Better mpg at 60-65 mph than at 55 - 60 mph

I hear what you're saying HelloMyPrius. Don't be disheartened by some of them though. I had a similar reaction a few months ago when I had experienced the Prius brakes issue. Some posters who hadn't experienced the problem denied that it even existed and made out I couldn't drive or was inexperienced etc etc. Just because they haven't experienced it it didn't exist in their mind.

Same almost applies here. I appreciate that the car is technically more efficient at lower speeds, I am aware of wind resistance etc but I find the car generally gets better mileage more easily at 60 mph than 50 mph on the open road. Can I prove it scientifically? No. But the car seems to run easier at the higher speed and others have reported this too. Obviously there is something there or some reason but whatever it is (or isn't) I don't care. I know it appears happier at 60 mph and I personally appear to get better economy at that speed.

It's still a good forum and there are still lots of good folk on here - whether they agree with me or not (or vice versa). And I do like the wide variety of people on this forum, from all walks of life, from all around the world, brought together because of a car.

 

The ultimate judge is the odometer/trip meter and fuel receipts and they still don't post at PriusChat. <grins>

My recommendation is to find a web site that you can use to track mileage. Then over time, perform experiments and track the results.

GOOD LUCK!
Bob Wilson

 

This is my experience as well - I seem to get the worst mileage between 45-55.

Possible reasons:
Heretical mode operating in a low-efficiency RPM range
ICE must keep spinning at 47mph or higher

Pulse&glide helps some, if using warp stealth for the glides - but at that speed, the glides are pretty short. I try to time it with slopes in the road, which helps a little more.

 

Someone (can't remember who) posted a graph on the forum (I think it was PriusChat, but might have been somewhere else) about the "sweet spot" for the Gen III engine being bigger than Gen II and hypothesizing that the Gen III may have been optimized for 90 mph to run on the autobahn. Also there was something in there about an aerodynamic bubble where the drag reduced over a certain speed. Maybe this applies to the OPs original question.

Edit: Here's the post: http://priuschat.com/forums/gen-iii...2010-prius-2zr-fxe-engine-efficiency-map.html

 

Understand that local conditions, temperature, road, traffic, vehicle maintenance, can change but this is what I got with our new, ZVW30:


This is a more detailed curve for the 1.5L NHW11:

In this case, you'll notice there are observed performances below, on and above the drag based, power required curve. That is because the 1.5L engine has distinct power ranges that are less efficient than others.

I don't have a drag formula for our ZVW30, yet. I know the EPA has a web site where they keep the three drag parameters. I just haven't picked it up. The drag curve with the vehicle overhead dictates the best case, theory of what our ZVW30 should get on a standard day in standard configuration. It is the performance baseline. But we can often 'make mods' that improve or in some cases, decrease performance.

Understand, I don't discount anecdotal reports but rather it takes replication of the same results with a know protocol to help understand what is going on. For example, the recent brake pause, I could not replicate it for a month but about the time I got my accelerometer, a rainy day provided the missing element needed. It is metrics that change anecdotal reports into something engineering and others can reliabily use.

Bob Wilson

 

post your data...other than that, u will believe what you want to believe and so will i.

 

Sorry if some took offence.

Allow me to thumbnail a few years of this theme.

The majority of gas @ 50mph and greater is no longer friction, but wind resistance - it goes up like the hockey stick in a graph. With the exception of supercars and a few other performance cars, the absolute sweet spot in fuel economy is at or slightly above the highest gear - typically 45-50. Since the Prius is definitely not performance-oriented, to suggest it gets better fuel economy at higher speeds is dubious - in fact I know this is not the case.

I've experienced many greenwashers that have advocated cruising at 75 and the like as if a hybrid plate exempts it from the laws of physics....something about the human condition of craving for a pain-free way out like Water4Gas or 100mpg carb, yet the suggestion of going 60 instead of 75 often gets condemned as dangerous because it's inconvient. When it comes to that, rational thinking has ceased and it becomes a behaviorial issue.

I can wish all day long driving a Prius at 70 gets better fuel economy because it''s more gratifying than doing 60, but reality has a different story.

 

OK, so the earth isn't flat?
the moon isn't made of green cheese?
and I'm not a sex God?

You have really burst my bubble! lol

 

It means Gen3 Prius is more efficient at 90 mph than Gen2.
It does not mean Gen3 is more efficient at 60 mph than 50 mph.

It never happens, I believe.

Ken@Japan

 

I hear at 88 mph you actually go back in time.

 

Trip C, Trip D, Trip E, etc. are on spreadsheets on your home computer.

 

Do you have a ScanGauge or other engine monitor? If so, search here and at CleanMPG.com for 'Super Highway Mode' to get a better idea how to repeat and make use of this 'sweet spot'. SHM is tied more closely to ignition advance and throttle position than to speed.

This mode is harder to use on GenIII than on GenII or the Civic Hybrid. I have only barely tested it, as it doesn't fit my commute pattern, and the GenIII details hadn't yet been fleshed out when I had road trip opportunities to use it.

 

I use controlled benchmark runs of at least 10 miles over the same, flat course in both directions. After driving for at least 20-30 minutes to make sure the engine, transmission and tires are warmed up, I use a tripmeter to record the two runs. If traffic aborts one run, I repeat until I get two runs in opposite directions. This takes out the wind effects. Data is recorded using a tripmeter that is reset after reaching the target speed and a known landmark.

The green dots were gathered in regular commutes with our 1.5L, 2003 Prius, and one way trip segments from gas pump calculated values. They were my first attempts at data gathering and span hours and days of travel but using cruise control to hold the speeds. During those time intervals weather conditions and terrain would change and any hills would push the car into less efficient regions.

When I changed the test methodology to controlled drives over known distances with instrumentation recorded mileage and through warm-up, I get numbers closer to the theoretical curve.

Speculation, I suspect the earlier green dots include cases where I didn't realize how inefficient the engine can become at higher power settings. Also, they would have included engine and transaxle warm-up. In fact my commuting distance is 10 miles including warm-up and today, I use 10 miles after warm-up for test drives.

Bob Wilson

 

I don't think it's at all unlikely that trips at 65mph could be done at greater fuel economy than at 55mph.
I KNOW that drag goes up (by v^2). AND it's probably the largest factor in resistance. But the engine of the Prius is NOT a continuous curve, there are many other factors (such as air temperature), and driving methods have probably the greatest impacts on mileage. It's quite conceivable that at 65, a pulse and glide approach provides longer periods of glide at 65, that at 55.

By the same token, I feel that 'normal' gives me a sweeter-sounding engine when going up small inclines, and PWR gives me a 'sweeter-ride' up steep hills. Though I haven't tried it (the hills aren't that long), it wouldn't surprise me if those sweet-spots are actually better mileage points too.

I'm just saying, that engine efficiency and driving techniques may account for some people getting better mileage at a higher speed, under some road conditions. I get a huge variation in my regular commutes of 30 miles over the same route: from an indicated 72.2 to an indicated 46 mpg, all in one month.