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Gascolators in Fuel Injection Systems

A

andrewbutler

Member
Hello,

Can someone help me understand why a Gascolator shouldn't be used in a fuel injection fuel system? I am installing an IO360 XP Superior in my RV7 in a few months. Some time back, I came across a FI Fuel System schematic from Titan that had a Gascolator included, so earlier this year I went and bought an Andir Gascolator with my Firewall forward kit. Digging deeper, I can't see any further references to such a set up. Was is a waste of $160?

Best regards,
Andrew Butler,
RV7100,
Galway, Ireland.
 
Nope....

.....not a waste, Andrew,
We're building a -7A with a Lycoming IO-360 and it'll have a gascolator as well. If it's rated for the pressure, you're good to go. A lot of guys on here poo-poo a gascolator on FI engines but my question is, "Where does the trash and water collect then?" I've seen both on an IO-520 Conti on an Agwagon in the past.

Regards,
 
A search for gascolators will yield much discussion and debate on this topic for you.
 
I used a gascolator with the Subaru installation but it was before the fuel pumps just after the fuel valve. Over a 4 year period of checking it periodically, no appreciable amount of dirt was found and no water was ever found.

As I proceed with the Lycoming installation, the gascolator is out of the picture. It will be AFP in line filter only. I have not decided where to place it in the system, before or after pumps, but there will be no gascolator.
 
yes and no

Absolutely nothing wrong with a gascolator on a FI system..Almost fitted one myself. There is no difference between a FI and carbed system..If your going to fit one to a carb'd airplane then the same argument is there to fit one to a FI system.

It is at the low point in the system and would be your last line of defense if you had water in your fuel...Hmm as Im now running 10% ethanol maybe i should have fitted one..but I digress..:)

BUUUT...330 hours (airplane mostly in a hangar) of IFR rain flying etc has not shown any problems, in fact I have yet to see a single drop of water in my main tank drains so I'm comfortable without it.

But I would also be comfortable in NOT putting one on a carb's motor for the same reasons.

Frank
 
The question should not be "gascolator for fuel injection systems" but "gascolator for low wing aircraft."

Gascolators are typically used in high wing aircraft because when the aircraft is sitting, if there is water in the tanks, water being heavier than gasoline will flow to the lowest point. In a high wing aircraft the lowest point in the fuel system will be below the tank drains in the fuel lines so just draining the wing tanks will not remove water from the system. A gascolator in high wing aircraft allows the draining of water in the system that is already lower than the wing tank drains.

In a low wing system however, the fuel tanks are at the LOWEST position in the system so any water in the tanks can be removed by the tank drains. A gascolator on the firewall in a low wing aircraft should never have any water in it from the aircraft just sitting. Additional, a gascolator will not stop water that is being force by the pumping action since the flow will not allow it to settle. For this reason a gascolator on a aircraft with the engine higher than the lowest point (fuel plumbing that goes "up-hill") of the tank is useless. As for filtering, you already have the Airflow filter before the electric fuel pump.

For those that have gascolators on RVs--have you ever found any water in them on draining? If so, you have found a new secret to flight, water that can defy gravity.
 
Gasolators on FI engines

Gasolators are MANDATORY on amateur builds here in Canada. At least here in South Western Ontario. The MDRA inspectors insist on them and will not pass an inspection without one. I installed mine as per the Van's drawings for a carb engine and my 10-360 runs like a charm. No problems at all. And it gies me, that one extra fuel check before I fire up and turn hard earned cash into exhaust vapour.

Dave
RV-7
C-GCPD
 
On FI systems with return fuel flow, they are of little or no value as the return fuel flow may exceed a gallon per minute. Any water is thoroughly mixed up with the fuel due to this recirculation.

On returnless systems, they may have some value, depending on where they are placed in the system. Gascolators placed under high pressure are not of much value.

Quick drains at all low points work fine and are highly recommended.

In short, won't hurt other than more plumbing and more money but may not be of any benefit either. Check your local requirements.

In my view the Canadian regs don't make sense for all FI applications but they cover everyone the same way regardless of system because they don't understand some of these systems and how they work. Proper filters are far more important here but I've never seen them checked for.
 
Im guessing that gascolators add little value when mogas is used or anywhere a bit of ethanol is added to fuel- the alcohol scavenges the water and holds it until its burned. Comments?
 
outboard gascolators

What i am planning due to regs in Canada and AFP discussions, is one gascolator on each wing root as low as i can, hard plumbed to outside of fues. Then, a flex line from gascolator to fuel line. On a 9 thats not easy but seems to be worth the trouble, i am not sold on mounting it Fwfwd on FI. Would really like to see more pics if other have done it this way, or criticism if this is dumb
 
Two of them?

Thats well overkill..Hmm

But I understand your reluctance to put ONE of them North of the firewall too.

If i did I would probably insulate it.

I understand that the Vans gascolator is rated for the pressure so it can go downstream of the boost pump.

Not sure why it would not work at high pressure..Not that it will ever see any water anyway.

Frank
 
RickWoodall said:
What i am planning due to regs in Canada and AFP discussions, is one gascolator on each wing root as low as i can, hard plumbed to outside of fues. Then, a flex line from gascolator to fuel line. On a 9 thats not easy but seems to be worth the trouble, i am not sold on mounting it Fwfwd on FI. Would really like to see more pics if other have done it this way, or criticism if this is dumb
Click to expand...

Rick, when you get yours done post some pics;). I have two Andair gascolators in hand and plan on the same installation.
I remember seeing an 8 somewhere with the wing root install...just can't remember where.

