Altitude adjustment for Carbs Options

[Harpo]

Good morning everyone,

Exactly what is involved to adjust the carbs for an elevation change from 4800 to 500 feet.

Thanks

David

[brant]

changing out the amount of fuel and air that reaches the combution chamber...

usually bigger (or smaller) Mains, idles, and air correction jets.
sometimes also Emulsion tubes and primary venturi's

A wide band gauge will help determine air fuel ratio for a specific motor to get it right... Borrowing one and the knowledge of an expert to help is a huge thing to be absolutely spot on.

there is also a lot of experience on this board to get a pretty good estimate for a similar motor or similar car without being exactly spot on for your motor by using a gauge.

Locally we have a guru with an engine dyno and a box of jets (thousands of dollars worth of jets). Using a pro shop with a dyno like this can actually be cheaper than buying all of those jets yourself. I don't know how precise you want to be but you may want to see if there is such a local shop in your area that specializes in porsche air cooled motors.

you can get pretty good for street use by using similar set ups that others use. Remember correct air fuel is about Altitude and Humidity. The amount of moisture in the air effects the amount of oxygen in the air and can change jetting a lot also. So your location and weather patterns need to match up with those who are giving advice.

Its really intersting to go to the local saturday night drag strip in thousands of towns across the US. A lot of the amateur drag racers are using very accurate and expensive home weather stations at the tracks to fine tune their jetting.