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bwilson4web · 03-09-2009, 12:28 AM

Actually it works quite nicely for the Toyota and Ford hybrids. The Atkinson cycle and hybrid transmissions provide a relatively flat ICE efficiency. When I put in my NHW11 Prius numbers there was good agreement on:

100 mph mileage - 22 MPG measured and calculated
18 mph maximum range - the model shows ~92 MPG and mine show ~84 MPG
5 mph MPG - the model shows 65 MPG and mine 55 MPG

This is close enough without going nuts but you are right that Otto cycle vehicles need an 'efficiency' curve or table, not a single number.

One of the less well know aspects of hybrids is their ability to keep the engine in an extended, peak BSFC range. There are a two inflection points, the maximum EV speed, 42 mph for Prius, and maximum MG1 rpm that at higher speeds requires the engine to turn faster than idle. But these are subtle effects not well understood outside of the hybrid community. Think of them as shift points and that is close enough.

Bob Wilson

03-09-2009, 12:28 AM	#41 (permalink)
bwilson4web Engineering first Join Date: Mar 2009 Location: Huntsville, AL Posts: 843 17 i3-REx - '14 BMW i3-REx Last 3: 45.67 mpg (US) Blue Bob's - '19 Tesla Std Rng Plus Thanks: 94 Thanked 248 Times in 157 Posts	Actually it works quite nicely for the Toyota and Ford hybrids. The Atkinson cycle and hybrid transmissions provide a relatively flat ICE efficiency. When I put in my NHW11 Prius numbers there was good agreement on: 100 mph mileage - 22 MPG measured and calculated 18 mph maximum range - the model shows ~92 MPG and mine show ~84 MPG 5 mph MPG - the model shows 65 MPG and mine 55 MPG This is close enough without going nuts but you are right that Otto cycle vehicles need an 'efficiency' curve or table, not a single number. One of the less well know aspects of hybrids is their ability to keep the engine in an extended, peak BSFC range. There are a two inflection points, the maximum EV speed, 42 mph for Prius, and maximum MG1 rpm that at higher speeds requires the engine to turn faster than idle. But these are subtle effects not well understood outside of the hybrid community. Think of them as shift points and that is close enough. Bob Wilson __________________ 2019 Tesla Model 3 Std. Range Plus - 215 mi EV 2017 BMW i3-REx - 106 mi EV, 88 mi mid-grade Retired engineer, Huntsville, AL Last edited by bwilson4web; 03-09-2009 at 12:36 AM..