Speed graphs for Spitfire and Hurricane

[Buchon]

I know that there no Boost button but under a FM coding point of view the boost behavior is equal to WEP.

That´s because you should make overheating and damage for it so the best way is implement it in the code as is done with WEP.

[ramstein]

Originally Posted by Insuber

It is interesting to see the wide tolerance of the contractual performance of the Bf-109. The error of +/-5% on the top speed of 500 km/h translates into 10% or 50 km/h of allowed error in absolute figures. Add to that the wear of operations and you can easily have poor performers.
It would be equally interesting to know the tolerance of the British types, I would not be surprised to see higher tolerance values for the Spitfire, given the poor status of the Supermarine rigs and tools at the beginning of production (see the Leo McKinstry book on the Spitfire to have an idea about the mess of the Supermarine works in 1938-39).

PS: how nice if this variability is modeled ... it shouldn't be that difficult ...

speaking tolerances..., in piston engines, I learned while attending a college in auto mechanics.. and engine rebuilding, that the tolerance for engine pistons in cylinders was purposely set a bit loose like .004 of an inch for faster break ins for engines that needed less break in times from the factory... , though you could set the tolerance down to .003 inch clearance of the pistons and cylinder for a much tighter fit, but slower break in times..

I would bore the cylinder and put a .003 inch clearance in the cylinder of v8 engines.
I also cut valves, rods, etc, on machining equipment.

Taking into account this was a long time ago in engines from the 1960's. the engine parts from the 1930's and 40's were still much older and had much different metal properties that the engines I worked on... and now they are completely different metal properties and break in periods..

the differences are the metals, and cast and forged engine components.. and the rings are totally different too... The oils were absolutely different back then, they were non detergent oils...

I was thinking the tolerances must have been much looser, as they really didn't have time to run long break ins to get performance.

The altitude difference and the condensation from going up and coming down in altitude is considerable and must have introduced a lot more water into the engines and oil, from more open breathing designs of engines...

The condensation buildup or moisture in aircraft (of any age) is significant from the changes in altitude and humidity, inside and outside of aircraft, and even more so when pressurized. Those engines must have been through hell to go into war when new, and no time to break in parts..

I could see how there could be large differences in the performance of the same type aircraft... as the first few hours of engine running made a lot of difference in the life of the aircraft parts.. so a 50-100 kmh difference makes sense..

[TheGrunch]

Originally Posted by Buchon

I know that there no Boost button but under a FM coding point of view the boost behavior is equal to WEP.

That´s because you should make overheating and damage for it so the best way is implement it in the code as is done with WEP.

When they say "boost" they just mean manifold pressure i.e. the throttle setting. The term doesn't always refer to any kind of emergency power. The overheating behaviour doesn't necessarily correspond between the aircraft capable of operating at +12lb/sq. in. and previous variants because different fuels were used. What was previously unsafe using 87 octane fuel would be achievable for limited periods and what was previously a 5 minute limit might then be a 15 minute limit, etc. Likewise there might be no changes to some of the operating limits. The devil is in the details. It's a struggle to find all the details because amendments to RAF Pilots' Notes and other such documents were often pasted on or clipped in as loose paper, and we usually only have scans or facsimiles of full editions to refer to.

[camber]

Originally Posted by klem

They made that line I added from B6's data by incorrectly amending the Spitfire FM. They need to make the Patch boost line align with the 6 1/4 lbs (thin pale blue) line. Then it will be modelled correctly for 87 Octane, +6 1/4lbs, 3 blade constant speed propeller, i.e. the Spitfire MkI we have now.

Its the +12lbs line achieved using 100 octane and boost cutout override that we hope they are working on because without it we don't have the BoB. We have "thank god they didn't come in November 1939".

Klem, I agree totally.

So to summarise as I understand it, we currently have a Spit I that has low alt performance about right for boost controlled at +4 psi (although the gauge reads +6 1/4 psi, the correct boost setpoint for 87 octane). The new plots suggest that this performance might be degraded in the patch to about equivalent to if the boost controller setpoint was +2 1/4 psi. Of course this leaves aside that frontline BoB Spit Is had 100 octane and a modified boost control cutout that increased the boost setpoint to +12 psi, and we don't know if the devs have any plans to fix that.

B6 if this is correct, I don't think the Spit I will be useable in MP, it is almost unusable now.

Wouldn't it be cool if the Spit I and Hurricane boost cutout actually worked? Incidently this would tell us the octane number of the fuel in those virtual tanks.

If they are unmodified and running 87, pulling the cutout at full throttle on the deck would give an instant +17psi boost. The engine would make horrible noises, lose power and become damaged in short order. Sneaking the throttle up tells you the octane, if it starts making the predetonation plinking noise (that the game seems to model) at around +7psi, it is 87. +12 psi, it is 100 octane. Greater than that, it must be 150 octane (seems a bit unlikely ). Of course with 100 octane the boost cutout should have been virtually modified so that it is no longer a cutout, but instead controls boost at the higher +12 psi value.

The boost cutout in the Spit II is a bit strange, it just unlocks a bit more boost but clearly it has 87 octane inside as it starts to predetonate at around +7 psi.

EDIT INCORRECT STATEMENT with mixture/ rpm changes the Spit II will sit happily on +9 psi and go 320 mph IAS/TAS on the deck So it models 100 octane boost behaviour.

But if we have to have to use Spit Is and Hurris in their pre-Battle of France fuel configuration, the original (working) boost cutout would be fun! People would be using it to squeeze a little more power from their 87 octane but blowing up motors left right and centre. A bit arcade I know but I would love seeing it in MP. Perhaps a server side setting would be useful if you didn't want it ("crew chief secretly used extra thick wire on boost cutout after what happened last time" setting).

It is a problem that WEP configurations for combat edge carry little penalty if modelled correctly..because the problem is for the virtual erks or the next guy that flies your plane if problems are not addressed. Again most people would consider it arcade, but I would love to see that if you used combat concessions, you are that "next guy"...engine wear is accellerated over reality to "simulate" that effect. People would only use WEP configurations if they really thought their virtual life was in danger or interception was critical.

Well, you can dream,
camber

BTW Ramstein, great post on engine stuff

[fruitbat]

iirc camber, what you see in the spit II is acurate for what you would see when the boost cut out is used, as the actual gauge at that time only went up to 8, so that is your indication of 100 octane fuel.

[camber]

Originally Posted by fruitbat

iirc camber, what you see in the spit II is acurate for what you would see when the boost cut out is used, as the actual gauge at that time only went up to 8, so that is your indication of 100 octane fuel.

Thanks Fruitbat,

I will have another look offline where you can turn off the cockpit and get a higher reaching boost guage.

I was basing that on flying in ATAG MP in the II and pulling the cutout, the engine was making the odd distressed noise I considered the devs use to signal predetonation at around +7psi, so I assumed 87 octane but I will recheck.

Would be interesting if the II modelled a modified boost cutout system but where a confused erk but in 87 octane limiting the useful boost to +7 psi

[fruitbat]

when using the boost cut out with the spit II adjust the fuel mix, and the engine runs fine. Have no idea if that is historical, but thats how it is in game.

[camber]

Originally Posted by fruitbat

when using the boost cut out with the spit II adjust the fuel mix, and the engine runs fine. Have no idea if that is historical, but thats how it is in game.

Really!? I had no idea! I already felt overly advantaged in the II and that was without using the boost cutout.

Any idea of how 1) how much total boost can you get this way and 2) how much boost can you get with a healthy sounding engine? If 2) is > +7psi you are correct, 100 octane is in the tank.

Edit: In the end Spit II can happily function at +9psi and so is 100 octane

[41Sqn_Banks]

Originally Posted by Kurfürst

I know an easy fix for that, since the graph WEP shows performance which was achiveable without WEP in real life, simply rewrite the WEP line to Nominal in the FM.

Then add a new WEP line in the FM which is only useable for 1 min / ca 1.5 km and boost performance even further.

Things would be perffect then, and very historical.



I don't remember seeing such restriction. It would be strange in the DB manual anyways.

Note that "1 minute power" is only given "am Boden beim Abflug" (on ground for take-off) and not given for "in Bodennähe" (near ground level). There is nothing that indicates that "1 minute power" could be used up to FTH.

But I agree that the "5 minute power" at sea level is to slow for most of the presented post-patch graphs.

[FFCW_Urizen]

Originally Posted by fruitbat

when using the boost cut out with the spit II adjust the fuel mix, and the engine runs fine. Have no idea if that is historical, but thats how it is in game.

i remember having read on these very forums, that +12 boost was cleared only in conjunction with weak mixture. however ingame i could use boost cut-out for ages whilst having rich mixture (below 3000ft).