mpg numbers are shown on website for 2016 Prius

For awhile I was trying to accelerate slowly, but the heavy traffic behind me during my commute was not too happy (I have so many stop lights I haven't counted them yet). I try to accelerate all the way into the power range and I still get about 55 mpg going to work and 60 mpg coming home most of the time (that's from zeroing out the trip "A" before I start moving). It's about a 37 mile commute (65 minute average).



Not saying this is good or bad, just that driving slower, coasting and easy braking are why I get good mileage even though I accelerate fast. Does your wife track her mileage per trip?

By the way, I'm in the process of listening to all 300 + podcasts of Autoline After Hours. It's a one hour talk show (video and audio) all about the automotive industry. That's where I got the information that Johnson Controls is promoting.

Here's the link if anyone is interested: Autoline - Automotive news, reviews, and auto industry analysis

I'm in my car over 2 hours a day during my work commute. It makes the commute seem to go by quickly.

 

I find on level roads it's easy to stay outa the power zone, and accelerate reasonably quickly. I'll push up near it, then let it fall back to about the middle of that right side zone. On an upgrade that goes out the window, but hey. I just don't see lead-footing to satisfy the following lead-footers. You're probably right tho, those few moments of red zone are not going to impact much.

 

JCI doesn't make engines. Watched the beginning of the podcast, but its long, do you have a time that she talks about 60%. I heard her talk about Argonne as a source but they aren't talking 60%.
JCI does know batteries and their customers which is big auto.

They clearly see 48V being a big driver of auto efficiency. Here they want to sell either a hybrid lead acid/lithium battery, or two batteries one of each.

Upgraded starter and alternator for start stop are cheap (~$100).

She praises toyota for getting electric ac into cars. A 48V electric ac by 2020 will be cheaper and lighter than current mechanically driven AC. Also talks about cooled egr leading to higher engine efficiency. This is an old diesel trick, but the gen III prius as the first to put it in a gasoline car.

European regulations and NEDC bonuses for start stop will drive this first. They can be met she thinks with a 48VDC microhybrid. JCI has a single packaged hybrid battery, with a 12 VDC lead acid and 48 VDC lithium, and dc converters to charge the lead acid from the lithium, all packaged to fit under the hood. Once these are majority in europe, she thinks they will spread fast in china and the US.

She sees with low oil prices a large niche (5%) of people that will buy electrified cars - hybrids or plug-ins, plus demand from the california government. That's the minority, until higher gas prices hit. If micro hybrids work well for the low fuel consumption/government regulations, she can see non-plug-in hybrids going away. This is a very different vission than toyota's vision. The key differences are outlook for oil prices and regulations. If lithium gets cheap why not add a plug to hybrids (PHEVs), you already have an expensive system. She didn't weigh in on hydrogen, but we are talking outlook into the 2020s, and not even toyota thinks there will be many by 2025.

 

2016 Toyota Prius MPG ratings now official

 

nice little write up, thanks!

 

Yes, Especially the 67.3 mpg

 

i liked that part too.

 

I asked the curator of the EPA data and he reports:

I've been waiting for the 2016 Prius mpg values also. To date, Toyota hasn't provided them to EPA's database. After they are provided to EPA, we don't release them until a certain "release date" which is provided by Toyota---which typically is the date of a Toyota press release.​

When the EPA tables are updated, we'll have the roll-down coefficients. These are enough to plot a drag power curve. Then we can make a reasonable, first approximation of fuel efficiency as a function of speed. It still needs confirmation by benchmarking but we're on the road.

Bob Wilson

 

I agree 100%, it's not acceleration that kills MPG it's speed an braking. So, if you accelerate faster leaving everyone behind and then coasting to the next traffic light instead of braking, you will get better MPG, than those behind you that just catched you (with brakes) coasting to a stop.

 

It depends. Rpm-HSI zones increase with speed. At 35MPH, those figures may roughly check, but at 55-60MPH are at 2,500//3,000 and so on.

 

disagree. While maximizing regen braking and keeping speeds low is very important, keeping RPMs low is equally so. I can get 10%+ improvement in C on the same route with the same avg speed by keeping RPMs under 2k for most part. Prius ICE is optimized for low RPMs revving it to 3.5-5k will cost you. You can look at Gen3 ICE efficiency map and figure out what is usable RPM range good luck.

 

Ok maybe I didn't make it clear enough: In my hypothetical example both cars drove at the same average speed (same distance in same time), one was slow accelerating but braking at the end, the other accelerated quickly but coasted to a stop.

I'm 100% sure my statement is correct even if you include regen braking.

