Vented tank.... Whats the difference?

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voo2doo

voo2doo

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Hiya all,Can anyone tell me the difference between a vented tank and a standard? I've noticed when I have ran my Marders for a bit and open the filler cap theres a release of gas or is the tank sucking in air.....? If there is a vacum in the tank won't this stop fuel delivery? and thus making a vented tank being the better out of the two.
Also on the same subject,what do you guys run in the way of fuel? i.e RON (octane content).
Thanks (or should I say Tanks) in advance.:blush:
J.
 
When it comes to RON and Octane don't worry about it. Run the best you can afford.

The tank caps on the FG's are a vented type but, your right they don't vent as well as a vented cap or tube vented tank.

When the fuel expands the tank it pressurizes. The pressure pushes the fuel into the carb and reduces the amount of fuel that can re-enter the tank from the carb. It changes your settings and your idle.:(

There are two things that can be done to non vented tanks. One is you can buy some rubber grommets, drill a hole in the tank and run the hose to the rear for venting. Two you can buy a vented cap that has a hose attached and run it to the rear of the model.
I did the second one - Cap - for my MT which always pressurized when it was hot out.
 
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Ah,I see,but you said(Bigger) that the cap pressurises the tank so as to push the fuel into the carb.So if I use a vented cap or tank there would be no pressure in the tank thus no fuel delivery? As you probably already know,nitro's run the pressure off their pipes so is it feasable to run a line from the pipe to the tank to get an even pressure?
Thanks
J.
 
The head of the motor has a pressure hole that drives a small fuel pump in the carb... So the tapped exhaust is not needed with a mechanical fuel pump..

The cap does not pressurize the tank, the stock FG caps are "Supposed" to vent, but they never do.. So, there is pressure built up in the tank from heat expansion and from the fuel sloshing around.

Big difference from nitro!

Trip..
 
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Here is a vented alloy cap. It looks plastic but its not its shinny aluminum. I just bought one of these from ebay for a steel.
You can make your FG cap just like it with a nipple on the cap and a piece of tygon fuel line from a chainsaw/lawn mower shop.
CNRgascap.webp
 
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