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  #31  
Old 06-27-2018, 10:53 AM
Mark33 Mark33 is offline
 
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Quote:
Originally Posted by crabandy View Post
Boost pump generally doesn't help when very heat soaked, It clicks loudly like there is no fuel. Sometimes it helps if it is only marginally heat soaked.
My buddy had basically the same problem with fuel getting hot and vapor locking. He ended up installing a small 1/8" return line to his left tank. He "T'd" in to the fuel line just prior to the red cube so that even when he has the "sweep" line/valve open, it doesn't interfere with the calculation of the fuel count. With it being such a small "metered" 1/8" line, even if he forgets it open it really doesn't affect his fuel pressure....(or very little). Even though it only sweeps out about 1 cup of fuel per minute, it completely 100% cured his vapor lock issues. He actually even installed a second red cube on that little return line and he gets an annunciation on the G3x that reminds him that the sweep line is open. You can hear the electric pump change sounds as it starts to pick up the cold fresh fuel and get rid of those hot vapors. It really did make it a whole new airplane and he has never once had to deal with vapor lock issues again. The only thing that he has to even slightly be aware of is that if both tanks are completely full he just makes sure that he has the left tank selected...because that's the tank that the little return line is going to. Even in that situation with full tanks, if he were to forget to select the left tank, the worst case scenario is that he'd loose one or two cups of fuel through the overflow. Once again, for him, it was the absolute cure to all of his hot fuel issues.

Mark

Last edited by Mark33 : 06-27-2018 at 10:59 AM. Reason: Typo
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  #32  
Old 06-27-2018, 11:25 AM
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DanH DanH is offline
 
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Andy, got it. You do have a lot of fuel line routed around the compartment, plus the gascolator and red cube are uninsulated, so fuel is certainly picking up heat from the air. Still, I'd try a cheap and easy experiment.

The clamp-on heat shields are easy to make. Whip up two, each about 12 inches long, or whatever length fits the long straight section of tailpipe which parallels the carb and fuel line. However, don't leave 'em plain. The typical sheet aluminum "heat shield" re-radiates a lot of energy from the side opposite the hot pipe. So, add an insulator and a cover sheet to the side facing the carb, All it takes is a layer of fiberfrax or similar, covered with metallic aluminum duct tape.

If it doesn't work, well, I can't knock a cowl flap for adding mass flow, and Mark's report on the use of a recirculating line is interesting.
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  #33  
Old 06-27-2018, 11:39 AM
Turbo69bird Turbo69bird is offline
 
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My apology to the OP donít want to hijack his thread bout felt my info may in so,e way be connected to his issue as well.

This is interesting to ,e because I get no ( or very little) pull pressure on my gauge sometimes,
It is unchanged by turning on the boost pump. However when I turn on my boost pump the fuel flow goes up. Which left me scratching my head a bit. If the fuel was dead heading the fuel flow shouldnít go up from 7.5 to 10.5/just from turning on the boost pump, and if itís dead heading the pressure should show up.

No there are times when turning on the boost pump will raise the pressure and there are times when itíll show mechanical pressure and boost pressure on the gauge, usually in first start up.
I also hear my boost pump ticking much louder at times.

I have to de cowl the airplane and look at how the lines are plumbed itís one of the few things I havenít been familiarized with on my airplane yet,







Quote:
Originally Posted by Mark33 View Post
My buddy had basically the same problem with fuel getting hot and vapor locking. He ended up installing a small 1/8" return line to his left tank. He "T'd" in to the fuel line just prior to the red cube so that even when he has the "sweep" line/valve open, it doesn't interfere with the calculation of the fuel count. With it being such a small "metered" 1/8" line, even if he forgets it open it really doesn't affect his fuel pressure....(or very little). Even though it only sweeps out about 1 cup of fuel per minute, it completely 100% cured his vapor lock issues. He actually even installed a second red cube on that little return line and he gets an annunciation on the G3x that reminds him that the sweep line is open. You can hear the electric pump change sounds as it starts to pick up the cold fresh fuel and get rid of those hot vapors. It really did make it a whole new airplane and he has never once had to deal with vapor lock issues again. The only thing that he has to even slightly be aware of is that if both tanks are completely full he just makes sure that he has the left tank selected...because that's the tank that the little return line is going to. Even in that situation with full tanks, if he were to forget to select the left tank, the worst case scenario is that he'd loose one or two cups of fuel through the overflow. Once again, for him, it was the absolute cure to all of his hot fuel issues.

Mark
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  #34  
Old 06-27-2018, 11:52 AM
crabandy crabandy is offline
 
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Quote:
Originally Posted by Mark33 View Post
My buddy had basically the same problem with fuel getting hot and vapor locking. He ended up installing a small 1/8" return line to his left tank. He "T'd" in to the fuel line just prior to the red cube so that even when he has the "sweep" line/valve open, it doesn't interfere with the calculation of the fuel count. With it being such a small "metered" 1/8" line, even if he forgets it open it really doesn't affect his fuel pressure....(or very little). Even though it only sweeps out about 1 cup of fuel per minute, it completely 100% cured his vapor lock issues. He actually even installed a second red cube on that little return line and he gets an annunciation on the G3x that reminds him that the sweep line is open. You can hear the electric pump change sounds as it starts to pick up the cold fresh fuel and get rid of those hot vapors. It really did make it a whole new airplane and he has never once had to deal with vapor lock issues again. The only thing that he has to even slightly be aware of is that if both tanks are completely full he just makes sure that he has the left tank selected...because that's the tank that the little return line is going to. Even in that situation with full tanks, if he were to forget to select the left tank, the worst case scenario is that he'd loose one or two cups of fuel through the overflow. Once again, for him, it was the absolute cure to all of his hot fuel issues.

