Thread: Horsepower Fuel Flow

Tweet

Does anyone know how to calculate the required fuel flow for a given amount of horsepower?

The accepted ratio that I am familiar with for normally aspirated engines is: 1-horsepower for 1-hour requires approximately .5 (1/2) pound of gasoline i.e., a single-cylinder engine producing 1-horsepower for 1-hour uses approximately .5 pound.

On a dyno this is expressed as Brake Specific Fuel Consumption (BSFC). Depending on the engine tuning, BSFC is typically .40 -.50, i.e., .4 to .5 pounds of fuel, per horsepower, per hour. Alcohol is approximately twice the ratio or 1-lb of fuel, per horsepower. “Streetable” turbocharged engines go about .65 BSFC.

Using this formula, a typical 300 horsepower engine will consume 150 pounds of fuel per hour; a 600 horsepower engine will require 300 pounds of gasoline per hour. Bear in mind that the fuel has to flow past the needles and seats and the fuel pressure regulator, etc. This is important because a carburetor cannot provide correct air/fuel mixture unless the fuel system can supply enough fuel to maintain correct float bowl levels.

You can perform a simple test your fuel system by measuring how quickly your pump fills a one gallon can. Direct the fuel line into a metal can on the setting on the floor. Have a fire extinguisher near by and have an assistant switch on the system and time the fill to one gallon. For reference, a high 10-second car must pump 1-gallon in 25-seconds or less, a 9-second car needs to be 20-seconds or less.

I'm sure others will chime in
Glenn

Knowing this, can you design your engine for a specific power output instead of just making a guess combination? I want to improve the performance on my 2003 Northstar engine.

Originally Posted by glennsexton

The accepted ratio that I am familiar with for normally aspirated engines is: 1-horsepower for 1-hour requires approximately .5 (1/2) pound of gasoline i.e., a single-cylinder engine producing 1-horsepower for 1-hour uses approximately .5 pound.

Glenn,

Why would the amount of fuel required to make one horsepower for one hour vary for naturally aspirated and forced induction engines?

Yes - turbo is typically .65 pounds per hp per hour. Blown engines can go 1 pound if overdriven.

Originally Posted by glennsexton

Yes - turbo is typically .65 pounds per hp per hour. Blown engines can go 1 pound if overdriven.

Why is that?

You have to maintain the air-fuel ratio to get proper burn and performance. A blower compresses (increases) air flow to the cylinders so you need to add fuel to balance things out again ..............

Kitz

Originally Posted by kitz

You have to maintain the air-fuel ratio to get proper burn and performance. A blower compresses (increases) air flow to the cylinders so you need to add fuel to balance things out again ..............

Kitz

Ahhhhh

Now it makes sense.