jwx
RCTalk Rookie
Has anybody ever used a block of the foam that they use in fuel cells to help combat this? I'm thinking about getting a block and cutting it to fit.
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Lessen
Super Awesome!
Supporter
You want to put a piece of foam in the fuel tank?
jwx
RCTalk Rookie
- Thread starter
- #3
Have you ever heard of fuel cells? They have foam in them that helps combat this SAME EXACT issue in 1:1 scale race cars. Along with other issues. I was actually surprised that no one had done this when I was searching for it.
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2revo1maxx
Hardcore RCTalk User
How were you planning to get the foam in there any way? I'm not familiar with fuel cells.....I mean yeah, I know what they are, but I've never used one.
alien13
Hardcore RCTalk User
I know what he's referring to, it's a foam block, with holes in it. It's actual purpose it to prevent sloshing. In theory, it could work, and it could be squished down to fit in the filler hole, but I don't know that it would do any good.
Almost better off to find a fuel tank with the anti-slosh already built in. My Losi Speed-NT doesn't have it, but my OFNA Mutilator does. It's only flat uprights molded in the tank to prevent it from making a wave.
Personally, I don't think it's worth it, as I haven't really had a problem with it, and I have to whip tight 180 degree turns with hard braking in front of my house. Sounds like a waste.
Almost better off to find a fuel tank with the anti-slosh already built in. My Losi Speed-NT doesn't have it, but my OFNA Mutilator does. It's only flat uprights molded in the tank to prevent it from making a wave.
Personally, I don't think it's worth it, as I haven't really had a problem with it, and I have to whip tight 180 degree turns with hard braking in front of my house. Sounds like a waste.
rak12
RCTalk Addict
Supporter
I have not expereienced any lean out conditions myself due to low fuel, but maybe that as the fuel levels drops, the pressure in the tank is diminishing. more specifically, if the backpressure from the exhaust can be considered a constant it will not change much other than RPM's of the motor. however, the volume of the tank will change greatly E.G (full vs. empty tank), then the backpressure would have to be increased as the tank ran low in order to maintain a constant fuel pressure. but remember if the backpressure is constant it cannot maintain fuel pressure with changing tank conditions.
RC Addict
RCTalk VIP
Except for this: When the fuel level drops the backpressure SHOULD actually increase because you now have MORE room for said pressure due to less tank volume being used by the fuel. Less fuel=more air volume for back pressure to exist. Kinda like a boost bottle!
There goes another two cents...
There goes another two cents...
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Lessen
Super Awesome!
Supporter
Not really RCA. My hypothesis is more inline with rak. As the fuel level in the tank decreases the air level increases. As this happens there is more air to absorb the pulses and pressure from the exhaust, thus as the tank empties more pressure is absorbed (air comresses, fuel does not) and less pressure is transferred to the fuel lines and the carb. It's not really that the air in the tank just soaks up the pressure, it has to go somewhere, but I think a portion of that pressure may be lost back to the exhaust line during the voids between the pulses. When the tank is full there is minimal air to absorb and redirect so the pressure is more constant to the carb. 
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2revo1maxx
Hardcore RCTalk User
I just think that when a tank runs low, there's going to be a small delay in pressure. You'll always have the same pressure, but when it gets low on fuel there will be a small delay in the pressure from idle to full throttle. I don't think it possible to ever lose pressure without an actual leak. I have had trouble with stock t-maxx tanks because there's not much baffling in them. But as long as everything's ok an air bubble should shoot right through and have little or no effect on performance.
I just don't run 'em low anyway.:
I just don't run 'em low anyway.
:
RC Addict
RCTalk VIP
Not really RCA. My hypothesis is more inline with rak. As the fuel level in the tank decreases the air level increases. As this happens there is more air to absorb the pulses and pressure from the exhaust, thus as the tank empties more pressure is absorbed (air comresses, fuel does not) and less pressure is transferred to the fuel lines and the carb. It's not really that the air in the tank just soaks up the pressure, it has to go somewhere, but I think a portion of that pressure may be lost back to the exhaust line during the voids between the pulses. When the tank is full there is minimal air to absorb and redirect so the pressure is more constant to the carb.
