e.a.wicklund
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Is there a formula for determining horsepower in the .air file? Certainly, cylinder cu in, stroke, and number of cylinders are factors. But how do you calculate horsepower from these?
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The Staff of SOH
Determining Horsepower
- Thread starter e.a.wicklund
- Start date
e.a.wicklund
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Can you supply an example? So far I'm getting about 1100 HP for the default Corsair. That can't be right.
e.a.wicklund
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I don't have anything to read HP. I'm trying to calculate it out. What I'm missing is Torque. With that, there's a formula for calculating HP.
I saw in a download for the OH corsair the creator said the HP for the default was too low. I want to know how they figured that out. I need to work this out for a different aircraft.
I would use AirWrench 1 if you can get it. or JWB.gau. (Rami do we have a copy of it here since it AirWrench 1 is now longer available from its website?)
I use JWB.gau from the 1_percent_gauges.zip. The fs2000dr list lots of info about the aircraft being flow in real time for fine tuning.
I use JWB.gau from the 1_percent_gauges.zip. The fs2000dr list lots of info about the aircraft being flow in real time for fine tuning.
You are probably biting off more than you want to. Calculating the HP of an engine is complex. You need to have a long list of specifications - cylinder displacement and number, compression ratio, camshaft specifications and timing, fuel octane, fuel and air delivery specifications, torque - which is also related to prop gearing ratio, rpm specifications and more.
Engine power specifications are readily available for almost all aircraft engines just by Googling the engine type.
Is this an odd ball engine that the horsepower rating is not available for? If so, how are you going to get the myriad of detail specifications needed to calculate its horsepower?
Engine power specifications are readily available for almost all aircraft engines just by Googling the engine type.
Is this an odd ball engine that the horsepower rating is not available for? If so, how are you going to get the myriad of detail specifications needed to calculate its horsepower?
BTW I checked the stock F4U with AirWrench. The engine specifications - including horsepower - are all right on. The only thing that is off is the propeller. It is set for only 2 blades, not 3. That might account for some loss in performance.
Whatever you are using that is giving you a reading of 1100 HP is not a good tool or formula.
Whatever you are using that is giving you a reading of 1100 HP is not a good tool or formula.
That's true Allen. I mention it only in that I am not sure how CFS2 handles the prop blade number with regards to performance without that entry. Does it have a one size fits all default?
e.a.wicklund
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Someone mentioned the prop blade number a while back. Since then, I've been adding the prop blade count to every aircraft.cfg file. It really makes a difference.
e.a.wicklund
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Hey Kurt - can you confirm that AirWrench includes performance data by altitude? I've looked at the output and I don't see anything to that effect. Am I missing something?
I have no idea...
From all my testing over the years I have found adding propeller_blades= to the .cfg to be snake oil, placebo AKA junk. I've looked at the .dlls the game has and propeller_blades is not listed any where.
Not really. It allows the specification of critical altitude - which is the point where a supercharger kicks in, if there is one specified. The game programming decreases the plane performance as altitude increases. One size fits all of course.
It has an altitude/performance chart that shows the estimated power required to reach a certain speed at a specified altitude. You can enter the chart altitude and adjust the power estimate which will then show the speed the plane should max out at. The chart shows a thrust curve available and a thrust curve required based on the figures you input.
But that does not make any changes to the air file. It just shows the HP necessary to make a speed at a specific altitude. You can change the horsepower setting of the engine to match the estimated power needed as shown in the chart, but that will wreck the engine performance at all the other altitudes. Horsepower specifications are calculated at sea level altitude, so leaving the chart at zero altitude makes the most sense.
Instead, to get close matches to performance I first make sure I have the engine specifications and all of the air frame specifications correct in AirWrench. There is a min / max zero lift drag scale which indicates the calculated drag. If the plane is performing too slow the drag scale usually shows that drag is too high and out of a low/high balance. I then adjust the drag coefficients in the air file until I get the drag scale more in line. At that point I also make sure that the plane is flying level at the specified cruise speed. Nose up or down and having to trim it means holding the plane away from where it wants to fly and it impacts performance.
After that I am usually close to the minimum and critical altitude speeds specified for the aircraft. Final incremental tweaking of the power and thrust scalars in the AirWrench or aircraft.cfg file will make the final adjustments. I have to let the game adjust the performance in the other altitudes as there is no capability for the user to program that.
It's an imprecise process. But we need to be aware that each individual plane's performance in real life was very much variable - depending on engine condition, fuel quality, air frame cleanliness, skin repairs, paint condition, weather conditions including humidity, and even pilot skill. Specifications were always recorded under the most ideal conditions possible to achieve. As long as we are in the ball park, it's realistic.
e.a.wicklund
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No, it's nothing exotic. Napier-Sabre IIA engine with 2180 HP. Tempest V should top out at 375 at sea level. Got it doing that. I'm just doing all I can to ensure it's as accurate as I can get it. I hoped there was an ironclad way I can be sure the engine specs are set right.
e.a.wicklund
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Great info. That tells me what I needed to know. Thank you for that, Kurt.