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  #11  
Old 04-07-2021, 04:04 PM
Piper J3's Avatar
Piper J3 Piper J3 is online now
 
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Quote:
Originally Posted by Mich48041 View Post
Piper J3, the Dynon D-180 has a thermocouple input on EFIS pins 27 & 28. If that input is free,
a type J thermocouple can be connected. Omega has part number WTJ-14-36 for $14.
Joe -

Where would the temps display? I think the screen position where MAP is can be assigned to a different sensor.
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 670

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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  #12  
Old 04-07-2021, 05:54 PM
Mich48041 Mich48041 is offline
 
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Here is an old picture showing gascolator temperature.
I moved the thermocouple so that now it measures voltage regulator temperature.
The ammeter might have been in that location. The ammeter never worked anyway.
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Last edited by Mich48041 : 04-07-2021 at 05:58 PM. Reason: Added sentence
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  #13  
Old 04-07-2021, 07:25 PM
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cactusman cactusman is offline
 
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Quote:
Originally Posted by greghughespdx View Post
What you’ve described regarding running winter blend fuel and heat soaking on the ground is quite possibly the cause of your problem. Did you shut down and restart at all during these ground ops? Depending on the specific winter blend, OAT and heat soaking you could be boiling your fuel. The bigger the difference between winter temps and warmer present temps the greater the potential for problems.

Personally, I would not run in hot temps with winter blend fuel, ever. Especially winter fuel from northers states where it gets friggin cold and blends are made for the more extreme cold temps. Much better to put 100LL in the engine of summer fuel isn’t available, to better ensure you don’t have potential vaporization. The vapor pressures on winter blend fuels can be remarkably different than standard blend fuel in some locales. Fuel blended for cold-air ops just won’t perform in hot environments. Engines can potentially quit. That’s definitely one of the potential risks one must actively understand and manage when running auto fuel. 100LL with a little Decalin scavenging agent added can bring a lot of Pearce of mind when an appropriate auto fuel isn’t available.
What Greg said is correct. Avoid winter pump gas, try to buy from high quality Shell or similar gas stations (avoid brand x - I purchased an outboard motor recently and the owner of the shop hated Costco, most supermarket and 7-11 type gas stations - he said stick with Shell, Mobil or Chevron - higher quality gas sold) - also avoid 93 or other octanes that don't have high turnover. Top off with a little 100LL and an oz of decalin. YMMV.

I also upgraded to the newer high pressure Facet fuel pump, haven't had a vapor lock symptom since.
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  #14  
Old 04-08-2021, 09:28 AM
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I hear what everyone is saying about not using Winter blend auto fuel (lower vapor pressure) in warm weather. I experienced vapor lock on the ground several years ago and now it happened again in the air – see post #255 above.

All this gets me thinking… obviously, automobiles don’t have a problem operating with low vapor pressure fuel in warm temperatures - either carb or fuel injected. Likewise, lawnmowers, motorcycles, chainsaws, etc. – none of these have problem with low vapor pressure fuel when operated in warm OAT. I suspect even Rotax 912 in either loosely-cowled aircraft, or no cowling like Air Camper, don’t have this problem.

The RV-12 has a tightly-cowled engine with two very small (2.5”) round air inlets. In addition, hot air from both the oil cooler and the water radiator dump into the cowling for exit at bottom of firewall opening. During ground ops, hot air can stagnate in the cowling causing elevated temperature of fuel lines and carburetors. The recirculating fuel line back to the tank does nothing to cool fuel in the individual carb feed lines or the carbs themselves. Also, when engine is idling on ground, fuel flow is minimal so fuel has huge opportunity to elevate in temperature.

Where am I going with this… It’s my contention that the RV-12 needs better cooling during ground operations. Maybe something similar to the cowl flap on a Cessna 182. Perhaps a louver on the top of the cowling to spill excess heat while airplane is on the ground. Could be a permanent louver like on the 12iS or perhaps a spring-operated flap (C-182) that would open on the ground and automatically close at higher airspeeds. I think for ground ops, the prop blast over the louvers would act like a venturi and hot air will get sucked out of the top of the cowling…
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 670

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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  #15  
Old 04-08-2021, 12:37 PM
NinerBikes NinerBikes is offline
 
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Quote:
Originally Posted by Piper J3 View Post
I hear what everyone is saying about not using Winter blend auto fuel (lower vapor pressure) in warm weather. I experienced vapor lock on the ground several years ago and now it happened again in the air – see post #255 above.

All this gets me thinking… obviously, automobiles don’t have a problem operating with low vapor pressure fuel in warm temperatures - either carb or fuel injected. Likewise, lawnmowers, motorcycles, chainsaws, etc. – none of these have problem with low vapor pressure fuel when operated in warm OAT. I suspect even Rotax 912 in either loosely-cowled aircraft, or no cowling like Air Camper, don’t have this problem.

The RV-12 has a tightly-cowled engine with two very small (2.5”) round air inlets. In addition, hot air from both the oil cooler and the water radiator dump into the cowling for exit at bottom of firewall opening. During ground ops, hot air can stagnate in the cowling causing elevated temperature of fuel lines and carburetors. The recirculating fuel line back to the tank does nothing to cool fuel in the individual carb feed lines or the carbs themselves. Also, when engine is idling on ground, fuel flow is minimal so fuel has huge opportunity to elevate in temperature.

Where am I going with this… It’s my contention that the RV-12 needs better cooling during ground operations. Maybe something similar to the cowl flap on a Cessna 182. Perhaps a louver on the top of the cowling to spill excess heat while airplane is on the ground. Could be a permanent louver like on the 12iS or perhaps a spring-operated flap (C-182) that would open on the ground and automatically close at higher airspeeds. I think for ground ops, the prop blast over the louvers would act like a venturi and hot air will get sucked out of the top of the cowling…
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  #16  
Old 04-08-2021, 12:49 PM
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And another thought... The carbs on RV-12 do not intake cold air like most other airplanes. So, the hot under-cowl air contributes to increase carb body temperatures. Lots of things going in the wrong direction temperature-wise...
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 670

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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  #17  
Old 04-08-2021, 01:16 PM
NinerBikes NinerBikes is offline
 
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Quote:
Originally Posted by Piper J3 View Post
And another thought... The carbs on RV-12 do not intake cold air like most other airplanes. So, the hot under-cowl air contributes to increase carb body temperatures. Lots of things going in the wrong direction temperature-wise...
That was a trade off so that carb heat was not a necessity on a LSA aircraft, and icing of the carburetors is now a non issue.
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  #18  
Old 04-08-2021, 01:49 PM
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A sensitivity to the use of winter blend fuel in warmer temps is not limited to just the RV-12.
There are many other aircraft models that have had issues as well.

Avoiding use of 100% winter blend auto fuel in hot temps is the best course of action. This is standard practice for most people using it in Lycoming power aircraft as well.
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  #19  
Old 04-08-2021, 01:59 PM
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Quote:
Originally Posted by Piper J3 View Post
And another thought... The carbs on RV-12 do not intake cold air like most other airplanes. So, the hot under-cowl air contributes to increase carb body temperatures. Lots of things going in the wrong direction temperature-wise...
We have done quite a bit of testing while instrumented with temp probes under the cowl and in flight the induction air temps are not elevated a significant amount to where it would increase the temp. of the carburetors.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #20  
Old 04-08-2021, 02:23 PM
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Quote:
Originally Posted by rvbuilder2002 View Post
We have done quite a bit of testing while instrumented with temp probes under the cowl and in flight the induction air temps are not elevated a significant amount to where it would increase the temp. of the carburetors.
I would guess there is plenty of cool air ingested during flight. It's the ground ops that cause elevated carb body temp and elevated temp of the fuel in both hoses feeding the carbs and the fuel in the float bowls themselves.
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 670

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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