So I want Terrible Frank (Ki-84).

[Sikboy]

Originally posted by gofaster
I wouldn't introduce the Ki-84 unless there was some way to balance it out, either with a small ammo load or some sort of performance inhibitor, and since I'm not a programmer, I can't make any suggestions about which way to go.

Yeah, the main thrust of this second page has been about wheather or not the data the Kesmoids used to model the Frank in AW was porked. If the Frank were only a 400mph plane I don't think it would be any worse than the La-7 we have in AH now. And of course, there are always perk points to leverage in case it does turn out to be uber.

-Sikboy

[Mitsu]

disagreed, gofaster.

[Karnak]

FDutchmn,

The N1K2's performance matches the Japanese numbers.

You don't get a 8,800lb fighter with a 1,900hp engine maxing out at 369mph without something holding it back.  That thing is its fuel.

[-=Silo=-]

Can someone explain exactly how fuel octane affects engine performance?

I am not clear on this. If an engine is rated at 1990hp using 92 octane, wouldln't higher octane fuel mean it would just hit it's max power rating at a lower altitude. How would this create any great increase in the max speed (at any altitude) of an airplane?

[Karnak]

Silo,

As I understand it, the higher the octane the higher the boost can go without causing detonation in the cylinders.  Also, higher octane fuel is better at higher altitude.  Thus, more power is produced at altitude.  More power = more speed.  Higher altitude = less drag = more speed.  More power at altitude = best speed.

I could be entirely mistaken, but that is how I understand it.

[-=Silo=-]

Hmm okay... higher octane fuel raises the engine power curve at altitude.
So would raising the engine hp curve mean worse lower altitude hp output?

[Spritle]

Silo,

I think the term 'curve' gets tossed around a little too carelessly.  With respect to octane and hp it works like this.  An engine is rated at 1,900 hp at max performance using a given octane rated fuel.  If at a later point a higher octane fuel is available the engine "can" make more power however only if certain changes are made with respect to it's operation.  The easiest changes are boost and ignition advance.  

With boost you increase the amount of fuel/air mixture that each cylinder receives resulting in more power.  This is at all altitudes.  

The second thing I mentioned is ignition advance.  Advance is the amount of time in degrees of crank rotation that the spark plug fires before the piston actually reaches top dead center (it's highest point before it starts its journy back down the cylinder).  The reason that this is important is that it takes a certain amount of time for the flame to propegate from the spark plug throughout the combustion chamber.  During that time the piston is busily traveling up the cylinder.  Now if you can fire the spark plug a little earlier you can make a little more power.  This is because by the time the fuel air mixture actually combusts the piston should be just at the brink of starting it's decent in the cylinder (power stroke).  If you waited too late to fire the spark plug the piston would already be traveling downward and you would be losing efficiency.  The reason being that the volume of the fuel air mixture in the combustion chamber would be increasing thus decreasing the pressure.  That decrease in pressure will have a corresponding decrease in the amount of power that is released when it combusts.  

There are programs now that mathmatically model the entire combustion process in an engine taking every possible event into consideration.  Using the latest super computers it can take several hours of calculations before the final results of just a few revolutions of the crank can be output.  Pretty amazing stuff, but they can predict with a fair amount of accuracy how much power an engine will make without ever putting it on a dyno.

So anyway a given engine can make more power with a higher octane fuel, but NOT without making some changes to its operation.  The increase in power would be seen throughout the entire rpm range and at all altitudes.

Spritle

[Mitsu]

I think that Ki-84 of the Japanese Record wasn't with 2000hp engine. maybe 1800hp around...so, if HTC models "Homare 21" engine as 2000hp one, they should use Ki-84 Data which has been tested by USA.

-Hermit

[easymo]

Hope you get it Mit.

 I would love to have had it with the old AH FM.  Flying on the edge of that nasty spin would have been big fun.

[Mitsu]

I loved old FM.
N1K2-J was just "cool" plane in it.

[kreighund]

Hey guys the Ki-84 carries 142 liters of methanol-water, this is how it gets an extra 200-250 hp on the deck but the engine is really a 1700 hp (if it's a lucky engine). You can't run more than 5 minutes at its WEP rating anyway and at 20000ft you only have about 1300-1400hp in max continuous power...

Its CuIn is 2185inches at 3000rpm and it is pushing it to its limit to produce 2000hp

Look at the BMW801D   2560Cuin at 27-2900 rpm with petrol injection comes close to 1900 hp and with MW50 is credited with 2100 hp