Thanks, Jim

    Good to know that timing has that much effect and the crucial manifold
pressure to set it at.  I think Tracy's latest guidance is simple to set the
static timing to around 31DEG BTDC and then adjust the ignition timing with
the controller. If you have his version that has the adjustable ignition
timing.

 However, the Spark Plug Sag is due to the spark plugs.  Using 100LL the
spark plugs will give good performance for around 25-30 hours, if you use
no-lead auto fuel then you can get over 100 hours.  The Sparkplug sag
normally happens during high power setting - such as take off, but can
happen any time.  It generally starts with maybe one incident per flight for
just a short period perhaps less than 1 minute, then the frequency and
duration of the SAG increases.  When it happens on both rotors at the same
time, it really gets your attention.

For a long time I thought I had an injector acting up as the EGT would
suddenly decrease 300F and rpm would drop maybe 150 rpm, then all by itself
it would clear itself up.  Then it started happening more frequently and for
longer durations, 'bout drove me batty trying to figure out what it was.
Then Tracy reminded me that he had encounter similar happenings and had
figured out it was the spark plugs.  Apparently, carbon and in my case lead
accumulates on the ceramic cone until it is capable of conducing and
bleeding off some of the ignition voltage before it can build up to high
enough potential to jump the gap and ignite the gas.  The longer you run on
the plugs the more build up, the worst the situation becomes.

I recently got a spark plug cleaner and intend to clean some of the old SAG
plugs and see it that fixes the situation.

Ed



..Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
----- Original Message -----
From: "Jim Mosur" <jmosur@interlog.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Wednesday, October 01, 2003 10:27 PM
Subject: [FlyRotary] Re: Coil problem or is it?


> EDDY,
>
> You mentioned RPM sag, I had been going through this problem since I
> reinstalled my engine, I was dropping 300 RPM on takeoff or full power run
> up, started at 5200 and dropped to 4900 before I got off the ground. I
> checked with Tracey and he thought it might be plugs, as it turns out it
was
> timing. I had made my final timing adjustment with the timing light at 23
> degrees before TDC but had only run the engine to 4000 RPM and had not
payed
> any attention to the manifold pressure . I have since retimed with the
> manifold pressure at 22.3 " RPM 4250, since then no sag, now holds 5200
RPM
> on takeoff and has a lot more balls. Tracey had said the manifold pressure
> must be over 22" regardless of the RPM.
>
> Jim Mosur
> ----- Original Message -----
>
> >
 .html