---- John Slade <sladerj@bellsouth.net> wrote:
> Yesterday I took a friend for a ride and the engine purred sweetly for
> the entire trip. Looking back, the only thing different was that there
> didn't seem to be an rpm drop when I disabled leading or trailing coils
> during the runup.
>
> Today all was normal during runup (except perhaps the coil disable
> causing no rpm drop) and full power got me 5300 before I couldn't hold
> it any more on the brakes. Take-off and climb were normal. On the
> downwind I was showing 5800 rpm so I decide to coursen the prop. When I
> did I felt a splutter. I reduced throttle and the engine ran normally. I
> increased throttle. More splutter. I reduced throttle and it ran
> normally at 4600. Any more throttle and all I got was reduced power &
> popping and spitting. I circled the field trying mixture adjustments,
> checking fuel pressure on both pumps, coil & injector defeat and
> swapping to B computer. Nothing seemed to make any difference, so I landed.
>
> The only change since the previous flight was that I'd replaced the
> plugs with a clean set - not new - just clean. Suspecting a bad plug I
> let the engine cool down a bit, then installed new ones. Later in the
> day the engine ran fine during taxi and again reached 5300 on runup.
> Acceleration seemed normal then, halfway through the takeoff roll, I
> felt a splutter, so I aborted and rolled off the runway.
>
> When I added power to taxi clear of the runway the spitting got much
> worse. So bad, in fact that it seemed to be running on one rotor and
> there was insufficient thrust to move the plane forward. I tried
> adjusting mixture and defeating injectors & coils again and the engine
> eventually stopped. I was able to restart, but had the same symptoms.
> The rpm was fairly steady at 1100 or so, but this was the max rpm I
> could get. The EM2 was flip flopping rpm readings
> 2300...400...2100..800...every couple of seconds.
>
> I called Tracy from right there on the taxiway. As always - he took the
> call and listened to my unscientific whining. Thank you Tracy :)  
> Anyway, his best thought was that it sounded like it might be a coil
> heat-soak problem. It definitely seems heat related, and my cowl has
> been running a bit hotter since I installed the new T04 turbo.
>
> I pushed (yes pushed) the plane back to the hangar, then tried turning
> the prop to feel all six compression strokes. To my untrained arm
> muscles the compressions all felt the same. I ordered 4 new coils and
> will report if this corrects the problem. Whether it does or not, I see
> a separate air duct for the coils in my future. The blow tube I
> installed may not be providing enough cooling. I once tried installing a
> temp sensor at the coils, but this sent other EM2 temp readings haywire
> - induced current from the ignition? - so unfortunately I don't have
> temp readings on the coils.
>
> Anyone have additional thoughts on this?
>

How about those heat stickers? they use on the Rotorway helicopter gear boxes and such I guess if the sticker gets over a certain temp it changes color or something like that.

Tony