Fuel System Tech Education with Weldon High Performance
Written by Steve Baur with Jim Craig
Photography curtesy of Weldon High Performance and Derek Putnam
You can learn a great many things by talking to manufacturers about their products, and they’re the best source for answers whether you are starting a new build, considering upgrading, or having issues with existing components. We recently sat down with Weldon High Performance’s Jim Craig to discuss common fuel system issues and problems he comes across when talking to enthusiasts either on the Weldon tech line, or even at the track.
Filtering the Problem
With more and more racers turning to ethanol fuels such as E85, and even oxygenated fuels like Q16 or methanol, cellulose fuel filters are simply not compatible.
“Stock vehicles use paper cellulose elements, but they are running all the time,” explained Craig. “Racing vehicles sit a lot, so a stainless element is required. These always go on the inlet size of the fuel pump and you need to run a 40-100 micron stainless filter.”
Likewise the outlet filter is equally important.
“It’s critical that on the outlet, there is a 10-micron stainless steel filter on fuel-injected applications, and the best location is closest to the injectors. With the ethanol fuels, they can break down fuel lines as well, and it’s better to have the filter right at the injectors so the particles breaking down in the line hit that before the injectors.” Craig noted that these stainless filters can be cleaned several times, but beyond that, they should be replaced. He also pointed out that fuel regulators can get jammed up from these particles as well.
Fuel Lines—Size Matters
A common issue Craig hears from enthusiasts is not feeding the fuel pump with the appropriately sized fuel line.
“Line sizing is very important and should be larger on the inlet side with an external fuel pump. If they have a fuel cell with two -8s, combined into a single -10 or -12 into the fuel pump, it might not be enough.”
As we have talked about inlet fuel line sizing, Craig noted that return line sizing is equally important.
“It’s just a dump for the fuel and it should have no pressure in it—it should be free-flowing to allow the regulator to do its job. It’s just a transfer hose and needs to breathe, otherwise you might not be able to tune the fuel pressure down to where you need it. I’ve even seen top teams tune around a poorly sized fuel system because it was easier than replacing the components.”
And just as a fuel filter’s medium should be considered for each application, so, too, should the fuel line medium be assessed per application.
“You might have stainless steel braided hose, but the inside is rubber and breaks down from the ethanol,” Craig said. He was also keen to point out that “PTFE-lined hose, and all hoses, and fittings are not the same despite what they might be labeled as.” Be sure to do your research on each component, and/or ask each manufacturer for their recommendations.
Fuel Fitting Fiasco
As with any aftermarket component, there are varying levels of quality and this is no different for the expensive fuel fittings that one might need to assemble his/her for system.
“There’s a big difference between house brand fittings and performance fittings from companies like XRP, Earls, Fragola, or if they’re really willing to step up, Brown and Miller,” Craig said. “You can have XRP or Brown and Miller remake new lines with fittings if you send them your old hoses.”
Fuel Tank Vents
Something that many racers don’t often think of that can cause a multitude of issues is the often overlooked fuel tank vent and its size.
“You’ve got to use a tank vent and the right size one,” noted Craig. “Old cars use a 5/16-inch vent, which is fine for a stock car, but if you’re trying to move 300 gallons per hour, you’re displacing that much volume in the tank, so you need to move that much air, otherwise the pump goes under suction and begins to cavitate. You probably need minimum of a -8 to a -12 [vent], which most aftermarket fuel cells have.”
One problem with aftermarket fuels that Craig noted, however, is that, “These cells can often last the lifetime of the car, and people don’t pay attention to the fuel cell’s capabilities as the fuel system progresses to follow engine development. For something like a mechanical fuel pump, a lot of times a weird pump sound is a symptom of this. A chattering sound can be cavitation.”
Craig noted that fixing this issue is rather simple, with the greater importance placed on not forgetting that the vent is an active part of the fuel system.
“With stock fuel tanks, you can just drill a hole and put a properly sized bulkhead fitting in it. Vents should have a small breather filter on them as well—If you’re driving in dusty pits, a non-filtered vent will suck up all of the dust that your car kicks up.”
Fuel Pumps—Bigger is not always Better
“Bigger is not always better, or even advised,” Craig told us about fuel pump sizing. “I try to feel the customer out when discussing what they need. If you’re going to make significant engine upgrades in the near future, you can go up in size, but if it’s going to be several years, you’re overspending. You want to size it for the horsepower of the vehicle. You need, ballpark, 10 gallons per hour for every 100 horsepower for gasoline combos, much more for methanol. Look at the fuel, horsepower, power adders, and what they are going to do with it.
With a centrifugal supercharger like a ProCharger or Vortech, some don’t realize that it takes horsepower to drive a blower, so you need to figure that in to your fuel pump sizing. Turbos are free fuel, Whipples/VMP types of blowers are more efficient types of blower and don’t consume as much horsepower. On Bardekoff’s and Chris Holbrook’s cars, they can use our 2345 pumps. They’re also running standard gasoline, not ethanol.”
Regulators, Mount Up
Craig also brought up the subject of fuel pressure regulators, and despite their relatively simple function, installation and adjustment is not always done properly. Craig stressed the importance of knowing that the return is always on the bottom of a bypass-style regulator. The vent or vacuum source is on top, and in regard to that open port, “I don’t like leaving them open, so we have brass filters to fill the hole,” Craig said.
Under Pressure—Best practices for setting fuel pressure
Craig recommends setting the fuel pressure with the pump running at full pressure.
“Some people adjust the pressure at pulse mode, and then when the pump is full on, it sends more volume than the regulator can handle, or what was desired. A fuel pump delivers a certain amount of fuel at a certain pressure, and if you are raising pressure to supplement an increase in horsepower, the pump may not be able to support the volume that is needed.
Supporting Cast—Making sure your fuel pump has the juice it needs
The last thing Craig talked to us about is the electrical side of things. According to Craig, properly sized wiring and suitable voltage is critical for electric pumps.
“They need to be sized for the amp load that your device is going to draw. A switched ignition relay should be used. Some guys are using power distribution modules and they have the capacity. In some cases, we’ve seen where the initial trigger of the pumps pull more amps than the system can handle and it will shutdown the pumps. You’ve got to have good power, good grounds, and good, properly sized connections to have a good connection to the device. It’s the same thought process as sizing the fuel lines—lines and connections need to be sized appropriately. If you can pick the pump up by the connector, you have a good connection!”
Just as you might expect, having good, properly sized relays is also imperative, as they take the in-rush of electrical amperage when the pumps are first turned on. And as with anything electrical, bad grounds affect fuel systems, too.
Hopefully these notes might help you should you have an issue that you haven’t been able to resolve, and at the very least, let you know that aftermarket companies like Weldon High Performance have a vast knowledge of their products, but are also on the ground and in the pits, talking to racers and are able to provide lots of feedback and support.
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