Today's Message Index:
----------------------
1. 01:11 AM - Re: plugs THE FINAL ANSWER! (kyle Ponsford)
2. 07:03 AM - Re: lean vs rich (Phil Flaugher)
3. 09:22 AM - Re: Engines-List Digest: 8 Msgs - 05/26/04 (Robert Ardis)
Message 1
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| Subject: | Re: plugs THE FINAL ANSWER! |
--> Engines-List message posted by: "kyle Ponsford" <wild_kyle@hotmail.com>
My Friends,
I can't tell you how much I appreciate all your valuable input and ideas/
sugestions.
with the help given I finally got ahold of a real live Rotax mechanic at
Lockwood in Florida.
but before I go into that, I did get the 8E plugs, (9E plugs where
unavailable for weeks and $120)
I installed the 8Es in my rear cylindars (totaling 4 plugs).
It was immediately quite obvious I had a significant loss in smooth
operation during the ground test, which gave me enough knowledge to know
that is NOT an option. ( I was actually surprized how much change.)
sooo, (short story) I got ahold of "Shane" at lockwood, and asked him how
many rotax 912s he has worked on, and he said, "hundreds, [he] knew them
well."
I told him my problem with the fouling front plugs and chalky white rear.
His first responce was, "are you running at 5000-5500 RPMs? because it
sounds like you are running more at 4000."
He hit it dead on. when I fly it, rarely and carefully, I have been crusing
at 4200 RPMs.
then to make matters worse in the ground tests that followed I can only get
3000 RPMs before my breaks won't hold. (matcos) so all my tests have been
done at 3000. which I know now just made the problem worse. So with the very
black wet plugs, I leaned out the mixture to try to find a happy ballance
between the front and rear, and thus my current situation.
Shane told me to, "re-fix the mixture, fly at 5000 RPM and stop worying!" he
had no concern, (as many of you have said) about the very black or very
white plugs.
He gave me the reasons so acurately described by "Healy, Joseph" included
below.
I wanted to post this for anyone else concerned about the same thing.
I have wasted hundreds of $ and even more Hours, and lost a lot of hair over
this issue.
So now I'm going flying!
Thanks all for your many postings and concerns.
Clear Skies,
Kyle
>From: "Johnny Johnson" <Johnny@wiktel.com>
>Reply-To: engines-list@matronics.com
>To: <engines-list@matronics.com>
>Subject: RE: Engines-List: Re: plugs
>Date: Wed, 26 May 2004 22:46:50 -0500
>
>--> Engines-List message posted by: "Johnny Johnson" <Johnny@wiktel.com>
>
>From a lurker that knows basically nothing about 912's but feels compelled
>to comment... IIRC you said this happens on both sides, so maybe it is just
>plain bad design of the intake runners or something. It sounds like a
>pretty major difference in mixture and so just doesn't seem like it would
>be
>designed to run that way... but, I may be all wet.
>
>In any event and FWIW, I think I would want to be certain there are no
>induction system leaks causing the lean mixture in the "white cylinders"
>before I leaned it out some more. A bent or warped flange, loose fastener,
>bad gasket, really lousy intake manifold to block fit, holes in a casting
>or
>weld, something like that. It might be impossible to spot the culprit with
>the Mk I eyeball--a way to check for leaks with the engine running has been
>previously suggested but, as noted, can be a bit dicey with a prop
>spinning... figuring a way to safely do that test would be well worth the
>effort IMHO. Having satisfied myself that there are no leaks, I guess I
>would then lean it a tad and go flying, as Lowell suggests.
>
>Best of luck--hopefully you can get in the air very soon, with calmness of
>heart :=))
>
>Johnny
>
> -----Original Message-----
>From: owner-engines-list-server@matronics.com
>[mailto:owner-engines-list-server@matronics.com] On Behalf Of Lowell Fitt
>Sent: Wednesday, May 26, 2004 9:22 PM
>To: engines-list@matronics.com
>Subject: Re: Engines-List: Re: plugs
>
>--> Engines-List message posted by: "Lowell Fitt" <lcfitt@inreach.com>
>
>Joe's post pretty much explains the plug issue. The vast majority of the
>engines in these configurations do not have baffling so the temp
>differential will be there.
