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  #11  
Old 05-30-2017, 06:12 AM
todehnal todehnal is offline
 
Join Date: Jan 2005
Location: Kentucky Lakes area in KY
Posts: 888
Default No Winter Blend Here

First, I am in a small community in Western KY, and I use ethanol free 93 octane premium auto fuel that I purchase from and independent in Hopkinsville, KY. I asked the owner of this small petroleum products chain when the change back from winter blend would occur. He assured me that they never get winter blend in their locations. I fill my 55 gal barrel there, as needed, and I must admit that I have never had a problem using his fuel. Anyone else find that to be true, that they do not receive winter blend auto fuel in their area?
Tom
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2013- RV12, Kit #119. N123M First flight Nov21. It's a keeper!
1998- RV-9 tail kit, built and sold
1989- RV-6 tail kit, built and sold

Last edited by todehnal : 05-30-2017 at 06:14 AM.
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  #12  
Old 05-30-2017, 06:26 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
Join Date: Nov 2014
Location: Hinckley, Ohio
Posts: 736
Default

The OP is located in Scottsdale, AZ. Pretty hard to believe they have winter blend fuel to make starting internal combustion engine easier to start in cold temps. Kinda like when people in Florida put up Christmas lights...

This sounds like vapor lock - fuel boiling in carb bowls due to high temps under the cowling. My guess is 100LL should fix problem because it is less volatile.

Also... don't add switch to shutoff electric fuel pump. It is there for a reason. Cool fuel is circulated thru the fuel distribution system to help prevent vapor lock. Electric fuel pump should always be running. If starting a hot engine that has heat-socked the cowling it is best practice to allow electric fuel pump to recirculate fuel for ~ 5 minutes prior to engine start so cool fuel is available at the carbs.
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Jim Stricker
Hinckley, Ohio
P/ASEL 1970 Sport Pilot since '04
80 hrs Flying Aeronca Chief 11AC
1130 hrs Flying 46 Piper J-3 Cub
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RV-12 E-LSA #120058 AWC 7/12 Bought Flying 10/15 with 48TT - Hobbs now 317

Last edited by Piper J3 : 05-30-2017 at 06:35 AM.
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  #13  
Old 05-30-2017, 06:58 AM
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tomkk tomkk is offline
 
Join Date: Apr 2014
Location: Port Orange, Fl
Posts: 677
Default

Quote:
Originally Posted by Piper J3 View Post
This sounds like vapor lock - fuel boiling in carb bowls due to high temps under the cowling. My guess is 100LL should fix problem because it is less volatile.

Also... don't add switch to shutoff electric fuel pump. It is there for a reason. Cool fuel is circulated thru the fuel distribution system to help prevent vapor lock. Electric fuel pump should always be running. If starting a hot engine that has heat-socked the cowling it is best practice to allow electric fuel pump to recirculate fuel for ~ 5 minutes prior to engine start so cool fuel is available at the carbs.
I've always wondered about this. IIRC, the fuel return line taps off the spider block at the top of the engine and the cooler fuel doesn't get down to the carbs. Seems like any fuel that was boiled off would go into the intake manifold and result in a very rich mixture when the engine is started. I suppose some cooler fuel would refill the carb bowl after the boil-off.
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Port Orange, Fl
RV-12 N121TK ELSA #120845
First flight 06/10/2015
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  #14  
Old 05-30-2017, 07:22 PM
Azjulian Azjulian is offline
 
Join Date: Dec 2015
Location: Scottsdale, Arizona
Posts: 123
Angry

I got a chance to fly again this morning (6am and it was already 80F OAT)

The 100LL did NOT fix this issue, I didn't experience the issue on initial climbout but I did when transitioning to a WOT climbout from a slow flight test.

I did test my WOT cruise, it took some time but the max I could get was 5500RPM.

