Borematic pressure

[viper55]

Borematic pressure, any one know anything about it ??? was being asked about it today and have no idear about it.

[ewenm]

Borematic? Or do you mean Barometric?

[viper55]

umm something to do with a engine ????

[ewenm]

Well google and wikipedia come up blank apart from a company's product. Shrug.

[viper55]

yeah i did that before i asked on here dident know if i spelt it wrong aww well .

[Happy Jim]

Yep, It's Air Pressure and is usually relevent to cars that whizz up and down bloody great big mountains (thin air/lower pressure) and how it affects the fueling (taken care of nowadays by MAP sensor and MAF sensors)

Rgds

Jim

[viper55]

oh right rele well it was at a race weekend and we run two stroke engines so is it to do with carb tuneing then ??

[ewenm]

viper55 said:

oh right rele well it was at a race weekend and we run two stroke engines so is it to do with carb tuneing then ??

Yep, carbs need adjusting for variation in air-pressure (or barometric pressure). Less oxygen per unit volume of air if the pressure is lower.

[viper55]

ohh right starting to make sense so if it was a cold day with a low air pressre you would adjust the air screws ?

[ewenm]

viper55 said:

ohh right starting to make sense so if it was a cold day with a low air pressre you would adjust the air screws ?

I guess so, I have no idea how to adjust carbs. Really should learn. If the air pressure drops it'll probably start running rich.

[jeff m]

Happy Jim said:

Yep, It's Air Pressure and is usually relevent to cars that whizz up and down bloody great big mountains (thin air/lower pressure) and how it affects the fueling (taken care of nowadays by MAP sensor and MAF sensors)

Rgds

Jim

And prior to these sensors little aneroids did the job

[anonymous-user]

You wouldn't touch the carbs because of weather difference, you will if you are running at higher altitude than it's setup for. If tuned at sea level below 3000ft leave it alone, above 3000ft

Idle Jets: You will normally need to drop 1 Idle jet size (Meaning a step of 5. 50 to 45) for every 2000 feet above 3000 feet of altitude.
Main Jets: You will normally need to drop 1 main jet size (Meaning a step of 5. 150 to 145) for every 1000 feet above 3000 feet of altitude.
Air Jets: You will normally need to Increase 2 Air jet sizes (Meaning a step of 10. 150 to 160) for every 1000 feet above 3000 feet of altitude.

[viper55]

johnfelstead said:

You wouldn't touch the carbs because of weather difference, you will if you are running at higher altitude than it's setup for. If tuned at sea level below 3000ft leave it alone, above 3000ft

Idle Jets: You will normally need to drop 1 Idle jet size (Meaning a step of 5. 50 to 45) for every 2000 feet above 3000 feet of altitude.
Main Jets: You will normally need to drop 1 main jet size (Meaning a step of 5. 150 to 145) for every 1000 feet above 3000 feet of altitude.
Air Jets: You will normally need to Increase 2 Air jet sizes (Meaning a step of 10. 150 to 160) for every 1000 feet above 3000 feet of altitude.

oh right so what your saying is where were racing at sea level dont adjust air screws ect as were not changeing altatude ??

[anonymous-user]

Yup. A few apostrophes and commas would be useful, it took me 3 reads of that to fathom what you meant.