Docroonie

I'm new......lets get that out right now. But I know a few things The Half tank lean situation is easy: The reason lies in the way we feed the carb... We use exhaust pressure, and so here it goes - The more fuel you have in the tank the easier it is for that pressure to push it out, as the exhaust gas has less air to compress you end up with higher tank PSI. As the fuel is drained from the vessel it gets replaced with more exhaust gas, however at some point (I believe at the "Step" in the tank) the rate at which the gasses are being pushed in cannot maintain the PSI due to the amount of space in the tank(larger space = more volume = too much exh. gasses needed to maintain tank press.)

It's a bad design. It would be best to have a uniform shape for this tank, the exhaust would have an easier time keeping up....


Let me know if I'm dumb?

Vigilante212

As far as I know your completly correct.

calvino

I also think you are right, the easiest way to combat the lean is to get a new tank, no two ways around it[]

black mamba

The real question here is why hasn't HPI fixed this yet? There's been like 8 different versions of the Savage now and the tank is still all screwed up. What's up HPI?[&:]

proptop

My Feedback: (8)

Tank design is part of it...and the height of it in relation to the needle valve.
There are several vehicles that have leaning issues as the tank empties.

One other way to avoid it would be a bladder tank...similar to what Q40 pylon racers (airplanes ) use...they are completely sealed and have a bag inside the tank that does not allow any air in with the fuel so there are no bubbles, no foam, and as the bag empties the mixture stays the same.

You still use an exhaust pressure line, and it pressurizes tha plastic (outer ) tank container and squeezes the bag inside. It works and has been used for decades in airplanes...maybe someone here can try it out and tell us if it works?

You would need a uniform shaped tank, like a round/cylindrical shape.

Another side benefit would be that the engine would stay running for as long as there is fuel in the tank...even if the vehicle was upside-down, or on it's side.

WHIP

My Feedback: (7)

What I have been doining is running a lot longer fuel line and so far its been working good. But you are right about the tank it needs to be fix or you need to run a fuel pump, thats my next project.
Keep thinking!

Parputt537

To be completely honest I do not even notice it. When I first got my truck I put on a OFNA tank before I ever cranked the truck after reading all this half tank lean talk. Recently I go really tired of the short run times and put my stock tank back on. If the motor does lean at half tank I can not tell. I do run a little on the rich side to start with, but for the general bashing and running around I do I honestly do not notice any lean out at half tank.

Danju

nope..i believe there is another way...it has something to do with how you route your fuel tubing and also the pressure tubing. there was this guy at the traxxas forums who put a small fuel filter on the pressure line, and then put a bigger filter between the engine and tank. i think with the bigger filter, you have to slant it so that its slanting toward the carb....its something like this and you could search it yourself....ive never tried it though...but atleast i know that changing to certain tanks will almost eliminate tank lean.

Docroonie

I've had my X RTR for like a week, and since day one I've had the issue...I'm not sure which route i'm gonna take on it... I have concerns about the perry pump, in that is there a fuel return for excess unused fuel? Or does it just presurize it and force feed you???

jbb

well iv'e been thinking and a little browsing. i think this will solve the problem. if it does what it says it will. the hyper valve from RB [link]http://www.rbinnovations.com/catalog/product_info.php/cPath/25/products_id/48?osCsid=f13de502560fe692abfb1b6f767f3fed[/link]

also heres how it works [link]http://www.rbinnovations.com/hypervalve%20simulation2.swf[/link]

Docroonie

How many RPM's do these motors turn ? between 20k and 30k? thats between 330 rps and 500 rps. (revolutions per second) I think that the amount of time spent without exhaust gas flow is so minute that it wouldn't work???? Maybe that millisecond of no pressure makes a difference. so far i dont see the best way to deal with this.