Inaccurate performance data for BOB fighters in COD comparing to RL data

[41Sqn_Banks]

Originally Posted by Seadog

as has been pointed out the boost over-ride needed to be modded to allow for greater than 6.25lb boost, and this was only done when 100 octane fuel was used.

This is not correct. In the unmodified condition there was no restriction of the maximum boost when the boost control cut-out was used, thus the boost could be increased to about +17 lbs at full throttle at sea level.

See:
http://forum.1cpublishing.eu/attachm...1&d=1337242614
http://www.spitfireperformance.com/spit1-12lbs.jpg

[NZtyphoon]

Having found a 1942 (?) copy of R A Beaumont Aeronautical Engineering: A Practical Guide for Everyone Connected with the Aero Industry (modern reprint http://www.pitstop.net.au/view/aviat...uery/plu/23199) it's interesting to read what he says about the "four degrees (types) of boost" used by British aero engines:

(1) Take-off Boost - ...an additional amount of induction-pipe pressure....accompanied by an extra richening of the mixture which prevents an unstable combustion termed detonation...(p. 105)

(2) The Rated Boost - often known as maximum climbing boost....boost pressure is reduced to a value which permits the engine to run continuously at that particular power output...(p. 105-106)

(3)Override Boost - For the greatest possible power output for take-off or emergency, an increase in pressure above the normal take-off boost is permitted on some engines. This condition is used in conjunction with a special fuel. (p. 106)

(4) Maximum Cruising Boost....

Thus it is specifically stated that override or emergency boost was used only in conjunction with a fuel that permitted the higher boost rating.

[Ernst]

Acctualy the SIM should be: SUPERMARINE SPITFIRE: CLIFFS OF DOVER. I almost sure the right the devs must go to BoM. At least no spitfires there. Most of data here come only from two sources: spitfireperformance.com or from Kurfurst site. I am almost sure that the DEVS had other data, maybe from URSS evaluations of the SPITS and 109s that not exactly match the data presented here.

[Crumpp]

No, the engine couldn't run at 10.5lb boost with 87 octane fuel. The story about the pilot modding his engine with a match stick pertained to a Merlin III using 100 octane fuel and an unauthorised mod to obtain 16lb boost at low altitude Here's the some info on the use of 100 octane for development at RR:

No Seadog, it was possible as we can see from the Operating Notes. I am sure that engine was trashed after overboosting to +16lbs but it was definately possible on 87 Octane fuel.

It definately was not good but it was possible. Pulling the tit and overboosting the engine is not proof of the use of 100 Octane fuel.

[Seadog]

Originally Posted by Crumpp

No Seadog, it was possible as we can see from the Operating Notes. I am sure that engine was trashed after overboosting to +16lbs but it was definately possible on 87 Octane fuel.

It definately was not good but it was possible. Pulling the tit and overboosting the engine is not proof of the use of 100 Octane fuel.

read:


The above story clearly pertains to an engine that was already modded for 12lb boost (and thus using 100 octane) and the match stick mod permit boost up to 18lb, and it has already been established that Hurricanes in France were using 100 octane fuel by May 1940.

Maximum boost with 87 octane was 7lb:

http://www.spitfireperformance.com/spit2pnfs3.jpg

[NZtyphoon]

Originally Posted by Crumpp

Pulling the tit and overboosting the engine is not proof of the use of 100 Octane fuel.

Wrong - there are two engine tests, one on 87 Octane and one on 100 which both ran up to 10.5 lbs boost - there was no boost override used which, as Beaumont observed, required special fuel - ie: 100 Octane - to achieve. Later Merlin engines, such as the 45 series, were capable of boost override of +18 lbs but needed, and were designed to use, 100 Octane to do so. Later still +25 lbs boost could only be achieved using 150 Octane.

[Crumpp]

It is clearly not allowed during combat situations.

Where does it clearly say that?

It does not, the General Operating Notes clearly say he can use it.

[bongodriver]

Originally Posted by Crumpp

Where does it clearly say that?

It does not, the General Operating Notes clearly say he can use it.

Yes but only with 100 octane.

p.s. who did you quote?

[NZtyphoon]

Originally Posted by Crumpp

Where does it clearly say that?

It does not, the General Operating Notes clearly say he can use it.

Read the Merlin Operating notes again; "It is emphasised that high boost for emergency may only be employed with 100 Octane fuel..."

The Pilot's Notes General were to be be used in conjunction with the aircraft's Pilot's Notes, and with any limitations pasted into those notes using supplementary slips, and with the Merlin Engine operating notes: the Pilot's Notes General were never specific to any particular aircraft type.

[41Sqn_Banks]

Originally Posted by Crumpp

Where does it clearly say that?

"it is emphasized that the high boost for emergency may only be employed with 100 octane fuel"

It does not, the General Operating Notes clearly say he can use it.

http://forum.1cpublishing.eu/attachm...8&d=1337207418

"Clearly say ..." we obviously have a different understanding what clearly means.

That's what I call clearly:
January 1939: http://forum.1cpublishing.eu/attachm...0&d=1334682385
"100 octane must be used"

March 1940: http://www.spitfireperformance.com/ap1590b.jpg
"100 octane must be used"

April 1940: http://www.wwiiaircraftperformance.o...erlin3-pg6.jpg
"100 octane ... must be used"

November 1940: http://forum.1cpublishing.eu/attachm...5&d=1337196053
"only be employed with 100 octane fuel"

June 1941: http://forum.1cpublishing.eu/attachm...0&d=1334727256
http://forum.1cpublishing.eu/attachm...1&d=1334727263
"only of 100 octane fuel is in the tanks"