Chainsaw Repair
How To Basics - Carb Fixes + Mods - IPL and Service Manuals => How To Basics and Fixes => Topic started by: 1manband on December 22, 2014, 08:02:44 pm
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average saw
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I had to look up bsfc. http://en.wikipedia.org/wiki/Brake_specific_fuel_consumption
Not a term I have seen before. But trying to learn new stuff. Thanks for sharing.
I'm so lost. http://ecomodder.com/wiki/index.php/Brake_Specific_Fuel_Consumption_%28BSFC%29_Maps
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Me TOO!
Shep
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if motor was held on a dyno at a steady XXXX rpm, under load... the bsfc at that particular rpm, represents the fuel used/necessary to do so.
the lowest bsfc shown on the actual graph line, is still pig rich. (this is average graph of 30+ motors i had data for. some are quite a bit higher, some quite a bit lower of course).
as motor performance is optimized, a lesser safe bsfc is usually shot for on a dyno.
this graph does not have anything to do with "gas mileage" (ie. cuts per gallon).
usually a bsfc graph looks like an oyster. will post one up of this type.
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some notes on the photo....
......the best "cuts per gallon" is the range of rpms within 300 circle in the middle.... at 1/2 load, ~4200 rpm.
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forgot to add one more thing.
the top arc on the graph labled WOT, just means the carby throttle butterfly was held wfo for that test line.
that arc also represents the torque curve of the motor.
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Joe, cool stuff!
Amazing the fuel use down low and above the torque peak. I know you used some strato motors for the average, any idea what the strato motors bsfc is Compared to traditional piston ports?
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believe the husqvarna site lists numbers there?
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numbers lead to more numbers and eventually lead into a model of something like this. (just a toy right now).
old 066.
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double post
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here's a working file of the toy.
surprisingly accurate. hahaha. put in some numbers to see the fuels effect on power.
the true rolloff on these motors resembles something else though............ after peak tq.
see if it can be modeled? hahaha.
test is to post the true curve if you can.
have some Christmas fun y'all
regards
-joe
works in openoffice program, or m$ equivalent. some of the graphing gets lost in the language translation between the two programs.
hopefully this one will open?
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effect of lower - average- higher bsfc
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smaller 40cc motor effect of lower - average - higher bsfc
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deleted the english horsepower and torque lines off of these graphs to get a clearer view with just metric.
the kW and Nm cross at 9549 rpm. clearer for high rpm motors, imo.
the age old 6,7 hp 75cc motor vs. the 6.7 hp 90cc motor trick.
not the same?
is HP a good way to compare?
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Joe, neat stuff.
Why would the 066 be have higher bfsc/kw vs the smaller motor?
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bsfc is directly (edit:inversely) dependent on how thermally efficient a motor is. motor size only plays a very small role, if any.
edit: compare the 'average' graphs of the 40cc to the 91.6cc motors. the bsfc's used were exactly the same for each graph. (on the graph, bsfc is the lowest line).
somewhere on here in another thread, made a chart that shows how therm eff each motor is. there you can see what i mean.
edit: found the link http://chainsawrepair.createaforum.com/ported-saws/saw-motor-data-technical-chart-(things-mfg's-don't-tell-you)/?message=44955
what's interesting to me however, is the effect of fuel on the small vs. big motor.
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one last graph. thank goodness right?!
1 hp 60cc motor
had to make the numbers small to show what this particular bsfc curve looks like close up.
the lowest curve is bsfc. the torque and bmep (pressure) curves are above.
bsfc curve flipped = torque and bmep
realize that this is not the forum for this kind of thing.
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cfm info: http://www.asia.donaldson.com/en/exhaust/support/datalibrary/1053747.pdf
goes hand in hand with bsfc and A/F ratio.
(just putting it here, so i don't forget where i found it).