My static WOT is 5200, on my climbout i'm seeing my RPM dropping slightly as I climb, by 3000' AGL i'm at 5060RPM
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  #15  
Old 05-30-2017, 08:19 PM
Salter Salter is offline
 
Join Date: May 2017
Location: Elberta, AL
Posts: 45
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Just throwing this out there. Check the screen on the fuel pump. Had an issue like this once and that was the cause. To this day can't figure out where the trash came from, new tanks lines etc. But cleaned it and all was well.
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  #16  
Old 05-30-2017, 08:22 PM
JBPILOT JBPILOT is offline
 
Join Date: Nov 2007
Location: Jesup, Iowa
Posts: 1,562
Default Something else to try - -

Take fuel line off at carb one at a time and put in a container and turn on elec pump. Note volume of fuel, then put hose back on and do other side for the SAME amount of time. Use a stop watch or whatever. I am suggesting this will eliminate a slight restriction in one of the lines. Not likely, but a maybe.
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  #17  
Old 05-30-2017, 10:08 PM
Azjulian Azjulian is offline
 
Join Date: Dec 2015
Location: Scottsdale, Arizona
Posts: 123
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John - I had the same idea as you and I didn't do anything scientific with measuring the volume over time, but I did run fuel through both lines when off the carbs and I got good flow...

I'm wondering if this is overload of the engine and that I need to flatten the pitch of the prop, which I will try next. Especially with the high temps here the inlet air to the carbs has to be very high
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  #18  
Old 05-30-2017, 10:20 PM
sf3543 sf3543 is offline
 
Join Date: Jan 2005
Location: San Antonio, TX
Posts: 871
Default Just as a point of interest

I noticed that my oil temps were going up rather quickly last summer, just after I re pitched my prop to a more coarse setting. After checking out a list of possible causes, I repitched the prop back to a finer pitch and the temps went right back down. Im a few mph slower, but the plane seems a lot smoother and definitely runs cooler. I never had issues like what you describe, though.
I'm of the opinion you should leave the fuel pump on all the time in the RV12 just because we mostly run Mogas and it is more susceptible to vapor lock.
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  #19  
Old 05-31-2017, 12:50 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 7,064
Default

Quote:
Originally Posted by Azjulian View Post
I got a chance to fly again this morning (6am and it was already 80F OAT)

The 100LL did NOT fix this issue, I didn't experience the issue on initial climbout but I did when transitioning to a WOT climbout from a slow flight test.

I did test my WOT cruise, it took some time but the max I could get was 5500RPM.

My static WOT is 5200, on my climbout i'm seeing my RPM dropping slightly as I climb, by 3000' AGL i'm at 5060RPM
As I wrote in my other reply, if your static full throttle RPM is higher than your climb RPM then something is wrong. The flight RPM (even in a climb... should always be higher by at least a little bit but the actual difference depends on your climb speed)

As for your roughness issue, if 100LL did not solve it then the next thing I would recommend is inspect for debris in the carbs. It is somewhat common with a brand new build. Stuff can get flushed from the new hoses and lines into the carbs and often causes problems intermittently. It may even be in some way causing a slight power loss only in flight that is effecting your climb RPM.

Your max level RPM of only 5500 when the static is 5200 is another indicator that something is out of wack. A static of 5200 should cause a level full throttle to probably be above red line (5800)
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Last edited by rvbuilder2002 : 05-31-2017 at 12:54 AM.
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  #20  
Old 05-31-2017, 10:13 AM
cactusman cactusman is offline
 
Join Date: Oct 2012
Posts: 421
Default

Quote:
Originally Posted by Azjulian View Post
John - I had the same idea as you and I didn't do anything scientific with measuring the volume over time, but I did run fuel through both lines when off the carbs and I got good flow...

I'm wondering if this is overload of the engine and that I need to flatten the pitch of the prop, which I will try next. Especially with the high temps here the inlet air to the carbs has to be very high
I would check the gascolator filter (clean it - I usually order spares from Vans - pretty cheap), and check the fuel tank screen. Then unhook the gas line into the engine driven fuel pump and check the fuel flow per the PAP. (1 gal min in 180 sec) If you are meeting the flow requirements, then you can rule out everything behind that engine driven pump. If not, look at the lines or a possible partial blockage in the electric driven pump.

Next I would weigh my floats, double check my fuel manifold block, and consider the engine fuel pump. Finally, I might consider sending my carbs in to Lockwood for a look over. Keep in mind that some of those checks require a supply of those copper washers possibly.

Last edited by cactusman : 05-31-2017 at 10:15 AM.
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