The Murphy Builders Site

irishfield wrote:As I slowly work my way towards the inevitable here....

What spark plugs are you guys running with your P mags?

Wayne ....

BR8ES is what they say to use .... (14mm NGK) .... (don't forget you'll need the step down adaptors - from the 18mm A/C ones ......... but you KNEW that already ! )
The "R" is for "Resistor" ................. which apparently helps with reducing the RF / radio interference

If the plug is a bit dark (darker colour) or "wet" - OR "oily" - go a step hotter (to BR7ES) .... and so on - until you get the right burn / colour on the plug ....
The great thing about using the 14mm auto plugs - is that you have an INFINITE range of plugs that can be tailored to suit the situation / cylinder condition etc etc etc

I run a .030" gap too ....... the bigger fatter spark has NO prob's jumping that gap - and is part of the reason WHY the flame front propagation is soooo much better !

FWIW, Klaus at LSE now recommends the Denso IK27. His pecking order from the bottom are NGKs (can break down and wear faster resulting in weaker spark), regular Denso (more reliable), and the iridium Denso IK27 (best). From what I understand the regular Denso's and cheaper NGK's were OK for the older Plasma II models with the 10 degree rotation duration, but the newer Plasma III have a hotter 20 degree duration spark, and the IK27 will perform better and last longer.

Here is a good place to buy plugs online.
https://www.sparkplugs.com/product.aspx?zpid=11181

We got 200 hrs out of a set of NGK BR8ES with the plasma III.

Apologies but I have the urge to stir the pot a bit ;)

Reduced fuel flow at altitude and/or less than full throttle is well proven with a solid foundation in physics.

Increased power compared to rated power - not really other than a small increase if you trade off safety margins and engine life.
Mags are already timed for optimum sea level full power.
Higher spark energy can hide other problems for awhile but increased power or lower fuel burn - again not really.

Ken

Yes Ken... why I'm still a Dinosaur and flying behind WWII technology! I'm only considering it because I have what appears to be a cold start issue... which I suspect is a failed impulse coupling as I'm not hearing a loud click (although I am starting to go deaf!). Other than that she started fine and worked fine all summer, other than I now appear to have a 125 rpm mag drop on one mag only now. Hoping that's just timing and I don't have to spend 2 grand for a Pmag and accessories.

Was leaning towards Walter's idea of putting a Pmag on my left side only, if I find my impulse coupling and mag needs an overhaul. I was leaning this way as I "knew" I had another O-320-A2B in parts to get the regular mag gear from to do so at no expense. SURPRISE... my engine shop appears to have screwed me and threw two impulse coupling drive gears in my parts box, to go with my one impulse.. one not Slick mags! Funny how one gear changed design from disassembly to clean and inspect! The gear sells for over $400... but I see Emag sells them at $185US if you order direct. Throws using ACS and avoiding import BS out the window...

Well I finally got a day out of the madness that we call life here and tried out my new buzz box and TDC tool that snaps on the spinner with elastics. Perfect day in the hangar for January, at +2C. Was sceptical about the TDC tool, but it worked like a dream and with ease.... and I was also able to verify 25 BTDC on it matched my flywheel mark with the top case centerline.

Found my left mag was firing early at 27* BTDC and the right was late at about 21* BTDC. I managed to get them both set pretty close to 25* BTDC and she fired right up without any preheat. I could only run up to about 1500rpm in the hangar before stuff started to blow away, but looks like no more than 30rpm mag drop between running on both and a single mag.. and L / R are almost identical. I was about 100 rpm differential before adjustments.

Of course the main question would be why... what has worn.....etc to change the timing, but I'll fly it for now (well when the weather improves) and see where I go from here.

Thanks for all the electronic ideas... I'm still a dinosaur for now !! :shh: