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  #131  
Old 09-25-2022, 08:47 PM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by Freemasm View Post
Wow. Just wow.

Impossible is a dangerous term. Guess all that thermo work involving pressure versus temperature tables was a waste of time.

When someone operates their car at 20k feet, please post about the experience. If we want to stick with anecdote, look at the difficulties the somewhat older cars have in the high Rockies; over-rich roughness, poor sometimes no starting, and yes, vapor lock on some summer days. Thatís only +\- 10K elevation.

Iíve stated here before, if designs where only bounded by a single set of conditions then most anyone could be a system designer.
Not sure what you mean by older. Any EFI car built in the last 30-40 years will go to the top of Pikes Peak and run just fine. Carb car maybe not. Few people here are flying at 20K but Greg has flown at 21K DA with mogas on a hot day.

I have dozens of customers flying auto engines at 10-18K feet with EFI on mogas, works just fine.



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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 460.7 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ


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  #132  
Old 09-26-2022, 07:24 AM
Freemasm Freemasm is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
Not sure what you mean by older. Any EFI car built in the last 30-40 years will go to the top of Pikes Peak and run just fine. Carb car maybe not. Few people here are flying at 20K but Greg has flown at 21K DA with mogas on a hot day.

I have dozens of customers flying auto engines at 10-18K feet with EFI on mogas, works just fine.
My problem is the "It is mathematically impossible to have a vapor lock issue if the fuel to the engine is pressurized!" Practically? for our purposes with even a little local environment consideration = yes. If there's a fuel that has a perfectly flat line on the phase diagram, I've never seen it.

We have property in Summit County, CO with a base of ~9700 ft. We're out there a lot. Within the last 7-8 years in rental cars; I've been in a Jeep that chugged violently going over Independence Pass, a Mitsubishi that wouldn't start after a hot shut down (raising the hood and letting the fuel pump run sped things up), another hot restart problem car that I can't remember the details. Sure, I don't know how these cars had been treated but they were new enough that they had probably only had routine maintenance performed.

I'm a big proponent for some auto applications, configuring fuel systems for fuel flexibility, etc. The anecdote often stated here can get worrisome at times.

Side note. Your Pikes Peak reference is a much better example of modern braking advancement; e.g. tourist that don't understand or practice compression braking.

Man, it's only Monday and a hurricane is on the way. Enjoy your work week.
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  #133  
Old 09-26-2022, 07:58 AM
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gmcjetpilot gmcjetpilot is offline
 
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I see we are back to EI, which is related I guess to G100UL. I know GAMI has worked on this for years. I know the blend is not new or earth shaking, UL fuel, gasoline has been around for a long time. Rhe trick is getting to well over 100 Octane.

I like to see wide spread (all over USA) trials in GA community, BEFORE, going all in.

Besides cost what is the lubrication or lubricity of the new fuel. Will we see long term wear issues of values? No offense to FAA or GAMI. Just because the Feds approved it does not mean it's golden.
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  #134  
Old 09-26-2022, 07:59 AM
moosepileit moosepileit is offline
 
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The GDI rentals with some miles and no port injectors will run horrid. Just had it in the NE US. No check engine light, light knock, multiple refills.
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  #135  
Old 09-26-2022, 11:07 AM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by Freemasm View Post

We have property in Summit County, CO with a base of ~9700 ft. We're out there a lot. Within the last 7-8 years in rental cars; I've been in a Jeep that chugged violently going over Independence Pass, a Mitsubishi that wouldn't start after a hot shut down (raising the hood and letting the fuel pump run sped things up), another hot restart problem car that I can't remember the details. Sure, I don't know how these cars had been treated but they were new enough that they had probably only had routine maintenance performed.

I'm a big proponent for some auto applications, configuring fuel systems for fuel flexibility, etc. The anecdote often stated here can get worrisome at times.
Direct injection without also having port injection, has additional issues that port injection alone doesn't have due to the engine mounted, ultra high pressure, mechanical pumps and injectors spraying into the combustion chamber. That doesn't apply to this discussion though as most engines we fly here are carbed or have port injection.

What I'm saying is- we know what to do here to make mogas work and collectively have tens of thousands of reliable flight hours on aircraft in summer heat conditions. Follow the same recipe and cautions and you'll get the same results.

Yup, using winter mogas in a Rotax 912 or a carbed Lyc on a summer day and you'll almost certainly have vapor lock issues as many have. Do some other unwise things in the fuel system, ditto.

Nobody is defying physics here. We're staying inside the safety zone.

