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Mixture too rich?

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john_graham

Joined: 09 Aug 2007
Posts: 45
Location: Algonquin, IL

Posted: Sat Nov 17, 2007 8:09 am Post subject: Mixture too rich?

When flying at altitude I presume we just leave things

alone and run a rich mixture as there is no way to

lean it...true?



Thanks,



John P. Graham

CubFlyer1940(at)Yahoo.com

Cell phone  (847) 641-1330

Be a better sports nut!  Let your teams follow you 

with Yahoo Mobile. Try it now.  http://mobile.yahoo.com/sports;_ylt=At9_qDKvtAbMuh1G1SQtBI7ntAcJ

_________________
John Graham
N15YK 1993 Yak-52
CubFlyer1940@Yahoo.com
(847) 641-1330

dsavarese(at)elmore.rr.co
Guest

Posted: Sat Nov 17, 2007 8:51 am Post subject: Mixture too rich?

No such thing as a "rich" mixture with the pressure carb John.  The 

barometric chamber on the carb does it for us.  True - there is no way to 

lean it.

Dennis



---

brian-1927(at)lloyd.com
Guest

Posted: Sat Nov 17, 2007 4:53 pm Post subject: Mixture too rich?

On Nov 17, 2007, at 8:08 AM, John Graham wrote:



 	  Quote: 	
		   



 When flying at altitude I presume we just leave things

 alone and run a rich mixture as there is no way to

 lean it...true?


	


The M14P has an aneroid that automatically compensates for altitude.  

Think if it as automatic mixture control.



Regardless, the pressure carb senses mass airflow and therefore does  

a credible job of keeping the mixture in the ballpark without  

requiring the pilot to fiddle with the mixture control.



--

Brian Lloyd                         3191 Western Drive

brian HYPHEN 1927 AT lloyd DOT com    Cameron Park, CA 95682

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry



PGP key ID:          12095C52A32A1B6C

PGP key fingerprint: 3B1D BA11 4913 3254 B6E0  CC09 1209 5C52 A32A 1B6C

brian-1927(at)lloyd.com
Guest

Posted: Sat Nov 17, 2007 4:56 pm Post subject: Mixture too rich?

On Nov 17, 2007, at 8:50 AM, A. Dennis Savarese wrote:



 	  Quote: 	
		   

 <dsavarese(at)elmore.rr.com>



 No such thing as a "rich" mixture with the pressure carb John.  The  

 barometric chamber on the carb does it for us.  True - there is no  

 way to lean it.


	


Unless you have an improperly-calibrated carb.



You know, all M14Ps should have the same fuel-flow at the same  

pressure altitude, temperature, and power setting. It might be useful  

to know what that is for several common altitudes and power settings  

so that people can get an idea if their carb adjustment is in the  

ball-park.



--

Brian Lloyd                         3191 Western Drive

brian HYPHEN 1927 AT lloyd DOT com    Cameron Park, CA 95682

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry



PGP key ID:          12095C52A32A1B6C

PGP key fingerprint: 3B1D BA11 4913 3254 B6E0  CC09 1209 5C52 A32A 1B6C

tjyak50

Joined: 31 May 2007
Posts: 81
Location: Phoenix, AZ

Posted: Sun Nov 18, 2007 10:12 am Post subject: Re: Mixture too rich?

I have a JPI FS-450 Fuel Flow in my -50 and it is accurate to about .2 Gallons at the end of a long flight, so I am confident the flow values are correct.



At takeoff I get around 40 gph.

At 82% and full throttle around the 3000' to 6000' range it is not uncommon to see anywhere from 25gph down low to 20+ up higher.



On a recent long cross country with low power cruise at maybe  70% and throttle back (actually to about adjacent to the prop lever seems to work well) we were consistently under 15gph, and more like 13 to 14.



I have my mixture trimmed pretty lean at idle, down to under 2.8 gph at 40%.



Like many M14s, mine will sometimes stumble when putting in throttle slowly from idle.  You can watch the fuel flow spike from idle flow under 3.0 to about 13gph when it stumbles, then back to the stabilized flow once it settles down.



The computer in the FS-450 is linked by a serial bus to the GPS and knows where we are going and when we will be there.  It also computes MPG and I get about 11 Nautical miles per gallon.  Mostly useless trivia I suppose.



Tj

jan.mevis(at)informavia.b
Guest

Posted: Sun Nov 18, 2007 10:26 pm Post subject: Mixture too rich?

What MAP settings did you have when flying at 70%(you mention the throttle

adjacent to the prop lever).



Jan Mevis



--

viperdoc(at)mindspring.co
Guest

Posted: Mon Nov 19, 2007 6:42 am Post subject: Mixture too rich?

Tj,

Noticed you T.O. at 82% and ? 800-850 mm Hg manifold pressure. She is quiet

impressive when you depart at 100% and 850 mmHg is she not? The tail is up

in a heartbeat or she will just climb straight out from a 3 point attitude.

She tends to like to torque hard right also at 100% and full advance. As

Mozam said "quiet a machine".

