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Power loss, on taxi, vapour locking?

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Richard Lamprey

Joined: 15 Jul 2011
Posts: 95
Location: Kenya

Posted: Wed Aug 24, 2011 1:09 am Post subject: Power loss, on taxi, vapour locking?

Greetings from Kenya, using the new modern approach of communication with the forum (thanks Ira!)



My Europa is classic, Rotax 912 UL, Warpdrive ground-adjusted prop.  550 hours on the engine.  The airfield altitude is 5500’, the temperature was 28 C, so hot and high but we are used to that.



Yesterday, I landed and back-tracked the runway, and on backtrack the engine suddenly lost power.  Full power to expedite the backtrack, she ran very rough, almost cutting out.  Reducing on the throttle just gave me a smooth 3000 rpm, enough to move slowly.  Back at the hangar, I opened up the cowlings, ran a fuel flow check, no problems, plenty of fuel pressure (200% of max requirements).  Cleaned the plugs (quite clean, nothing unusual).  Checked for full deflection of the throttle cable at both carb ends, no problem there.  The vapour return line was clear, so no problem there.  I closed up, did full power run up, no problems, flew for another 15 minutes without incident.



Could this be due to vapour lock in the fuel lines under the cowling?  The fuel lines from fuel pump back to carbs runs in fire-sleeve along the top right side of the engine, but I think this is pretty standard.  On the previous landing I had to go around, so full power and she was running quite hot, but nothing unusual.  We use unleaded petrol (95 octane), and I have read somewhere that in UK you should not use mogas above 6000’ density altitude due to vapour locking characteristics.  So every takeoff we do here is above this altitude anyway.  



Does anyone have an idea of what caused this?



Best 

Richard

Classic 5Y-LRY

Rocketman

Joined: 07 Sep 2010
Posts: 87
Location: USA, Earth

Posted: Wed Aug 24, 2011 6:53 am Post subject: Power loss, on taxi, vapour locking?

Richard,



Two things... Yes, it could be vapor lock.  Check fuel lines and 

insulate as needed.  I used the orange silicone, 2000 degree cover and 

it works well.  Second, check to see that you don't have a leaky exhaust 

that might allow heat to get to the carb bowls.  This will boil the fuel 

in them and cause the same effect as vapor lock.



Hope this helps.



Jeff - Baby Blue



On 8/24/2011 4:09 AM, Richard Lamprey wrote:

 	  Quote: 	
		   



 Greetings from Kenya, using the new modern approach of communication with the forum (thanks Ira!)



 My Europa is classic, Rotax 912 UL, Warpdrive ground-adjusted prop.  550 hours on the engine.  The airfield altitude is 5500’, the temperature was 28 C, so hot and high but we are used to that.



 Yesterday, I landed and back-tracked the runway, and on backtrack the engine suddenly lost power.  Full power to expedite the backtrack, she ran very rough, almost cutting out.  Reducing on the throttle just gave me a smooth 3000 rpm, enough to move slowly.  Back at the hangar, I opened up the cowlings, ran a fuel flow check, no problems, plenty of fuel pressure (200% of max requirements).  Cleaned the plugs (quite clean, nothing unusual).  Checked for full deflection of the throttle cable at both carb ends, no problem there.  The vapour return line was clear, so no problem there.  I closed up, did full power run up, no problems, flew for another 15 minutes without incident.



 Could this be due to vapour lock in the fuel lines under the cowling?  The fuel lines from fuel pump back to carbs runs in fire-sleeve along the top right side of the engine, but I think this is pretty standard.  On the previous landing I had to go around, so full power and she was running quite hot, but nothing unusual.  We use unleaded petrol (95 octane), and I have read somewhere that in UK you should not use mogas above 6000’ density altitude due to vapour locking characteristics.  So every takeoff we do here is above this altitude anyway.



 Does anyone have an idea of what caused this?



 Best

 Richard

 Classic 5Y-LRY





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=350410#350410





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terrys(at)cisco.com
Guest

Posted: Wed Aug 24, 2011 9:40 am Post subject: Power loss, on taxi, vapour locking?

We have a mono-wheel XS with a 912S and have had vapor lock on several occasions, on the ground and in the air.  We solved the problem by putting some aluminized heat mat on the underside of the carb bowls and fuel lines and fittings near the carbs that are too small to be covered in fire sleeve.  This protected those parts from the heat of the rear exhaust headers.



Regards,

Terry Seaver

A135/N135TD



 



--

tennant

Joined: 19 Apr 2011
Posts: 121

Posted: Wed Aug 24, 2011 11:12 pm Post subject: Re: Power loss, on taxi, vapour locking?

Hi Richard,



I have had the same on a 36deg C day taxying through long grass to the runway after a short stop. (1500 ft high)



I have since routed my fuel lines along the cowling edge away from the engine and sleeved with a silver colored insulating material. Since then I have not had a problem but I try to use Avgas when the temp is above 30 deg C although this is not always possible.