 

Correct:

Using miniVCI, I found the maximum, EGR valve opening occurs at 3,200 rpm with the HSI power bar just shy of the right most edge of the power section. Using cooled exhaust gas recirculate (EGR) minimizes the throttle plate losses and is well within the 1.8L engine efficiency peak. Above this rpm, the car has to use other means to cool the exhaust which can include running a richer mixture. But I did not try to measure this the fuel trim.

The older, 1.5L engine in our 2003 Prius had a hard limit at 3,900 rpm when the car would enrich the mixture to reduce exhaust gas temperature. It was easy to see. Still, I prefer to keep the 03 Prius at or under 2,400-2,600 rpm and don't get too bent out of shape up to 3,200 rpm. But if traffic demands, drive the dang car.

Finally, the internal resistance of the traction battery means the resistance heating is (I**2)*R. The current squared time the resistance. Lower regenerative current means significantly lower heating loss. But the ultimate is to avoid regeneration when possible:

In this driving stunt, I would do laps on a loop with a 10-15 m rise:

1. Engine on up the hill at 25 mph, cruise control.
2. At peak, engine shuts off, shift into "N" to coast down hill.
3. At bottom when speed decays to 25 mph, "D" and cruise control.
4. Wait for #1.

Very, very boring so I stretched it out on my daily drives between July 3 and 21.

Bob Wilson

 

Not sure if this is of if throttle plate losses are an issue with Gen3. On C with improved Gen2 engine throttle plate losses non-existent, for most part it runs ICE with 1.5PSI manifold vacuum. About 0.6-0.8 of it come from filter, and from what is left probably snorkel and the rest of piping have as much or more impact as throttle plate.

Question is how the RPMs affect losses in HSD?

 

• Not sure if this is of if throttle plate losses are an issue with Gen3. - I haven't measured the 1.8L engine manifold vacuum. Just I know cooled EGR is used by all serious engines to reduce combustion gas temperatures saving NOx as well as the catalytic converters.
• On C with improved Gen2 engine throttle plate losses non-existent, for most part it runs ICE with 1.5PSI vacuum. About 0.6-0.8 of it come from filter, and from what is left probably snorkel and the rest of piping have as much or more impact as throttle plate. - Never had a C or Gen2 to study.
  
• Question is how the RPMs affect losses in HSD? - I think you are asking about the degree HSD efficiency is a function of both ICE and wheel rpm. I once bought a SAE paper from a U. of Georgia professor who claimed the HSD was too inefficient compared to the 'two-mode.' The paper was BS, a disappointment.

The model I use that seems to work:

• use 92% for the generator to motor path, 92% x 92% ~= 84% electrical path
  
• use 2% loss for each gear stage, 4*.2% = 8% or ~92% efficient mechanical path
• Power split device:
  • 28 hp * 84% electrical path ~= 23.5 hp
    
  • 72 hp * 92% mechanical path ~= 66.2 hp
  • 100 hp * HSD ~= 89.7 hp ~90% efficient

I am looking forward to getting the roll-down coefficients. I think we'll be able to use benchmark MPGs to map out the HSD efficiency.

Bob Wilson

 

Was curious about RPMs, no wonder even filling out the Eco gauge is so slow at 2K RPM... I usually fill out the PWR gauge on acceleration from stop lights, it's just barely enough to keep up with the normal acceleration of other cars around me. In stop and go traffic, I'd rather speed up, and then coast on braking, it's a lot less of an annoying way to drive.

 

I'm not quite sure what you're saying "no" to, lol. Anyway, I'm someone with a ScanGauge: we had to run somewhere last night so I set one gauge to RPM, and your numbers seem about right.

But I'm not sure what that proves. First off, it proved mightily distracting to try to hit a certain spot on the HSI and watch RPM. And I think I'll stick to my easy-does-it method: more aggressive acceleration does seem to knock the accumulating mpg down. I'll stick to pushing it just enough to keep the speedo numbers ticking up towards the target speed, works for me.

 

From observation throttle plate losses are not an issue on C, the only time ICE is ran at high vacuum (8-11psi) is during warm up, and that is when MPG is really bad. I can borrow Gen3 but would be surprised if they didn't use the same approach as C.

So it is really down to ICE efficiency vs RPM and HSD losses. Prius C MPG is ~38-39MPG at 73mph with RPMs in 22-2600 range. Ecomodder calculator linear approximation suggest ~42, 10% more. Have not seen the efficiency map for C, but if it is similar to Gen2 that would mean that HSD and other friction loss gain is the major factor, not loss of ICE efficiency at higher RPMs.

 

On the adjusted EPA rating...
Just wonder:
Will a European Gen 3 driver see the full NEDC 30% improvement in fuel economy when switching to Gen 4 all other factors equal? I doubt it will be that high.
Will an American driver see only 4% improvement (all others equal)? I certainly doubt it.