How does air pressure influence the performance of a kart engine?

I have been wondering lately, how the atmospheric pressure affects the carburation of an engine.

Does lower air pressure mean leaner air/fuel mixture?

And how much do you close the H and L screws on the x30 when driving in rain conditions compared to dry conditions?

Thanks in advance.
Alex Maansen

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Lower air pressure (Well, density) would mean richer running conditions.

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Alex there’s a really good app called jetting for IAME. Hit GPS, then get data from weather station, use this data then go to results. It tells you exactly where to set high and low screws. I use it all the time.


How often do you find yourself adjusting the carb needles? I find (so far) that i barely need to play with the high and low.

I set them every day I go on track.

I usually find myself fiddling around with the needles for the whole first heat of a practice, and only adjusting it very lightly throughout the day.
(and then of course close them a little if grip worsens like if it starts to rain)

Hmm i guess i need to tamper with them more, im really only used to those air cooled engines.

What engine are you running with now? =)

I’m curious why you close them off (Lean out the mixture) when grip is low?

Just curious, not used to rain :joy:

When the grip is poor, the kart will not have enough grip and be as fast and therefore not obtain as high rpm, wich results in the carburetion being too rich (it doesn’t burn as much fuel). You lean the mixture to outweigh the lower speeds of the engine =)

Interesting - every days a school day. Thanks for explaining :slight_smile:


Longacre has some interesting reading on their website concerning the use of the air density gauge.
I have some articles, on Facebook under the heading Mayko Products, that explains how to use the EGT (exhaust gas temperature) gauge. If, or after, you read them, and have questions, I’d be glad to help.

Sounds too simple right!! Try it, you’ll like it.

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Here’s a real simplification;
high air density (heavy air) means more air gets pushed into the engine.
Low air density (lighter air) means less air gets pushed into the engine.

There’s no such thing as “suck”, everything gets pushed. The idea that everything gets pushed can change your way of looking at a carburetor.

More or less air = more or less fuel, to keep the mixture ratio the same.

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The idea that a carburetor/engine “sucks” fuel/air, is almost a universal concept, unfortunately, it’s wrong! The concept has changed my way of thinking about how carburetors work.

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