best solution to half tank lean

[likeshittoff]

i know this has been covered a million times in different posts on the net, and before anyone says lipo, i want to stick to nitro

i recently went into my model shop to buy an altrnative tank to try and the guy there tried to sell me a standard savage tank saying the mid tank lean problem had been cured with their new design, which looked exactly like the standard tank with the shelf half way down

i've had header tanks, and shortened fuel lines, one way valves in pressure lines etc and dont really want to go down the mid tank mod route ideally but having only run the k5.9 which is known for its issues anyway i never really found a good solution

any input would be much appreciated

 

[Greywolf74]

I have no idea why this works for mid tank lean but it does seem to.

[ame="http://www.youtube.com/watch?v=jF-VJn2eOGU"]Mid Tank Lean, FIlters, and Fuel Line Loops- A proper setup - YouTube[/ame]

 

[lesclaypool]

The extra loops won't really help for MTL. All it really does is give you more run time when you flip upside down. The Savage is plagued with a fuel tank that half of it is lower than the carb inlet. So the top half of the tank, you have gravity feeding, as well as fuel pressure(exhaust) of course. But when you get down to below the half tank point, the engine relies on 100% fuel/exhaust pressure.

Warm up your engine and tune it at a half tank, or slightly below. When you fuel up you'll be a hair rich, but not pig rich at all. So when you get down below half tank you'll be at a perfect tune.

I honestly think guys waaay over think this with Savages. It's really not a big deal at all, seeing as we are bashing with them, and not required to pull every last second out of a tank trying to shave off lap times. I've ran my Savages with stock tanks for ever and a day, and don't see a 'need' to change them(although some of the conversions look mighty cool). The only reason I could ever see myself doing a mid tank mod would be for weight distribution, but then again - when you're bashing, jumping and doing hillclimbs - who really cares.

 

[rcaddic]

I installed the OFNA ULTRA LX2 150CC on my XL and that took care of it , having a tank that don't have a shelf in it will take out a lot of your MTL problems , I allso put fuel tank sponge in the tank

 

[bifft it]

i dunno, i just tune at half tank. big blocks suck enough gas and i have to travel to bash and i find it a headache to fill more often with the smaller tanks. I'm really surprised that one of the many RC geniuses havent come up with a way to build a bigger, better, more efficient tank.
maybe one of these days i will weld one together out of aluminum, that will hold a quart..........lol.

 

[Greywolf74]

When my friend Lee added a big fuel loop to his savage it did seem to cut down on his MTL problem. I wont say it did away with the problem but he said it did seem to help. IDK...

I dont think the position of the fuel tank has anything to do with it, 2/3 of the fuel tank on my XXL is below the carb inlet and it doesn't have that problem. Maybe the fuel tank its self is poorly designed since RCaddict solved the problem by using a different fuel tank?

 

[lesclaypool]

The tank design might certainly have something to do with it. But what I do know is, in my experience on my 2 Savages, the amount of fuel tube makes no difference. At one point I experimented with adding more and more tube until I got up to almost 2' of extra tubing lol. The MTL never got better; in fact it eventually got worse, as the added loops create so much pressure drop that it started to cause it to run lean - even with a full tank.

Again - IMHO its just waaaaay over thought. With a good performance tune at half tank, the difference at full tank is negligible.

 

[bifft it]

i used a stock tank on my FLM build. mounted it up where the reciever box is. tank is now 3/4 above carb inlet, and its also slightly tilted to the outlet line to maybe solve the "sloshing" problem when you stop and go. i dont believe there is much of a baffold in a stock tank.
what HPI should have done was mounted fuel tank to a plate where the electronics box is(tank would not have been stepped or very deep, but could have been wide and long) and mounted electronics where fuel tank is(could have used a smaller box

 

[likeshittoff]

hi all, thanks for the replies, this forum is amazing

i had tried a few mods including the header tank which seemed ok for a while but i think the more kit you add the more there is to go wrong. my xl would suffer really badly so that if i tuned at a 3/4 + tank the temps would be 220 f and then rocket to 300+ at 1/4 tank, which was a big problem. it had no power with a full tank then cremate itself at low fuel

i tried having the fuel / pressure pipes really short and even turned the inlet around on the carb to face the tank, i also included a one way valve in the pressure line but this eventually blocked and then caused a worse problem but seemed to help for a while

i also sealed my engine to prevent any air leaks as an added precaution

i have just bought an LRP zr.32 and i dont want to cook it so i have ordered a hyper 7 tank to try which doesn't have the shelf, but like the look of the ofna tank rcaddic, and looks like a good size. I've not heard of fuel tank sponge before though so will have a look into that too

i have also ordered a fuel pressure stabiliser off fleabay to go in the exhaust line which might do something but i am hoping the new tank will solve it anyway.

the guy in the local model shop finished off by saying it was my leaky 5.9 engine so he didnt really help much

thanks again for all the replies, i'll keep you all posted

 

[DarthRacer]

What I always did for my 'ol SS was to have about 8 inches of fuel line with a large filter, then tune the tank at half full. Don't spend too much time and money on the problem. :thumbup: