Before my airplane hobby I was a hot-rodder and one of the early adopters of EFI on a Chevy powered Datsun Z. I learned the hard way that EFI pumps dont like to draw fuel over great distances. On the RV-4 the pumps are just inside the fuselage at the wingroot. The only possible way to make the path shorter would be to put them between the wing and fuselage and I looked at doing that but couldnt make the plumbing work. When I switch on the pump, I see fuel pressure instantly on the gauge. I can hear the pump prime and pick up fuel - its a fraction of a second.

 

I use filters between the tank and pumps that have a sintered bronze element. They are rated @ 300 GPH and can be disassembled for cleaning. The first time I found contamination each filter contained about 1/8 tsp of junk in it.

 

Thanks for the idea about the hose possibly being affected and returned to the tank Mark. Earls isnt real specific about what the hose is made of. May be time to do some testing.

 

Al, I dont routinely test but every sample I have tested from various gas stations around the county has had ethanol in it. I found a number of websites that indicated there is NO MTBE in CA gas anymore and that all gas sold here contains a minimum of approx 6% ethanol as an oxygenate.

 

Mike

----- Original Message -----

From: Tracy Crook

To: Rotary motors in aircraft

Sent: Friday, February 27, 2009 7:43 AM

Subject: [FlyRotary] Re: ethanol

FWIW,
Possible source of the 'black flakes'  is fuel pump impeller pieces.  When these pumps run dry their lifetime is measured in minutes.  The impellers will abraid and shed small pieces.  Insure that the path from tank to pump is down hill or at least level with the fuel and there are no restrictive filters or other obstacles in this path.  I don't even like to see boost pumps there because there is a significant drop in pressure across their check valves.

Tracy

On Thu, Feb 26, 2009 at 10:59 PM, Mike Wills <rv-4mike@cox.net> wrote:

Well things seem a little slow today so how about re-opening a can of worms? We had a brief discussion a while back regarding ethanol in fuel. Frankly at the time I didnt know much about the subject but have been reading a little since I'm burning auto fuel.

 

At the time I think it was Al G. who said so far he hasnt found any auto fuel with ethanol in it. If I got that wrong I apologize. So far I havent found any auto fuel that DOESNT. As far as I can tell from my reading ALL auto fuel in CA has at least 6% and most is at 10% now.

 

Looks like the concerns are:

1) Vapor lock

2) Potential corrosion of aluminum components in the fuel system.

3) Deterioration of rubber (and other?) components in the fuel system.

4) Water.

5) Dislodging contaminants from previously used fuels.

 

I believe (hope?) the vapor lock issues to be a non-problem with our EFI systems. The potential corrosion issues seem to be overstated for ethanol, clearly a problem with methanol. All the hose in my airplane is Earls Perform-O-Flex which according to their website is "synthetic rubber". I assume they mean neoprene which I gather is ethanol safe. I assume the injectors themselves are safe? I thought Pro-Seal is also supposed to be ethanol safe. My airplane is new so there should be no issue with dislodged contaminants.

 

This leaves the issue of ethanol's affinity for water. Other than always keeping the tanks full to minimize airspace in the tank and condensation any ideas on how to deal with this other than hoping it doesnt happen?

 

I bring this subject up because for the second time since I've started flying I've found a little contamination during my pre-flight when sumping the tanks. Each fuel sample has a few ground pepper sized black flakes in it. Whatever it is it crumbles to powder between the fingers. The first time I completely drained the tanks and pulled the fuel filters and cleaned them. When I refilled the tanks I used a Mr. Funnel to make sure nothing bad got added. So whatever this is, its residual junk in the tanks from when they were built. Or its something (like ethanol) attacking the Pro Seal.

 

Any comments on ethanol in general or my fuel contamination issue are welcome.

 

Mike Wills

RV-4 N144MW