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05-15-2014, 02:17 PM
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Join Date: May 2006
Location: Houston
Posts: 2,012
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Quote:
Originally Posted by MBISMAN
When I test the CS in my preflight to 1800RPM, the RPM down but I push slowly the blue lever when the RPM arrive to 1500RPM. I don't know in this condition the exactly drop, but I can make a test next time. The take-off is always to 2700RPM at sea level, in mountain to 6500ft I can't put the full power at take-off for stay under 2700 RPM.
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If you firewall the engine (full, open throttle) at takeoff, does your propeller control and maintain aprox. 2700 rpm?
The way I read your last sentence, you have to pull/reduce power to maintain 2700 rpm. If this is the case, it sounds like you have a propeller control problem of some sort.
You should be able to apply full power (regardless of altitude) and the propeller governor control the prop pitch, maintaining 2700 rpm.
Last edited by Low Pass : 05-15-2014 at 02:19 PM.
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05-15-2014, 02:19 PM
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Join Date: May 2009
Location: Colorado
Posts: 302
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Internal timming?
I helped a friend several years ago with a very similar problem on his RV8. We had gone through many checks and tests before we came to this. I would have never guessed that an engine could run so well with the internal timming off one tooth but it will. A simple check can be performed in about 20 minuets.
First set the number one cylinder to TDC on the compression stroke.
Second, remove the rocker cover on the #2 cylinder and make sure both valves indicate closed. Move the prop in one direction you should see one rocker arm begin to move almost immediately. Rotate the prop back to TDC and try again in the other direction you should see the same on the other rocker.
If it takes several more degrees of movement on one side or the other from TDC to move a rocker you may be off a tooth in your accessory case causing a large loss in power. Easy to check. The only reason I might suspect this is the low time you indicated on your engine. It's an easy mistake to make during overhaul.
Ryan
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05-15-2014, 02:27 PM
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Join Date: Sep 2011
Location: Edgewater, FL. KSFB
Posts: 1,118
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I hate to tell on myself but I found an out of time PMag by doing a mag check at altitude. When doing a regular pre-flight mag check everything was fine. Although I got very little RPM drop. At altitude and cruise power I did a mag check only to find an increase in RPM when on one mag. It took me a while to figure this out but I knew it wasn't right.
The two mags were fighting each other. One more advanced than the other. Corrected my timing and now I get a 60 RPM drop during a mag check. Sure sounds like MBSMAN's problem is a prop that won't go course.
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05-15-2014, 03:02 PM
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Join Date: Oct 2011
Location: Kennesaw, Ga
Posts: 825
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Quote:
Originally Posted by petersb
I also gained 20 mph with fairings
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Wow!!! Should put mine back on 
__________________
Amir
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RV-7
RV-10 - Sold
Supporting VAF since the first visit
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05-15-2014, 03:39 PM
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Join Date: Dec 2005
Posts: 976
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Quote:
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The take-off is always to 2700RPM at sea level, in mountain to 6500ft I can't put the full power at take-off for stay under 2700 RPM.
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If you slowly (say over 5 seconds) select full power on takeoff, what RPM do you reach?
If you rapidly select full power on takeoff (less than 1 second) what RPM to do you reach? And does it then reduce?
I appreciate you may not want to do literally what I say if the answer would be much more than 2700RPM, but even if the answers were "more than 2800RPM" etc. it would give a useful guide as to whether there is a prop / governor issue?
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05-15-2014, 04:02 PM
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Join Date: Dec 2004
Location: Gold Hill, NC25
Posts: 2,400
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2300tr/MP23 32 litres 110/130kts 2000/4000ft
2400tr/MP24 36 litres 130kts max 4000/6000ft
2300tr/MP19 29 litres 130kts max 8000/10000ft
Not sure where all the prop concerns are coming from. Those numbers say the prop MUST be working fine.
__________________
Kahuna
6A, S8 ,
Gold Hill, NC25
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05-15-2014, 04:12 PM
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Join Date: May 2006
Location: Houston
Posts: 2,012
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Yea, my comment may have lead off track but I thought he was saying he has to pull power at takeoff to stay below "2700". *Thought* he may also be pulling power at full power in flight. Bad line of thought/assumption.
Sure sounds like ignition or valve timing. But I'm just a voice on the Internet... 
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05-15-2014, 04:22 PM
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Join Date: Dec 2004
Location: Gold Hill, NC25
Posts: 2,400
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Couple of things next.
1. You said "Are you able to go from very rich to lean and do all cylinders react accordingly? No!" Please tell us what it does please. This will be a clue.
2. Timing. Id like to know if the timing was checked per the manufactures requirements.
3. If 2 is yes, Id pull a mag off and view the gear timing on all accessory gears per lycoming requirements.
4. Do you have an inductive timing light and do you know how to use it?
__________________
Kahuna
6A, S8 ,
Gold Hill, NC25
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05-15-2014, 04:38 PM
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Join Date: Feb 2006
Location: Anywhere, USA
Posts: 1,132
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Quote:
Originally Posted by Kahuna
2300tr/MP23 32 litres 110/130kts 2000/4000ft
2400tr/MP24 36 litres 130kts max 4000/6000ft
2300tr/MP19 29 litres 130kts max 8000/10000ft
Not sure where all the prop concerns are coming from. Those numbers say the prop MUST be working fine.
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With these numbers I would check AS indicator and pitot system and cross check
GPS speed.
Also can you have someone with verified AS fly formation with you to check out.
__________________
Bruce (BOOMER) Pauley
Kathy (KAT) Pauley
RV 7A--"MISS MARIE"--- N177WD (SOLD FLYING)72742
VAF #582-----------------EAA LIFETIME MEMBER
EX -KC-135A -------------BOOM OPERATOR #3633
VAN'S FLIGHT------------#6930
See you in OSHKOSH
http://www.mykitlog.com/users/index....ley&project=84
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05-15-2014, 06:03 PM
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Join Date: Oct 2009
Location: Victoria, BC, Canada
Posts: 3,932
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Quote:
Originally Posted by Bruce
With these numbers I would check AS indicator and pitot system and cross check GPS speed.
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This. I'd want to know what the GPS says on a speed run as well. My first guess reading this was that you have a pitot leak, or your pitot tube isn't aligned with the airflow properly.
__________________
Rob Prior
1996 RV-6 "Tweety" C-FRBP (formerly N196RV)
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