Mark
I think my problem is very similar, if I get the fuel moving with more throttle RPM the surging richness goes away. I think at idle the fuel is sitting and cooking.
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  #35  
Old 06-27-2018, 12:04 PM
crabandy crabandy is offline
 
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Dan,
I was thinking of a similar heat shield on the exhaust next to the carb and fuel line.

My fuel lines are on the long side, as a first time builder I was thinking ďflexibility.Ē

Iím also thinking about removing the gascolator, doesnít seem to do anything for the taildragger. Is it possible to remove the gascolator bowl and cap it off or just easier to remove it and use a bulkhead type fitting?

I think I will continue the oil door cowl flap as well, the door/hinge/hole is already there.
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  #36  
Old 06-27-2018, 12:08 PM
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Zuldarin Zuldarin is offline
 
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Hi Andy, you've had a lot of good advise in this thread but I thought I would add one more voice. I have similar heat soak issues and I was able to greatly limit the severity by wrapping all of my FWF fuel lines (already fire sleeved by Tom) with a reflective/insulated tape. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

It did not eliminate the problem completely but it did help noticeably. Now my engine doesn't sound like its on its last leg when I'm on the ground hot.
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  #37  
Old 06-27-2018, 12:14 PM
krw5927 krw5927 is offline
 
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Quote:
Originally Posted by crabandy View Post
Boost pump generally doesn't help when very heat soaked, It clicks loudly like there is no fuel.
This is an interesting statement. My per-plans Facet cube pump also clicks loudly when there is no fuel present at the INLET, but when operating at full pressure and zero flow (deadhead) it gets quiet. I assume others are the same.

Totally just guessing here, but might there be an outside chance the problem is not forward of the firewall?
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Last edited by krw5927 : 06-27-2018 at 12:21 PM.
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  #38  
Old 06-27-2018, 12:29 PM
Mark33 Mark33 is offline
 
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Quote:
Originally Posted by crabandy View Post
I think my problem is very similar, if I get the fuel moving with more throttle RPM the surging richness goes away. I think at idle the fuel is sitting and cooking.
If we landed for some reason we'd usually have to wait an hour or more to let everything cool down enough so that it wouldn't vapor lock, but with the mod in place, it's never an issue. Two summers ago we were trying to take off in the middle of the summer in Lubbock Texas. If any of you are familiar with summers in Lubbock, than you know what I'm talking about. Lubbock has a runway that appears to be at least 10 miles long...well maybe not quite that long....but it's long. We started out takeoff run at the very end of the runway and we almost had to abort because we were running out of runway. I'll bet the engine wasn't making 50hp. Well long story short, we did make it out of there and as cool fuel started flowing into the system the engine continued to run better and better...but it was a close call. After that event he installed that little sweep system and has never once experience vapor lock again. To this very day though, and just to confirm that it's the modification that did the trick, he can purposely not turn the bypass valve on just to see if he can make it vapor lock...and he can. He'll then open the little valve, listing for the change in sound to the electric pump, apply full power, and away he goes.

Mark
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  #39  
Old 06-27-2018, 04:59 PM
crabandy crabandy is offline
 
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Quote:
Originally Posted by krw5927 View Post
This is an interesting statement. My per-plans Facet cube pump also clicks loudly when there is no fuel present at the INLET, but when operating at full pressure and zero flow (deadhead) it gets quiet. I assume others are the same.

Totally just guessing here, but might there be an outside chance the problem is not forward of the firewall?
“There’s always a chance,” but the issue is defenitely heat related FWF. I generally have fuel pressure and the loud clicks of the fuel pump go away shortly after turning it on when hot and on the ground. I have also had erratic and 0 fuel pressure and continuous loud clicking from the fuel pump, very hard to keep running at that point. I’ve also done flow checks and can fly 9 months out of the year without an issue.

As others have said I think with the airplane wings shining in 95+ temps the fuel starts out over 100*. Metal parts specifically gascolator/red cube/carb/fuel pump are bathed in 180-220 degree cooling air not to mention the temp of the accessory case and sump and radiant heat from the exhaust adds to this temp. I’m guessing when the cooling air stops the temp goes up and boils the fuel in the carb first, if really heat soaked also possibly boiling in sections of the FWF fuel lines.
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  #40  
Old 06-28-2018, 10:49 AM
krw5927 krw5927 is offline
 
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I wonder if anyone has ever tried a fuel sump on the carb bowl itself. The idea would be when you suspect high temps on a quick turn, flip on the electric pump and sump off a couple cups of fuel until the pump sounds happy and the fuel you're sumping feels like cool gas out of the tank. Then dump what you've sumped off right back into the tank, climb in, and go.

An admittedly odd idea, but it would be cheap and potentially simple to implement.
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