I have bought the JustFlight PA28-161, it’s great but I’ve realized I was actually looking for the PA28-181.
I was wondering how can I tweak the plane to give it a 20hp horsepower increase? The rest is fine with the plane as it is.
Running the Steam version, I tried editing engines.cfg
[PISTON_ENGINE]
power_scalar=1.12
I increased this from 1.0 to 1.12 to give it a 12% increase which would roughly add 20hp which is what I want.
This seemed to work nicely before the latest plane update from JustFlight, but now it appears it doesn’t work as well and it barely breaks a 100kt cruise speed, whereas it should be about 120kt.
Am I supposed to edit other parameters for a quick and easy +20hp increase? such as max_rated_hp=160, or others…
The engine weight and therefore CG etc will be different with a bigger engine. You can’t just hack more HP into an add-on to end up with an entirely different plane.
Also from my experience flying 180HP Archers they cruise at more like 110kts, not 120
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100kt cruising speed you mention is IAS or TAS?
You need to tweak the prop thrust, not the engine power. However, as has been correctly noted, this alone won’t make it a -181.
No, but you could give it the engine characteristics of a 181.
Is engine weight even taken into consideration? I can’t say I’ve ever looked for that.
An engine’s weight is not specifically considered. It is only represented in the overall numbers for the basic empty weight and CG of the aircraft. So you’d need to change those parameters in the aircraft cfg as well.
There may be several other engine tweaks necessary to make it realistic - carb vs fuel injected, specific fuel consumption, number of cylinders, cylinder displacement, compression ratio, all the temp scalars, etc.
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Would it also affect neutral trim at cruise, as I assume there would be a small increase in its cruising speed?
That is all figured into the weight and balance, airplane geometry (specifically the arm between the CG and htail), and thrust considerations (specifically the propwash over the htail). There may also be canted thrustline considerations on some aircraft.
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What parameter is that? Is it in the engines.cfg?
@PapaFox85 yes, IAS. But @NickD2576 is right, it’s more like 110 IRL
I used to fly Archer II IRL, cruising speed was more 120kts than 110kts… like a 118kts to be exact. The difference comes from the gear fairings installed or not, and of also the RPM setting. My flying club was recommanding an eco cruise RPM. At higher RPM 120/125kts was reachable.
To compare cruising speed, TAS must be read.
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Unfortunately, can’t look at the moment. Maybe ‘thrust_scalar=’?
“thrust_scalar” is in engines.cfg.
According to the SDK it looks like one of those settings you can tinker with if you put in accurate figures for the prop, and engine, and the sim doesn’t produce accurate results.
Looking over the config for the Warrior 2, I see a “prop_efficiency_table” filled out, and yet “prop_uselegacytables=0”, so the table is not used, but parameters are used instead.
It looks like it has all the values needed to use parameters instead of that table, but they are all set to default values.
prop_scalepowerabs
prop_effminval
prop_effmaxsmooth
prop_falloffpower
prop_falloffcoef
prop_lowbetareductionmid
prop_lowbetareduction
I have no clue what these should be set to to give accurate results for the propeller, but if the SDK defaults just happen to be the correct ones I’d be very surprised.
Same thing for “prop_power_cf”. The table is filled out, but won’t be used because use of legacy tables is disabled. It appears the tables are also set to SDK defaults, not that it applies here.
Where would one even begin to work out what correct values should be used for those attributes above? From a POH I found this:
But that doesn’t seem to list much information about the prop characteristics as far as performance is concerned.