VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Model Specific > RV-6/6A
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 05-25-2017, 02:19 PM
dkoughcpa dkoughcpa is offline
 
Join Date: Mar 2017
Location: Nashville, TN
Posts: 3
Default 0-320 DJ2 / 70CM Series Help

Mechanically-challenged newby 6A owner here with a few 0-320D2J / 70CM series powerplant questions Id love some assistance with. If it matters, engine time is approx. 600 since overhaul, prop is unknown history prior to 2002 when installed on this aircraft.

Q1: There is a yellow arc on tach between 1850 and 2250 RPM and red line at 2600 RPM. I get the 2600 RPM max operating limit as it is plastered all over the OM. As for the yellow arc, this is original marking on the tach, not taped/placarded. I cannot find anything in either the engine or prop operating manuals, nor the POH that addresses this. Can anyone point me to a reference here?

Q2: At my first conditional (Dec 16), it was discovered the #1 cylinder has a stuck valve guide. Mechanic suggested a regiment of Marvel Mystery Oil to address valve and excessive oil usage. Compressions 70/79/77/78. Would someone please comment on (a) the risks associated with a stuck valve, and (b) the appropriateness of the use of this additive. I am burning about a quart of oil per 5 hours tach time.

Q3: At 3k feet (I have not even been close to 8k) with wide open throttle, the engine is only pulling 2350 rpm and 139ktas. On takeoff roll and in climb, Im in the yellow arc at 2000-2100 at full throttle. These numbers seem a little low compared to performance numbers seen here and elsewhere. Prop logs reflect that prop was repitched from 81 to 79 several years ago. Any words of wisdom?

Thanks so much!

David
Reply With Quote
  #2  
Old 05-25-2017, 05:13 PM
JohnInReno's Avatar
JohnInReno JohnInReno is offline
 
Join Date: Jun 2005
Location: Fermley, NV
Posts: 245
Default Prop RPM

Quote:
Originally Posted by dkoughcpa View Post
Mechanically-challenged newby 6A owner here with a few 0-320D2J / 70CM series powerplant questions Id love some assistance with. If it matters, engine time is approx. 600 since overhaul, prop is unknown history prior to 2002 when installed on this aircraft.

Q1: There is a yellow arc on tach between 1850 and 2250 RPM and red line at 2600 RPM. I get the 2600 RPM max operating limit as it is plastered all over the OM. As for the yellow arc, this is original marking on the tach, not taped/placarded. I cannot find anything in either the engine or prop operating manuals, nor the POH that addresses this. Can anyone point me to a reference here?
I can contribute my best guesses. I have an IO-320 with a Whirlwind constant speed with a similar yellow arc due to the prop limitation. The engine is rated at 160hp at 2700 RPM and that is also the red line on the prop.

I have seen a 2600 red line on metal props but the Prince P-Tip wood/carbon fiber on my RV-4 had no such limitation.

What type of tach is it? Vans sells a tach with no yellow arc and a 2700 red line.

My POH is still a work in progress and you are lucky to have one.
__________________
John Morgensen
RV-9A N946PM 400+ hours since 2013
Nevada/Arizona
Reply With Quote
  #3  
Old 05-25-2017, 06:46 PM
Aggie78 Aggie78 is offline
 
Join Date: May 2014
Location: Fort Worth, Texas
Posts: 309
Default

David,

Search this website with the terms "sticking exhaust valve" and you will get hits with many threads, including one I started...

Not an uncommon malady in the Lycoming world...
__________________
Rob Schroer
RV-7, bought
N75WV
YIO-360-M1B
T67-Hicks Airport, Texas
Reply With Quote
  #4  
Old 05-25-2017, 08:12 PM
rv7charlie rv7charlie is online now
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 2,241
Default

The yellow arc sounds like a marking for a constant speed prop. The TC for that model Sensenich doesn't mention a yellow arc; just the 2600 rpm limit.

What's your fuel flow (leaned for best power) when you hit that 2300 rpm wall? That will help determine whether you have a pitch issue or a power issue. Could be measurement error in the tach.

