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06-29-2014, 07:13 PM
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Join Date: Sep 2007
Location: Central IL
Posts: 5,516
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What kind of exhaust system does this engine have, straight through? or muffler?
If muffler, you also might check to see if it is restricted.
__________________
Bill
RV-7
Lord Kelvin:
“I often say that when you can measure what you are speaking about,
and express it in numbers, you know something about it; but when you
cannot measure it, when you cannot express it in numbers, your knowledge
is of a meager and unsatisfactory kind.”
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06-29-2014, 07:20 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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An engine, any engine, is nothing more than an air pump. Restrict either the intake or exhaust and you harm efficiency.
Add to that the timing and carburetor jetting.
Assuming the hardware is good, it is either going to be restricted intake/exhaust or timing or fueling.
Timing is the easiest to check, so start there.
Good luck and report what you find.
__________________
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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06-29-2014, 09:26 PM
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Join Date: Jun 2014
Location: Lyman, Wyoming
Posts: 18
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Thanks for the replies!! You guys are awesome.
It has vetterman straight pipes without mufflers so I think I can rule the exhaust restriction out.
I am leaning heavily towards fuel and timing. Wish I had a buzz box to do my own timing check but my a&p can help me out on that.
I'm going to do a fuel flow at the nozzle test tomorrow with baby jars and check for even fuel distribution at the cylinders. Also going to check all my fuel lines from the tank to the pump to make sure there are no leaks.
I think I'll also pull the valve covers and see if the valves and springs are in good shape.
If none of that changes anything...I think I'll pull the fuel servo and have it flow tested.
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06-30-2014, 04:52 AM
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Join Date: Nov 2010
Location: ____
Posts: 829
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You might also check your fuel pressure. I have seen an IO -360 with .150" worn off the intake lobes(yes that is .150" missing from a .350" new/proper spec) and it would still make 2750 RPM on take off. However, the peanut can gas filter just ahead of the engine driven fuel pump would get a slight restriction at about 40 hours and you would only get 2600 RPM with an indicated fuel pressure of about 16 psi instead of the normal 20-26 psi at take off power. As soon as it was serviced, we would get 2750 RPM on the take off run.
There was a thread on here a couple of months ago regarding a new lycoming in France with a similar issue that you describe.
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06-30-2014, 07:21 PM
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Join Date: Jun 2014
Location: Lyman, Wyoming
Posts: 18
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Well I got a couple hours to work on it after work today and I think I found two possible causes.
First: did a nozzle flow test and found one injector nozzle that has a really poor fuel stream. The other 3 nozzles have a clean straight flow. The bad injector flowed about 1/4" more fuel than the other 3 for a 30 second flow test. This tells me that I've had 3 lean cylinders and one rich one. So I'm going to try to find a used nozzle.
Second: fuel filter had some gunk in it and found a possible leak in an -an fuel fitting. It's possible I was sucking air. I cleaned and tightened up all the -an fittings.
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06-30-2014, 08:01 PM
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Join Date: Aug 2005
Location: Pasadena CA
Posts: 2,484
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This does sound like exactly what my Carb'd 320 did when the intake lobe started to go on the back to cylinders. Low CHT's and Low power.
__________________
Stephen Samuelian, CFII, A&P IA, CTO
RV4 wing in Jig @ KPOC
RV7 emp built
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06-30-2014, 08:22 PM
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Join Date: Jun 2012
Location: Frederick, MD
Posts: 821
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Assuming a standard nozzle, you can clean the nozzle in Hoppes No 9 gun cleaning fluid and an ultrasonic jewelry cleaner for about 1 hr. If it is dirt this will take care of it. If not the nozzle can be disassembled and checked for obstructions.
__________________
Dan Morris
Frederick, MD
PA28-140
Hph 304CZ
RV6 built and sold
N199EC RV6A flying
Learn the facts. "Democracy dies in darkness"
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07-01-2014, 08:13 AM
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Join Date: Jun 2014
Location: Lyman, Wyoming
Posts: 18
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Are the precision airmotive nozzles a direct replacement for factory lycoming nozzles?
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07-03-2014, 07:15 PM
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Join Date: Jun 2014
Location: Lyman, Wyoming
Posts: 18
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Well I spent the afternoon tinkering some more and tried cleaning the bad injector again. Soaked it and blew it out with compressed air. Did the flow test again and it's definitely not flowing right. The other three have a nice tight straight stream and this one has a very erratic flow. It is flowing about 1/4" more fuel than the other 3. The 3 good ones flow the exact same amount. I found a used injector that I'm going to try. I'm crossing my fingers that it's really this simple.
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07-04-2014, 07:17 AM
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Join Date: Jun 2012
Location: Frederick, MD
Posts: 821
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Good article on injectors. You can fully disassemble them to clean/ inspect if necessary.
http://www.kellyaerospace.com/articl...lInjection.pdf
__________________
Dan Morris
Frederick, MD
PA28-140
Hph 304CZ
RV6 built and sold
N199EC RV6A flying
Learn the facts. "Democracy dies in darkness"
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