I'm in Italy right now, finishing up two weeks in Tuscany. Really missing my plane....is it OK to call it a plane even though the wings aren't quite on yet?:rolleyes:
 
Actually no

The pressure is the same with one pump running as it is with two..Assuming you follow my design.

Frank
 
lorne green said:
Pump(S)?

lots o' fuel pressure!;)
Click to expand...

Not so much...

Run two pumps (one in each wing) with no engine-driven fuel pump. The pumps run pressurized fuel from their respective wing tank directly to the FI divider, eliminating the risk of vapor lock. Changing tanks is accomplished by shutting off one pump and turning on the other. Both pumps on for takeoff and landing, since they have a return loop and pressure regulator on the output.

I doubt there would be enough room in the ring root for the pump assembly and a gascolator - besides the fact that the gascolator is not necessary on a low-wing aircraft.
 
Last edited:
I have asked this question in the past and I talked to Van's about it and the consensus was to not do it.

The reasons given to me were:

1. Any water that might collect will be blown right through the engine without significant problem.

2. Engine compartment heat will heat up the gascolator and increase the odds of vapor lock.

3. The engine driven pump will have to suck fuel through higher resistance (rather than being forced through it), and this could cause some issues. Don't remember right now what those issues are, though.

4. Another potential source for leaks, and a fuel leak in the engine compartment would not be good.

So, I don't know that having a gascolator is really a bad thing, but it doesn't seem the positives out weight the negative. My main thought for having one was an extra filtration stage, but I guess you really don't need any more than what the main FI filter can provide. At least that was the advice from Van's.
 
High Wing Low Wing

--------------------------------------------------------------------------------

The question should not be "gascolator for fuel injection systems" but "gascolator for low wing aircraft."

Gascolators are typically used in high wing aircraft because when the aircraft is sitting, if there is water in the tanks, water being heavier than gasoline will flow to the lowest point. In a high wing aircraft the lowest point in the fuel system will be below the tank drains in the fuel lines so just draining the wing tanks will not remove water from the system. A gascolator in high wing aircraft allows the draining of water in the system that is already lower than the wing tank drains.

In a low wing system however, the fuel tanks are at the LOWEST position in the system so any water in the tanks can be removed by the tank drains. A gascolator on the firewall in a low wing aircraft should never have any water in it from the aircraft just sitting. Additional, a gascolator will not stop water that is being force by the pumping action since the flow will not allow it to settle. For this reason a gascolator on a aircraft with the engine higher than the lowest point (fuel plumbing that goes "up-hill") of the tank is useless. As for filtering, you already have the Airflow filter before the electric fuel pump.

For those that have gascolators on RVs--have you ever found any water in them on draining? If so, you have found a new secret to flight, water that can defy gravity.
__________________
William Curtis

William,

You couldn't have said it any better. I had a gascolator on my RV-6 and never saw a drop of water in it. It was carbureted. Tank drains are the lowest point in the system. Gascolator in the system is just another point of potential failure.

Don't understand the Canada regs, but if that's what they are and your in Canada then you would have to use one.

Ted
 
Logically

"Logically, it could work. Also, logically, there are a hundred variables, any one of which could put us in a worse position than we're in now."

I guess that sums up exactly where I am on this one right now! The feedback has been great. Decisions! Decisions! It was much easier when all I had to do for four years was follow the plans!

Andrew.
RV71700
Galway, Ireland.
 
Follow Van's advice

andrewbutler said:
I guess that sums up exactly where I am on this one right now! The feedback has been great. Decisions! Decisions! It was much easier when all I had to do for four years was follow the plans!
Click to expand...
Almost every time I didn't take Van's advice I have regretted it. If Van's says no need for a Gascolator (and they do sell them, so they could make money selling you one) that's good enough for me. :)
 
my reasoning

Yes i know two gascolators seems silly but here is my dilema.
I must have one to pass the regs in Canada.
VANS and AFP do not suggest one FWFWD due to potential leaks, vapour lock, blah blah. Fair enough. I can hook one up on a wing root but then the plumbing from both tanks have to make their way to the fuel selector then back out to the gascolator and then back. Silly and lots of plubing. Just seems one extra gascolator and some proper engineering would allow it to be low on each wing root, easy to get samples from (close to fuel drains) and is the least difficult. Cant think of a better solution. Most builders here just go one on firewall....but when AFP suggests not to.. $200 is the safety cost to do what they recommend and i am ok with that. Will tackle that in the next couple months and post some pics when figured out.
 
How about

One gascolator South of the firwall drained thru the floor?....Thats what i had on my Zodiac and it worked fine.

Just a thought.

Oh and what exactly is a legal Gascolator north of the lower 48?...Zenair (makers of the Zodiac kits) sell a nice little 2" square welded up aluminium box with two inlet ports and a drain port in the bottom.

If you just need a wide spot in the line for a legal gascolator this may be better and has tabs on it so you cab pop rivet the thing directly to the floor.

I think I might even have one spare if you want it.

Its a whole lot more compact (and cheaper) than the Vans's monster gascolator

Frank
 
I replaced the AFP filter supplied with Van's injection pump kit with an Andair gascolator. Basically same position with a drain through an inspection plate in the bottom of the fuselage. I added the inspection plate to make removing the bowl easy to check the filter etc. Looking at the Andair filter element, it appears to be about the same as the AFP filter element, and this gives me a very low point in the system to drain water.

My Mooney had an injected 540 with a gascolator behind the firewall too! Never got any water, but it did stop a little trash occasionally. See http://picasaweb.google.com/frazitl/FIFuelSystemWGascolator
 
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