Charlie
Reply With Quote
  #5  
Old 05-25-2017, 08:37 PM
jrs14855 jrs14855 is offline
 
Join Date: Apr 2008
Location: Lake Havasu City AZ
Posts: 1,990
Default Power

How much time since the stuck valve was discovered. If the engine is not shaking and the compression stays at 70 or better the valve is probably not sticking. Oil consumption may indicate other problems more serious than valve sticking. If the wheel pants and gear fairings are installed speed indicates a lack of power. Was the ignition timing checked at condition inspection?
I flew a 0 320 powered Glasair I TD with Sensenich metal RV prop for about 50 hours and was very unimpressed with performance. Takeoff and climb performance were dismal.
Try to find someone that will loan you a wood or wood composite prop with pitch in the mid 70 range, even if just for one flight.
Highly unlikely tach error is more than 100 r/m.
Reply With Quote
  #6  
Old 05-25-2017, 09:00 PM
Kyle Boatright Kyle Boatright is offline
 
Join Date: Aug 2005
Location: Atlanta, GA
Posts: 2,866
Default

John,

I have an RV-6 with an O-320-D2J. When I rebuilt the engine, I changed the accessory case and added a mechanical fuel pump.

I have an Aymar-Demuth composite prop on the airplane and can turn 2700 RPM or more at full throttle at any density altitude up to around 8,000', and the airplane trues out at anywhere between 190 and 200 mph depending on altitude. With your metal prop, you are limited to 2600 rpm, but there is no reason you should settle for the low RPM and low performance you are experiencing. Based on what I know about your engine/prop combo, there shouldn't be a yellow arc in the 1850-2250 rpm range.

Several questions:

Q: Are all of the fairings installed on your airplane?

Q: Have you checked the accuracy of the tachometer?

Q: Have you checked all of the throws on your carburetor? Maybe something is binding or you're hitting a mechanical stop before the arm on the carb reaches full throttle.

Q: Have you done the idle mixture check where you run the engine at 800-1,000 rpm and slowly pull the mixture lean until the engine stops? You should see a 50 rpm rise at some point during the "pull". This tells you that your carburetor isn't running lean.

Q: Have you obtained a second verification that your mags are correctly timed?

Keep us posted and good luck!
__________________
Kyle Boatright
Atlanta, GA
2001 RV-6 N46KB
Reply With Quote
  #7  
Old 05-25-2017, 09:36 PM
rv7charlie rv7charlie is online now
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 2,241
Default

Forgot to add, 1 qt oil consumption in 5 hours is not a problem, in and of itself. IIRC, that's about half the max allowed by Lyc.

.006 x BHP x 4 / 7.4 = Qt./Hr
https://www.lycoming.com/sites/defau...onsumption.pdf

Charlie
Reply With Quote
  #8  
Old 05-25-2017, 10:29 PM
lr172 lr172 is online now
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 2,369
Default

Comments in line

Larry

Quote:
Originally Posted by dkoughcpa View Post
Mechanically-challenged newby 6A owner here with a few 0-320D2J / 70CM series powerplant questions Id love some assistance with. If it matters, engine time is approx. 600 since overhaul, prop is unknown history prior to 2002 when installed on this aircraft.

Q1: There is a yellow arc on tach between 1850 and 2250 RPM and red line at 2600 RPM. I get the 2600 RPM max operating limit as it is plastered all over the OM. As for the yellow arc, this is original marking on the tach, not taped/placarded. I cannot find anything in either the engine or prop operating manuals, nor the POH that addresses this. Can anyone point me to a reference here?

Q2: At my first conditional (Dec 16), it was discovered the #1 cylinder has a stuck valve guide. Mechanic suggested a regiment of Marvel Mystery Oil to address valve and excessive oil usage. Compressions 70/79/77/78. Would someone please comment on (a) the risks associated with a stuck valve, and (b) the appropriateness of the use of this additive. I am burning about a quart of oil per 5 hours tach time.

I have heard that MMO will bread down carbon deposits and I assume this applies to coked oil as well. I have not tried or experienced this method. You will find a post with good instructions and pics on a relatively simple process to remove the coked oild from the guide with a reamer.

Q3: At 3k feet (I have not even been close to 8k) with wide open throttle, the engine is only pulling 2350 rpm and 139ktas. On takeoff roll and in climb, Im in the yellow arc at 2000-2100 at full throttle. These numbers seem a little low compared to performance numbers seen here and elsewhere. Prop logs reflect that prop was repitched from 81 to 79 several years ago. Any words of wisdom?

As others mentioned, your engine is not likely producing full power and a sticking valve can cause that, along with many other things. Is the engine smooth or rough at full power?

You should also try to confirm that the pitch listed in the logs matches what is on the plane. An over-pitched prop can lkeep your RPMs way down.

Thanks so much!

