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I thik you've only counted one piston for piston area SR6.
Total piston area for the Merlin is 1773cm².
Total piston area for the Dagger is 1768cm².
The question was about valve sizes and valve cooling. If the cylinder head had a similar size to the piston top the Merlin had twice the area to stick 4 valves in compared to the Dagger and it's 2 valves. The Daggers valves wouldn't have been that different in size to give either engine a real advantage in dissipating heat though the valve seats.
Why isn't it streamlined?
The Dagger needs a bigger supercharger and some work just to beat the Peregrine, what it needs to equal a Merlin III (1030hp at 16,250 ft) is a lot more.
Yes, its slender as an air cooled engine, but it's a rectangle; it doesn't taper at the front
not only that, but the location of the cooling accessories; glycol tank, ducting etc has to go alongside the engine,
Based on what Shortround has produced, what would this engine go in?
I am continuing the theme from the what-if-no-Merlin thread. I imagine that the LC Dagger woul dbe an alternative for aircraft like the Spitfire and Hurricane.
Not a lot of space around the reduction gear not already being used.
This is NOT going to be a cheap engine to make or service.
To be a viable engine even in a MK I Spitfire or Hurricane it needs to make close to 1000hp at 15-16,000ft. which means it needs to make closer to the 'equivalent' of 1100-1200hp at 8,000ft. It needs more power to drive the supercharger and it needs more "power" to overcome increased internal losses (friction, etc) while doing so.
Now you could drop the compression a bit and use higher manifold pressure, up to 15% could be gained this way, NOT counting power to run the supercharger but fuel economy suffers and you are loosing part of the advantage of the smaller cylinders.
Now what happens when you try to push beyond Merlin III performance to Merlin XX/45 performance? Granted you get Hooker to work on the supercharger and you have the 100/130 fuel but you now are trying to pull almost 1.5hp per cu. in. and you are trying to do it at altitude.