Bracket Race & Street-Strip Fuel Delivery Systems
In our last segment we shared the details on a couple of big performance electric fuel pumps designed expressly for big power street-strip cars or bracket racers. To rewind a bit, these pumps from Weldon and MagnaFuel are both engineered to run constantly, pull a prime, provide big fuel volume and pressure for high horsepower applications, mandate minimal amperage draw and operate quietly. Those are tall orders and both of those high -quality fuel pumps provide those features in spades.
This time around, we’ll dig deeper into the fuel delivery systems required on multiple-use cars. Believe it or not, setting up the fuel system on a street-strip car is actually more difficult than it is on something like an old Pro Stock car (or even a current mountain motor example)! For more details, check out the following:
MagnaFuel offers a by-pass package for their pumps and it is much like the system used in the big Pro Stock fuel delivery systems. It simply threads on the outlet of the pump. In operation, you set the final outlet pressure (from the pump to the regulator) you desire by swapping out by-pass springs. The balance of the fuel (excess) is by-passed and sent back to the tank. Meanwhile, Weldon doesn’t bypass the fuel at the pump. Instead, it works with a bypass system at the regular. Either way, this eliminates the “dead-heading” dilemma we alluded to earlier.
So how do you regulate the fuel? Obviously, some form of device to control fuel pressure is essential (that’s no secret). Typically, two different types of fuel pressure regulators are available for either pump. One group is engineered for carburetors while the other is for fuel injected engines. Electronically fuel injected engines mandate operating pressures ranging from 35-85 PSI. Meanwhile, carbureted engines typically see operating pressures in the 4-12 PSI range. You can get two or four port (outlet) regulators, and you can usually obtain them with or without boost reference capability (meaning the regulator is designed to work in conjunction with a blower of some sort). In both families (EFI or carburetor), you’ll find regulators grouped into the horsepower level (engine) they are designed to sustain. For a serious performance application, an adjustable regulator is an absolute necessity. We should point out the Weldon pump is compatible with gasolines containing up to 40% alcohol as well as most race fuels. Weldon advises that for carbureted applications, it will meet the demands of engines up to 800 HP at 7.5 PSI, normally aspirated. For fuel injected applications, it will meet the demands of a 700 HP engine at 50 PSI, normally aspirated.
We’re not quite done yet: Fuel is dirty stuff. Pump gas is likely worse than race gas. And that’s why fuel filters are especially important in a modified car. Use a high-capacity aftermarket in-line filter, or even a pair of them – one before the pump (pre-filter) and one after. We’re not talking about the easy-to-get jobs that you can find at your local dealership or auto parts store. Most of these filters are just too small and cannot handle the volume of fuel required for a healthy modified engine. They can constitute a restriction in the fuel delivery system — even if they aren’t plugged.
What about disposable plastic filters? They’re a complete waste of time and dollars. Cheap plastic filters create a considerable fuel system restriction, can easily be plugged and almost all examples we’ve seen have far too small an inlet/outlet port for real high-performance use. There’s more too: Virtually all of disposable filters out there are designed so that you use worm gear clamps to hold them in place. With the high-pressure electric pumps currently used in modified applications, these filters can easily be collapsed (internally) by the force of the fuel pump or if they aren’t secured properly, they can be blown right off the fuel line (not good).
Here’s what you can do about the fuel filter situation: Several aftermarket companies offer high quality in-line filters that are up to the rigors of performance use. These filters are positively huge and are designed to handle high pressures along with plenty of volume. By adding a pre-filter along with an after-filter you won’t choke the fuel delivery, and at the same time, it can protect your engine from debris and junk in the fuel. These filters aren’t small and they aren’t cheap. But then again, performance never was inexpensive.
In the end, can the average little guy quick-street or bracket race car pick up performance with the latest high volume fuel delivery systems? There’s no question it’s possible and today’s fuel delivery combinations will most definitely improve the performance level. You’ll also find your car will become much more consistent and reliable (and no vapor-lock, heat-soaked issues like we regularly experienced decades ago). But in some cases, be prepared to find a completely new tuning combination. The reason is a good fuel delivery system will pump more fuel and less air and vapor to the carburetor or the injector nozzle. Finally, if you have a car with small fuel bowl capacity, there’s a very good chance you’ll find it needs more fuel pump capacity than a 1900+ HP mountain motor pro stock car. Don’t forget, at the launch, a Pro racecar might have well over 2.5 G’s of force applied to it (which the fuel has to overcome). But there are four needle and seat assemblies, and four rather healthy fuel bowls available to accept this load. On something like a 1X4 BBL bracket car you might be dealing with 1.1 G’s on the launch. Unfortunately, the fuel often has just a pair of needle and seat assemblies and two fuel bowls to spread the load over (and something with a Quadrajet or Carter carb is worse with only has a single needle and seat along with a rather small bowl). It’s something to think about.
In the meantime, keep reading for a closer look at the basic hardware required to feed a high horsepower, big cubic inch street-strip or bracket race engine. You might want to copy it.
Fueling the Fire – Bracket Race & Street-Strip Fuel Delivery Systems Part 2
Bracket Race & Street-Strip Fuel Delivery Systems