Lightning-List Digest Archive

Sat 07/16/11


Total Messages Posted: 4



Today's Message Index:
----------------------
 
     1. 07:26 AM - Mixture (Bernard Melendez, Jr.)
     2. 02:21 PM - Re: Mixture (Nick Otternack)
     3. 05:25 PM - oshkosh (Tex Mantell)
     4. 06:05 PM - Re: oshkosh (N1BZRich@AOL.COM)
 
 
 


Message 1


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    Time: 07:26:28 AM PST US
    From: "Bernard Melendez, Jr." <n45bm@yahoo.com>
    Subject: Mixture
    Group, This thread is from the Corby Starlet Yahoo group. Thought it might be inte resting to some of you. Bernardo Hi Russ, =C2-I've=0A been thinking of using some form of mixture control too. A mate with a =0A2.2 Jab in a Sonerai introduces a bit of vacuum into the balance tube =0Awhich lowers the fuel level in the bowl resulting in le aner mixture. The=0A greatest EGT increase he has been able to achieve is 3 0 degrees C. =0A=C2-What he does is have a tube connected to a point like a static vent =0Aabout 2" above the highest point in the wing camber in th e fuselage. =0AThis runs through a valve/tap (lawn mower type fuel tap) the n into a 't'=0A in the balance tube. Opening the tap introduces a small amo unt of =0Anegative pressure from the low pressure above the wing. When you close =0Athe tap off things return to factory standard. =C2-Hope this mak es =0Asense.... =C2-What have you been doing? =C2-Laurie =C2-Yes,=0A my system works on that principle although I have variable control. =0AIt =99s important to realize that changing the air pressure above the fl oat=0A bowl fuel surface does not change the level =93 the float stil l has total=0A control of this. The metered fuel through the jets is contro lled by the=0A pressure difference between float bowl surface and venture. Thus =0Achanging the float bowl pressure varies this difference for any giv en =0Acarby air flow and air density. =C2-I=0A would not recommend headin g down this path because you finish up with =0Atoo many variables working. First of all the normal carby adjustments =0Aare all still happening with c hanges in air density, power settings etc.=0A My system still has a vent to the cowl area so any change in cowl flap =0Aalso changes mixture. Change i n airspeed will also change mixture. A =0Arange of other variables also com e into play. =C2-My=0A aim was to investigate the engine behavior and te mperatures under =0Avarying mixture conditions and I have achieved a reason able =0Aunderstanding of what will happen. =C2-I have a Grand Rapids=0A E IS fitted which quickly warns me if anything untoward is happening. =0ABeli eve me the EGT and CHT can move rapidly with slight changes in =0Aflight co nditions and mixture. I wouldn=99t fiddle too much without a =0Amonit oring system of at least this caliber. My findings back up the =0Atuning fi gures recently mentioned from the US Jabiru distributors which =0Aare more stringent than the EGT range in our manuals for full power. =C2-In=0A gen eral, the engine works well with quite lean mixtures but is a dogs =0Abreak fast to manage on a trip because of all the variable changing all =0Athe ti me. Better to be flying the plane. I think there are good benefits=0A to be achieved, but with a carby that offers proper and accurate =0Amixture cont rol. I think the Rotec carby will offer this. =C2-On=0A a final note, it =99s worth reading a lot of engine management articles =0Athat can be found applying to the bigger traditional aircraft engines. =0ACheck out =9CPelicans Perch=9D and articles from the GAMI injector resear ch.=0A Some of these articles quickly made me realize how quickly we can =0Adestroy our engines when drifting into unacceptable sets of conditions. =C2-Russ


