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Low RPM

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john.pearson757

Joined: 03 Oct 2013
Posts: 5

Posted: Fri Oct 04, 2013 11:08 am Post subject: Low RPM

I was getting only 90% RPM and for other reasons, changed engines on my Skybolt.

I'm still getting 90% at best, more like 87 or 88%.

The carb is different and is rebuilt by Jill at M-14P.com so that can't be the problem.  The mag timing is spot on and checked and re-checked.  The blade angle is finer that standard.  All linkages and travel have been checked.  The tach is accurate and actual RPM has been checked.

When I reach full RPM, there is still quite a bit of throttle left so I guess I'm just pouring more fuel into the mix.

If anyone has suggestions or advice, thanks.

J.P.

dsavarese0812(at)bellsout
Guest

Posted: Fri Oct 04, 2013 11:30 am Post subject: Low RPM

Do I understand you correctly?  Same prop?  Different engine?  What prop 

is on the airplane?  If an MT 3 blade prop, does the prop governor have 

the correct spring in it for the MT prop?  Do check with MT regarding 

the correct spring for the prop governor.



You said all linkages and travel have been checked.  Have you verified 

the carburetor throttle arm is at WOT when the throttle cable is pushed 

fully forward?  Do this by removing the throttle linkage from the 

carburetor throttle arm, move the throttle arm on the carb to WOT.  Now 

hold the throttle linkage next to the throttle arm and then see where 

the linkage is positioned with the throttle fully forward.



A. Dennis Savarese

334-285-6263

334-546-8182 (mobile)

www.yak-52.com

Skype - Yakguy1



On 10/4/2013 2:08 PM, john.pearson757 wrote:

 	  Quote: 	
		   



 I was getting only 90% RPM and for other reasons, changed engines on my Skybolt.

 I'm still getting 90% at best, more like 87 or 88%.

 The carb is different and is rebuilt by Jill at M-14P.com so that can't be the problem.  The mag timing is spot on and checked and re-checked.  The blade angle is finer that standard.  All linkages and travel have been checked.  The tach is accurate and actual RPM has been checked.

 When I reach full RPM, there is still quite a bit of throttle left so I guess I'm just pouring more fuel into the mix.

 If anyone has suggestions or advice, thanks.

 J.P.





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=409860#409860

GeorgeCoy

Joined: 02 Dec 2010
Posts: 310

Posted: Fri Oct 04, 2013 11:41 am Post subject: Low RPM

Is the governor arm moving to the stop? Have you re adjusted the stop?



--

john.pearson757

Joined: 03 Oct 2013
Posts: 5

Posted: Fri Oct 04, 2013 12:00 pm Post subject: Re: Low RPM

Thanks for the reply.

The prop is a 2 blade V530 - different governors.  It is going to the stop.

I think the throttle is OK.  When I reach 87%, I can push the throttle forward quite a bit more.

dsavarese0812(at)bellsout
Guest

Posted: Fri Oct 04, 2013 12:19 pm Post subject: Low RPM

Was the prop governor swapped from the old engine to the new engine?  

Dennis





        From: George Coy <george.coy(at)gmail.com>

 To: m14pengines-list(at)matronics.com 

 Sent: Friday, October 4, 2013 2:39 PM

 Subject: RE: Low RPM

  

 

 --> M14PEngines-List message posted by: "George Coy" <george.coy(at)gmail.com (george.coy(at)gmail.com)>



Is the governor arm moving to the stop? Have you re adjusted the stop?



--

john.pearson757

Joined: 03 Oct 2013
Posts: 5

Posted: Fri Oct 04, 2013 12:24 pm Post subject: Re: Low RPM

No, the governor wasn't swapped - new or different governor and I've played with the stops with no result.

J.P.

dsavarese0812(at)bellsout
Guest

Posted: Fri Oct 04, 2013 12:26 pm Post subject: Low RPM

Look at the things that are common to both engines since the symptom has not changed when you changed the engine.

- Prop

- Throttle Cable



What did you set the blade angles to on the V530?  ie:  How many degrees and at what reference point on the blades?



The throttle cable sleeve might be slipping.  If it slips at all, you will not get full throw at the carburetor.  That could be why you feel like you can push it further with no increase in RPM.   Check to see if the sleeve is moving anywhere from the throttle lever through the firewall and then to the carburetor.



Do you have a fuel flow instrument in the airplane?  If so, what is the fuel flow at WOT on take off?  Normal for an M14P 360HP engine is between 37 and 41 gallons per  hour.

Dennis





        From: john.pearson757 <ssvpearson(at)hotmail.com>

 To: m14pengines-list(at)matronics.com 

 Sent: Friday, October 4, 2013 3:00 PM

 Subject: Re: Low RPM

  

 

 --> M14PEngines-List message posted by: "john.pearson757" <ssvpearson(at)hotmail.com (ssvpearson(at)hotmail.com)>



Thanks for the reply.

The prop is a 2 blade V530 - different governors.  It is going to the stop.

I think the throttle is OK.  When I reach 87%, I can push the throttle forward quite a bit more.





Read this topic online here:



http://forums.matrosp;                     -================

 

 

  

 [quote][b]

john.pearson757

Joined: 03 Oct 2013
Posts: 5

Posted: Fri Oct 04, 2013 12:37 pm Post subject: Re: Low RPM

Thanks Dennis,

I'll double check all those things.  I agree, it has to be something like that.

J.P.

mark.bitterlich(at)navy.m
Guest

Posted: Mon Oct 07, 2013 7:19 am Post subject: Low RPM

When you have everything wide open... pushed to the firewall, and you take the aircraft into a dive leaving everything wide open... and I am talking a steep dive here, does the RPM go up, or does it stay governed at 88%?   



Note:   If you are not developing enough power to take the engine to 100% due to fuel flow, carburetion issues, or throttle cable sleeve clamping, then in a dive the engine RPM will increase and go to the maximum setting that the governor will regulate.  In other words, RPM will go up.  



If you are in the dive, and the engine RPM stays close to exactly the same, then you've got a prop governor issue, or possibly blade angle.  



I defer to Dennis on all engine issues, but this test might be of some help.  



Mark

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jrpearson(at)brant.net
Guest

Posted: Wed Oct 09, 2013 3:06 pm Post subject: Low RPM

Thanks Mark,

I think I've narrowed it down to the governor linkage.

J.P.



--

dsavarese0812(at)bellsout
Guest

Posted: Thu Oct 10, 2013 5:11 am Post subject: Low RPM

J.P., 

Linkage?  Since you said it was a different governor on this engine and the symptom was the same on the older engine, what "linkage" are you talking about?   Possibly the cable SLEEVE moving in one or more of the cable clamps?  I've seen this several times.

Dennis  





        From: "jrpearson(at)brant.net" <jrpearson(at)brant.net>

 To: m14pengines-list(at)matronics.com 

 Sent: Wednesday, October 9, 2013  6:06 PM

 Subject: RE: Re: Low RPM

  

 

 --> M14PEngines-List message posted by: jrpearson(at)brant.net (jrpearson(at)brant.net)

Thanks Mark,

I think I've narrowed it down to the governor linkage.

J.P.



--

john.pearson757

Joined: 03 Oct 2013
Posts: 5

Posted: Mon Oct 28, 2013 2:17 pm Post subject: Re: Low RPM

Thanks to all who provided advice.  I revisited the linkage and that was the problem.

Thanks  again,

J.P.

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