UK Karting - Notice Board (4-Stroke Karting) : Re: technical question

Notice Board (4-Stroke Karting)

Re: technical question
Posted by 'SimonS' on 30 Oct 2008 @ 18:06

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SimonSJoined: December 2004
Total Posts: 4
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Regardless of the direction you are turning the screw:

Changing the mixture is designed to take the engine to a position where it performs to the most effect.

That will alter depending on what you are doing. If you start off too rich, leaning the engine will increase both revs and temperature, until you meet the peak fuel point. You can lean off beyond that point (being Lean of Peak) but all that happens is that the temperature goes up and the revs do not increase. About 50F beyond PFP is your max fuel economy, something we usually aren't interested in.

About 50F below Peak you meet Maximum Power. This is the point where the engine produces its maximum power and is slightly too rich to develop maximum revs.

So if you are flatout at a maximum power setting down the straight but need just a few more revs, leaning off might give you enough to get by the kart in front, but you have to richen up again if you want to get out of the next corner.

Unfortunately Max Power is a bit of a misnomer, at low throttle openings you actually need to richen up the mixture to get acceleration. (why expensive carbs have accelerator pumps or the SU carb needle position was controlled by manifold pressure.

So depending exactly where you are on the circuit, richening up and leaning off can both increase your revs. In addition, in the old aircooleds you could actually cool down the cylinder by putting too much fuel through it, and if you loose your coolant in a watercooled, you can finish the race by 'choking' the engine.

Message Thread:

technical question by 'stephenh7hou' (29 Oct 2008 @ 17:26)

Re: technical question by 'Stig' (29 Oct 2008 @ 17:34)

Re: technical question by 'stephenh7hou' (29 Oct 2008 @ 17:48)

Re: technical question by 'Jeff Johnson' (29 Oct 2008 @ 17:56)

Re: technical question by 'kudos' (29 Oct 2008 @ 23:20)

Re: technical question by 'stephenh7hou' (30 Oct 2008 @ 13:15)

Re: technical question by 'SimonS' << You are here!

Re: technical question by 'stephenh7hou' (30 Oct 2008 @ 18:28)

Re: technical question by 'SimonS' (31 Oct 2008 @ 9:18)

Re: technical question by 'itpro' (31 Oct 2008 @ 10:24)

Of course...... by 'vic' (04 Nov 2008 @ 8:19)

Re: Of course...... by 'itpro' (04 Nov 2008 @ 11:17)

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