View Single Post
Old 04-09-2022, 07:46 AM   #16 (permalink)
EcoModding Apprentice
Join Date: Apr 2022
Location: California
Posts: 166

Cx9 - '18 Mazda CX9 Grand Touring
90 day: 31.41 mpg (US)

Prius - '10 Toyota Prius III
90 day: 57.8 mpg (US)

Tundra - '00 Tundra V6 long bed base work truck
90 day: 19.4 mpg (US)
Thanks: 95
Thanked 88 Times in 60 Posts
Originally Posted by #SaveTheManuals View Post
Of course I'll still be flying blind without the BSFC map, unless the torque/RPM/MPG map published by Toyota is (accurate and) more or less equivalent. In that case, per my annotations below, it sure looks like the most efficient region is between 2,200 - 3,100 RPM, with load between ~76% - ~95%. The sweet spot is 2,700 RPM at 88% load:

76% - 95% load is higher than I expected based on the general consensus around the forums, but I suppose there are always outliers. At some point I'd like to verify or debunk whether I can really drive my car around at 90% load for peak efficiency. That seems a little like having my cake and eating it too. Therefore I'm skeptical of this chart.
That chart should be accurate. Toyota published a similar one for the sister 2.5L which the EPA tested & verified.

You can convert that thermodynamic efficiency chart to a classic BSFC chart by taking 81.8 and dividing it by the efficiency. E.g. 81.8/.39 = 210 in the peak efficiency island. 81.8/.35 in the "expanded" zone = 234 (which is still quite efficient).

You can convert Nm torque to horsepower with the formula:

Horsepower = Nm x RPM / 7127

or vice versa:
Nm = HP x 7127 / RPM

So if you need to make 20 horsepower to cruise on the freeway at 2000 rpm, that would be ~71 Nm which your engine makes with ~ 35% efficiency at 2000 rpm.
  Reply With Quote
The Following User Says Thank You to Drifter For This Useful Post:
Ecky (04-09-2022)