Hp and Kw ratings are like bra sizes, usually overated and alot hidden.
What is the value of HP/KW ratings?
- Thread starter cmarti
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SawTroll
Information Collector
one.man.band
ArboristSite Guru
i do not know if the dyno ratings published by the manufacturer are the same as the data from a site like:
http://www.kwf-online.de/deutsch/pruef/pruefergebnisse/aagw/motorsaegen/6384_12.pdf
do some of the maufacturers give the saws to that company for testing? are the saws given tweaked up before the test? how much money is given for the testing?
who knows.
but comparisons of TQ/HP can usually be made using the same single dynomometer for both tests. if all is kept on the up and up.
depending on how well atmoshperic data is plugged in at time of testing has alot to do with corrections that massage the output numbers for TQ/HP. if it's anything like motorcycle dynos, the brand of dyno used will give different results as well.
-omb
SawTroll
Information Collector
As far as I know, the Husky and Jonsered power specs come from dyno tests done by "Svensk Maskinprovning", which is totally independant from Husky. Apart from that, I know that Dolmar has their own dyno (that KWF also has been known to use, at least occationally).
one.man.band
ArboristSite Guru
my opinion is that if a given saw:
18" bar length
with approx. 16" of usable bar length (from dogs to tip)
needs a certain amount of torque to cut a certain species of hardwood with all 16 inches buried with constant pressure from the operator. if it can spin the chain at whatever the TQ it takes to do that, any additional TQ will make the chain spin faster. this continues up to the point where the RPM climbs so much that the TQ starts falling below the point needed to accelerate the chain any faster. then the chain will slow down to the RPM point where there is adequate torque.
top HP is nothing, unless it can maintain the minimum amount of torque at that RPM required to do the job. believe that operator/chain of the saw is a large influence and this does not depend on numbers alone.
-omb
18" bar length
with approx. 16" of usable bar length (from dogs to tip)
needs a certain amount of torque to cut a certain species of hardwood with all 16 inches buried with constant pressure from the operator. if it can spin the chain at whatever the TQ it takes to do that, any additional TQ will make the chain spin faster. this continues up to the point where the RPM climbs so much that the TQ starts falling below the point needed to accelerate the chain any faster. then the chain will slow down to the RPM point where there is adequate torque.
top HP is nothing, unless it can maintain the minimum amount of torque at that RPM required to do the job. believe that operator/chain of the saw is a large influence and this does not depend on numbers alone.
-omb
one.man.band
ArboristSite Guru
do you know if the dyno results are only had as an afterthought due to emissions testing?
In order to get the noise and vibration values it would seem necessary to use a dyno. One third each idle, wide open no load and max load. Not sure if that is max hp or max torque for that third. If you want or are curious about grams per kilowatt hour you need a dyno for that as well.
Small sprockets are inefficient, probably chain saw sprockets and drive links are not as good as a roller chain and those kind of sprockets. Spur vs rim probably have differing efficiencies.
SawTroll
Information Collector
Afaik, they did it long before emission testing became a major concern.
Actually that is all that I am after. I am enjoying buying saws, repairing, modding, and even started playing with ports. I share/give em to family and friends for us to cut firewood and maintain rural property. Older saws are cheaper to play with and I don't have extensive knowledge of many models. I appreciate you sharing the specs, it gives me a starting point while I am nosing around to make a purchase.
Displacement to HP is somewhat inconsistent, but it is interesting to learn why. What did the builders do different?...., is like learning the old muscle car engines. I drove a Mopar 383, but always wanted the 426! Take care.
mrnecsteve
ArboristSite Operative
When it comes to HP (horsepower) or KW (kilowatt) rateings of internal combustion engines being sold to the general consumer market, peak horsepower rateings are of limited value . I usually only pay attention to those specs when shopping, within a given manufacturer.
Most manufacturers could easily publish what you might want to know by issueing a horsepower/torque (or KW (damn metrics))chart at 100 duty cycle, 95 percent duty ,90 percent duty cycle etc....
along with fuel consumption ratios per work performed ........but really,how many of us out here would truely understand the mathematics behind the numbers and charts???
As an older guy with many years of an engineering background (41yrs), I will share a bit of wisdom passed on to me first in my younger days....:msp_rolleyes:
"figures lie and liars figure! "
Generally speaking....the design engineers design a product with accurate specifications and known limitations....
and then the marketing,sales, and advertiseing departments get involved.
Most manufacturers could easily publish what you might want to know by issueing a horsepower/torque (or KW (damn metrics))chart at 100 duty cycle, 95 percent duty ,90 percent duty cycle etc....
along with fuel consumption ratios per work performed ........but really,how many of us out here would truely understand the mathematics behind the numbers and charts???
As an older guy with many years of an engineering background (41yrs), I will share a bit of wisdom passed on to me first in my younger days....:msp_rolleyes:
"figures lie and liars figure! "
Generally speaking....the design engineers design a product with accurate specifications and known limitations....
and then the marketing,sales, and advertiseing departments get involved.
SawTroll
Information Collector
Yes, :agree2:
