Can you get away with under- or over-speccing a fuel system for a given scenario?
“Sure you can,” Craig says. “I have import guys that do it all the time. They might drive on the street with E85 but when they get to the track they convert over to methanol. E85 uses twice the amount of fuel. So now they’re well within range, but they put up with it on the street. They understand the likelihood that if they drive it a little too long, they’re going to be encountering vapor lock and fuel boil and erratic pressure.”
Weldon generally aims to keep a fuel system spec’ed to the maximum horsepower of the engine, so that the customer isn’t over-fueled. Craig notes this is very much a case-by-case basis thing, depending on precisely what the customer intends to do with the car. In the event that engine or chassis dyno numbers aren’t available, he and his team can often take engine size and the power adder into account to estimate fuel system needs.
“Many of the numbers we get are a bit inflated. They’re looking in magazines and coming up with numbers, but you have to be careful not to over-fuel a car. Some customers feel they can’t have too much fuel, but you definitely can. So we have to be realistic about that engine and what it’s producing.”
This comes down to not the pump, but the entire system — say for example you have a given pump but undersize the inlet line, will put a significant and damaging load on the pump. Or, if you used the proper -12 inlet line, but choked it down with only a -10 Micron filter, you’d run into similar problems.
“It’s not an exact science, and hopefully everyone has the same thought,” Craig states in closing. “There are just so many variables that come into play, with the fuels, the power adders, the customer, and you can’t sell them short and you can’t oversell them, because either way, it comes back and bites them. So you have to walk a real fine line, but enough to cover them if they’re going to roll to that next level. Because the guy that leaps and jumps, or runs E85 today and ethanol tomorrow, that whole combination changes completely — it’s like they turned the car over and dumped everything out and put something new in it, and everything changes at that point.”
Plumbing The Fuel System
Building an adequate fuel system for a street/strip machine doesn’t stop with the pumps, regulators, and filters — the hard parts, if you will. As Craig noted, sizing of your AN fittings and hoses is key to flowing enough fuel to suit the engine’s demands. But fuel compatibility and reliability are both key, as well.
For the fuel system on True SStreet, we turned to
Russell Performance, a division of Edelbrock, for an array of hoses, fittings, and adapters to plumb the fuel system from the trunk up to the fuel rails and back.
We began with Russell’s Pro Classic II hose, a traditional-in-appearance hose made with an all-black nylon fiber braided outer cover over a Chlorinated Polyethylene (CPE) synthetic rubber inner line designed for abrasion resistance. Russell designed this hose with the intricacies of an engine compartment in mind, as the CPE inner liner sports a bonded, multi-braid stainless wire so you can bend it around tight radiuses without it collapsing.
The main thing that racers were after when they saw this hose line was weight. John Urist switched over and found they were 44-percent lighter than our old braided stainless hoses. – Smitty Smith, Russell Performance
The ProClassic II has a maximum working pressure of 350 psi and is compatible with gasoline, oil, and antifreeze. Those running methanol or E85 will, of course, want a PTFE-style hose (pump gas containing 10-15-percent ethanol is fine, according to Russell). The hoses can also withstand temperatures from -40 to 350-degrees Fahrenheit, meaning it’s right at home on mid-summer or mid-winter stop-and-go driving as much as it is on the dragstrip.
According to Russell’s Smitty Smith, it was discovered early on by R&D drivers like Billy Glidden and John Urist that any vacuum greater than 27-inches, the hose would collapse. And so they outfitted the hose with inner coils that act as wide-banded spring inside to prevent such scenarios.
The inside layer of the ProClassic II are made from extruded CPE synthetic rubber, while the outer shell is a high-quality nylon fiber braid for flexibility and abrasion-resistance.