Dual Nitro fuel tanks

[trinbagonet]

I am thinking of putting in a second fuel tank into my Hobao hyper 7 TQ2
Has anyone else done something similar?
Any advice?

 

[tudordewolf]

I've seen it done, both as pictured with the fuel tanks inline, and in parallel with Y-connectors. I think inline would affect your tuning by delaying the response between exhaust pressure and fuel flow; it'd be like having 40 feet of tubing between the exhaust and the fuel tank.

I've also seen someone replace the fuel tank with a 500ml airplane tank, that would run forever...

For the most part, I feel like nitro vehicles have fuel tanks appropriate to their consumption. I'm usually checking on the level 2-3 times a tank anyway to avoid running it dry. (just bashing, not racing, not that you'd be able to race a dual-tank setup anyway)

If the tank were larger, I could go longer before I have to refill it, but I'd probably check it just as often. If it were running for 20+ minutes per tank, it would be very difficult to estimate/keep track of where you are in the tank and approximate when you need to top up.

Only my 1/16ths feel limited by their fuel tanks, I basically get a pass in each direction before I need to refill their little 45cc tanks.

 

[Lukedavis]

is there a way to put a bigger fuel tank on the traxxas nitro rustler?

 

[trinbagonet]

I've seen it done, both as pictured with the fuel tanks inline, and in parallel with Y-connectors. I think inline would affect your tuning by delaying the response between exhaust pressure and fuel flow; it'd be like having 40 feet of tubing between the exhaust and the fuel tank.

I've also seen someone replace the fuel tank with a 500ml airplane tank, that would run forever...

For the most part, I feel like nitro vehicles have fuel tanks appropriate to their consumption. I'm usually checking on the level 2-3 times a tank anyway to avoid running it dry. (just bashing, not racing, not that you'd be able to race a dual-tank setup anyway)

If the tank were larger, I could go longer before I have to refill it, but I'd probably check it just as often. If it were running for 20+ minutes per tank, it would be very difficult to estimate/keep track of where you are in the tank and approximate when you need to top up.

Only my 1/16ths feel limited by their fuel tanks, I basically get a pass in each direction before I need to refill their little 45cc tanks.

Hi,
thanks for your response .. I am not too familiar with all the technical details/science on RC nitro cars.. I am planning to put in a .28 engine into the car.. would this make a difference to the pressurisation of the tanks? Would it be possible to explain the reason for the delay in the turning response a bit more..

 

[tudordewolf]

Hi,
thanks for your response .. I am not too familiar with all the technical details/science on RC nitro cars.. I am planning to put in a .28 engine into the car.. would this make a difference to the pressurisation of the tanks? Would it be possible to explain the reason for the delay in the turning response a bit more..

Nitros get fuel pressure by tapping the exhaust and running a line into the fuel tank. This has the advantage of automatically matching fuel pressure to desired fuel flow - when you open the throttle up, exhaust pressure rises, so fuel pressure does as well. The engine "feeds" itself when it needs it, a very elegant solution really.

This can lead to a condition commonly known as "half tank lean", which is where a nitro starts to run leaner towards the end of a tank. Not because it's running low, but because the volume of empty space in the tank acts like a dampener to the pressure changes from the exhaust. If you have an entire second tank in your system, that delay will be amplified because you'll have the exhaust going through a narrow tube into the emptied tank, then another narrow tube going to the tank with fuel still in it.

On the other hand, some people get around half-tank lean by deliberately running extra distance in the line between their exhaust pipe and fuel tank so that the tune they apply at a full tank is more like one with a little delay already, so you might be able to get around this by tuning it with only the "primary" fuel tank filled.

This also means leaks in the fuel tank cap or tubing can cause the engine to run lean by depriving it of fuel pressure.

Big engines have fuel pumps, small gas engines develop enough suction through the venturi effect to not need fuel pressure, and/or have the tank mounted above the carb so it's gravity-fed.