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

Notice Board (4-Stroke Karting)

Re: technical question
Posted by 'SimonS' on 31 Oct 2008 @ 09:18

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SimonSJoined: December 2004
Total Posts: 4
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"will try to acheive max power through the right mixture using small increments..."

There are two ways to discover Max Power.

One is to use little increments and compare the engine temperature / speed for a given bit of track. Not necessarily easy and subject to outside interference, such as not lapping consistently.

The other is to do a check choke. While at full throttle choke the engine (put your hand over the air intake, cutting off the air supply). As soon as the engine revs drop (engine dies), take your hand away and listen as the engine recovers its revs.

If the engine momentarily goes back to revs more than it was doing before you choked, then you are too lean (the extra fuel in the choke has increased your revs). If the engine slows to less than it was doing before you choked, then you are too rich, the choke has made the situation worse. If the revs return to the same speed, then you are on point (or near enough). Note that this is a temporary effect, clearly the effect of the choke goes away with time.

Aircooled running on the ragged edge always used a "full" choke, the effect of closing the throttle at full chat) the corner at the end of the straight, had the effect of momentarily leaning off the engine and sending the temperatures rocketing. At the same time, cutting off the fuel also cut off lubrication to the now overheated cylinder and piston. The combination of hot cylinder and hotter piston gave you a heat sieze.

The "full" choke (shutting off the air supply just before you closed the throttle to the point the engine died first) added extra fuel into the cylinder, cooling the flame and cylinder as you entered the corner and any residual fuel at the end of the corner acted as that 'accelerator' effect mentioned earlier.

Watercooled cylinders don't get that hot that quickly so heat siezing is a comparatively rare event, though it can still be done. A full choke visibly slowed the kart so one doesn't do it that often in a watercooled class, but a "check" choke as described still works but it also slows teh kart, so you don't want to do it as an overtaking manoeuvre!

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' (30 Oct 2008 @ 18:06)

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

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

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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