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914 Slight Hesitation going Full Throttle?

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darinh

Joined: 20 Apr 2006
Posts: 327
Location: Utah

Posted: Mon Jun 15, 2009 3:17 pm Post subject: 914 Slight Hesitation going Full Throttle?

First off, let me say that I fly a Kitfox not a Europa (although I would love one) but you guys fly way more 914's than do the Kitfox guys so I come to you with engine questions.  



I have a 914 (new with 45 hours thus far).  The issue I am having is a very short hesitation when going full throttle.  Basically, when I push the throttle up on take-off, it runs beautifully up to about 100% throttle or max. continuous power position (35" MAP or so).  Then as I go the last 15% and the boost kicks in full, I get a very slight hesitation (maybe .5 seconds) then it continues up to my 5700 rpm max. prop setting and 40" MAP.  It doesn't seem to do this when in the air and going WOT.  I have a Airmasters prop and sometimes think that this might be the cause as the electric motor that drives pitch lags slightly behind the engine.  Anyone experience this?

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_________________
Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah

Ivor Phillips

Joined: 16 Jan 2006
Posts: 253
Location: London UK

Posted: Mon Jun 15, 2009 10:53 pm Post subject: 914 Slight Hesitation going Full Throttle?

Hi Darin

I would check the waistgate cable to the turbo isnâ€™t sticking,

followed by both throttle cables are travelling the same amount towards their end of travel before they reach the end stops,

Ivor

---- darinh <gerns25(at)netscape.net> wrote: 

 	  Quote: 	
		   

 

 First off, let me say that I fly a Kitfox not a Europa (although I would love one) but you guys fly way more 914's than do the Kitfox guys so I come to you with engine questions.  

 

 I have a 914 (new with 45 hours thus far).  The issue I am having is a very short hesitation when going full throttle.  Basically, when I push the throttle up on take-off, it runs beautifully up to about 100% throttle or max. continuous power position (35" MAP or so).  Then as I go the last 15% and the boost kicks in full, I get a very slight hesitation (maybe .5 seconds) then it continues up to my 5700 rpm max. prop setting and 40" MAP.  It doesn't seem to do this when in the air and going WOT.  I have a Airmasters prop and sometimes think that this might be the cause as the electric motor that drives pitch lags slightly behind the engine.  Anyone experience this?

 

 --------

 Darin Hawkes

 Series 7 

 914 Turbo

 Kaysville, Utah

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p 48338#248338

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hervechaussures(at)tiscal
Guest

Posted: Mon Jun 15, 2009 11:54 pm Post subject: 914 Slight Hesitation going Full Throttle?

Hi Darin,

I did have this problem once and with me it was the 2 inch rubber pipe in between the carbs and the air box which have come loose and once split. Check??

Regards

Herve

Europa 914xs G.CHET.

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paul.the.aviator(at)gmail
Guest

Posted: Tue Jun 16, 2009 1:19 am Post subject: 914 Slight Hesitation going Full Throttle?

Hi Darin,



Have you checked your fuel flow ?  Is it better or no different with the second boost pump switched on ?



Paul 

  [quote][b]

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darinh

Joined: 20 Apr 2006
Posts: 327
Location: Utah

Posted: Tue Jun 16, 2009 9:07 am Post subject: Re: 914 Slight Hesitation going Full Throttle?

Ivor,



The wastegate travels through its full movement without binding and so do the throttles.  



Herve,



I will check these again but they seem to be good.



Paul,



It seems to be the same with one or both boost pumps running and fuel flow is good.  I did have an issue with a plugged fuel filter at about 20 hours but that has been replaced.  The plugged filter obviously caused significant hesitation and rough running, so much so that I couldn't get much more than 4800 RPM.  I also installed the Bell intercooler which I had to modify for my installation by cutting and rewelding the outlet 180 degrees to its original position.  Apparently, this modification changed the airflow characteristics just enough that I was not getting the air I needed and the engine would hesitate and sputter around 5000 rpm.  Both the filter problem and the intercooler issue have been remedied by either replacing or removing the items.  Now I just have the very short single hesitation described in the original post before it goes WOT.

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Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah

ptag.dev(at)tiscali.co.uk
Guest

Posted: Tue Jun 16, 2009 1:04 pm Post subject: 914 Slight Hesitation going Full Throttle?

Hi! Darin

I have a Bell Intercooler fitted to my 914 and have no hesitation

whatsoever.

I can't point you to a cure for your problem but it looks like it wasn't

the intercooler at least.

Do you slam the throttle wide open or advance it more deliberately? It

just may be temporarily flooding the intakes.

Regards

Bob Harrison G-PTAG 



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darinh

Joined: 20 Apr 2006
Posts: 327
Location: Utah

Posted: Tue Jun 16, 2009 8:06 pm Post subject: Re: 914 Slight Hesitation going Full Throttle?

Bob,



The big hesitation was no doubt my Bell intercooler as I could remove it and the problem would go away and then install it and the problem would come right back.  So it was definitely my intercooler.  I know these work when installed as designed but if you reread my post you will see that I modified it to fit my installation which I think changed the air flow characteristics through the intercooler just enough to be a problem.  I think they are great intercoolers and work well when installed as per design.

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_________________
Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah

europaflyer_3(at)msn.com
Guest

Posted: Wed Jun 17, 2009 4:46 am Post subject: 914 Slight Hesitation going Full Throttle?

I had similar on a T-67 I used to fly. It was due to the mixture going

momentarily rich as the throttle was opened - which rather matches the

effect Darin is talking about.



Worth looking into?



Regards,

Jeremy



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