David
__________________
N64LR
RV-6A / IO-320, Flying as of 8/2015
Reply With Quote
  #9  
Old 05-26-2017, 09:29 AM
dkoughcpa dkoughcpa is offline
 
Join Date: Mar 2017
Location: Nashville, TN
Posts: 3
Default Thanks!

Thank you all for the detailed responses and insight. Greatly appreciated!

It sounds like the tach installed was unlikely specific to the configuration - perhaps the builder just had one lying around from another airplane and stuck it in, or the original failed and was reinstalled with whatever was around. Who knows!

As for fuel flow, I do not have a gauge to meter it, but I am averaging 7.5 gph on the math. I always lean at 3k and above using the poor man's method, and I'm running about 1350 degrees on the one cylinder gauge that shows a reasonable reading. The tach could very well be wrong - all of the airplanes gauges are at least slightly off - so the tach reading is probably something I should confirm.

Regarding the stuck valve, I have put about 50 hours on it since it was discovered at last conditional. Although engine vibration has always bothered me a bit since I initially purchased the airplane, the mechanic and way-smarter-than-I experienced RVer/friend did not think it was a big deal when we discussed it at annual. I had the motor mounts changed out anyway, and it did help a bit. But this airplane still has more vibration than any other in my 1400 hours flying Cessnas, Pipers and DA20s. But without the benefit of ever flying in any other RV, I do not have a good apples/apples reference point on roughness/vibration. Perhaps the prop needs rebalancing (or replaced), but in the meantime, I am going to have the pitched confirmed to insure it agrees to what is logged. I do have a friend with a wood prop he used on an -8 who has been begging me to give it a try. I will take him up on that now.

Ignition is all electronic (which I am considering replacing half with magneto), and all fairings/wheel pants are installed. Mechanical fuel pump, which was also replaced at annual. I am going to have another mechanic check the carburetor throws as part of throttle linkage and carb heat check (having issues with that too). And I have not done the idle mixture check, but will do that today.

Thanks again to everyone!

David
Reply With Quote
  #10  
Old 05-26-2017, 03:04 PM
lr172 lr172 is online now
 
Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 2,369
Default

Quote:
Originally Posted by dkoughcpa View Post
Thank you all for the detailed responses and insight. Greatly appreciated!

It sounds like the tach installed was unlikely specific to the configuration - perhaps the builder just had one lying around from another airplane and stuck it in, or the original failed and was reinstalled with whatever was around. Who knows!

As for fuel flow, I do not have a gauge to meter it, but I am averaging 7.5 gph on the math. I always lean at 3k and above using the poor man's method, and I'm running about 1350 degrees on the one cylinder gauge that shows a reasonable reading. The tach could very well be wrong - all of the airplanes gauges are at least slightly off - so the tach reading is probably something I should confirm.
You can disconnect the spark plug from the cyl with the sticking valve and observe the vibrations during a run up. This should help to identify if the sticking valve is the cause of the vibration


Regarding the stuck valve, I have put about 50 hours on it since it was discovered at last conditional. Although engine vibration has always bothered me a bit since I initially purchased the airplane, the mechanic and way-smarter-than-I experienced RVer/friend did not think it was a big deal when we discussed it at annual. I had the motor mounts changed out anyway, and it did help a bit. But this airplane still has more vibration than any other in my 1400 hours flying Cessnas, Pipers and DA20s. But without the benefit of ever flying in any other RV, I do not have a good apples/apples reference point on roughness/vibration. Perhaps the prop needs rebalancing (or replaced), but in the meantime, I am going to have the pitched confirmed to insure it agrees to what is logged. I do have a friend with a wood prop he used on an -8 who has been begging me to give it a try. I will take him up on that now.

Ignition is all electronic (which I am considering replacing half with magneto), and all fairings/wheel pants are installed. Mechanical fuel pump, which was also replaced at annual. I am going to have another mechanic check the carburetor throws as part of throttle linkage and carb heat check (having issues with that too). And I have not done the idle mixture check, but will do that today.

Thanks again to everyone!

David
A stuck valve often for only sticks while le it is running. Once the engine stops, the valve ev eventually closes, giving normal compression readings. The vibration is a potential sign that you are running on 3 cylinders, backed up by th reduced power. I cruise at 185-190 at a leaned FF of 8 GPH, so 7.5 should be producing more than 150, assuming it is al being ignited and converted to power.
__________________
N64LR
RV-6A / IO-320, Flying as of 8/2015

Last edited by lr172 : 05-26-2017 at 03:09 PM.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 07:28 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.