REFLECTOR: First long Cross Country

[John Dibble]

Mark,

Don't know where to begin.  The problem is that over 900 hours, I didn't 
know for sure I was detonating until I discovered one cylinder liner and 
piston were eaten away at the top.  There were subtle hints, like when 
the #5 cylinder temp increased by 50 C during descent from 9500' with 
power near idle.  Going full rich brought the temp down.  Or when the #1 
cylinder EI plug gap would become filled solid with a dark material.  In 
the beginning I assumed that was carbon, but later figured out it was 
metal, usually steel.  The real attention getter was when the engine 
would stumble at 1000' right after T/O.  There's more, but let's move on 
to the contributing factors.

First of all my engine is a 10.5/1 compression Franklin.  I think the 
high compression engines simply do not need (or can tolerate) as much 
advance.

Second, at the peak of detonation problems, I discovered the EI had a 
bad ground ( 1 ohm of resistance) and I understand that a bad ground 
will cause an EI to further advance by 10-20 degrees.  Now I check the 
ground at every annual.

Third,

On 6/22/2012 10:48 PM, Mark Magee wrote:
> Hi John,
> Your issues with detonation are troubling me. I ran a Rose EI on a 
> Long EZ years ago and know that at 11,500 I was 41DEG advanced with a 
> reduced fuel burn of about 15%. We in the San Diego EZ squadron 
> designed the advance curve and Rose burned it in.
> How did you find out you were detonating?
> Detonation could lead us back to our Glide Distance thread. I don't 
> believe there are any working knock sensors out the for a LYC/CONT EI, 
> yet it seems to me that retarding back to mag advance will kill the 
> fuel savings advantage of an EI.
> I'd appreciate any additional data on EI advance curve and detonation 
> you've uncovered
>
> Mark B. Magee
> N34 XL
> Sent from IPhone 4
>
> On Jun 22, 2012, at 8:39 PM, John Dibble <aminetech at bluefrog.com 
> <mailto:aminetech at bluefrog.com>> wrote:
>
>> Cruise altitude depends on the weather.  On a rare SKC day I fly 
>> 9500/10500.  On a partly cloudy day, there are bound to be cloud tops 
>> to 13000, requiring O2 if you want to stay above the cloud bases 
>> where the air is far smoother.   When solid overcast, it's usually 
>> smooth air below the ceiling.
>> I'd go with the lesser advance timing, or even no advance at all 
>> until you determine how much advance is right for your engine.  I 
>> have one Rose EI on my Franklin and I had detonation damage from too 
>> much advance.  I ended up disabling the advance and setting the EI to 
>> the same advance as my mag.
>>
>> John
>>
>> On 6/22/2012 6:23 PM, Richard J. Gentil wrote:
>>> I am planning on taking my first long trip in my Normally Aspirated, Dual EI, MT, IO-390, SERG. Going from Naples, FL to Norfolk, NE. (Day VFR. Not ready to test her in IFR yet.)
>>>
>>> I figure I can make it with one stop to stretch the legs and relieve the bladder.
>>>
>>> My question is cruising altitudes. (I can take an O2 bottle if there is any good gain by going up 16,500 or 17,500).
>>>
>>> What altitudes do you find most efficient etc for a Velo.
>>>
>>> I have two timing advance curves with my E-Mag and P-Mag. I am currently using curve A as set by the factory not tried curve B yet. (I have not hooked them up at an EICAD yet.)
>>>
>>>
>>>
>>> I would be very interested in your recommendations.
>>>
>>> Richard
>>>
>>> Sent from my iPhone 4 Classic
>>>
>>>
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