Best regards



Barry

_________________
Barry Tennant
D-EHBT
At EDLM - Germany

Richard Lamprey

Joined: 15 Jul 2011
Posts: 95
Location: Kenya

Posted: Thu Aug 25, 2011 6:39 am Post subject: Re: Power loss, on taxi, vapour locking?

Many thanks for your replies, Jeff, Terry and Barry,



I'll cast about under the cowlings, do some insulation with firesleeve, check for hot carbs.  Strange that this is the first time this has happened in 550 hours!



With these altitudes and temperatures, I could revert back to Avgas, but it does cause that awful sludge in the engine if used alot...



All the best

Richard

kaarsberg(at)terra.com.br
Guest

Posted: Thu Aug 25, 2011 8:55 am Post subject: Power loss, on taxi, vapour locking?

I know that space under the hood is sparse, but has anybody tried shrouding the fuel pipe and venting it overboard? 



Alex, kit 529

stephen vestuti

Joined: 05 Jul 2011
Posts: 62
Location: Wales, UK

Posted: Fri Aug 26, 2011 9:36 am Post subject: Re: Power loss, on taxi, vapour locking?

Jeff - Baby Blue , 



Hi,

 I notice your comment about " a leaky exhaust 

that might allow heat to get to the carb bowls ".



I had this problem on the first Europa that I built , the fuel boiling 

in the Stb. carb bowl and causing rough running/power loss at the TOC.



Do you or any other builders know if any one has improved the cooling 

in this area - besides the drip trays which double as heat shields ?



I want to incorporate some type of mod to this one,

Steve.   #630

jeff(at)rmmm.net
Guest

Posted: Fri Aug 26, 2011 10:08 am Post subject: Power loss, on taxi, vapour locking?

Steve,

After you fit the cowl especially the lower. Drop your tunnel from where the book says till the lower radiator almost touches the bottom of the cowl. This will open the gap between the and the tunnel ceiling and allow gobs of hot air out the back. Once I did that it solved all my cooling issues and I never had fuel boiling on the hottest of days. 

Jeff

 



N128LJ Gold Rush



On Aug 26, 2011, at 12:36 PM, stephen vestuti wrote:



 	  Quote: 	
		   

 

 Jeff - Baby Blue , 

 

 Hi,

 I notice your comment about " a leaky exhaust 

 that might allow heat to get to the carb bowls ".

 

 I had this problem on the first Europa that I built , the fuel boiling 

 in the Stb. carb bowl and causing rough running/power loss at the TOC.

 

 Do you or any other builders know if any one has improved the cooling 

 in this area - besides the drip trays which double as heat shields ?

 

 I want to incorporate some type of mod to this one,

 

 

 Steve.   #630

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=350645#350645

Rocketman

Joined: 07 Sep 2010
Posts: 87
Location: USA, Earth

Posted: Fri Aug 26, 2011 1:24 pm Post subject: Power loss, on taxi, vapour locking?

Steve,



I fabricated an "L" shaped baffle that runs across the top of the 

exhaust and down the outside of the pipe, between it and the engine 

block.  It solved my problem and also deflects heat away from the coils 

and ignition modules; another heat sensitive area...



Jeff - Baby Blue



On 8/26/2011 12:36 PM, stephen vestuti wrote:

 	  Quote: 	
		   



 Jeff - Baby Blue ,



 Hi,

   I notice your comment about " a leaky exhaust

 that might allow heat to get to the carb bowls ".



 I had this problem on the first Europa that I built , the fuel boiling

 in the Stb. carb bowl and causing rough running/power loss at the TOC.



 Do you or any other builders know if any one has improved the cooling

 in this area - besides the drip trays which double as heat shields ?



 I want to incorporate some type of mod to this one,

 Steve.   #630





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=350645#350645





 -----

 No virus found in this message.

 Checked by AVG - www.avg.com

stephen vestuti

Joined: 05 Jul 2011
Posts: 62
Location: Wales, UK

Posted: Sun Sep 04, 2011 10:56 am Post subject: Re: Power loss, on taxi, vapour locking?

Thanks for the replies,

would you have any pictures of that arrangement?



Steve #630

hletkeman

Joined: 29 Jun 2011
Posts: 8

Posted: Wed Nov 09, 2011 12:31 pm Post subject: Re: Power loss, on taxi, vapour locking?

On my second takeoff, my engine lost gas pressure, and the engine stuttered. Luckily, I was still on the ground. 

I had been making some adjustments on the trim after the first flight, while the engine idled. I now believe that there was vapor in the pump, and therefore the pressure dropped. I installed a booster pump under the seat, to push vapor through the manual pump, and installed drip pans under the carb bowls, and have not had any problems since.

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