flyrotary@lancaironline.net Mailing List Archive

Anytime you increase the internal compression pressure (either by increasing the compression ratio or through forced induction - which in effect increases the compression ratio) - the more efficiency and power you gain AND the closer you move to the detonation regime. The engine doesn't know or care how this increase in pressure comes about - well, actually it does. If you use a turbo or supercharger you are also heating the air through their compression process (which is why you need an intercooler in many cases) thereby moving closer to detonation. Lower compression engine are further away from the detonation regime to start with and therefore can safely take a higher boost level (and benefits more from it) than a high compression engine. So as has been mentioned, you will see a higher performance enhancement by boosting a low compression engine than an high compression engine already running closer to the detonation regime. You can certainly boost high compression engine, but to do it safely you generally need some fairly sophisticated "Knock" sensing and ignition/boost control to keep it out of detonation. Naturally the more boost you run the less margin for any error in controlling the onset of detonation. Contrary to what you may have read, it is possible to get an N/A rotary engine to detonate - I managed to do that in early flight (1998) by inadvertently over-advancing my ignition timing. I mistakenly set the static timing to 45Deg BTDC. I took off and after getting airborne noticed that if I opened the throttle wide open (more combustion pressure), the exhaust sound changed to a staccato, popping sound. Retard the throttle and it went away, never liking it when the engine did anything abnormal I returned and landed. Upon pulling the spark plugs I found I had destroyed them (presumably through detonation). The leading plugs had the ceramic cones completely missing and the electrodes were almost completely eroded away so that the spark gap was over 3/16", The trailing plugs had not suffer quite as badly although the ceramic cone was cracked on both and their electrodes also eroded. So my personal opinion is that unless there is some flight regime that requires it (you fly out of mountain valleys, you normally cruise above 12000 MSL, etc), you need to assess whether the extra weight, complexity and cost are worth it. If it is then go for it. In my case, after thinking about how I normally fly, I came to the conclusion that for me a turbo would not be worthwhile - which is why I still have two sitting on my work bench - well, the other reason is that they are stock Mazda turbos and really not suited for aircraft use (unless perhaps used very modestly) as I think John Slade has demonstrated for us all. Turbocharging an aircraft is a very interesting challenge and I sometimes wish I had talked myself into it - but, the numbers just didn't work for me and my typical flying. Fortunately for those of you who are going to turbocharge the rotary, you have some pioneers who are providing you with knowledge that was gained at some expense (money, underwear, seat cusions, etc) {:>). So make use of it and good luck. Ed Ed Anderson Rv-6A N494BW Rotary Powered http://www.andersonee.com http://www.eicommander.com Http://www.dmack.net/mazda/index.html http://www.flyrotary.com -------------------------------------------------- From: "Dave" <david.staten@gmail.com> Sent: Saturday, August 14, 2010 9:37 PM To: "Rotary motors in aircraft" <flyrotary@lancaironline.net> Subject: [FlyRotary] Re: Turbo Questions My vote would be no if I was paying for it. More likely to have detonation problems and less likely to benefit as much from boost as a lower compression engine. Bill Bradburry wrote: Should the Renesis, with the 10:1 rotors, be turboed or supercharged? Isn’t this too much compression to add more air? Bill B ------------------------------------------------------------------------ *From:* Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] *On Behalf Of *David Leonard *Sent:* Friday, August 13, 2010 11:54 PM *To:* Rotary motors in aircraft *Subject:* [FlyRotary] Re: Turbo Questions I hope some of this real world info from Bob and John is helpful to others of the group that may be considering turboing their 13B or Renesis...........These guys plus a few others (Dave Leonard and Steve Brooks) are turboed........... Dave is flying a T3/T4 hybrid if I recall correctly.........Jump in here Dave.......... No, mine is a full big shaft TO4 with a 60-1 compressor and housing. For ease of installation it as just been put into the stock turbine housing. -- David Leonard Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.net http://RotaryRoster.net -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html Ed Anderson Rv-6A N494BW Rotary Powered http://www.andersonee.com http://www.eicommander.com Http://www.dmack.net/mazda/index.html http://www.flyrotary.com