Using Hobbit's BSFC graph with A Gen III Prius

Hi WaltD,

You might consider just "drive the car." It makes a lot of sense to get something to record metrics and then do some experiments where you hold as much constant as possible and change just one variable. The advantage is the experiments will reflect your local conditions and driving environment. Then as you make changes, you'll be able to compare your benchmark performance against the change.

My studies of the 1.8L engine suggest that peak, exhaust gas recirculation occurs around 3,200 rpm. So as a general rule of thumb, I try to stay under that number . . . but that belies what is really going on.

Our cars have no direct connection between the accelerator and the engine. We're simply providing signals to the control computers that actually operate the engine and transmission. So if we ask for more power, the control computer converts that into a 'target power'. The rest of the computers do what is needed to meet that power requirement.

Ken@Japan made an excellent posting many years ago about power levels on the power bar display. His recommendation was to try and avoid going past 3/4th of the normal bar and avoid the "red." Mostly I agree although there are times when more power is needed. But in reality, 'just drive the car' works pretty good.

GOOD LUCK!
Bob Wilson

 

I didn't see that article, but my own trial and error showed me I get the best MPG while driving decent speeds when I accelerate at the top of ECO zone. That incidentally meets the 2000 RPM target as RPMs vary from 1700 to 2200 in that position (depending on speeds). The main benefit of accelerating at this rate is one goes to glide phase faster and ICE spends more time off. That also helps not to be a road block as acceleration at lower rates is simply unacceptable while in traffic.
Now, that works for my suburban/city commute and may not work in some other type of driving.

 

Hi everyone

In this post I showed the following chart of the ICE delivered power Vs RPM. There is a high correlation of both values; that is, for any given ICE RPM (and coolant temperature) the ICE is prompted by the car computers to deliver always the same power, which is not the way any automatic or manual transmission cars behaves.



In the same post I also displayed the ICE efficiency Vs RPM which is the following graph:



The coolant temperature may have up to a 2.5 percentual points of impact in ICE efficiency when compared "cool" temperatures (below 60ºC, 140ºF) and "hot" temperatures (higher than 90ºC, 194ºF).

Those graphs completely agree with Bob Wilson statement: just "drive the car" knowing that the lower RPM you drive for a warm car, the lower fuel hourly consumption you get. Once you get the lowest fuel hourly consuption (maximum endurance) for a given road, just drive a few higher kph, mph to get the best fuel mileage (maximum range). This is well known in aircraft performance technics as in the following chart, showed in Maximum Endurance, Maximum Range, and Optimum Cruise Speeds :


Big hugs from Frank

 

that's beautiful frank, thank you!

 

Nice charts. All of that applies to steady speed driving only. My comment was specifically for pulse&glide (that makes most of my commute).