This rapid acceleration increases the demand
In oval track applications, a Belt Drive or Hex Drive Fuel Pump ispreferred where use of a mechanical fuel pump is specified. These pumps offerthe highest fuel delivery volume of any mechanical pump yet maintains low fuelpressure at low engine speeds. This feature alleviates "loading up"of the spark plugs. The BG Six-valve and Super Speedway mechanical fuel pumpswill also deliver ample fuel volume when used according to recommendations.For drag race cars, a BG400-2Electric FuelPumpis the best way to guard against fuel starvation. If a car is lazy orlays down at mid-track then pulls well in a higher gear, the engine may beexperiencing intermittent fuel starvation.Why? Typically, thecarburetorbowls arefull at the starting line so the car leaves hard but in the process, drains thebowls dry. In the lower gears, the car accelerates rapidly with the enginepicking up rpm very quickly.This rapid acceleration increases the demand forfuel. When the float bowl fuel level drops, the car lays down because of fuelstarvation. In high gear, engine speed increases more slowly allowing the bowlsto fill again.The Fuel Can TestThere's been no shortage of well-researched andwell-written articles and books explaining the workings of the fuel system.However, many racers, both novice and experienced alike do not fully understandthe physics of fuel flow and horsepower. To produce torque and horsepowerrequires a mixture of air and fuel. To produce 1-horsepower for 1-hour requiresapproximately .5-lbs of gasoline. If you ran a single-cylinder engine, like theone in your lawnmower, under a load of 1-horsepower for 1-hour and weighed thefuel tank before and after, the tank would weigh approximately .5-lb(five-tenths of a pound) lighter. Therefore the equation for fuel flow is1-H.P. = .5-lb of fuel, per hour.This is expressed on a dyno sheet as B.S.F.C.(Brake Specific Fuel Consumption). Highly-tuned racing engines can sometimes bemore efficient, yielding B.S.F.C. figures of around #.40 which means 4-tenthsof a lb. of fuel, per h.p., per hour. Incidentally, the formula for Alcohol isapproximately 1-lb of fuel, per h.p. per hour which, as a consequence,necessitates the running of a belt-drive pump, but that's another story.Typically, a 600-HP engine will require 300-lbs ofgasoline per hour and, by the same formula, an 800-HP engine needs 400-lbs perhour. Remember, these quantities of fuel have to be liquid soap lotion pump delivered past the needlesand seats and the fuel pressure regulator. Consider also, the fuel deliverysystem has to combat 'G' Forces: loadings that are so formidable they can threatento stall the fuel in the line (this may also give a clue as to why a fuel linethat is too large in diameter can be as harmful as one that is too small). Thisleads us to the area that is least understood.When you have only onecarburetorit shouldbe easier to feed than two, right? Wrong, in an engine with a tunnel-ramlayout, both the needle and seat area and the float bowl capacity have doubled!Whereas the single four-barrel car that is most prevalent today, has a muchharder task in keeping the fuel bowls full! A 700-HP tunnel-ram engine needs350-lbs of fuel per hour which equates to a little over 85-lbs per float bowl.A 700-HP engine running a single four-barrel (not so uncommon these days) needs175-lbs per float bowl, compared to a 1200-HP Pro Stock engine with demands of600-lbs max, 150-lbs per bowl.Find out more about Toyota 4Y carburetorby visit miparts.com.