>
>If the front plugs are fouling then my thought is that the mixture is too
>rich. That won't take care of the white plugs on the rear, but as I have
>said earlier, the color differential is not an issue for most 912 users. I
>have heard Erik Tucker the recognized Rotax Guru speak on a couple of
>occasions and this issue has never come up. My humble suggestion would be
>to adjust the mixture to get a dark but not fouling sooty color to the
>front plugs and go fly. Without a redesign of the induction system the
>color differential will persist and I honestly don't think Rotax thinks it
>to be a problem especially with the millions of hours on these engines.
>
>If a problem arises, Rotax is also very quick to announce problems with
>service bulletins. After only three or four instances with the stator
>shorting, they provided free parts and free loner tools for upgrades. And
>the problems that arose were with the certified version of the 912 used in
>trainers. The free fix was never-the-less available to all.
>
>Lowell
>----- Original Message -----
>From: "Healy, Joseph" <WJH@brplusa.com>
>To: <engines-list@matronics.com>
>Subject: RE: Engines-List: Re: plugs
>
>
> > --> Engines-List message posted by: "Healy, Joseph" <WJH@BRPLUSA.COM>
> >
> > It seems that several people are having the same problem. For that
> > reason I doubt that an induction leak or other mechanical explanation is
> > the cause. If it were, then the discoloration problem would be random,
> > not consistently sooty front plugs with white back plugs.
> >
> > The problem might be the pattern of cooling air under the cowl resulting
> > in a higher mass flow of air/fuel charge entering the front cylinders
> > compared with the rear cylinders. For example, if the air/fuel mixture
> > entering the front cylinders is at 75 degrees, and that for the rear is
> > 105 degrees, the front cylinders will receive a 5% greater charge (more
> > fuel and air) than the rear cylinders. This is due to the increased
> > density of the air/fuel mixture predicted by the ideal gas law and
> > assuming a relatively equal manifold pressure at all points in the
> > intake. More fuel burnt in the front cylinders will contribute to more
> > soot on the plugs compared with the rear cylinders.
> >
> > Also, if the intake manifold is experiencing a front to back
> > differential in temperature, then the cylinders will likewise have a
> > differential temperature front to back. The rear cylinders, being
> > hotter, will have more complete combustion and less soot than the front.
> >
> > Note, this is not a question of too much cooling vs. too little cooling.
> > It is the differential cooling effect at various points on the engine
> > that would cause the problem.
> >
> > Joe Healy
> >
> >
> > -----Original Message-----
> > From: kyle Ponsford [mailto:wild_kyle@hotmail.com]
> > To: engines-list@matronics.com
> > Subject: Re: Engines-List: Re: plugs
> >
> >
> > --> Engines-List message posted by: "kyle Ponsford"
> > --> <wild_kyle@hotmail.com>
> >
> > The intake manafolds connect the front and rear cylinders, and obviously
> >
> > they are not perfect because I am learning lots of owners have collor
> > discrepency between front and rear. but do we know why?
> >
> > > > Kinda hard to miss read a WHITE plug! and I do mean chalky white.
> > > > but no aluminum particles. the front plugs are so black and sooty
> > > > they foul at about 4 hours. it is hard for me to imagin guys flying
> > > > the things like that.
Message 2
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| Subject: | Re: lean vs rich |
--> Engines-List message posted by: "Phil Flaugher" <phil.flaugher@charter.net>
I am NOT an expert......but this still goes against everything I
thought I knew.....somebody please tell me where I am wrong....
- Assume air flow and air temperature to be equal to all cylinders
and spark plugs and spark voltage and duration equal and cylinder
configuration to be identical, exhaust gas temperature is then
limited to fuel variables; if fuel is atomized correctly and
identical for any given cylinder and entry velocity and distribution
is the same for each cylinder, exhaust gas temperature can be
controlled by fuel quantity for each cylinder.
- The most efficient burn of a given quantity of fuel produces the
highest temperature of combustion (exhaust gas temperature). Too
much fuel or too little fuel should result in lower exhaust gas
temperatures.
- Therefore, exhaust gas temperature is a function of, and can be
altered by, shape and size of combustion chamber, spark timing,
spark temperature, spark location, spark duration, air/fuel entering
velocity and turbulence and density, fuel/air ratio, other variables
I can't think to list.
