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914 starts to surge at 3950 RPM

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craigb(at)onthenet.com.au
Guest

Posted: Fri May 18, 2012 12:09 am Post subject: 914 starts to surge at 3950 RPM

I’m no expert, but, if memory serves, this problem has been encountered before, I think it was tracked to a bad earth on the ignition  

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       [quote][b]

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frans(at)privatepilots.nl
Guest

Posted: Fri May 18, 2012 4:48 am Post subject: 914 starts to surge at 3950 RPM

On 05/17/2012 12:36 AM, Robert Borger wrote:



 	  Quote: 	
		    Advance the throttle and it began to surge.  


	


Have you tried isolating the waste gate servo from the ECU?



Frans

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rehn(at)rockisland.com
Guest

Posted: Fri May 18, 2012 10:59 am Post subject: 914 starts to surge at 3950 RPM

I assume you mounted a switch for the servo motor on your panel. It's purpose is to break the circuit of the servo motor for a short time in case of surging of the TCU. Maybe this is your problem? Run the engine and then briefly switch servo switch off and back on. Hopefully it's that simple. It is suppose to stabilize the surging. 

Jerry



Sent from my iPad



On May 16, 2012, at 3:36 PM, Robert Borger <rlborger(at)mac.com (rlborger(at)mac.com)> wrote:



[quote]Friends,



As many of you know, my Europa has been down for about a year while it was converted it to tri-gear and I rebuilt the instrument panel.  We ran the engine about 2 weeks ago to check the carb balance and idle.  Those were OK at the time.  I didn't run the engine any further that day because of other commitments (preparing for a 2 week trip to SC).  Monday, I went out to do a full run-up and check of the engine.  Started fine, idled OK as long as I held the "Choke" out while warming up.  After it was warm it idled OK without the "Choke."  Engine nice and smooth.  I slowly applied throttle and as it approached 4000 RPM it began to surge.  Engine RPM dropped to about 3250 and would return to almost 4000 then drop down to 3250 and return to almost 4000, repeat, repeat, down/up/down/up/downâ€¦  Below 3950 RPM it ran smooth and fine.  Advance the throttle and it began to surge.  

EGTs & CHTs all normal and close to equal.  Mag drop at 3900 RPM were almost equal.  The lower plugs always have had a 50-75 RPM greater drop.  Turning on the boost pump made no difference.  Engine has about 25 hrs total time so far and has run like a sewing machine up to now.

Any ideas as to the source of the problem?  Any suggestions as what to check?  Could it be the Turbo or Turbo Controller?

For starters, I guess I need someone to help operate the throttle while I observe the turbo controller and wastegate operation.  Tommy will probably help there.

Any input would be appreciated. 

Thanks in advance!



 Blue skies & tailwinds,

Bob Borger

Europa XS Tri, Rotax 914, Airmaster C/S Prop.

Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP

3705 Lynchburg Dr.

Corinth, TX  76208-5331

Cel: 817-992-1117

[url=mailto:rlborger(at)mac.com]rlborger(at)mac.com (rlborger(at)mac.com)[/url]

 

 



[b]

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europapa

Joined: 30 Aug 2010
Posts: 63

Posted: Sat May 19, 2012 3:57 am Post subject: Re: 914 starts to surge at 3950 RPM

I had the a similar problem with my 912S, it has been the fuel line.

Have you got a fuel pressure gauge?

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rlborger(at)mac.com
Guest

Posted: Sat May 19, 2012 4:18 am Post subject: 914 starts to surge at 3950 RPM

For all those following this thread:



Bud made the suggestion, among others, that it could be leaky carb bowl gaskets.  I removed the drip trays to better check for leaks and, sure enough, there was blue staining and evidence of leakage around both carb bowls.  I have a carb re-build kit on order from Lockwood, supposed to arrive on the 23rd.  I am in the process of removing the carbs for the pending rebuild.  This is not a trivial operation.



Europapa, I had a fuel pressure gage installed and it showed good, constant fuel pressure.



I have replaced the fuel pressure gage with the UMA Differential Pressure gage which compares airbox pressure with fuel pressure and provided a reading of the difference.



For those who are interested, I will do my best to photo-document the carb removal, rebuild and replacement procedure in my Rotax Owners site.  I hope to start posting pictures in a new album tomorrow.  http://www.europaowners.org/main.php



Blue skies & tailwinds,

Bob Borger

Europa XS Tri, Rotax 914, Airmaster C/S Prop.

Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP

3705 Lynchburg Dr.

Corinth, TX  76208-5331

Cel: 817-992-1117

rlborger(at)mac.com



On May 19, 2012, at 6:57 AM, europapa wrote:






I had the a similar problem with my 912S, it has been the fuel line.

Have you got a fuel pressure gauge?

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