Fuel tank question

[JGRC]

Hi guys,

I have a question about my 1:8 scale nitro rc cars fuel tank : When I run it, should the nitro in the fuel tank start bubbling???

The car is a Hobao Dominator and I am using a cold glow plug with HPI power fuel 20%

Cheers,

Jgil

[Nitroholic]

The short answer is NO!

 

The slightly longer answer might help a bit more though!

 

The fuel tank on a nitro uses the exhaust gas to pressurise it, which pushes fuel up the feed pipe to the carb. This should mean a steady fuel flow will occur once you start the engine...but also explains why you have to prime the motor with fuel or it won;t start.

 

Now...

 

First thing I would check is that your fuel lines are the right way round.... and that the pressure feed isn't under the fuel level. Also check the pipes are firmly attached, as a split or leak may be letting air back into the tank where it shouldn't. Ultimately...this will cause a lean mix and overheating.

 

The other potential cause is heat. The volatile elements in nitro fuel can boil off under excess heat. Check your exhaust isn't too close to the tank. If your motor is running hot, you can boil the fuel in the carb when it's stopped....and this might be pushing vapour back up the fuel line into the tank. It's an indication of a lean mix and the engine getting a bit too hot if that is happening.

[JGRC]

Thanks Nitroholic I'll check on those points ASAP. I think there could be a split somewhere because I sometimes find air bubbles in the fuel line. Cheers, Jgil

Edited December 16, 2013 by JGRC

[jordanp]

air bubbles occur naturally when priming m8 they tell you to pump or blow down your exuast line into the tank till theres no air bubbles

[J.K]

I would only prime until the fuel reaches the carb, otherwise you risk flooding the engine.

[jordanp]

in the fuel line towards the carb

its the air thats in the line allready

[Nitroholic]

He's talking about bubbles in the fuel tank while running...not bubbles in the fuel line when the engine isn't, unless I am reading it wrong.

[J.K]

Aah gotcha, I think you're right...apologies!

The fuel tanks on my nitros all sit on rubber o-rings, maybe check their condition/existence as I believe they're there to reduce vibration and fuel foaming?

Edited December 17, 2013 by James1986

[JGRC]

I have found something which might have contributed to my probs: the filter inside the fuel tank was completely clogged up so it was restricting the fuel flow so it might have produced air bubbles (don't ask me how I came up with that theory, I just did ). The fuel line hasn't got any holes in (thankfully). I'm gonna get a new fuel tank and see where that gets me... Cheers, Jgil

Edited December 17, 2013 by JGRC

[JGRC]

He's talking about bubbles in the fuel tank while running...not bubbles in the fuel line when the engine isn't, unless I am reading it wrong.

You did read it right

Cheers,

Jgil

[Nitroholic]

A badly clogged fuel filter won;t help with running at all....and might be the source of the problem. Cleaning it out would be a good start

[JGRC]

Only prob is I can't get the filter out of the fuel tank as it is inside the tank itself so I'm gonna get another one

Cheers,

Jgil

[Honeybadger]

Could you spray brake cleaner in there to clean it?

[JGRC]

I don't know,probably, but I'm getting a new tank anyway as there is dirt in the tank.

Cheers,

Jgil

[ms_sjo]

There's a lot of turbulence inside the fuel tank under high load, it's perfectly normal.

[fatboyneil]

What normal go have a word with yourself in no way is it perfectly normal when setting up a fuel tank it should sit on rubber o-rings and be slightly loose so when its bouncing around you don't get it foaming up thus getting bubbles in the fuel.

Now with the op's problem yes clogged filter won't help but you can get it out look on you tube or google it it's not a hard job to do if this doesn't stop the problem it's either an air leak or your pressure line is too short but I see nitroholic is here helping already he has better ways of explaining things than I do

[ms_sjo]

What normal go have a word with yourself in no way is it perfectly normal when setting up a fuel tank it should sit on rubber o-rings and be slightly loose so when its bouncing around you don't get it foaming up thus getting bubbles in the fuel.

Now with the op's problem yes clogged filter won't help but you can get it out look on you tube or google it it's not a hard job to do if this doesn't stop the problem it's either an air leak or your pressure line is too short but I see nitroholic is here helping already he has better ways of explaining things than I do

 

The turbulence is caused by the pressure waves from the tuned pipe. I can take a video of an engine on my dyno if you want to demonstrate this?

[JGRC]

Thanks for the help guys, I have already taken the filter out (I still gave the filter on the fuel line though) but haven't tested it yet. I'll let you know how it goes

Cheers,

Jgil

[jordanp]

hope its sorted

[JGRC]

Thanks mate I'll update you ASAP.

Cheers,

Jgil