-If fuel quantity (% of air/fuel ratio) is the only variable, the
leaner the mixture can be adjusted to support acceptable engine
operation the LESS fuel is being used for a constant RPM and should
result in the highest EGT.
Where am I going wrong?
This is not a challenge to anyone else's position,but, rather, a
request for some education.
----- Original Message -----
From: "Scott Bilinski" <bilinski@kyocera-wireless.com>
Subject: Re: Engines-List: lean vs rich
> --> Engines-List message posted by: Scott Bilinski
<bilinski@kyocera-wireless.com>
>
> Yes it is confusing, just the opposite of what you would think.
When
> peaking each cylinder one at a time the EGT's should peak about he
same
> temp right? So the only real difference is the fuel flow. I have
to stand
> by my previous post that the cylinder which peaks with the highest
fuel
> flow is the leanest, and yes its fuel flow for all 4 cylinders.
Air Flow
> Performance helped me dial in my fuel flow per cylinder. I gave
them the
> info they sent me the nozzles and installed them and it brought
the fuel
> flow closer together using this method.
>
>
> At 08:40 PM 5/25/2004 -0400, you wrote:
> >--> Engines-List message posted by: TeamGrumman@aol.com
> >
> >Quote: "Yea me to. Apparently the way it works is, the cylinder
that peaks
> >with the highest fuel flow, means all the other cylinders are
getting more
> >fuel
> >so its the leanest. *** so the cylinder with the least fuel
flow is the
> >richest?=A0 somehow, I would have thought the opposite."
> >
> >I think someone is going to have to be a little more specific
here.
> >Cylinders with the highest fuel flow, i.e., receiving the most
fuel, are
> >the richest
> >cylinders. Now, if you are saying that the cylinder with the
first EGT to
> >peak at any given fuel flow is the leanest, then I'd agree. I'm
making the
> >assumption that you are NOT measuring individual fuel flow rates
for each
> >cylinder.
> >
> >I admit I got in on this thread at the most recent email so if I
am missing
> >something, please feel free to let me in on what I'm missing.
> >
> >
>
>
> Scott Bilinski
> Eng dept 305
> Phone (858) 657-2536
> Pager (858) 502-5190
>
>
======
>
======
>
======
>
======
>
>
Message 3
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| Subject: | RE: Engines-List Digest: 8 Msgs - 05/26/04 |
--> Engines-List message posted by: "Robert Ardis" <ardis_rb@hotmail.com>
Pardon me for changing the discussion from a 912 Rotax to a O-540
Lycoming.
The problem with flying the Cherokee 235 is that in Texas this time of
the year the oil temp runs about "a needle's width" from the red line. The
plane came from Utah and had been used in flight training and is equiped
with the 178 degree (85C) Vernatherm. The Vernatherm does not seat
correctly in the accessory case and it appears that the hole which it is
supposed to plug is so badly distorted and rough that a new Vernatherm will
not work much better.
What can be done short of a new accessory case? The reaming of the hole
will require enlarging
the hole beyond limits. Really, in NE Texas, the cooler needs to be 'on
line' as soon as the engine starts. I do not believe the thermostat is
necessary in this part of the country. I put over 1600 hours on a Comanche
and never knew about Vernatherms. Of course a filter attachment that
contained a Vernatherm might solve the problem but the question is "can the
engine run without the thermostat, and if so, be legal on a certified
aircraft"?
>From: Engines-List Digest Server <engines-list-digest@matronics.com>
>Reply-To: engines-list@matronics.com
>To: Engines-List Digest List <engines-list-digest@matronics.com>
>Subject: Engines-List Digest: 8 Msgs - 05/26/04
>Date: Wed, 26 May 2004 23:56:29 -0700
>
>*
>
> ==================================================
> Online Versions of Today's List Digest Archive
> ==================================================
>
>Today's complete Engines-List Digest can be also be found in either
>of the two Web Links listed below. The .html file includes the Digest
>formatted in HTML for viewing with a web browser and features Hyperlinked
>Indexes and Message Navigation. The .txt file includes the plain ASCII
>version of the Engines-List Digest and can be viewed with a generic
>text editor such as Notepad or with a web browser.