    Message 2


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    Time: 02:21:06 PM PST US
    From: Nick Otternack <vettin74@yahoo.com>
    Subject: Re: Mixture
    We use the HACman mixture control from green sky adventures with great resu lts. It is a kit for about $170. We can usually save a gallon an hour above 8 ,000ft when leaned to the jabiru specs, we do not run lean of peak Sent from my iPhone On Jul 16, 2011, at 9:24 AM, "Bernard Melendez, Jr." <n45bm@yahoo.com> wrote : > Group, > This thread is from the Corby Starlet Yahoo group. Thought it might be int eresting to some of you. > Bernardo > > Hi Russ, > > > > I've been thinking of using some form of mixture control too. A mate with a 2.2 Jab in a Sonerai introduces a bit of vacuum into the balance tube which lowers the fuel level in the bowl resulting in leaner mixture. The greatest EGT increase he has been able to achieve is 30 degrees C. What he does is h ave a tube connected to a point like a static vent about 2" above the highes t point in the wing camber in the fuselage. This runs through a valve/tap (l awn mower type fuel tap) then into a 't' in the balance tube. Opening the ta p introduces a small amount of negative pressure from the low pressure above the wing. When you close the tap off things return to factory standard. Ho pe this makes sense.... What have you been doing? > > > > Laurie > > > > Yes, my system works on that principle although I have variable control. I t=99s important to realize that changing the air pressure above the fl oat bowl fuel surface does not change the level =93 the float still ha s total control of this. The metered fuel through the jets is controlled by t he pressure difference between float bowl surface and venture. Thus changing the float bowl pressure varies this difference for any given carby air flow and air density. > > > > I would not recommend heading down this path because you finish up with to o many variables working. First of all the normal carby adjustments are all s till happening with changes in air density, power settings etc. My system st ill has a vent to the cowl area so any change in cowl flap also changes mixt ure. Change in airspeed will also change mixture. A range of other variables also come into play. > > > > My aim was to investigate the engine behavior and temperatures under varyi ng mixture conditions and I have achieved a reasonable understanding of what will happen. > > > > I have a Grand Rapids EIS fitted which quickly warns me if anything untowa rd is happening. Believe me the EGT and CHT can move rapidly with slight cha nges in flight conditions and mixture. I wouldn=99t fiddle too much wi thout a monitoring system of at least this caliber. My findings back up the t uning figures recently mentioned from the US Jabiru distributors which are m ore stringent than the EGT range in our manuals for full power. > > > > In general, the engine works well with quite lean mixtures but is a dogs b reakfast to manage on a trip because of all the variable changing all the ti me. Better to be flying the plane. I think there are good benefits to be ach ieved, but with a carby that offers proper and accurate mixture control. I t hink the Rotec carby will offer this. > > > > On a final note, it=99s worth reading a lot of engine management art icles that can be found applying to the bigger traditional aircraft engines. Check out =9CPelicans Perch=9D and articles from the GAMI injec tor research. Some of these articles quickly made me realize how quickly we c an destroy our engines when drifting into unacceptable sets of conditions. > > > Russ > > > > ========================== ========= ========================== ========= ========================== ========= ========================== ========= >


    Message 3


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    Time: 05:25:13 PM PST US
    From: "Tex Mantell" <wb2ssj@frontiernet.net>
    Subject: oshkosh
    Nick or Mark, I will be at Oshkosh all week and would like to share some experinces, tricks, tips & concerns with the other Lightning owners. Would it be appropiate at your forurm or at the get together Friday at noon? Tex


    Message 4


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    Time: 06:05:37 PM PST US
    From: N1BZRich@AOL.COM
    Subject: Re: oshkosh
    Tex, I think you have a great idea that would probably prove to be very helpful to current and future Lightning builders and flyers. My suggestion, since you are going to be there all week, and to give it the widest exposure, would be to do a "daily" mini forum at the Lightning booth. Since many people will only be at OSH for a day to two, the every day mini forum (at a set time each day) to meet with Tex (and any other builders/flyers that want to share) would give the widest exposure to the info you have to share. I am going to be in the Lightning and Jabiru booths all week (all day, every day) and would be willing to join you in this effort. Another thing I suggest so that your info is available long term, would be to write up all your tips and suggestions and send it in to the newsletter. Blue Skies, Buz In a message dated 7/16/2011 8:25:36 P.M. Eastern Daylight Time, wb2ssj@frontiernet.net writes: Nick or Mark, I will be at Oshkosh all week and would like to share some experinces, tricks, tips & concerns with the other Lightning owners. Would it be appropiate at your forurm or at the get together Friday at noon? Tex (http://www.matronics.com/Navigator?Lightning-List) (http://www.matronics.com/contribution)




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