Someone tried d to tell me the old P&W radials had Low compression. If so, why do many need 104 octane fuel ?
Someone tried d to tell me the old P&W radials had Low compression. If so, why do many need 104 octane fuel ?
Not an engine expert by any means, but it depends on the timing, doesn't it? Seems like the mechanics could back off on the spark advance a bit to make it compatible with lower-octane fuel. Also, ISTR they kept less of the high-octane fuel in the US during the war, and CONUS pilots were told to limit power levels.Originally Posted by Mallory
Ron Wanttaja
A lot of those engines were supercharged.
If you mean WW2 engines then the normal compression ratio was between 6:1 and 7:1 - Merlin - 6:1, Sabre - 7:1 - PW R-1830 - 6.7:1, PW R-4360 - 6.7:1 - DB 601 - DB 601 - 6.9:1 - BMW 801 6.5:1. Power was increased by using water-meths injection and/or supercharger/turbocharger output, the Ta152H had increased power by using nitrous oxide and/or watermeths.
Yes WWII. I consider 7:1 getting up. Low compression I regard as 4:.1
Shows what they known Y/A!
How about the RR Merlin or V12 Allison? Or the P & W Wasp junior from the 'thirties (Non- super charged)?
Quick check - Merlin - 6:1, Allison V-1710 - 6.65:1, Wasp Junior - 6:1, Bristol Hecules (sleeve valve) - 7:1, Bristol Centaurus 7.2:1 (sleeve valve) Nakajima Sakae - 7:1, Even the RR Griffon was only 6:1, WW1 - Clerget - 4.56:1 or 5.3:1 - Hispano Suiza 8a - 4.7:1 or 5.3:1, Gnome Rhone - 4.85:1. I did work on the Centaurus for a short while but please don't ask me to explain sleeve valves systems and theory - they are a nightmare and will give you a thumping headache. If you are interested then the best man to read is Sir Harry Ricardo - he got a single cylinder sleeve valve engine to 8,000 rpm back in the 30s !!!
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