I posted Greg's photo because we have lots of skeptics here. Greg lives in TX- not exactly known as a cool state. This shows a worst case scenario. Mike also has lots of hours flying his Rocket on mogas in severe heat around Mojave.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 460.7 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ



Last edited by rv6ejguy : 09-26-2022 at 09:50 PM.
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  #136  
Old 09-26-2022, 01:45 PM
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airguy airguy is offline
 
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Quote:
Originally Posted by rv6ejguy View Post

I posted Greg's photo because we have lots of skeptics here. Greg lives in TX- not exactly known as a cool state. This shows a worst case scenario. Mike also has lots of hours flying his Rocket on mogas in severe heat around Mojave.
Correct - I can take off with 104-106 F ground temps and sun-soaked wing tanks, and do a max performance climb into the upper teens without exceeding 400CHT or experiencing vapor lock.

It CAN be done.
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  #137  
Old 09-26-2022, 02:02 PM
Canadian_JOY Canadian_JOY is offline
 
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Quote:
Originally Posted by Carl Froehlich View Post
Or, when you replaced the fuel lines you fixed a fuel line air leak. My experience is such leaks allowing air in have symptoms similar to vapor lock. The offending air leak was on the mechanical fuel pump (non Lycoming engine).

Carl
Carl - thanks for this thought. I suspect air leakage to be improbable in this case but I can assure you that removing the mechanical fuel pump DID fix a long-standing oil leak from its crappy mounting gasket, a fact for which I'm quite thankful as it was the only oil leak on the engine.

EDIT: Why do I suspect air leakage to be improbable? Simply because I would see high fuel pressure after a short ground turn-around - this would be indicative of a fuel system actually holding air rather than leaking air, and fuel heating, vaporizing and expanding to cause an increase in fuel pressure in a sealed system. Maybe I'm all wrong on this but that's the direction the evidence led me. Keep in mind this is a carb'd engine, so fuel pressure from gravity feed alone is very little thus the 8-9PSI that I frequently saw before cranking the engine was abnormally high pressure.

Last edited by Canadian_JOY : 09-26-2022 at 02:05 PM.
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  #138  
Old 09-26-2022, 02:59 PM
Freemasm Freemasm is offline
 
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Quote:
Originally Posted by rv6ejguy View Post
Direct injection without also having port injection, stuff has additional issues that port injection alone doesn't have due to the engine mounted, ultra high pressure, mechanical pumps and injectors spraying into the combustion chamber. That doesn't apply to this discussion though as most engines we fly here are carbed or have port injection.

What I'm saying is- we know what to do here to make mogas work and collectively have tens of thousands of reliable flight hours on aircraft in summer heat conditions. Follow the same recipe and cautions and you'll get the same results.

Yup, using winter mogas in a Rotax 912 or a carbed Lyc on a summer day and you'll almost certainly have vapor lock issues as many have. Do some other unwise things in the fuel system, ditto.

Nobody is defying physics here. We're staying inside the safety zone.

I posted Greg's photo because we have lots of skeptics here. Greg lives in TX- not exactly known as a cool state. This shows a worst case scenario. Mike also has lots of hours flying his Rocket on mogas in severe heat around Mojave.
Never my point but guess I wasn’t clear. I’m also configuring my aircraft for mogas usage. I will test the suction system and pressure under 2 pump flow, half of the pick-up blocked off, half of the pre filter blocked, side with the highest frictional loss (flop tube), let the fuel warm, etc. Once I know the margin between actual and theoretic, I’ll push the temperature until I start seeing phase change.

I’ll state again my issue was with the statement "It is mathematically impossible to have a vapor lock issue if the fuel to the engine is pressurized!". Temperature affects the fuel properties. Pumps are delta P devices controlled by delta P devices (not absolute). Broad statements and non-quantified experience that declares there is no edge of the cliff is dangerous. Words matter.

Last edited by Freemasm : 09-26-2022 at 03:03 PM.
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  #139  
Old 09-26-2022, 09:46 PM
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rv6ejguy rv6ejguy is offline
 
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Quote:
Originally Posted by Freemasm View Post
Broad statements and non-quantified experience that declares there is no edge of the cliff is dangerous. Words matter.
In my world, validation by doing something repeatedly (shall we say thousands of times in this case) gives us good confidence that we have arrived at a sound and safe solution. Seems we are all qualified to experiment and establish our own safe limits based on that experience, knowing the potential dangers.
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Ross Farnham, Calgary, Alberta
Turbo Subaru EJ22, SDS EFI, Marcotte M-300, IVO, Shorai- RV6A C-GVZX flying from CYBW since 2003- 460.7 hrs. on the Hobbs,
RV10 95% built- Sold 2016
http://www.sdsefi.com/aircraft.html
https://www.youtube.com/channel/UCiy...g2GvQfelECCGoQ



Last edited by rv6ejguy : 09-28-2022 at 09:34 AM.
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  #140  
Old 09-27-2022, 10:00 AM
PilotjohnS PilotjohnS is offline
 
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Quote:
Originally Posted by gmcjetpilot View Post

Besides cost what is the lubrication or lubricity of the new fuel. Will we see long term wear issues of values?
from what my experts say, this is not required; it may be an old wives tale. JMHO.
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