But, if air DOES compress then a chamber filling with air (the tank as the fuel level drops) has MORE air to compress. More compressed air = more pressure to the tank. NO???
Lessen
Super Awesome!
Supporter
No.
An exhaust pulse is going to move x volume of air which is constant no matter where it is going.
I'll give you an example...
Take one of those skinny balloons and blow into it for 1 full second. Now, take a beach ball and blow into it for 1 full second. Which one is under more pressure?
An exhaust pulse is going to move x volume of air which is constant no matter where it is going.
I'll give you an example...
Take one of those skinny balloons and blow into it for 1 full second. Now, take a beach ball and blow into it for 1 full second. Which one is under more pressure?
2revo1maxx
Hardcore RCTalk User
Yeah the pressure is always a constant. I just think that if it idles for a few seconds with low fuel, then you take off, there will be a slight delay in getting back to max pressure. It shouldn't really affect much unless the fuel gets away from the pickup, and it always does. But that's enough rocket science for me, I got wrenchin' to do.
RC Addict
RCTalk VIP
Hmmm... OK. Fine. I am tapping out on this one!
I still wanna know how the TS is gonna get that block of foam in his tank. WITHOUT cutting it apart...
I still wanna know how the TS is gonna get that block of foam in his tank. WITHOUT cutting it apart...
jwx
RCTalk Rookie
- Thread starter
- #14
That's the easy part. Just cut it to fit and then shove it down the fill hole. It should expand right back into shape.
TS= trendsetter? That's a new one for me...
TS= trendsetter? That's a new one for me...
2revo1maxx
Hardcore RCTalk User
I think he meant thread starter.
beason
Bash, Fix, Repeat..
the only time I've heard of leaning with low fuel, is on the savage. the reason is the big notch in the tank. when the fuel is full, it has a large area for pressure to push down on. once it hits that notch (half tank) it cuts the surface area in half which gives you half of the pressure.
I just can't see a huge difference in pressure from a full tank and a 1/4 full tank. yea i understand joshes example with the balloon and the beach ball, but were talking about 30cc difference in size.. it would be a difference, but i can't see it being that big of a difference. the issue would be volume. it takes a lot more air volume to bring a tractor tire up 5lbs, then a passenger car tire.
the exhaust pressure setup is like an air compressor. it moves more volume of air per puff at lower pressure, then at high pressure. so maybe it balances out.
for sloshing, the foam may help, but remember, this isnt gas, its nitromethane and ethyl alcohol, mixed with some caster oil. it may make your foam into pudding.
For Josh ---> :duff: :duff: :duff:
I just can't see a huge difference in pressure from a full tank and a 1/4 full tank. yea i understand joshes example with the balloon and the beach ball, but were talking about 30cc difference in size.. it would be a difference, but i can't see it being that big of a difference. the issue would be volume. it takes a lot more air volume to bring a tractor tire up 5lbs, then a passenger car tire.
the exhaust pressure setup is like an air compressor. it moves more volume of air per puff at lower pressure, then at high pressure. so maybe it balances out.
for sloshing, the foam may help, but remember, this isnt gas, its nitromethane and ethyl alcohol, mixed with some caster oil. it may make your foam into pudding.
For Josh ---> :duff: :duff: :duff:
alien13
Hardcore RCTalk User
Maybe try a fuel tank from a Losi Speed-NT or Ten-T. It's a constant pressure tank, and there's something in the bottom (can't remember what it's called) that keeps it from cutting out on a rollover. I've had zero issues with fuel delivery, regardless of how I drive it. And it's been upside down long enough for me to walk two houses away to flip it, without dying.
beason
Bash, Fix, Repeat..
some tanks, (mostly helis) have a "clunk" in them. its a small piece of fuel tube with a weight on the end. when the rig turns over the weight pulls the fuel tube pickup to the fuel. i have a header tank with one in it.
2revo1maxx
Hardcore RCTalk User
I would just get a proline "runtime" tank....it's got a clunker and works well.
