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Rejetting a 914 during Winter?
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rampil

Joined: 04 May 2007
Posts: 870

Posted: Thu Jan 08, 2009 10:21 am Post subject: Re: Rejetting a 914 during Winter?

Hi Thom,



This spring I need to do my Commercial long cross country.  Buffalo

is just far enough from my base to qualify.  Maybe you can take a ride

with me and see what I am talking about.



PS: In science there is an important precept which goes:

 Absence of Evidence is Not Evidence of Absence.



If Diamond did not report measurements in the DA manual, that is not

positive proof that they measured no changes. (It would be hard to 

believe that the Bings are absolutely perfect in compensation over such a

wide altitude range anyway, something no one claims)

Europa XS 912uls  BMA EFIS/2  VFR/IFR Day/Night

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Ira N224XS

Gilles.Thesee(at)ac-greno
Guest

Posted: Thu Jan 08, 2009 10:56 am Post subject: Rejetting a 914 during Winter?

Darin,



Just found your post.

 	  Quote: 	
		  

 Does anyone rejet their 914 (or 912) during winter? 


	


We don't.

Our 914 airplane was flown without any problem between - 14°Celsius and 

+ 38°Celsius, and from zero foot density altitude up to FL 145.

We usually run at 31"/5000 rpm, and FF is a little lower at altitude,  

which I wonder may be due to bubbling in the fuel lines, and a slightly 

lower output.

 	  Quote: 	
		   Can any of you engine gurus tell me if this may be the source of my slightly diminished engine performance?  Also, one last thing that makes me think the engine is running a bit rich is that if I land at a small strip and shut down right after landing, 


	


We are based on a 2000' airstrip, but never shut down without one minute 

or so idling for the well-being of the turbo .



Best regards,

-- 

Gilles

http://contrails.free.fr

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Thu Jan 08, 2009 5:42 pm Post subject: Re: Rejetting a 914 during Winter?

Hi Darin,



If you have exhausted the fuel/carb issue then it's time to think electrical which can make it seem like a fuel issue. What makes you pretty sure it's fuel/carb? It could even be a ground on the ignition system or a chafed wire. 



Float Flyr,



I agree the prop pitch is a balance of specific performance characteristics that each person wants to achieve from their engine or plane. Most want it balanced between cruise, climb and fuel economy. The the average person with a 912, 5500 engine rpm works well and is suggested by Rotax.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Fri Jan 09, 2009 5:58 am Post subject: Re: Rejetting a 914 during Winter?

Rampil,



I'm based at KBQR and would welcome the opportunity to fly with you next spring. Just give me a heads up when you are headed this way.



Where are you based?

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Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

rampil

Joined: 04 May 2007
Posts: 870

Posted: Fri Jan 09, 2009 8:22 am Post subject: Re: Rejetting a 914 during Winter?

Hi Thom,



home base is HWV



ijr

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Ira N224XS

K Dilks

Joined: 22 Sep 2008
Posts: 108
Location: UK

Posted: Tue Jan 13, 2009 2:53 am Post subject: Re: Rejetting a 914 during Winter?

The carbs are jetted different left to right due to the airflow in the airbox  not being uniform. dont mix this up with the pressure , just that the intake to the air box is on one side so the volume through the carbs is not exactly symetrical.



 Are you running an intercooler?  What can happen is that at very low intake temps the fuel does not atomise correctly . In your case just check the fuel pressure is rising ( regulator is ok ) then observe the egt. 

 Oh check the threeway solonoid valve which richens the mixture up at high power settings. You should hear it click on the ground if somone opens the throttle up , engine not running of course. This is situated on the airbox on all but the early engines.

 Cheers Kev

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grahamsingleton(at)btinte
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Posted: Tue Jan 13, 2009 4:33 am Post subject: Rejetting a 914 during Winter?

K Dilks wrote:

 	  Quote: 	
		   



 The carbs are jetted different left to right due to the airflow in the airbox  not being uniform. dont mix this up with the pressure , just that the intake to the air box is on one side so the volume through the carbs is not exactly symetrical.

  Cheers Kev



 --------

 Austria .............



   

Kev
	


that indicates to me that fuel injection would be a lot better 

Graham

darinh

Joined: 20 Apr 2006
Posts: 327
Location: Utah

Posted: Tue Jan 13, 2009 9:27 pm Post subject: Re: Rejetting a 914 during Winter?

Kev,



I was running an intercooler but took it out today to check this...problem is still there.  I have not checked the solenoid valve and will do so.  My EGTs all read normal at all throttle settings except full but this is hard to determine as the rpm is fluctuating so much at full throttle.  I did try to pull the choke to see if a boost of fuel would help the problem and it doesn't.  Based on my Bing tuning manual, this is a method to determine if the engine is running rich.



At this point, I am at a complete loss as to the root of the problem and it is very frustrating.  I am half tempted to pull it off and put an IO-240 on regardless of the weight penalty...

_________________
Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah

K Dilks

Joined: 22 Sep 2008
Posts: 108
Location: UK

Posted: Wed Jan 14, 2009 12:03 am Post subject: Re: Rejetting a 914 during Winter?

Check the solonoid valve.

All Rotax engines are jetted quite lean. If the solonoid does not work then the Co is about 2,5% which on the turbo is too low at full wack so the valve opens up makes it around 5 to 7%.

 In the cold weather you are getting a very dense air charge so they will run a bit more lean so the situation gets worse.

 If this only occurs at full throttle then forget electrical  except this valve.  Also check that the little hoses that connect the valve to the carbs and the air box are good and check the nipple on the air box that feeds the alternate pressure to the carbs via the valve has not moved or is loose . The nipple must be aligned to get the small increase in pressure .A picture of that is in the installation manual.

 

 And last but not least let me know if you want to change the engine as I am looking for a 914 to stick on my 601 xl,  I have an S at the moment.

Kev

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conrad

Joined: 07 Feb 2007
Posts: 16
Location: Banbury. UK

Posted: Wed Jan 14, 2009 12:36 am Post subject: Re: Rejetting a 914 during Winter?

 	  Quote: 	
		  Oh check the threeway solonoid valve which richens the mixture up at high power settings. You should hear it click on the ground if somone opens the throttle up , engine not running of course. This is situated on the airbox on all but the early engines. 	


Kev

I understood the the solenoid valve changes over to the ram air pressure (ie. clicks) when the airbox pressure gets to 1270mbar. It does not click with throttle position. The way to check the solenoid valve it to remove the hose connecting the airbox to the pressure sensor and applying a small pressure with something like a small syringe.



Conrad

K Dilks

Joined: 22 Sep 2008
Posts: 108
Location: UK

Posted: Wed Jan 14, 2009 2:39 am Post subject: Re: Rejetting a 914 during Winter?

Woops that right not throttle position, airbox pressure changes the solonoid valve.

 Thanks Conrad for pointing that out.

Kev

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