Doc

--

tjyak50

Joined: 31 May 2007
Posts: 81
Location: Phoenix, AZ

Posted: Mon Nov 19, 2007 7:17 am Post subject: Re: Mixture too rich?

Doc: you misread.



1)  I take off at 103% and full throttle which is 40+ GPH in my -50.



2)  I climb / acro / fight at 82% and full throttle which is 20 to 25 gph in my -50.



Pretty standard M14 power settings except my governer is mis-adjusted just a bit on the top end.  Wonder how that happened.

TJ

viperdoc(at)mindspring.co
Guest

Posted: Mon Nov 19, 2007 10:39 am Post subject: Mixture too rich?

Copy.

Thanks. I have been taking off at 80-85% and 850 mm HG. Makes for a little

longer TO Roll by about ~ 100- 150 ft but it makes it easier for the 52's to

catch up for rejoin. I push the power up to 70% for last chance check then

gradually advance it to 100% and full advance (manifold pressure) if just

flying solo.

Cobbing it will get your attention.

Doc



--

mark.bitterlich(at)navy.m
Guest

Posted: Mon Nov 19, 2007 12:05 pm Post subject: Mixture too rich?

Tom, you're pushing to 103%  ??? 



Mark



From: owner-yak-list-server(at)matronics.com

[mailto:owner-yak-list-server(at)matronics.com] On Behalf Of tjyak50

Sent: Monday, November 19, 2007 9:18 AM

To: yak-list(at)matronics.com

Subject: Re: Mixture too rich?






Doc: you misread.



1)  I take off at 103% and full throttle which is 40+ GPH in my -50.



2)  I climb / acro / fight at 82% and full throttle which is 20 to 25

gph in my -50.



Pretty standard M14 power settings.



TJ





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=147095#147095

mark.bitterlich(at)navy.m
Guest

Posted: Mon Nov 19, 2007 12:47 pm Post subject: Mixture too rich?

There is a test procedure for checking that system Brian, (the auto lean system) but darn if I remember it off the top of my head.  If you would like, I will look it up and post it.   

Mark Bitterlich



--

tjyak50

Joined: 31 May 2007
Posts: 81
Location: Phoenix, AZ

Posted: Mon Nov 19, 2007 12:57 pm Post subject: Re: Mixture too rich?

There is a test procedure to check the initial position of the aneroid (Task Card 206).  And there is a chart to tell you what it should be based on your pressure altitude.   That is the good news.



The bad news is that it is nearly impossible to perform.

The amount of measurement you are looking for is VERY small.  You basically have to try to measure down to 0.5mm in a funky blind hole based off a certain flange position.  With the carb on the airplane it is impossible without special tooling.



In the words of Vladimir Yastremski--  "set by factory - better not to touch..."



I can send the section if you like.

brian-1927(at)lloyd.com
Guest

Posted: Mon Nov 19, 2007 4:51 pm Post subject: Mixture too rich?

On Nov 19, 2007, at 12:47 PM, Bitterlich, Mark G CIV Det Cherry  

Point, MALS-14 64E wrote:



 	  Quote: 	
		   

 Point, MALS-14 64E" <mark.bitterlich(at)navy.mil>



 There is a test procedure for checking that system Brian, (the auto  

 lean system) but darn if I remember it off the top of my head.  If  

 you would like, I will look it up and post it.


	


I would certainly be interested. I bet Dennis knows it off the top of  

his head.



You know, it would probably be useful to find someone who has a flow  

bench and could calibrate carburetors. My guess is that a shop that  

overhauls Bendix RSA injection systems could do the job. The Bendix  

RSA fuel control servo is virtually identical to our pressure carbs.



And then there is a very simple point. We can calculate it. If we  

know the MAP, engine RPM, displacement of the engine, and  

stoichiometric mixture, we can calculate the proper fuel flow. We can  

even work it up for various rich and lean mixtures.



--

Brian Lloyd                         3191 Western Drive

brian HYPHEN 1927 AT lloyd DOT com    Cameron Park, CA 95682

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry



PGP key ID:          12095C52A32A1B6C

PGP key fingerprint: 3B1D BA11 4913 3254 B6E0  CC09 1209 5C52 A32A 1B6C

brian-1927(at)lloyd.com
Guest

Posted: Mon Nov 19, 2007 5:04 pm Post subject: Mixture too rich?

On Nov 19, 2007, at 4:50 PM, Brian Lloyd wrote:



 	  Quote: 	
		   And then there is a very simple point. We can calculate it. If we  

 know the MAP, engine RPM, displacement of the engine, and  

 stoichiometric mixture, we can calculate the proper fuel flow. We  

 can even work it up for various rich and lean mixtures.


	


Oh, I forgot temperature.



--

Brian Lloyd                         3191 Western Drive

brian HYPHEN 1927 AT lloyd DOT com    Cameron Park, CA 95682

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

— Antoine de Saint-Exupéry



PGP key ID:          12095C52A32A1B6C

PGP key fingerprint: 3B1D BA11 4913 3254 B6E0  CC09 1209 5C52 A32A 1B6C

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