2.83	2.83	3.19	3.27
6	THC (g/mi)	0.01172	0.01438	0.00464	0.003985
7	CO (g/mi)	0.06442	0.08763	0.04183	0.358224
8	CO2 (g/mi)	105.40951	113.86017	117.82708	130.8100637
9	NOx (g/mi)	0.00295	0.00187	0.00106	0.0031105
10	CH4 (g/mi)	0.00195	0.00224	0.00077	0.0007799
11	N2O (g/mi)	0.00135		0.01
12	RND_ADJ_FE	84.1	78.0	75.0	72.4
13	Target Coef A (lbf)	17.130	18.272	17.919	20.234
14	Target Coef B (lbf/mph)	0.28731	0.29545	0.18180	0.01993
15	Target Coef C (lbf/mph**2)	0.01386	0.01379	0.01556	0.01874

• ECO weight hypothesis - not lower than Prius c yet Prius ECO Coef A is the lowest of all three.
• NOx, CH4, and N2O - suggest detuning emissions compared to Prius c
• Prius c - aerodynamic tuning could do some wonderful things along with high-pressure tires

Bob Wilson

 

What is interesting that EU measurements under we know how realistic NEDC, but still NOx values are higher than in US:
Yaris HSD (2012): 6 mg/km ~ 0.00375 g/mi
Auris HSD: 6 mg/km ~ 0.00375 g/mi
Prius (2012): 6 mg/km ~ 0.00375 g/mi
Prius+ (2012): 6 mg/km ~ 0.00375 g/mi
RAV4 HSD (2016): 7 mg/km ~0.00437 g/mi

EURO6 petrol limit is at 80 mg/km (13x higher), if it would be that simple to just run engine a little more lean, why didn't Toyota do it in EU build Auris ans Yaris? They are both for EU market only and no one here gives a damn about NOx emissions even if they are achieved with cheating.

 

It's a little like what I've been saying historically the USA Prius is a 50-state car which implies giving away MPG to meet CA emissions, especially when cold.

Therefore something like a FORD Fusion Hybrid, with a different car for CARB and non-CARB states. might be better MPG for those of us in non-CARB states, especially when cold. Maybe though Toyota is getting better at the issue.

 

The Gen-4 may be the first time detuning to achieve improved MPG has been tried. Combined with lower transmission internal drag and improved rolling resistance, it is proof of what continuous improvement can achieve.

In one respect, the Honda lean-burn worked BUT they didn't figure out how to tune it to meet emissions standards. I suspect having seen what Toyota accomplished, there are a bunch of curious engineers going back to their respective labs.

Now there is a new, fast acting, fuel-ratio meter that is rapid acting and has a linear scale in the Gen-4. The earlier generation O{2} sensors were ON/OFF, bang the stops. The engine controller was bouncing between RICH or LEAN. In contrast, the fuel-ratio meter has a 'linear' scale which allows for much finer control.

It may take a couple of years for this new sensor to get into the other models. But as it does, I would expect to see all Toyota models to get substantially better fuel efficiency. There is one more thing, moving towards lower rolling resistance.

Using higher tire inflation pressure and tuning the suspension to handle ride 'quality', the car can still be a joy to drive. The old torsion beam suspension had too much mass to deal with the road. But the wishbone rear suspension gives less coupled mass to react faster to road irregularities.

These are technologies that can go into the rest of the Toyota fleet and give them a commanding lead.

Thank you Toyota!

Bob Wilson

 

The more aggressive EGR should also help reduce NOx, just like in diesel engine but in petrol engine it also has the benefit - higher thermal efficiency.

 

How is that fast-acting AFR meter different from the wideband sensors that tuners have been using for the better part of a decade?

For example:
PLX Wideband O2 Air Fuel Ratio Sensor Modules, Gauges, and Kits

 

Bob Wilson