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2nd Fuel tank above rear shocks

3K views 11 replies 7 participants last post by  Peachey 
#1 · (Edited)
so im getting a picco motor, and im expecting run times will drop compared to the revo...

so my thoughts are that i get another tank, say 70-150cc max and mount it in place of the exhaust where the factory one sits (side pipe going on).

thinking this tank, anyone know what size it is and the dimensions?
http://www.amainhobbies.com/product...1077/products_id/34967/n/Losi-Fuel-Tank-8T-20

now i havent read too much into the leaning issue when the tank is empty, but scrolled through a thread and read something that a 2nd tank with or without a clunk dramatically reduces the mid tank lean?

any doc's about this tank leaning out issue and or photo of people that have mounted a 2nd tank would be great. also will the clunk be usefully with the picco? im expecting it to flip on its roof a lot as the stock 3.3 does it enough. how often does the clunk need to be replaced and is it just normal fuel line in the tank? i read that broken fuel line on the clunk causes a fair few tuning problems so im keen to stay away from that.
 
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#2 ·
There are some major pro's and cons with this idea.

Pro's

Longer run time
Reduced mid tank lean (if set up correctly)

Con's

More fuel line/connections to get pressure leaks
Extra weight at the rear of the truck where it is NOT needed
Two tank lids that may leak
Getting the pressure from the exhaust split to both tanks correctly (one line longer = more constriction)
Getting the fuel to flow from tank to tank
Tuning Issues due to pressure leaks, different exhaust pressures needed to move fuel.

IMO its to much stuffing around, why not swing past every 5-8 mins if your bashing and top the tank up, less mess, less stress an less stuffing around
 
#3 ·
If you intend to run a second tank inline(also known as a header tank), you will need to ensure it is sealed.

The header tank keeps fuel at a more constant pressure, the one thing that is necessary, the tank needs to be mounted at a point where it doesnt cause lean out (too low) or flooding (too high.
Using the height of the stock tank maidline will be helpful in determing the placement of the second tank.

Re-fueling does become a small PITA as you need to force feed the fuel through to the second tank via a fuel line (because the tank is sealed to maintain pressure during use). Having a filler cap on the tank exposes you to air leaks, which translates to poor running, and can make tuning an issue also.

When running with a header tank, it is always advisable to never allow the header to become completely empty, opting to shut the truck down once the fuel level drops to a few millimeters in the second tank.

A clunk will help if you spend a lot of time on the roof, as it will fall to the bottom of the tank courtesy of gravity no mater which way up the truck is.

Watch for air locks, (air trapped between the first and second tank) as this can be a real PITA. The primary tank will be easy to fill through the normal filler, but when you force feed the header through the fuel line from the carb, it is common to get an air bubble between the tanks, I found in the past, the easiest way to fill both tanks was to force feed both from the carb fuel line with a squeeze bottle, the fuel forces any air out of the line after the header is full and as it fills the primary tank. The excess air should escape through the exhaust pressure line.

Post up som pickies once your done fitting it all up.
 
#4 ·
My only thought is, why would you bother, its not like refuling takes all that much time to do and it is something IC racers do all the time, pull into pits, pit guy refuels and sends you back out to the race. I would just give yourself access to the fuel cap through your body shell and when you get close to empty, drive the car to your feet, refuel and go, no stopping no nothing and you and endless run time or until your fuel bottle is empty.
 
#5 ·
The header tank does'nt need to be as big as the primary tank as well.

That's 2c worth.
 
#6 ·
Agreed, I used a 100ml plane tank on the savage, and all that was for was too get rid of the bottom of the tank lean out that used to occur.

Cant use it when you are racing onyway, so it is only good for bashing
 
#7 ·
yeh towie i was thinking a small tank just to get rid of the leaning issue. the extra fuel is just a plus. anyone have any links to some thin tanks that can sit above the shocks. dont want it sitting too high.... and if i can get a sealed tank would that be better? just a line in and out with no filler cap?
 
#9 ·
simple, remove a line from the tank and fill using a syringe or something similar. it takes a little more time to fill, but if it saves the leaning issues ;)
 
#10 ·
Look to the heli and plank world, they use a "t" piece to refuel with. That with a crank pump your back in buisiness. :D
 
#11 ·
If yoou grab a fuel bottle with a small nipple on the end, after filling the main tank you can easily fuel the header tank through the line until the air is all out of the main fuel line...all easily done and with not too much fuss.

The main thing to remember is to keep the header tank at the same level as the carby to prevent leaning or rich running...keep the upper level of the tank no higher than the top of the main tank, and no lower than about 1/3 up from the bottom of the tank, and dont run as excessive amount of fuel linetry to keep the lines reasonably short but not so that they are pulling or about to pop off
 
#12 ·
When u initially fill the main tank and push/blow the fuel into the header tank it doesn't actually loose any fuel till the main tank is empty. So for the days bashing u only have to fill the main tank as per normal. Unless u let the header tank run empty then just fill the main tank, grab the exhaust pressure line. Give it a blow and it will fill the header tank
 
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