AirTalk.org Aviation discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  High compresstion in O-320          AirTalk.org Forum Index -> Aircraft Design & Building View previous topic :: View next topic   Author Message pittss1c Guest Posted: Wed Apr 18, 2007 9:37 pm    Post subject: High compresstion in O-320 Has anyone here done or considered 10:1 pistons for an E-series O-320. I have read the articles on how an E series differs from the others, but I am not sure that this closes the door on the subject. For example, if one was mostly interested in takeoff power or power at altitude... I am sure it will bring down the TBO, but I don't expect to pass TBO on the engine anyway (due to years more than wear). Besides, how many homebuilts do? (I doubt there is a statistically significant group with Quote: 2000 hrs on them) Mike Back to top Scott Skylane Guest Posted: Fri Apr 20, 2007 1:26 am    Post subject: Re: High compresstion in O-320 pittss1c wrote: Quote: Has anyone here done or considered 10:1 pistons for an E-series O-320. I have read the articles on how an E series differs from the others, but I am not sure that this closes the door on the subject. /snip/ Pitts, I don't know all the details, but I do know the "E" series 320's have a lighter duty front main bearing setup, as compared to the "D" models that came with higher horsepower ratings. However, I can't say whether the difference is that critical. How much HP do you suppose 10:1's would produce? If you limited your takeoff MP to a degree, and just used the extra efficiency at altitude, I can't imagine any harm being done, at all. Happy Flying! Scott Skylane Back to top pittss1c Guest Posted: Fri Apr 20, 2007 3:10 am    Post subject: Re: High compresstion in O-320 Scott Skylane wrote: Quote: pittss1c wrote: Has anyone here done or considered 10:1 pistons for an E-series O-320. I have read the articles on how an E series differs from the others, but I am not sure that this closes the door on the subject. /snip/ Pitts, I don't know all the details, but I do know the "E" series 320's have a lighter duty front main bearing setup, as compared to the "D" models that came with higher horsepower ratings. However, I can't say whether the difference is that critical. How much HP do you suppose 10:1's would produce? If you limited your takeoff MP to a degree, and just used the extra efficiency at altitude, I can't imagine any harm being done, at all. Happy Flying! Scott Skylane I believe changing from 7:1 to 8.5:1 gives you 10 HP I would hope for something like a 15 to 25 hp improvement over the 7:1. Back to top Guest Posted: Fri Apr 20, 2007 3:20 am    Post subject: Re: High compresstion in O-320 On Apr 19, 4:10 pm, pittss1c <pitts...@hotmal.com> wrote: Quote: I believe changing from 7:1 to 8.5:1 gives you 10 HP I would hope for something like a 15 to 25 hp improvement over the 7:1.- Hide quoted text - - Show quoted text - Detonation will be the biggest limiting factor. At 10:1 100LL or even straight 100 probably won't cut it. There used to be a 115/145 fuel (purple) for the old high-output engines used in piston- pounder airliners and so on. Dunno if it's available anymore, but the guys who use old airliners for firebombing might know. If you get detonation in an O-320, that engine won't last long at all. You'll either burn holes in the pistons or blow the heads off the cylinders. Cylinder bases have also been noted to pull right off the case. Dan Back to top pittss1c Guest Posted: Fri Apr 20, 2007 9:26 pm    Post subject: Re: High compresstion in O-320 Dan_Thomas_nospam (AT) yahoo (DOT) com wrote: Quote: On Apr 19, 4:10 pm, pittss1c <pitts...@hotmal.com> wrote: I believe changing from 7:1 to 8.5:1 gives you 10 HP I would hope for something like a 15 to 25 hp improvement over the 7:1.- Hide quoted text - - Show quoted text - Detonation will be the biggest limiting factor. At 10:1 100LL or even straight 100 probably won't cut it. There used to be a 115/145 fuel (purple) for the old high-output engines used in piston- pounder airliners and so on. Dunno if it's available anymore, but the guys who use old airliners for firebombing might know. If you get detonation in an O-320, that engine won't last long at all. You'll either burn holes in the pistons or blow the heads off the cylinders. Cylinder bases have also been noted to pull right off the case. Dan I think people still use 100LL even with 12:1... I am going to be surprised it 10:1 is an issue. Back to top flynrider via AviationKB. Guest Posted: Fri Apr 20, 2007 10:55 pm    Post subject: Re: High compresstion in O-320 pittss1c wrote: Quote: I think people still use 100LL even with 12:1... I am going to be surprised it 10:1 is an issue. The 8.5 to 1 jugs were designed with adequate detonation margins using the old 91/96 octane blue gas. Logic would tell us that you should be able to go with higher compression using 100LL, but I don't know of any version of the O- 320 where that has actually been tested, so the question of how much over 8.5 to 1 is adequate, remains a mystery. Good luck. John Galban=====>N4BQ (PA28-180) -- Message posted via AviationKB.com http://www.aviationkb.com/Uwe/Forums.aspx/homebuilt/200704/1 Back to top trent Guest Posted: Sat Apr 21, 2007 1:50 am    Post subject: Re: High compresstion in O-320 "pittss1c" <pittss1c (AT) hotmal (DOT) com> wrote in message news:f0apiq$3ve$1 (AT) news (DOT) ks.uiuc.edu... Quote: Dan_Thomas_nospam (AT) yahoo (DOT) com wrote: On Apr 19, 4:10 pm, pittss1c <pitts...