>
>HTML Version:
>
>
>http://www.matronics.com/digest/engines-list/Digest.Engines-List.2004-05-26.html
>
>Text Version:
>
>
>http://www.matronics.com/digest/engines-list/Digest.Engines-List.2004-05-26.txt
>
>
> ================================================
> EMail Version of Today's List Digest Archive
> ================================================
>
>
> Engines-List Digest Archive
> ---
> Total Messages Posted Wed 05/26/04: 8
>
>
>Today's Message Index:
>----------------------
>
> 1. 06:03 AM - Re: Lycoming service bulletins (Gary Casey)
> 2. 06:28 AM - Re: lean vs rich (Scott Bilinski)
> 3. 08:24 AM - Re: lean vs rich (Marvin Dupree)
> 4. 09:00 AM - Re: Re: plugs (Healy, Joseph)
> 5. 09:47 AM - Re: Lycoming service bulletins (Christopher Stone)
> 6. 10:43 AM - Re: lean vs rich (Scott Bilinski)
> 7. 07:24 PM - Re: Re: plugs (Lowell Fitt)
> 8. 08:48 PM - Re: Re: plugs (Johnny Johnson)
>
>
>________________________________ Message 1
>_____________________________________
>
>
>Time: 06:03:22 AM PST US
>From: "Gary Casey" <glcasey@adelphia.net>
>Subject: Engines-List: Re: Lycoming service bulletins
>
>--> Engines-List message posted by: "Gary Casey" <glcasey@adelphia.net>
>
>Steve - thanks for the great link! I maneuvered through the Lycoming
>website and came up empty - they present a few SB's, but you have to pay
>$$$
>for most.
>
>Gary Casey
>
>
>________________________________ Message 2
>_____________________________________
>
>
>Time: 06:28:22 AM PST US
>From: Scott Bilinski <bilinski@kyocera-wireless.com>
>Subject: Re: Engines-List: lean vs rich
>
>--> Engines-List message posted by: Scott Bilinski
><bilinski@kyocera-wireless.com>
>
>Yes it is confusing, just the opposite of what you would think. When
>peaking each cylinder one at a time the EGT's should peak about he same
>temp right? So the only real difference is the fuel flow. I have to stand
>by my previous post that the cylinder which peaks with the highest fuel
>flow is the leanest, and yes its fuel flow for all 4 cylinders. Air Flow
>Performance helped me dial in my fuel flow per cylinder. I gave them the
>info they sent me the nozzles and installed them and it brought the fuel
>flow closer together using this method.
>
>
>At 08:40 PM 5/25/2004 -0400, you wrote:
> >--> Engines-List message posted by: TeamGrumman@aol.com
> >
> >Quote: "Yea me to. Apparently the way it works is, the cylinder that
>peaks
> >with the highest fuel flow, means all the other cylinders are getting
>more
> >fuel
> >so its the leanest. *** so the cylinder with the least fuel flow is
>the
> >richest?=A0 somehow, I would have thought the opposite."
> >
> >I think someone is going to have to be a little more specific here.
> >Cylinders with the highest fuel flow, i.e., receiving the most fuel, are
> >the richest
> >cylinders. Now, if you are saying that the cylinder with the first EGT
>to
> >peak at any given fuel flow is the leanest, then I'd agree. I'm making
>the
> >assumption that you are NOT measuring individual fuel flow rates for each
> >cylinder.
> >
> >I admit I got in on this thread at the most recent email so if I am
>missing
> >something, please feel free to let me in on what I'm missing.
> >
> >
>
>
>Scott Bilinski
>Eng dept 305
>Phone (858) 657-2536
>Pager (858) 502-5190
>
>
>________________________________ Message 3
>_____________________________________
>
>
>Time: 08:24:18 AM PST US
>Subject: Re: Engines-List: lean vs rich
>From: Marvin Dupree <97corvette@cox.net>
>
>--> Engines-List message posted by: Marvin Dupree <97corvette@cox.net>
>
>scott....i questioned you on this earlier and from your response, i
>thought i had it figured out. but, i read this one and i am still not
>sure. are you saying that --- at highest fuel flow to all cylinders,
>the cylinder that has the highest peak egt is the leanest----? or are
>you saying the individual cylinder with the highest fuel flow is the
>leanest?
