Yes!!

Read the instructions for using +12lbs boost. First you have to override the normal controls and it emphasized that it is a very overloaded condition.

+12lbs is almost 3 times more pressure than the engine was designed to handle.

The modifications to the cylinder heads changes the frequency harmonics in order to reduce the incidence of cylinder head cracking. It does not increase the design strength of the engine.

BMW did the same thing when attempting to raise the motor to 1.8ata in the BMW801D2. The service trials resulted in a high incidence of cylinder cracks so they changed the cylinder barrel liners to ones that conformed harmonically under the new load.

Think of a tuning fork, if you want to change the frequency you adjust the length of the tines. To change the frequency in the merlin III, they added .020 inches to the spigot.

If we are now taking the 1938-9 Spitfire pilot's notes literally (like Crumpp is) then we also need to replace the reflector sight with an iron sight, remove the bullet proof glass and at least 30 other modifications that were in the original notes that were simply out of date in 1940.

The pilot's notes were written using the 2nd production Mk1 (it went specifically to the RAF for this exact purpose)

Like it says in the front of the notes.

"Air Ministry Orders and Vol. II leaflets as issued may affect the subject matter from time to time. It should be understood that amendment lists are not always issued to bring the publication into line with orders or leaflets and it is for holders of this book to arrange the necessary link up.

When an order or leaflet contradicts any portion of this publication an amendment list will generally be issued, but when this is not done, the order or leaflet must be taken as the over-riding authority"


I'd like to see a scan of the amendment certificate in the front of this "June 1940" pilot's note book.

Yes of course, but it was possible therefore it should be possible in the sim, too. No matter how you look at it, I really try hard to see your point, but you're wrong on so many levels I am afraid. Why are you doing this anyway? :o

It is approximately 2 times more than original nominal rating. And the RR engineers have had slightly different approach to getting more power from their designs - testing, breaking and consequently reinforcing what breaks first, hence so many mods and pilot notes amendmets that seem to confuse you.

+16lbs was 3 times more pressure and it was still used on Sea Hurricanes on the very same engine for obvious reason - no problem except drastically limited lifespan of the engine.

Honestly, Crumpp :eek::eek::eek:

Crumpp is right that +12 boost is about 3 times higher than the maximum continuous rating (+ 4 1/2), which is the highest rating that is not considered a overload condition (see attachment). I don't know if this was the rating the engine was designed for.

IIRC we know that +12 boost reduced the life-time to about 20 hours instead of 100 hours at maximum continuous rating.

The 12lb boost was a reduction from the 17lb boost that there normally would be. Yes there are references to this boost of 17lb. The boost was cut back to 12lb for reliability.

Crumpp still is evading identifying the 16 squadron that he claims were the only squadrons that used 100 octane fuel.

I see what he means now, thank you. It doesn't make much sense though - engines are designed for certain HP and that was never achieved at max. continuous rating as far I can tell.

Rolls Royce gives 990 b.h.p as "international power rating" (+ 6 1/4 Boost with 2,600 RPM at 12,250 feet), see http://forum.1cpublishing.eu/attachm...8&d=1334724563.

Don't we have to convert the boost values to ata before we compare them make a statement about the factor between them? Otherwise the atmospheric pressure offset is not eliminated.

Actually 12lbs of boost is not "three times" what the engine was designed for; 4lbs of boost = 15psi (1 atmosphere) + 4psi = 19psi while 12lbs = 15psi (1 atmosphere) + 12psi = 27 psi, so 12lb of boost is actually about 1.5x the pressure level.

This can be more easily seen by using inches of mercury instead of lbs of boost:

inches of mercury (inHg)or absolute pressure = Pounds per square inch of boost or gauge pressure.
80 inHg= +25 lbf/in² boost
67 inHg= +18 lbf/in² boost
61 inHg= +15 lbf/in² boost
46 inHg= +8 lbf/in² boost
44.5 inHg= +6 lbf/in² boost

Funny part is five or so years ago these two were viewed as the end all be all souce of info at the ubi and other forums!

Back then only a few people saw through thier biased smoke screens

Thus I can not tell you how happy it makes me to see so many more people comming to the same conclusion!

S!