cigar hose regarding vegetable oil
 

I was looking at this website (http://greasebenz.com/node/9) for vegetable oil conversion and saw "cigar hose" in the return of this setup (see image of schematic). What exactly is the purpose of cigar hose and why is it specified as opposed to properly sized fuel line?

Thanks!

I've read and have been told that the cigar hose is shaped as such and used to dampen vibrations from the opposing hard lines.

Would others concur?

Yes it is to dampen fuel pulsations in the return fuel. On most cars you can't tell a difference if you put on a straight hose. I couldn't on my 240. My wagon however I could hear an audible noise when I put a straight hose on. Put the cigar hose back on and it went away.

Some cars really dislike it missing others seem to tollerate it well.This is besides the noise component. I suspect your concern is the hoses rubber composition.

If your base fuel pump pressure is not normal but very substandard there is no interaction to speak of. The fuel will not flow into the return line from the top of the injection pump. Although there will still be the overflow from the small injector return lines.

Thanks for all the responses!

I made the (incorrect I guess) assumption that the hose was a synthetic material, like all of the additional fuel line I have bought for my conversion. Yes, rubber is definitely a concern. Thanks for pointing this out.

My question was regarding the importance of the shape of the line. The first few responses pointed out reduction of vibrations as being the purpose of the cigar hose. Would vibration in the return line be negligible if I made that section of hose out of typical flexible fuel line and make the length of the line long enough so that it has some decent bend to it, or do you all feel that the cigar hose has its irreplaceable purpose, and if my car wants it, it's gonna let me know, such as how BioDiesel300TD's wagon did?

Unless you can come up with a stretchy synthetic material you will just have to try it. Symptomaticlly you should watch if the car runs better with say an eighth of a tank of fuel versus 1/2 tank. If there is a difference you will have to reinstate the proper hose or design something. Again you will not know until you try.

I am gessing it has about a 5/16 inch inside dameter.

You could use that much stiffer Fuel Injection type hose that has a blue interior lining that is said to be Viton. It is thicker and stiffer than regular Fuel Hose and might do the same job as the Cigar Hose due to it being thicker and stiffer.

There is a thread somewhere with the GoodYear number of the Hose.

I am not sure if this is it or not:
SAE 30R9, recommended for gasoline, ethanol, sour gas,diesel and BIODIESEL fuels. It's FKM fluoroelastomer tube provides excellent chemical resistance and exceptional permeation properties to meet the latest EPA and CARB emmissions requirements.

http://www.goodyearep.com/BuLandingPage.aspx?id=17700&terms=fuel+injection+hose

I have read the regular autpart stores and NAPA have it.

Putting on a straight hose will not hurt anything, you may just notice a little pulsating noise when cold. That is when my wagon made the most noise, once it warmed up the noise went a way some but I could still hear it.
If you want to try a stretchy hose I would try some solid viton. You'll want 5/16" ID hose. Solid viton is pretty soft and stretchy, but rather spending. The SAE30R9 hose is viton lined, not stretchy at all, but much cheaper. Both work well and will last for many years.

Use VO compatible hose, but loop it. The extra length will achieve the same thing, especially if you loop it upwards, so the center point is higher than the inlet and outlet ends. This will create a shifting air pocket that will prevent vibrations from traveling.