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I've recorded each time I replaced plugs and
always notice the black coating on the ceramic center cone, but a very high
impedance resistance measurement would have been more objective. But,
don't have the equipment to do that.
Read much about other effects of lead on
piston engines and the reported poor interaction (or lack) of lead in
gasoline and synthetic oil, lead "sludge" build up etc. But, so far the
only adverse effect I have detected was with the spark plugs.
But, I will try to remember to check the rings next time, I have the engine
apart, Al {:>)
Tracy has always flow with a mixture of 2
cycle and Marvel oil and has gotten over 200 hours on a set of plugs, but I
always attributed that longevity to his minimal use of 100LL - perhaps not
completely due to that. Could be the Marvel Mystery {:>)
Ed
----- Original Message -----
Sent: Monday, May 22, 2006 12:35 PM
Subject: [FlyRotary] Re: Questions from a
potential rotaryphile
The Marvel Mystery Oil solution is relatively new. So it's not definitive
yet, but I'd be pretty quick to test it if I were you. I'd be tempted to swap
plugs out, then use Marvel at recommended strength. If you have recorded # of
hours of previous plugs, I'd be tempted to do visual comparison for lead
deposits, or some manner of resistance check. Would be nice if you didn't have
to treat it as attribute, rather you had measure to anticipate fouling. I'd
also consider richer marvel mixture test.
Consensus on piston engines is lead builds up on rings. (Better check
your rings Ed. LOL). As I recall, when they first encountered it they changed
plug and stuff, with no effect.
Hi Al,
Well, as I said I was a bit surprised to
have the that attributed to you. Relating the comments to sole
use of Av Fuel, it provides a more comprehensive context. I find
the use of Marvel Mystery oil in the context of unfouling plugs certainly
interesting. I happen to have purchased a couple of pints to mix with
my 2 stroke oil for a different reason, but will be great if it extended my
spark plug replacement interval.
No question use of 100LL in the rotary
does lead to plug fouling after 20-30 hours - at least that is my experience
over 300+ hours of rotary flying. I tried a different plug but could
tell no significant difference.
The drop in rpm due to fouling appears
have a tendency to occur in any high power situation - such as during take
off - but even during cruise if running at a high power level. My
theory is with WOT the combustion chamber pressure is higher (due to the
denser air/mixture ingested) and higher pressure makes it tougher for the
spark to jump the gap. So if lead fouling has started to occur, its
easier for the electrical energy to follow the lead deposit than jump the
gap. Back off on throttle thereby reducing manifold pressure resulting
in less combustion chamber pressure makes the job of jumping the gap a bit
easier and the spark plug starts to function normally resulting in power
recovery.
Normally you do not have both rotors (at
least my experience) encounter this situation simultaneously - unless
you have ignored the problem for a considerable amount of time.
Normally its one or the other. However, I did have both rotors go into
SAG mode (once before I fully understood what was happening)
taking off fully loaded. Performance WAS adversely
affected and the pucker factor was there until I realized that even
with both rotors SAGGING, I still had over 500 fpm rate of climb -
what I could only have hoped for flying a Cessna 150. So I
just climbed up to altitude over the airport I had taken off from, pulled
back on the throttle and in approx 3 minutes the SAG situation had cleared
up.
When SAG occurs I first notice a
change in the drone of the engine, then I find EGT of the afflicted rotor
drops about 300F. Rpm will tend to drop a bit as well - although not as
much as in cruise as during take off. I presume the lower temps
are because the unburnt fuel is causing a cooler exhaust condition in
that exhaust port's header.
So, anyhow, thanks for setting the
matter straight, Al.
Ed
----- Original Message -----
Sent: Monday, May 22, 2006 10:43
AM
Subject: [FlyRotary] Re: Questions
from a potential rotaryphile
I'm here Ed. Appreciate your consideration given you were
inadvertently set up. The original post is below. You will note the
paragraph above the section you read talks about negative effect of
EXCLUSIVE use of av fuel. Also described with "this happens every 20
hours".
Original post fwiw:
<<Al- just let me in on the system for the auto engine
logistics- do all the FBO's serve up auto fuel?
Auto fuel relatively difficult to find at airports. You can do web
search for all the ones within flying distance. I planned my flight from
west coast to Osh last year. Two different routes. With the cruise range
of the Cozy it was no big deal to buy auto all the way. I recall one
location I'd have to buy a few gallons of aviation fuel.
In the past, auto engines would notice slight rpm drop during
cruise if they exclusively burned aviation fuel. Week after week it would
increase. If they ran one tank of auto fuel, it would fix itself until
around 10 avgas tanks later. They now use Marvel Mystery oil of all
things, and it reportedly eliminates all negative effects. Marvel better
than 2 other lead scavengers.
<<Do the rotory fliers carry chain saw oil mix with them when
going cross country to pour in their tanks after a fill up?
Rotary is different issue. Their unusual combustion
chamber requires them to mix 2 cycle oil with each tank. If they don't
their compression seals die prematurely. Just like your boat motor mix, I
don't see it as a big deal. In addition, if they use aviation fuel,
they develop power drop on departure and have to replace all their
plugs before next flight. This happens every 20 hours. They don't have
solution for this.
<<somebody said they were using jerry cans of auto gas and
bringing them to their hanger to fill up their tanks- is this right?
I find almost all my flying is from home base, returning later that
day. So I fill (3) 5 gallon cans at gas station 1 mile away from airport.
While I'm doing preflight, these drain into my mobile 30 gallon tank. I
then wheel it over to the plane and it takes 20 seconds to fill tank.
(compressed air transfers it very rapidly). Neat trick I learned from
motorcycle buddy. No more inconvenient than taxiing over to HBO to get
fuel, way less expensive.
If I don't value auto fuel savings, just add some Marvel each av
tank, off I go.
-al wick
I'm a bit surprised hearing it
came from Al Wick as he was on this list for a while. I
thought he had a better understanding of what was going on with the
rotary. But, you're right a little knowledge means incomplete
knowledge which can be dangerous.
Ed
-al wick
Artificial intelligence in
cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on
engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk
assessment, Glass panel design
info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
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