Float Chamber

[Olly]

I was reading another post and they mentioned float chambers which got me thinking Would this work with a tank higher than the carb? I know you guys in Europe use float chambers a lot. If it would work, where would I get one for a scale boat?

Thanks

Olly

 

[Norm Doerr]

I was reading another post and they mentioned float chambers which got me thinking   Would this work with a tank higher than the carb? I know you guys in Europe use float chambers a lot. If it would work, where would I get one for a scale boat?
Thanks

Olly

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I have a few that Marty Davis bought to test on the dyno. From the data I am seeing they did not do that much good. BUT that does not mean we could not improve them. I don't know how exstensive they got into it ..but I may revisit the idea. If we could dial in fuel pressure the possibilities are limitless

 

[TimD]

Norm,

I may be wrong but I believe the benefits of the float chamber are more for reliability and consistency, and not outright performance gains as such that you would see on a dyno.

I am rather curious to know more about them and the effect that they have on fuel pressure during throttle transitions and during tight turns. Also, what physical size they would need to be to become effective.

Tim.

 

[Bart Drieghe]

sizes :

http://www.prestwich.ndirect.co.uk/fsrv/trimtabsfloats.htm

I've seen smaller but they aren't easy when using , only a little bit of time to put the boat into the lake .

fuel pressure during throttle transitions

Thats just the thing , there's no difference , the float takes care of the difference in pressure .

We race 30 mins , pressure coming from the tank is way diff then the pressure coming from the tank after 20 mins

Read this , it might answer your questions :

http://p197.ezboard.com/frcracingboatsfrm1...picID=385.topic

Regards ,

Bart

 

[Don Ferrette]

We race 30 mins , pressure coming from the tank is way diff then the pressure coming from the tank after 20 mins

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30 minutes, how much fuel do you carry???? :blink: :blink:

 

[TimD]

Don,

Just imagine the fuel needed to run your twin for 30 minutes :lol: :lol:

Thanks Bart!

Unfortunately the size of those float chambers are too big to fit in my riggers. Particularly the 21 boat!

Tim.

 

[Nigtmare]

We race 30 mins , pressure coming from the tank is way diff then the pressure coming from the tank after 20 mins

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30 minutes, how much fuel do you carry???? :blink: :blink:

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They turn left all the time so they get better gas millage :lol: :lol: :lol:

 

[Don Ferrette]

Don,Just imagine the fuel needed to run your twin for 30 minutes  :lol:   :lol:

Tim.

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Geez, it would be a floating fuel tank. Let's see, one run is 3 minutes max. on about 36oz. of fuel...........

 

[not2bright]

**** thats gotta be expensive

 

[TimD]

Getting back on track,

My belief that this device in part takes us closer to a constant fuel pressure than where we are currently, which could be part of the way to being able to "dial in" a pressure rate. I would imagine that by using a float, the stinger diameter on the pipes would make differences to the performance of the pipe without the different fuel pressure rate at the carb masking the results.

Is this a fair assumption?

Also, does a float chamber work with a discharge outlet type of carb as fitted to the MAC's or only on carbs that use a needle valve assembly as the fuel outlet such as an OS carb?

 

[Brian MAhoney]

Tim

Your assumption is correct, this is the main advantage of the float chamber. Also useful with multi tank setups, helps get all the fuel.

Can't see any problem with the different carb types if the carb has suffiucient fuel draw. Only adjustment is to changed the height of the chamber to get more or less gravity feed, can lead to flooding etc if too high.

The only problem I have ever had with the float chambers is locating them in the boat. On a rigger this would need to be dealt with at the design stage.

Brian

 

[Bart Drieghe]

Placing it is indeed sometimes a prob , for the rest , none ( in usage )

@ Don and others :

30 mins race :

3.5 : 1.8 liter

7.5 : 2.4 - 2.6 liter

15 : 3.4 - 3.6 liter

( and for the record , im using 20% nitro in 7.5 & 15 , i don't race 3.5 )

gr,

Bart

 

[Ian Folkson]

My Homebuilt float I have used for 10 years in my 3.5 boats and the tank system it is filled from.

I used it in 1994 to win the Naviga championships it enables the motor to suck the fuel from a constant supply close to the motor the needle setting remains the same the whole 30 minutes. I can use full pressure into my main tanks and because the cut off valve in the float is pushed with a lever the force will cut off the fuel when full. the only time I would not use a float is when I let kids run the boats and they want to go at a slow speed then there is not enough pressure to fill the float chamber they are really used for racing.

Float

http://www.iansboats.co.uk/float%20Ian.htm

Float in boat

http://www.iansboats.co.uk/DSC3.JPG

Tanks

http://www.iansboats.co.uk/DSC4.JPG

Ian Folkson

 

[DaveMarles]

To answer the first post on this. A float chamber would work with a fuel tank that is higher than the carb. The fuel tank position can be anywhere in the boat because the carb always has the same fuel pressure applied to it depending on the fuel height in the float chamber. The float chamber is normally fitted very close to the carb and preferably in front of it. My first float chambers for 3.5 and 7.5 were the size of a film canister. This means we can fit the fuel tank close to the CG so that CG changes little during the race.

Tim is corrct, if you used a float chamber then stinger size could be adjusted for max power, not just to aid throttling.

Dave

 

[Mike Broad]

The problem I have found using a float chamber with a MAC 21 in my mono, is that I was unable to supply enough fuel to the motor. The carb seems to be too large to suck the fuel. I suppose you could put a smaller carb on the motor to increase the suck but it would probably reduce the engine's power.

Mike Broad

 

[EatMyShortsRacing]

Norm,I may be wrong but I believe the benefits of the float chamber are more for reliability and consistency, and not outright performance gains as such that you would see on a dyno.

I am rather curious to know more about them and the effect that they have on fuel pressure during throttle transitions and during tight turns. Also, what physical size they would need to be to become effective.

Tim.

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Tim,

I went through this when trying to get my last 90 multiboat going. The major drama is that the long fuel lines and large fuel tanks mean there is usually a lag in pressure equalisation in the whole fuel system. Best example is when you open the throttle you get the right mixture initially but then the motor will go rich as the added pressure from the pipe starts forcing more fuel through. So the boat slows, pressure in the fuel system reduces and the motor leans out again....

The resultant effect is a boat that "pig roots"

Running without some sort of pressure feed doesnt work in a multiboat because the fuel level varies so much during a race. The float chamber is the only way to get a decent mixture in a big multiboat.