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morid(at)northland.lib.mi
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 Posted: Fri Jul 21, 2006 7:23 am Post subject: HP formula |
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Some time ago one of our members provided a formula for figuring horsepower by knowing fuel burn, rpm, CCs, etc. There was also an efficiency factor in there that was different for air cooled and liquid cooled engines.
Can anybody provide this formula. My algebra is mostly long forgotten so any variations would be appreciated.
Thanks,
Deke
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nebchmp(at)wcc.net
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| Posted: Fri Jul 21, 2006 5:31 pm Post subject: HP formula |
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Deke, Is this what you are looking for? Norm
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Some of us may be getting a bit off track with fuel burn and horsepower and
all that stuff.
The key thing here is specific fuel consumption (SFC).
A typical air cooled engine (Lyc) will burn about .45 pounds of fuel per
horsepower produced per hour.
A more efficient water cooled engine will get about .40.
These are just about the best numbers you will ever ever get. In other
words, you can NOT get more horsepower without increasing your fuel burn.
This is an absolute.
So, with a well tuned Soob engine, you will burn .40 pounds per hp per hr.
A 6 gal per hr fuel burn at 6 pounds per gal. (weight) will be 36 pounds of
fuel burned per hour. (6 x 6)
36 divided by .40 (your SFC rate) is 90 horsepower.
This means that if you are flying along and burning 6 gph of fuel, your Soob
engine is cranking out 90 horsepower.
6.25 ghp = 94 HP
5.2 gph = 78 HP and so on.
A Lycoming has a less efficient SFC and so a fuel burn rate of say 9 gph
would be:
9 x 6 / .45 = 120 HP
Be very sceptical if someone says that they are getting 170 HP on 5 to 7 gph
fuel burn. It just can't be done.
P/S Diesel engines (automobile type) have SFC's at around .35 pounds per HP
per hr. This is why they get such great mileage.
Jeff Liot
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Fox5flyer wrote:
| Quote: | Some time ago one of our members provided a formula for figuring horsepower by knowing fuel burn, rpm, CCs, etc. There was also an efficiency factor in there that was different for air cooled and liquid cooled engines.
Can anybody provide this formula. My algebra is mostly long forgotten so any variations would be appreciated.
Thanks,
Deke
|
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janderson412(at)hotmail.c
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| Posted: Sat Jul 22, 2006 2:20 am Post subject: HP formula |
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Jeff, are you talking imperial or US gallons..Metric John A.
| Quote: | Deke, Is this what you are looking for? Norm
-------------------------------------------------------------------------------------------------
Some of us may be getting a bit off track with fuel burn and horsepower and
all that stuff.
The key thing here is specific fuel consumption (SFC).
A typical air cooled engine (Lyc) will burn about .45 pounds of fuel per
horsepower produced per hour.
A more efficient water cooled engine will get about .40.
These are just about the best numbers you will ever ever get. In other
words, you can NOT get more horsepower without increasing your fuel burn.
This is an absolute.
So, with a well tuned Soob engine, you will burn .40 pounds per hp per hr.
A 6 gal per hr fuel burn at 6 pounds per gal. (weight) will be 36 pounds of
fuel burned per hour. (6 x 6)
36 divided by .40 (your SFC rate) is 90 horsepower.
This means that if you are flying along and burning 6 gph of fuel, your Soob
engine is cranking out 90 horsepower.
6.25 ghp = 94 HP
5.2 gph = 78 HP and so on.
A Lycoming has a less efficient SFC and so a fuel burn rate of say 9 gph
would be:
9 x 6 / .45 = 120 HP
Be very sceptical if someone says that they are getting 170 HP on 5 to 7 gph
fuel burn. It just can't be done.
P/S Diesel engines (automobile type) have SFC's at around .35 pounds per HP
per hr. This is why they get such great mileage.
Jeff Liot
----------------------------------------------------------------------------------------------
Fox5flyer wrote:
| Quote: | Some time ago one of our members provided a formula for figuring horsepower by knowing fuel burn, rpm, CCs, etc. There was also an efficiency factor in there that was different for air cooled and liquid cooled engines.
Can anybody provide this formula. My algebra is mostly long forgotten so any variations would be appreciated.
Thanks,
Deke
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morid(at)northland.lib.mi
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| Posted: Sat Jul 22, 2006 2:24 am Post subject: HP formula |
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Thank you Norm. I think this is what I'm looking for.
Deke
leaving in 30 minutes for the Mecca!
[quote] ---
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