Fuel line routing, carb, O-320

Michael Burbidge · #1 06-02-2013, 06:21 PM

I'm using the standard Vans firewall forward kit, and following the standard firewall forward installation using the plans from Vans.

I recently read the following post by Pierre Smith about his fuel line laying against the exhaust pipe on his RV-10. It got me thinking about my fuel line. In the post folks were opining that fuel lines should be several inches away from exhaust pipes.

http://www.vansairforce.com/communit...highlight=fuel

The standard plans from Vans and the length of the hoses that come with the firewall forward make it impossible to route the line from the pump to the carburator more than about an inch from the exhaust. I've installed the heat shield on the exhaust per plans.

Here's a couple of pictures of my install:

From these pictures it looks like one could bend the hose a little more and slip it inside the engine frame, but the bend is already pretty tight on the hose. I don't know what the minimum radius is for bends, but I'm guessing that trying to fit it inside the frame would exceed that and damage the hose.

Is this how others did their install using Vans plans and components? Does this look dangerous?

http://www.vansairforce.com/communit...highlight=fuel

I could probably get different fittings on both the carb and fuel pump and a shorter fuel hose and then route more directly, inside the engine mount.

I definitely want a safe airplane, but would like to slow down the cash outflow if possible.

Opinions?

Thanks,
Michael-

David Paule · #2 06-02-2013, 08:14 PM

While it might be possible to reroute the line further away, such as by rotating the left blue fitting counter-clockwise 30 degrees (in the bottom photo, at the engine end of the fuel line) there are two steps that can be taken as-is:

1. Make a much longer heat-shield for the exhaust.

2. Get a larger piece of firesleeve, bigger diameter, and put over the original firesleeve on the fuel line for more insulation. Double-wrap it.

Dave

TS Flightlines · #3 06-03-2013, 05:25 AM

Michael, even though a hose is firesleeved, you still want to keep it away from obvious heat sources. Even teflon hose. If the routeing doesnt make that happen, then make sure to mount the hose so it cant droop on the exhaust, or make a hose that will.
I made the hose for Pierre you referred to, and he gave it back to me for show and tell purposes. Quite enlightening. But rest assured, teflon is the way to go in my opinion, for what its worth. On his, even though the firesleeve was worn and burnt, the stainless braid was discolored, the teflon liner was not damaged at all. Remarkable.
Tom

kevinrv6 · #4 06-04-2013, 10:04 AM

I have an O-320 with carb on my RV-6A and I was able to get much more clearance between the hose and the exhaust pipe. I am using the Vetterman crossover system. I rotated the 45 degree fitting on the carb inlet much higher so the hose has a more "S" bend to it. I have about 1.5 inches of clearance to my heat shield. Also, my heat shield is much longer and I think it is farther away from the exhaust pipe. It is about 4 inches long. this set up has worked well for over 100 hours.

I have experienced vapor lock only twice and only on the ground. It will only occur when the air temp is over 90 degrees and the engine is heat soaked from sitting about 20 minutes after a flight. It will vapor lock on start up if I don't use the electric fuel pump. When I switch on the pump the pressure immediately returns to normal. As soon as the air is moving through the engine the electric pump is not needed to maintain pressure.

cjhammes · #5 06-04-2013, 11:09 AM

Michael-

I had a similar issue on my RV8 and struggled for a solution. Then realized I could simply route to the other side of the carb. Your carb my be different, but worked for me.

647jc · #6 06-04-2013, 11:40 AM

Michael,

The fuel line routing on my RV9-A, O-320 is similar to your picture. I researched at the time and was told that's why Van includes the heat shield and it should be used at the location in your picture. Anyway, I've been flying my 9 for about 4 years and no problems. You may want to send an email and picture to Vans for piece of mind. Of course you can spend additional time and money rerouting the line but if it is not a problem (according to Vans), why bother.

gasman · #7 06-04-2013, 01:41 PM

It looks like the fuel line is a little too long. I would purchase some clear tubing from ACE hardware that would slide over the male fittings, so I could try different angles with the fittings, and cut down the tubing to see if shorter works. You may need to send your line and have it shortened.

My 6A has way more clearance than in your picture. But Van's didn't sell us finished lines then. We built the size that fit our application. If he sold you a line that was too short, then it would be junk! Selling you a line a little too long..... well, you can make it fit. If you custom make yours, you will have a perfect fit for your application.

jrs14855 · #8 06-04-2013, 05:58 PM

That close to the exhaust does not meet my standards, I don't care how big the heat shield is or how many layers of fire sleeve you use. A 90 degree HOSE END at the carb with a shorter hose routed well away from the exhaust is the way to go. Straight AN fitting on the carb with the 90 degree hose end. The 90 degree hose end will flow fuel better than a 90 degree AN fitting but this is not really a concern with a fuel pump system. The fitting at the fuel pump could be oriented more towards 7-8 o clock as viewed in your pictures and the hose shortened appropriately.

airtractor8 · #9 06-04-2013, 08:23 PM

Quote:

Originally Posted by jrs14855

That close to the exhaust does not meet my standards, I don't care how big the heat shield is or how many layers of fire sleeve you use. A 90 degree HOSE END at the carb with a shorter hose routed well away from the exhaust is the way to go. Straight AN fitting on the carb with the 90 degree hose end. The 90 degree hose end will flow fuel better than a 90 degree AN fitting but this is not really a concern with a fuel pump system. The fitting at the fuel pump could be oriented more towards 7-8 o clock as viewed in your pictures and the hose shortened appropriately.

+1. My thoughts exactly.

Michael Burbidge · #10 06-14-2013, 10:31 PM

This fuel line bothered me for a few days. Finally I called up Tom at TS Flightlines and came up with a solution. Here's a few pictures. I feel a lot better about this routing.

Tom custom made the house and also carries the fuel pump fitting with the fuel line straight out and the pressure line off the Tee.

Michael-