REFLECTOR: It's been really quiet this week

[John Dibble]

On 2/18/2014 9:43 AM, Brian Michalk wrote:
> Hmm, I am a proponent of reducing timing to lower CHT's, and have my 
> mag and EI set to 28BTDC, advancing to 32BTDC above 2600 RPM.  The 
> book value is 28-32 degrees.
>
> I will retard it some more and we'll see what happens.
>
> On the EI, I am running NGK Iridium IX plugs, with a fairly shallow 
> reach.  I don't have the exact rating available at the moment.
>
> I am seeing conflicting data.  My gasket thermocouples are reading 
> redline temps on takeoff, but the bayonet thermocouples are reading 
> cool.  Do you know what could be causing this?

Are they on the same side of the cylinder?  There's typically a 100F 
difference between the inlet and exit air sides.
>
> On 2/18/2014 8:51 AM, John Dibble wrote:
>> On 2/17/2014 11:44 AM, Brian Michalk wrote:
>>> I've been flight testing.  It's a slow process for me, since my 
>>> engine design while Franklin based, has EFI and EI.
>>> I have been battling high CHT's even in the cooler weather, and am 
>>> seeing positive results as the engine breaks in.
>> Sorry for repeating myself, but I really think you need to reduce the 
>> timing advance to 24-25 degrees.  My anecdotal experience has been 
>> that any departure from the mag/massive electrode combination 
>> increases the detonation tendency for the Franklin engine.  Further, 
>> multiple changes compound the problem.  When I bought my plane it had 
>> one mag and one EI, both using massive electrode plugs.  I 
>> experienced minor detonation symptoms such as an occasional plug 
>> fouled with metal and an occasional high CHT.  When I switched to 
>> auto plugs for the EI, the symptoms worsened with more frequent plug 
>> fouling, erosion of the electrode and an occasional engine stumble 
>> right after takeoff, a real attention getter.  When I switched the 
>> mag plugs to fine wire, the engine stumbling became more frequent and 
>> I had to replace a cylinder and piston due to severe pitting.  I have 
>> eliminated the symptoms by reducing the timing advance.  I manually 
>> increase the EI advance once I'm above 9k for max power.  Maybe Mike 
>> W will comment also.
>>
>> John



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