>regards, marv
>On Wednesday, May 26, 2004, at 08:25 AM, Scott Bilinski wrote:
>
> > --> Engines-List message posted by: Scott Bilinski
> > <bilinski@kyocera-wireless.com>
> >
> > Yes it is confusing, just the opposite of what you would think. When
> > peaking each cylinder one at a time the EGT's should peak about he same
> > temp right? So the only real difference is the fuel flow. I have to
> > stand
> > by my previous post that the cylinder which peaks with the highest fuel
> > flow is the leanest, and yes its fuel flow for all 4 cylinders. Air Flow
> > Performance helped me dial in my fuel flow per cylinder. I gave them the
> > info they sent me the nozzles and installed them and it brought the fuel
> > flow closer together using this method.
> >
> >
> > At 08:40 PM 5/25/2004 -0400, you wrote:
> >> --> Engines-List message posted by: TeamGrumman@aol.com
> >>
> >> Quote: "Yea me to. Apparently the way it works is, the cylinder that
> >> peaks
> >> with the highest fuel flow, means all the other cylinders are getting
> >> more
> >> fuel
> >> so its the leanest. *** so the cylinder with the least fuel flow
> >> is the
> >> richest?=A0 somehow, I would have thought the opposite."
> >>
> >> I think someone is going to have to be a little more specific here.
> >> Cylinders with the highest fuel flow, i.e., receiving the most fuel,
> >> are
> >> the richest
> >> cylinders. Now, if you are saying that the cylinder with the first
> >> EGT to
> >> peak at any given fuel flow is the leanest, then I'd agree. I'm
> >> making the
> >> assumption that you are NOT measuring individual fuel flow rates for
> >> each
> >> cylinder.
> >>
> >> I admit I got in on this thread at the most recent email so if I am
> >> missing
> >> something, please feel free to let me in on what I'm missing.
> >>
> >>
> >
> >
> > Scott Bilinski
> > Eng dept 305
> > Phone (858) 657-2536
> > Pager (858) 502-5190
> >
> >
> > >
> >
> >
>
>
>________________________________ Message 4
>_____________________________________
>
>
>Time: 09:00:34 AM PST US
>Subject: RE: Engines-List: Re: plugs
>From: "Healy, Joseph" <WJH@brplusa.com>
>
>--> Engines-List message posted by: "Healy, Joseph" <WJH@BRPLUSA.COM>
>
>It seems that several people are having the same problem. For that
>reason I doubt that an induction leak or other mechanical explanation is
>the cause. If it were, then the discoloration problem would be random,
>not consistently sooty front plugs with white back plugs.
>
>The problem might be the pattern of cooling air under the cowl resulting
>in a higher mass flow of air/fuel charge entering the front cylinders
>compared with the rear cylinders. For example, if the air/fuel mixture
>entering the front cylinders is at 75 degrees, and that for the rear is
>105 degrees, the front cylinders will receive a 5% greater charge (more
>fuel and air) than the rear cylinders. This is due to the increased
>density of the air/fuel mixture predicted by the ideal gas law and
>assuming a relatively equal manifold pressure at all points in the
>intake. More fuel burnt in the front cylinders will contribute to more
>soot on the plugs compared with the rear cylinders.
>
>Also, if the intake manifold is experiencing a front to back
>differential in temperature, then the cylinders will likewise have a
>differential temperature front to back. The rear cylinders, being
>hotter, will have more complete combustion and less soot than the front.
>
>Note, this is not a question of too much cooling vs. too little cooling.
>It is the differential cooling effect at various points on the engine
>that would cause the problem.
>
>Joe Healy
>
>
>-----Original Message-----
>From: kyle Ponsford [mailto:wild_kyle@hotmail.com]
>Subject: Re: Engines-List: Re: plugs
>
>
>--> Engines-List message posted by: "kyle Ponsford"
>--> <wild_kyle@hotmail.com>
>
>The intake manafolds connect the front and rear cylinders, and obviously
>
>they are not perfect because I am learning lots of owners have collor
>discrepency between front and rear. but do we know why?
>
> > > Kinda hard to miss read a WHITE plug! and I do mean chalky white.
> > > but no aluminum particles. the front plugs are so black and sooty
> > > they foul at about 4 hours. it is hard for me to imagin guys flying
> > > the things like that.
