We reached out to the guys in Summit Racing’s renowned tech department—the largest full-time staff in the industry—to identify and answer the five common tech questions they hear on a consistent basis. With help from Summit Racing’s tech advisors and other industry experts, we’ll answer those questions here at OnAllCylinders. Today’s topic: fuel pumps.

When we refer to fuel pump size here, we’re talking about the size or amount of fuel flownot the pump’s physical size. More accurately, we’re talking about the fuel flow volume as measured in gallons-per-hour (GPH).

So here’s the real question (and it’s one of the most common questions asked of the Summit Racing tech department):

What is the optimum GPH for my engine?

There’s a simple formula to calculate GPH or LPH (liters per hour), but there are some variables to this formula, depending on your application. Norm Koval, a team leader in the Summit Racing technical department, typically follows this formula as laid out by the air/fuel experts at Holley:

Optimal GPH = (Max. HP x BSFC) / 6

Optimal LPH = (Max. HP x BSFC) / 1.585

In order to make the proper calculation, you need to determine your variables for this equation, starting with your vehicle’s maximum horsepower (Max. HP). You can determine this by having your vehicle dyno tested or by making a reasonable horsepower estimate based on the manufacturer’s advertised horsepower plus a conservative estimate of power gains made by aftermarket modifications.

The second variable in the equation is BSFC, or brake-specific fuel consumption. BSFC is a measurement of the amount of fuel consumed per unit of power produced. According to Holley, an engine typically requires .5 pounds of fuel per horsepower every hour at wide open throttle. However, this number generally applies to naturally aspirated engines.

“There are exceptions,” Koval said. “What if it’s supercharged or turbocharged? Then I might give that number a fudge factor to bump up the GPH.” If you have a highly modified, naturally aspirated engine, for example, you can tweak the BSFC number up to .55 pounds. Aeromotive recommends the following adjustments for power adders:

• Nitrous combinations: .5 to .6 pounds
• Forced induction engines .6 to .75 pounds

Once you’ve determined your realistic horsepower and BSFC numbers, multiply them together and divide the product by six (the typical weight of a gallon of gasoline). For example, if you have a stock engine that makes 350 horsepower, your equation will look like this:

(350HP x .5 lbs) / 6 lbs =

175 lbs/hr of fuel / 6 lbs = 29 GPH

In our example, you’d need a fuel pump that delivers 29 GPH of fuel.