01-01-2015, 11:56 AM
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#91 (permalink)
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Mechanical engineer
Join Date: Jan 2009
Location: Kitee (Finland)
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Just played around the tool and it would be super sweet if you could add multiple engine efficiency numbers based on speed. You can "easily" calculate those from BSFC maps. Then the calculations would be more accurate at wider range of speeds.
Now in this calculation I know I will get 3 liters at 62 MPH with actual 36% efficiency speed but its off 40 MPH speed. I know the efficiency at 40 MPH in my car will be about 33%. That aint big difference but if you use that 5-200 MPH calculation there start to be some real differences in engine efficiency. I can calculate multiple points and make my own chart but maybe it would be easier if the program would do it automatically if you add your engine efficiency point there?
Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com
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01-01-2015, 12:23 PM
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#92 (permalink)
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EcoModding Apprentice
Join Date: Aug 2014
Location: Pekin, IL
Posts: 149
Crown Vic - '99 Ford Crown Victoria Base (P74) 90 day: 24.1 mpg (US) Turtle - '98 Subaru Outback Sport 90 day: 30.53 mpg (US)
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I plugged in my numbers using .015 for Crr and .8 as drivetrain efficiency and the mpg numbers matched what I've been seeing on the instantaneous readout from my tripminder.
Now to see which metric returns the biggest difference in mpg with the least amount of change!
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'99 Crown Victoria
'97 Impreza 2.2, 5-speed
'98 Impreza Outback Sport 2.2, 5-speed
'05 Outback 3.0R (wife's)
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01-01-2015, 12:48 PM
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#93 (permalink)
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EcoModding Apprentice
Join Date: Aug 2014
Location: Pekin, IL
Posts: 149
Crown Vic - '99 Ford Crown Victoria Base (P74) 90 day: 24.1 mpg (US) Turtle - '98 Subaru Outback Sport 90 day: 30.53 mpg (US)
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It looks like, if I reduce my curb weight by 200lbs, swap in a manual transmission and shave .02 off of my drag coefficient I should be able to hit 31.3 mpg @ 55 mph... in theory. 
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'99 Crown Victoria
'97 Impreza 2.2, 5-speed
'98 Impreza Outback Sport 2.2, 5-speed
'05 Outback 3.0R (wife's)
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04-17-2016, 12:24 PM
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#94 (permalink)
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Master EcoModder
Join Date: Sep 2012
Location: Victoria, BC
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Hmm...I'm not sure if my "metro" 1.0l engine will be able to put out the 282,372 watts of power required to get me up to 200mph. Maybe if I remove the passenger side mirror...
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06-09-2018, 03:27 PM
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#95 (permalink)
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Cyborg ECU
Join Date: Mar 2011
Location: Coastal Southern California
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I just ran some calculations with this tool. I appear to only need 10.71 to sustain 60mph in my current configuration, give or take depending on my assumptions for the calculator. That is not a lot of horsepower!
Yesterday I had to commute 150 miles for work & got a 64.4 mpg average WITHOUT nearly as much EOC as I used to do (which was all the time). My new taller tires and the repaired head gasket have produced better numbers, I think.
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See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.
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06-09-2018, 04:48 PM
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#96 (permalink)
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Just cruisin’ along
Join Date: Jul 2009
Location: Rochester, NY
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Assuming the most correct numbers I can cobble together, it's a bit pessimistic, but I'm (educatedly) guessing at too many variables to begin with.
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'97 Honda Civic DX Coupe 5MT - dead 2/23
'00 Echo - dead 2/17
'14 Chrysler Town + Country - My DD, for now
'67 Mustang Convertible - gone 1/17
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06-14-2018, 03:24 PM
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#97 (permalink)
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Easter McoModder
Join Date: Mar 2010
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Quote:
Originally Posted by MetroMPG
Aerodynamic & rolling resistance calculator - EcoModder.com
Back in the day, krousdb made a spreadsheet to calculate aero & rolling resistance forces against his del Sol, their respective power requirements, and effect on fuel consumption at various speeds.
I've ported/expanded the spreadsheet into an online tool which asks you to enter or accept default values for... - vehicle weight
- Crr (coefficient of rolling resistance - .008 represents a low rolling resistance tire on a smooth surface - see Wikipedia for other sample values)
- Cd
- Frontal Area
- Fuel energy density (in Watt hours / US gallon)
- Engine efficiency
- Air density (rho)
... and it spits out a table showing resistance force values, estimated power requirements and fuel consumption across a range of speeds.
It's online at EM here: Aerodynamic & rolling resistance calculator - EcoModder.com
It's not perfect (e.g. engine efficiency changes with load in real life, but remains fixed at the value you supply for all speeds in the calculations for fuel consumption).
Discussion, questions, suggestions welcome.
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Is there some kind of a database that offers this information for all make and models? Thanks!
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06-14-2018, 04:29 PM
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#98 (permalink)
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Master EcoModder
Join Date: Jan 2011
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09-11-2019, 01:59 PM
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#99 (permalink)
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Mechanical engineer
Join Date: Jan 2009
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There should be also some kind of compensation calculated for rolling resistance. In EU R117 tire test there is a correction formula which correlateds to outside temperature. Rolling resistance part begins at annex 6
https://eur-lex.europa.eu/legal-cont...23(03)&from=EN
10 celsius diffenrence in temperature equals 8% change in rolling resistance on passenger tires. This has even bigger impact than the reduced drag has and basicly doubles the impact of temperature change. |
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06-29-2021, 10:29 AM
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#100 (permalink)
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Mechanical engineer
Join Date: Jan 2009
Location: Kitee (Finland)
Posts: 1,275
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Thanked 843 Times in 416 Posts
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For electric cars the drivetrain efficiency does not effect results. So there should be option to select electric car and then the results are calculated different way.
Like my ID3 I know the extra load is 2000-2500w it goes nicely to watts, but drivetrain efficiency does not effect the watts. I wondered that a long time before I found it out. Now you have to calculate that extra from watts to get correct results...
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