>
>
>________________________________ Message 5
>_____________________________________
>
>
>Time: 09:47:34 AM PST US
>From: Christopher Stone <rv8iator@earthlink.net>
>Subject: Re: Engines-List: Lycoming service bulletins
>
>--> Engines-List message posted by: Christopher Stone
><rv8iator@earthlink.net>
>
>I will send you a copy (.pdf) off list of the SI 1425a
>
>Chris Stone
>
>-----Original Message-----
>From: Gary Casey <glcasey@adelphia.net>
>Subject: Engines-List: Lycoming service bulletins
>
>--> Engines-List message posted by: "Gary Casey" <glcasey@adelphia.net>
>
>I have been trying, with no luck, to find a copy of Lycoming Service
>Bulletin SB388B and Service Instruction 1425A. Can anyone help?
>
>Gary Casey
>
>
>________________________________ Message 6
>_____________________________________
>
>
>Time: 10:43:35 AM PST US
>From: Scott Bilinski <bilinski@kyocera-wireless.com>
>Subject: Re: Engines-List: lean vs rich
>
>--> Engines-List message posted by: Scott Bilinski
><bilinski@kyocera-wireless.com>
>
>Lets try this one more time. You look at one cylinder at a time, peak the
>EGT, and note the fuel flow meter reading (which is all cyl fuel flow). Do
>this on all cylinders. Look at the numbers and the cylinder that shows the
>highest fuel flow, is the leanest. I put a larger nozzle in it and the
>numbers come closer together. I really dont know another way to explain it.
>
>
>At 10:22 AM 5/26/2004 -0500, you wrote:
> >--> Engines-List message posted by: Marvin Dupree <97corvette@cox.net>
> >
> >scott....i questioned you on this earlier and from your response, i
> >thought i had it figured out. but, i read this one and i am still not
> >sure. are you saying that --- at highest fuel flow to all cylinders,
> >the cylinder that has the highest peak egt is the leanest----? or are
> >you saying the individual cylinder with the highest fuel flow is the
> >leanest?
> >regards, marv
> >On Wednesday, May 26, 2004, at 08:25 AM, Scott Bilinski wrote:
> >
> > > --> Engines-List message posted by: Scott Bilinski
> > > <bilinski@kyocera-wireless.com>
> > >
> > > Yes it is confusing, just the opposite of what you would think. When
> > > peaking each cylinder one at a time the EGT's should peak about he
>same
> > > temp right? So the only real difference is the fuel flow. I have to
> > > stand
> > > by my previous post that the cylinder which peaks with the highest
>fuel
> > > flow is the leanest, and yes its fuel flow for all 4 cylinders. Air
>Flow
> > > Performance helped me dial in my fuel flow per cylinder. I gave them
>the
> > > info they sent me the nozzles and installed them and it brought the
>fuel
> > > flow closer together using this method.
> > >
> > >
> > > At 08:40 PM 5/25/2004 -0400, you wrote:
> > >> --> Engines-List message posted by: TeamGrumman@aol.com
> > >>
> > >> Quote: "Yea me to. Apparently the way it works is, the cylinder that
> > >> peaks
> > >> with the highest fuel flow, means all the other cylinders are getting
> > >> more
> > >> fuel
> > >> so its the leanest. *** so the cylinder with the least fuel flow
> > >> is the
> > >> richest?=A0 somehow, I would have thought the opposite."
> > >>
> > >> I think someone is going to have to be a little more specific here.
> > >> Cylinders with the highest fuel flow, i.e., receiving the most fuel,
> > >> are
> > >> the richest
> > >> cylinders. Now, if you are saying that the cylinder with the first
> > >> EGT to
> > >> peak at any given fuel flow is the leanest, then I'd agree. I'm
> > >> making the
> > >> assumption that you are NOT measuring individual fuel flow rates for
> > >> each
> > >> cylinder.
> > >>
> > >> I admit I got in on this thread at the most recent email so if I am
> > >> missing
> > >> something, please feel free to let me in on what I'm missing.
> > >>
> > >>
> > >
> > >
> > > Scott Bilinski
> > > Eng dept 305
> > > Phone (858) 657-2536
> > > Pager (858) 502-5190
> > >
> > >
> > > >
> > >
> > >
> >
> >
>
>
>Scott Bilinski
>Eng dept 305
>Phone (858) 657-2536
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>
>
>________________________________ Message 7
>_____________________________________
>
>
>Time: 07:24:07 PM PST US
>From: "Lowell Fitt" <lcfitt@inreach.com>
>Subject: Re: Engines-List: Re: plugs
>
>--> Engines-List message posted by: "Lowell Fitt" <lcfitt@inreach.com>
>
>Joe's post pretty much explains the plug issue. The vast majority of the
>engines in these configurations do not have baffling so the temp
>differential will be there.
