moper
Well-Known Member
TX - excellent post.
I'll add a couple points relative to carbs -
-Advertised sizing - there are two ways carbs are rated: dry flowed, which includes measuring the amount of air volume that can be passed through a carb at a given pressure drop (I can't recall what the industry accepted test pressure is...) with the throttle wide open; and wet flowed which is the same test, however a simulated fuel is run through the carb at the same time. Because the liquid replaces some of the air being pulled through the carb, the measured amount of air is smaller for the same given physical size. The difference is not huge but is a percentage. Roughly 13-14% or so. So if you have a dry flowed 750cfm carb (like the 4150/4160/3310 Holleys, Carters, Edelbrocks) and add fuel, they will flow less than rated. 750cfm drops to about 645cfm. Carbs from custom shops, Dominators, Holley HP and Avenger series, and Demons are all wet flowed because it's a much more accurate way to test. So a Demon 750cfm when tested without liquid and compared to a 4150 series 750 will flow close to 860cfm.
-Airflow in relation to fuel - In order for any carb to work, there has to be motion to the air in the throttle body. It's the movement of the air that causes the fuel to be pulled in. That's true with every circuit in the carb but the accelerator pump. The faster the air moves, the stronger the signal and the better it can be metered and controlled. So a specialized carb can be huge, and still deliever great response and economy so long as the circuits are sized properly for the engine it's on and the atmosphere it's sucking.
I routinely use wet flowed 870cfm Avengers on 4" stroker engines. The best milage so far is over 17mpg in mixed driving, and it makes about 460-470hp. But it's really about making it all work together.
I'll add a couple points relative to carbs -
-Advertised sizing - there are two ways carbs are rated: dry flowed, which includes measuring the amount of air volume that can be passed through a carb at a given pressure drop (I can't recall what the industry accepted test pressure is...) with the throttle wide open; and wet flowed which is the same test, however a simulated fuel is run through the carb at the same time. Because the liquid replaces some of the air being pulled through the carb, the measured amount of air is smaller for the same given physical size. The difference is not huge but is a percentage. Roughly 13-14% or so. So if you have a dry flowed 750cfm carb (like the 4150/4160/3310 Holleys, Carters, Edelbrocks) and add fuel, they will flow less than rated. 750cfm drops to about 645cfm. Carbs from custom shops, Dominators, Holley HP and Avenger series, and Demons are all wet flowed because it's a much more accurate way to test. So a Demon 750cfm when tested without liquid and compared to a 4150 series 750 will flow close to 860cfm.
-Airflow in relation to fuel - In order for any carb to work, there has to be motion to the air in the throttle body. It's the movement of the air that causes the fuel to be pulled in. That's true with every circuit in the carb but the accelerator pump. The faster the air moves, the stronger the signal and the better it can be metered and controlled. So a specialized carb can be huge, and still deliever great response and economy so long as the circuits are sized properly for the engine it's on and the atmosphere it's sucking.
I routinely use wet flowed 870cfm Avengers on 4" stroker engines. The best milage so far is over 17mpg in mixed driving, and it makes about 460-470hp. But it's really about making it all work together.
