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From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-4431143@logan.com>
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Subject: Re: [FlyRotary] Re: Turbo Questions
Date: Sun, 15 Aug 2010 09:03:15 -0400
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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