New World Record Challenge: over 50km/L(117mpg) tank

Thanks for the route info and this brings up another side question I had: I remember seeing lists of top MPG logs from users in one of the web sites (cleanMPG maybe?) and there were lots of Insights with very high MPG numbers (more than 100 IIRC) and only a few Prius with relatively lower MPG numbers. Is Insight inherantly better than Prius in fuel economy?

 

Yes, Insight I is clearly ahead of Prius. But that is a 2-seater against a 5-seat mid-size hatchback.

 

It also was a very light all aluminum bodied car with a 1.0L 3 cylinder engine. The hypermilers always use the 5 speed since the CVT was hard to glide and it could do lean burn at higher speeds.

Wayne

 

Is this a standard Prius with 45L tank that he pumped to the brim? I hear that it's easily done by raising the left rear wheel 3 inches but I find it hard to believe 15 additional litres can go in !

How did he calculate the 'fuel refill' ?

 

This almost makes me want to take of my 17" tires and put the 15s back on. Unfortunately my commute has a huge hill that kills my mpg such that I can never break 56mpg. The 65mph freeway speeds over 50 miles don't help either. With the 17s I can only acheive 46mpg-47mpg.

 

I find stories like thisentertaining, which is to say not really meaningful.

That the record was achieved at ~ 18 MPH is not surprising, it is a necessity,
given the Prius Gen II's MPG vs. MPH relationship. Two examples:



This one from Bob Wilson. Its the red line:



I keep wondering, to avoid start-up inefficiencies, was the record run one continuous
1800+ mile drive? That would be ~100 hours, 4+ unbroken, unrelieved days behind the
wheel at the very limits of our understanding/application of the Prius' operating algorithms.

If so, that is something truly amazing.

 

Rokeby, are the mph numbers based on an average mph or what was observed with instantaneous mph over a short period?

For example, I am pretty confident that if I mainted a speed of 60mph on a flat high that I could acheive between 58mpg and 60mpg. That jives with the first chart your posted. A Geniii should do even better. My average speed for the trip would obviously be lower so then if we use my average speed the first chart doesn't work but Bob's chart does.

 

I don't know. I have the first graph on my computer, but I can't find it
on the web. I probably "grabbed" it from a document, but I failed to
note where it came from.

It pretty much reflects my experiences with my Gen II. I have used it
to formulate strategies to max my MPGs. For example: Driving local
streets, get up to 20 MPH asap. Even though PSL is 25, traffic allowing
stay around 20.

This graph also shows that in a Gen II 60 MPG at 60MPH is achievable.
What the graph does not show, or even suggest, is that MPG is also a
function of air temps. My understanding is that 60 MPG at 60 MPH at 60
degF is achievable.

I do not know exactly how MPG varies with temps. However, from my
experience I do know that for my specific ~28 mi round trip daily
commuter route with temps below 60 degF, a very good target MPG is:

VGM (Very Good MPH) = Air Temp + 1/2(60 - Air Temp)

The formula only sort of works above 60 degF.

CAUTION: I now suspect the Bob Wilson graph is for the Gen I; it shows
only about 48 MPG at 60 MPH. I'd edit/delete it but it's now part of the
conversation.

Here is another MPG vs. MPH graph pretty-much like the first.
It is from CleanMPG. Lots of discussion in the thread, a must read.

 

Wowsers!
He must be FAS/NICE 80% of the time...

 

This is an excellent result, well done. However, I'd like to add some details that might not be obvious in some of these charts:


DISCLAIMER: Please feel free to make local copies of this chart while I'm on 'this side of the grass.' You have my permission to use it. Please realize the drag formula came from a Toyota sales document shared by Ken@Japan and the vehicle electrical overhead from my measurements using a Graham miniscanner. The set of black-dots came from the first Prius marathon drive, an NHW20 model.

Some other things to share:

• 10 miles (16 km) - is my standard benchmark distance because the Prius normally has engine ON/OFF cycles and this distance is long enough to minimize variations from Prius cycling impacting the results. Shorter distances, 2.5 (4 km) can be used if the start and stop correspond to the same point of the Prius ON/OFF cycle.
• heat is critical - the "hack" is an engine coolant spoof that causes the engine to show at least 70C as long as the actual coolant temperature is 40C and above. Below 40C, the engine is subject to stalling.
• engine warm-up to 70C takes ~300-360 seconds - this is the time it takes for that mass of metal to get warm enough to enable full hybrid mode. The NHW20 improved the warm-up cycle with better control laws and the North American thermos. The ZVW30 threw the game with the exhaust heat recovery system.
• transaxle warm-up to ~60C takes ~20-30 minutes - transaxle temperature controls lubricant viscosity and there is about a 3-4x reduction as it reaches operational temperature. This was improved with the "Prius c" that optimizes heat transfer via the transaxle oil. It is part of rolling resistance
• tire rolling resistance - maximum pressure which is even higher than max sidewall and perfect, four wheel alignment. Thinnest possible tread (aka., worn tires) reduces tire rubber flex.
• minimize aerodynamic drag - blocking the air inlets results in measurable, lower drag, as the engine compartment is in effect a parachute at the front.
• reduce weight - wheel/tire rolling drag is a function of vehicle and payload weight.
• optimum temperature ~80-85F (27-30C) - experimental data suggests temperatures above 90F (32C) see a reduction in vehicle efficiency. It may be due to increased engine and battery cooling fan losses. There is a knee in efficiency loss around 55F (13C) as the heat losses lead to higher drag.

At one time, I researched how I would approach a marathon drive. But the only way that made sense for me was to have a robot driver, a "Johnny Cab," driving on a closed course:

Source: "Total Recall" TriStar Pictures (Sony) 1991

There is a human part of marathon driving, the 50+ hour, seat time following a narrow set of rules on an optimized course. Using a "Johnny Cab" or super sophisticated cruise-control eliminates the human part but then I've always been fascinated by the vehicle engineering and my heros look like this guy:

The chief Toyota engineer on the ZVW30 project.

Bob Wilson

 

ahhh, cant get GT3 (in the right sizes) here in au, but can get Ecopia EP100 (not s)

 

As the chart is an image I just had a look for it using software designed to search for images re copyright and fraud, the chart is also located here:
MPG vs Speed - Hybrid driving strategy - GreenHybrid - Hybrid Cars
and here:
How are you making so many MPGs!?! | PriusChat

hope that helps