Does anyone know the calculation used to determine engine efficiency?

[rekless1229]

I have a feeling it has something to do with curve and resource ratio but not too sure.

[Karol van Kermin]

Do you mean the specific Impulse ( I_sp)? If yes, then the formula for it is_:

• is the burn time
• is the fuel mass
• is the average engine thrust
• the thrust at the time t

[Kielm]

Kind of depends on what you mean by efficiency. ISP is a good indicator of fuel efficiency, but an engine has limited uses if the thrust is too low. 

You can have a delta-v of 10,000 with ion engines without trying too hard, but your burn times will be... excessive.

 

If you're referring to atmospheric engines, try looking at the velcurve and atmcurve tables for different engines to see if that gives you a hint, or just google "KSP velcurve" / "KSP atmcurve". 

[Mecripp]

And you might look at this

think some one picked it up will try and found a new thread

EDIT- Here i think is the last one

 

Edited October 28, 2016 by Mecripp2

[Streetwind]

12 hours ago, rekless1229 said:

I have a feeling it has something to do with curve and resource ratio but not too sure.

I've written about this at length before, here.

Includes a how-to tutorial. Maybe it will help you