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Old 03-08-2009, 11:28 PM   #41 (permalink)
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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

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Last edited by bwilson4web; 03-08-2009 at 11:36 PM..
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Old 03-09-2009, 10:03 PM   #42 (permalink)
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Blackfly - '98 Geo Metro
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Added to the tool: you can now "save" the results of your form input by copying the "Permalink" link at the top of the output table. This'll be useful if you want to post a link so other people can view your entire results.

EG: View the calculations / output for project Sipster (Top Gear USA's 70 mpg @ 60 mph diesel Rabbit being discussed in this thread) from these values:

Quote:
Vehicle weight: 1043.3 kg / 2300 lbs
Crr: .01
Cd: .42
A: 1.9 m2 / 20 ft2
Fuel energy density (Wh/US gal.): 37953
Engine efficiency: .37 *
Drivetrain efficiency: .95 *
Parasitic overhead (Watts): 400 *
rho: 1.184 kg/m3

* These are flat out guesses on my part.
I still plan to add a link from your garage entry(/entries) so whatever values you have entered for your vehicle(s) will automatically be filled out in the input form when you click your link.
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Old 04-09-2009, 04:11 PM   #43 (permalink)
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I'm still getting the hang of interpreting the data..... considering engines change efficiency based on operating RPM and Transmission gearing

two thoughts:

1. Ability to put in data for Efficency:RPM:Speed for say 3 (or more) data points?
say:
.15:2500rpm:35mph
.20:3000rpm:40mph
.22:4000rpm:55mph

2. Also... should "Air Density" take into account your altitude, not just temp?
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Old 04-28-2009, 02:01 PM   #44 (permalink)
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What engine efficiency % to use for Honda's lean burn VX and HX engines?
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Old 06-01-2009, 10:31 AM   #45 (permalink)
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Online tool give results really similar to a spreadsheet we have used at automotive engineering for a similar simulation, comparing a truck, a city car and a Formula 1 car.
I will ask to my professors if I can share it ^ ^
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Old 06-18-2009, 11:24 PM   #46 (permalink)
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MetroMPG, Would you be willing to share the source to the calculator? I'd love to play around with it. Great info and links in this thread guys!
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Old 06-23-2009, 09:38 AM   #47 (permalink)
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The formula used can be found in this spreadsheet:

http://www.geocities.com/frontsidesk8er/delsolaero.xls
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Old 06-23-2009, 10:22 AM   #48 (permalink)
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Right I got the spreadsheet. I was hoping for the PHP so I wouldn't have to rewrite it. I'd be happy to share my changes if they're of interest.
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Old 02-09-2010, 04:51 PM   #49 (permalink)
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The Truck - '99 Nissan Frontier xe
90 day: 25.74 mpg (US)

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Vehicle weight: 1360.8 kg / 3000 lbs
Crr: .012
Cd: .45
A: 2.6 m2 / 28 ft2
Fuel energy density (Wh/US gal.): 33557
Engine efficiency: .17
Drivetrain efficiency: .90
Parasitic overhead (Watts): 3500
rho: 1.164 kg/m3

Gets me pretty close to what I have observed on an 84 Jeep CJ7
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Old 02-28-2010, 10:03 PM   #50 (permalink)
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civic - '95 Honda Civic DX 3 door hatchback
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Great tool that can be used for comparison. Maybe the users can try to adjust some values as they see fit to correct the spreadsheet's values to match to their experimental mpg, then use it for comparison.

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