>
>If the front plugs are fouling then my thought is that the mixture is too
>rich. That won't take care of the white plugs on the rear, but as I have
>said earlier, the color differential is not an issue for most 912 users. I
>have heard Erik Tucker the recognized Rotax Guru speak on a couple of
>occasions and this issue has never come up. My humble suggestion would be
>to adjust the mixture to get a dark but not fouling sooty color to the
>front plugs and go fly. Without a redesign of the induction system the
>color differential will persist and I honestly don't think Rotax thinks it
>to be a problem especially with the millions of hours on these engines.
>
>If a problem arises, Rotax is also very quick to announce problems with
>service bulletins. After only three or four instances with the stator
>shorting, they provided free parts and free loner tools for upgrades. And
>the problems that arose were with the certified version of the 912 used in
>trainers. The free fix was never-the-less available to all.
>
>Lowell
>----- Original Message -----
>From: "Healy, Joseph" <WJH@brplusa.com>
>Subject: RE: Engines-List: Re: plugs
>
>
> > --> Engines-List message posted by: "Healy, Joseph" <WJH@BRPLUSA.COM>
> >
> > It seems that several people are having the same problem. For that
> > reason I doubt that an induction leak or other mechanical explanation is
> > the cause. If it were, then the discoloration problem would be random,
> > not consistently sooty front plugs with white back plugs.
> >
> > The problem might be the pattern of cooling air under the cowl resulting
> > in a higher mass flow of air/fuel charge entering the front cylinders
> > compared with the rear cylinders. For example, if the air/fuel mixture
> > entering the front cylinders is at 75 degrees, and that for the rear is
> > 105 degrees, the front cylinders will receive a 5% greater charge (more
> > fuel and air) than the rear cylinders. This is due to the increased
> > density of the air/fuel mixture predicted by the ideal gas law and
> > assuming a relatively equal manifold pressure at all points in the
> > intake. More fuel burnt in the front cylinders will contribute to more
> > soot on the plugs compared with the rear cylinders.
> >
> > Also, if the intake manifold is experiencing a front to back
> > differential in temperature, then the cylinders will likewise have a
> > differential temperature front to back. The rear cylinders, being
> > hotter, will have more complete combustion and less soot than the front.
> >
> > Note, this is not a question of too much cooling vs. too little cooling.
> > It is the differential cooling effect at various points on the engine
> > that would cause the problem.
> >
> > Joe Healy
> >
> >
> > -----Original Message-----
> > From: kyle Ponsford [mailto:wild_kyle@hotmail.com]
> > To: engines-list@matronics.com
> > Subject: Re: Engines-List: Re: plugs
> >
> >
> > --> Engines-List message posted by: "kyle Ponsford"
> > --> <wild_kyle@hotmail.com>
> >
> > The intake manafolds connect the front and rear cylinders, and obviously
> >
> > they are not perfect because I am learning lots of owners have collor
> > discrepency between front and rear. but do we know why?
> >
> > > > Kinda hard to miss read a WHITE plug! and I do mean chalky white.
> > > > but no aluminum particles. the front plugs are so black and sooty
> > > > they foul at about 4 hours. it is hard for me to imagin guys flying
> > > > the things like that.
> >
> >
>
>
>________________________________ Message 8
>_____________________________________
>
>
>Time: 08:48:38 PM PST US
>From: "Johnny Johnson" <Johnny@wiktel.com>
>Subject: RE: Engines-List: Re: plugs
>
>--> Engines-List message posted by: "Johnny Johnson" <Johnny@wiktel.com>
>
>From a lurker that knows basically nothing about 912's but feels compelled
>to comment... IIRC you said this happens on both sides, so maybe it is just
>plain bad design of the intake runners or something. It sounds like a
>pretty major difference in mixture and so just doesn't seem like it would
>be
>designed to run that way... but, I may be all wet.
