Spit Mk1 Boost?

[SEE]

Originally Posted by =XIII=Wedge

So given that we currently have an earlier Spitfire using only 87 octane fuel:-


With the ABC enabled (normal situation)

• The maximum boost obtainable will be +6.25 lbs.
• Once set the selected boost (datum) will be maintained regardless of changes in altitude up to the rated altitude.
• Above rated altitude the pressure will drop off, but the datum point will remain the same.
• Pilot workload is reduced and there is no risk of overboosting the engine.

With the ABC disabled (done by operating the cutout)

• The maximum boost obtainable would be +17 lbs @ sea level.
• Any rise above + 6.25 would have disasterous impact on the engine due to pre-ignition of the fuel.
• Provided that the pilot retarded the throttle they would have manual control of the boost, but would have to be careful not to overboost the engine.
• The indicated boost pressure would change as the altitude changed.

Thanks guys, just one qestion. At alt 17K and above, the manifold pressure in Clods Spit Mk1 drops significantly (less than 2 Ibs per Sq.in.) - full throttle - straight and level - The boost cut out has no effect as pointed out earlier in the thread. So, based on the above - this appears to be incorrect for that altitude?