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.
Ron Wanttaja
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 !!!