>
>In any event and FWIW, I think I would want to be certain there are no
>induction system leaks causing the lean mixture in the "white cylinders"
>before I leaned it out some more. A bent or warped flange, loose fastener,
>bad gasket, really lousy intake manifold to block fit, holes in a casting
>or
>weld, something like that. It might be impossible to spot the culprit with
>the Mk I eyeball--a way to check for leaks with the engine running has been
>previously suggested but, as noted, can be a bit dicey with a prop
>spinning... figuring a way to safely do that test would be well worth the
>effort IMHO. Having satisfied myself that there are no leaks, I guess I
>would then lean it a tad and go flying, as Lowell suggests.
>
>Best of luck--hopefully you can get in the air very soon, with calmness of
>heart :=))
>
>Johnny
>
> -----Original Message-----
>From: owner-engines-list-server@matronics.com
>[mailto:owner-engines-list-server@matronics.com] On Behalf Of Lowell Fitt
>Subject: Re: Engines-List: Re: plugs
>
>--> Engines-List message posted by: "Lowell Fitt" <lcfitt@inreach.com>
>
>Joe's post pretty much explains the plug issue. The vast majority of the
>engines in these configurations do not have baffling so the temp
>differential will be there.
>
>If the front plugs are fouling then my thought is that the mixture is too
>rich. That won't take care of the white plugs on the rear, but as I have
>said earlier, the color differential is not an issue for most 912 users. I
>have heard Erik Tucker the recognized Rotax Guru speak on a couple of
>occasions and this issue has never come up. My humble suggestion would be
>to adjust the mixture to get a dark but not fouling sooty color to the
>front plugs and go fly. Without a redesign of the induction system the
>color differential will persist and I honestly don't think Rotax thinks it
>to be a problem especially with the millions of hours on these engines.
>
>If a problem arises, Rotax is also very quick to announce problems with
>service bulletins. After only three or four instances with the stator
>shorting, they provided free parts and free loner tools for upgrades. And
>the problems that arose were with the certified version of the 912 used in
>trainers. The free fix was never-the-less available to all.
>
>Lowell
>----- Original Message -----
>From: "Healy, Joseph" <WJH@brplusa.com>
>Subject: RE: Engines-List: Re: plugs
>
>
> > --> Engines-List message posted by: "Healy, Joseph" <WJH@BRPLUSA.COM>
> >
> > It seems that several people are having the same problem. For that
> > reason I doubt that an induction leak or other mechanical explanation is
> > the cause. If it were, then the discoloration problem would be random,
> > not consistently sooty front plugs with white back plugs.
> >
> > The problem might be the pattern of cooling air under the cowl resulting
> > in a higher mass flow of air/fuel charge entering the front cylinders
> > compared with the rear cylinders. For example, if the air/fuel mixture
> > entering the front cylinders is at 75 degrees, and that for the rear is
> > 105 degrees, the front cylinders will receive a 5% greater charge (more
> > fuel and air) than the rear cylinders. This is due to the increased
> > density of the air/fuel mixture predicted by the ideal gas law and
> > assuming a relatively equal manifold pressure at all points in the
> > intake. More fuel burnt in the front cylinders will contribute to more
> > soot on the plugs compared with the rear cylinders.
> >
> > Also, if the intake manifold is experiencing a front to back
> > differential in temperature, then the cylinders will likewise have a
> > differential temperature front to back. The rear cylinders, being
> > hotter, will have more complete combustion and less soot than the front.
> >
> > Note, this is not a question of too much cooling vs. too little cooling.
> > It is the differential cooling effect at various points on the engine
> > that would cause the problem.
> >
> > Joe Healy
> >
> >
> > -----Original Message-----
> > From: kyle Ponsford [mailto:wild_kyle@hotmail.com]
> > To: engines-list@matronics.com
> > Subject: Re: Engines-List: Re: plugs
> >
> >
> > --> Engines-List message posted by: "kyle Ponsford"
> > --> <wild_kyle@hotmail.com>
> >
> > The intake manafolds connect the front and rear cylinders, and obviously
> >
> > they are not perfect because I am learning lots of owners have collor
> > discrepency between front and rear. but do we know why?
> >
> > > > Kinda hard to miss read a WHITE plug! and I do mean chalky white.
> > > > but no aluminum particles. the front plugs are so black and sooty
> > > > they foul at about 4 hours. it is hard for me to imagin guys flying
> > > > the things like that.
> >
> >
>
>
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