UK Karting - Notice Board (General Karting) : Simple answer

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Simple answer
Posted by 'itpro' on 25 Mar 2011 @ 17:06

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itproJoined: August 2001
Total Posts: 6
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The reason is simple.

Karts work best with 'clunk tanks'. That's the sort where the fuel is pulled through a dangly, floppy pipe with a heavy weight on the end. For example, as the kart slows under braking, the fuel sloshes forward.... and so does the weight which still remains under the fuel. The same happens under high acceleration and cornering.

Just about the only way you can make a 'clunk' work for us is to dangle it from the top. This wouldn't work well if we needed to run while upside down...... luckily, once we are upside down... we'd rather the engine ran out of fuel quite quickly....

A 'clunk' from a BOTTOM feed would work only work half as well BUT would work nicely, upside down........

The second part is that there is often confusion in the minds of karters about the fuel feed. Many people will tell you that the fuel pump has to work harder pulling the fuel UP hill to the top of the tank than from a bottom feed. This MAY be true when the pipe is empty butis plain WRONG once the fuel is 'in' the pipe. The 'effort' of pulling the fuel 'up' is ALL done by the weight of the fuel dropping down again, outside the tank. This is done by 'syphonic' action!

Bottom feed, unless it has spectacularly clever valves systemn from multiple feeds.... is a DISASTER!

When you corner or brake at (for example) 1g, the fuel sits in your fuel tank at 45 degrees! If you start hitting PEAK braking/cornering of 3 or so G, then the fuel is up at 72 degrees!

To see this, imagine a brake braking smoothly at 1G on a kart with a bottom feed at the REAR of the tank. Once the fuel gets low, the fuel will expose the feed to fresh air as all the fuel will be 'up the front'.

With a clunk tank, the fuel will STILL be 'up the front'....... but so will the 'clunk'.....

Forget bottom feed, it's HOPELESS!

Ian

Message Thread:

Why are fuel tanks top outlet ? by 'hetherip' (25 Mar 2011 @ 13:32)

Re: Why are fuel tanks top outlet ? by 'BrianP' (25 Mar 2011 @ 14:02)

Re: Why are fuel tanks top outlet ? by 'buzzinrussell' (25 Mar 2011 @ 14:34)

buzzinrussell by 'Bod' (25 Mar 2011 @ 15:11)

Re: bod by 'buzzinrussell' (28 Mar 2011 @ 14:02)

Re: bod by 'Bod' (28 Mar 2011 @ 15:26)

Re: Why are fuel tanks top outlet ? by 'BrianP' (25 Mar 2011 @ 15:51)

Re: Why are fuel tanks top outlet ? by 'SimonS' (25 Mar 2011 @ 15:56)

Simple answer by 'itpro' << You are here!

Re: Simple answer by 'TKM177' (25 Mar 2011 @ 17:12)

Re: Simple answer by 'hetherip' (25 Mar 2011 @ 17:38)

Re: Simple answer by 'dth07' (25 Mar 2011 @ 18:00)

Re: Simple answer by 'itpro' (25 Mar 2011 @ 18:07)

Re: Simple answer by 'Bod' (25 Mar 2011 @ 18:23)

Re: Simple answer by 'Newshound' (25 Mar 2011 @ 18:38)

Re: Simple answer by 'Bod' (25 Mar 2011 @ 22:03)

Bod... by 'itpro' (25 Mar 2011 @ 18:50)

Re: Bod... by 'Bod' (25 Mar 2011 @ 21:54)

Re: Simple answer by 'PaulMRotax' (25 Mar 2011 @ 19:29)

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