REFLECTOR: Fw: IO-550 Fuel Flow Issues and running LOP

[Dave Philipsen]

Yeah, they use that at the Reno air races.  I think they actually use a 
mix of water and alcohol.  I've always thought it would be neat to 
experiment with that idea.  Only problem is that you can't hear the 
detonation when it happens on ann airplane engine, I think.


Brian Michalk wrote:

>Water injection.
>Cost pretty much nothing per gallon, unless you buy the fancy bottled type.
>
>It's how the big racing radial guys make so much power.
>
>Dave Philipsen wrote:
>  
>
>>I also find this very interesting.  In fact, if you think about it, 100 
>>octane is probably overkill for cruising at 8000 feet since your engine 
>>is probably developing less than 75% of rated horsepower there.  How 
>>about this idea:
>>
>>Run mogas and retard ignition timing during takeoff and climb to prevent 
>>detonation/pre-ignition then restore ignition timing while in cruise.  
>>You would lose a little power during takeoff that might lengthen your 
>>takeoff roll but...
>>
>>Or, keep a small separate sump tank that can hold 100LL and switch to it 
>>for takeoff and climb then switch to mogas for cruise.
>>
>>
>>
>>John Dibble wrote:
>>    
>>
>>>Sid Knox wrote:
>>>
>>>Sid,
>>>
>>>Very interesting.  I have been thinking that 100 octane is overkill for my Franklin
>>>engine, especailly with dual ignition which helps reduce detonation.  I just wasn't
>>>sure how to go about determining how low an octane is acceptable.  My engine always
>>>runs cool so it seems like a good candidate for lower octane.  What is the compression
>>>of your engine?
>>>
>>>  
>>>      
>>>
>>>>  And I burn mostly (GASP!!) auto fuel in
>>>>a high-compression engine.  How can I get away with this?  By paying
>>>>attention to what my engine tells me via the instrumentation.  Once at
>>>>altitude I set about 2250 rpm, about 22 in Hg MAP, and set fuel flow to
>>>>about 6.5 gph.  This figures to about 26 mpg (statute)... better than many
>>>>autos.
>>>>    
>>>>        
>>>>
>>>What about for take-off?
>>>
>>>  
>>>      
>>>
>>>>The auto fuel (NO ethanol!) keeps the cylinders and spark plugs clean.
>>>>    
>>>>        
>>>>
>>>What about the lead deposits for the valves?  How many hours have you been running
>>>this way?
>>>
>>>John
>>>
>>>  
>>>      
>>>
>>>> If I
>>>>have to buy 100LL at a destination airport, I buy only enough to get me home
>>>>(with a generous reserve), so in practice I will actually have anywhere from
>>>>say 10 to 30 % 100LL.  Back when I could buy 93 octane auto fuel, I usually
>>>>did not mess with 100LL but now the best available around here is 91 octane,
>>>>so I feel better mixing a little 100LL to raise the average octane level.
>>>>And these performance numbers hold, year-after-year, so it isn't a one-time
>>>>fluke, but real-world results.
>>>>As Stephen Stilles says   "I love my aeroplane 'cause she's got style".
>>>>
>>>>Sid Knox
>>>>Oklahoma Tree Top Flyer
>>>>
>>>>Velocity  173 RG  N199RS
>>>>Starduster  N666SK
>>>>KR2         N24TC
>>>>W7QJQ  2m ssb, EM25
>>>>
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>>>>        
>>>>
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>>>      
>>>
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