@hotmal.com> wrote: If you get detonation in an O-320, that engine won't last long at all. You'll either burn holes in the pistons or blow the heads off the cylinders. Cylinder bases have also been noted to pull right off the case. Dan I think people still use 100LL even with 12:1... I am going to be surprised it 10:1 is an issue. It's not all down to compression ratio. Modern cars and motorcycles are managing compressions over 12:1 with regular gas and very lean mixtures. The design of the combusion chamber has a great deal to do with detonation. Get some time with a design team and a computer model of your flame front and you'll be fine. Back to top Charles Vincent Guest Posted: Sat Apr 21, 2007 4:34 am    Post subject: Re: High compresstion in O-320 trent wrote: Quote: It's not all down to compression ratio. Modern cars and motorcycles are managing compressions over 12:1 with regular gas and very lean mixtures. The design of the combusion chamber has a great deal to do with detonation. Get some time with a design team and a computer model of your flame front and you'll be fine. Were any of these 12:1 + engines air-cooled sporting carbs and fixed advance ignition systems? Were they operated at 70% of peak for hours at a time? I remember wasting all sorts of time looking for real premium back in the early eighties for my watercooled V8 that ran 12.5:1 compression (without which it would sound like a paint can full of marbles if I stayed on it too long). As regards the question at hand, Lycoming deemed it necessary to upgrade the bottom end and the jugs on the 0-320 when they pushed the compression up a point and a half, Pitts is considering pushing it three points, which is definitely going to increase the peak cylinder pressures and the bearing loads. Looking through the Aircraft Engines of the World for several years in 1950s and 1960s, the highest compression engines I see are 8.7:1. Somehow I recall a Lycoming helicopter engines did use a 10:1 ratio, but I can't come up with a reference. Charles Back to top Charles Vincent Guest Posted: Sat Apr 21, 2007 6:11 am    Post subject: Re: High compresstion in O-320 Charles Vincent wrote: Quote: trent wrote: It's not all down to compression ratio. Modern cars and motorcycles are managing compressions over 12:1 with regular gas and very lean mixtures. The design of the combusion chamber has a great deal to do with detonation. Get some time with a design team and a computer model of your flame front and you'll be fine. Were any of these 12:1 + engines air-cooled sporting carbs and fixed advance ignition systems? Were they operated at 70% of peak for hours at a time? I remember wasting all sorts of time looking for real premium back in the early eighties for my watercooled V8 that ran 12.5:1 compression (without which it would sound like a paint can full of marbles if I stayed on it too long). As regards the question at hand, Lycoming deemed it necessary to upgrade the bottom end and the jugs on the 0-320 when they pushed the compression up a point and a half, Pitts is considering pushing it three points, which is definitely going to increase the peak cylinder pressures and the bearing loads. Looking through the Aircraft Engines of the World for several years in 1950s and 1960s, the highest compression engines I see are 8.7:1. Somehow I recall a Lycoming helicopter engines did use a 10:1 ratio, but I can't come up with a reference. Charles Found the reference -- it was the HIO-360, a beefed up version of the IO-360 that had 10:1 ratio. The IO-360 had very different heads than the O-360 (and 0-320)that would make it more resistant to detonation. It seems there are examples of the IO-360 flying with 10:1 compression pistons. Charles Back to top Stuart & Kathryn Fields Guest Posted: Sun May 20, 2007 6:46 pm    Post subject: Re: High compresstion in O-320 I've heard reports of 0320s in NZ modified with 10:1 pistons in a helicopter operation. "pittss1c" <pittss1c (AT) hotmal (DOT) com> wrote in message news:f05hfj$4l8$1 (AT) news (DOT) ks.uiuc.edu... Quote: Has anyone here done or considered 10:1 pistons for an E-series O-320. I have read the articles on how an E series differs from the others, but I am not sure that this closes the door on the subject. For example, if one was mostly interested in takeoff power or power at altitude... I am sure it will bring down the TBO, but I don't expect to pass TBO on the engine anyway (due to years more than wear). Besides, how many homebuilts do? (I doubt there is a statistically significant group with 2000 hrs on them) Mike Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         AirTalk.org Forum Index -> Aircraft Design & Building All times are GMT Page 1 of 1   Jump to: Select a forum Aviation----------------alt.aviationAviation safety EnhancementPlanes, gliders and flying in AustraliaAviation et pilotage (Français)rec.aviationAviation (Aerobatics)Hot air, gas balloons and airshipsHang-gliding, paragliding, foot-launched flightAircraft Design & BuildingInstrument Flight RulesAviation (Classifieds)Military AircraftNaval AviationAviation (Miscellaneous Topics)Owning AirplanesAviators (General Discussions)Aviation related productsAircraft RestorationHelicopters and rotary wing aircraftsFlight SimulationSailplanesAviation (Students)Light aircraftFlying related activities in the UK Airports----------------alt.airportsEdinburgh Airport Glasgow Airport Humberside Airport Luton Airport Aberdeen Airport Glasgow Prestwick Airport  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.