The SL-C supports multiple drivetrain options. Therefore, there is no one "factory" fuel system- every builder has to create their own, to meet their power requirements, their budget, and the specific requirements of their engine. However, there can be much commonality across engines, and if you are selecting the popular LS series engine (about 80-90% of SL-C builders do so), there is a wealth of information about successful fuel systems here on this wiki, and elsewhere on the web. The diagram shown below is from an LS engine installation, and it can be a model for any other EFI engine with a returnless fuel rail.
For some time, the factory has offered an optional fuel system package consisting of low- and high-pressure pumps, filters fuel regulator, and a mounting plate, designed to be mounted on the chassis rails, and using the included (with the car) surge tank. You just bolt the plate with all the parts installed to the chassis, connect the lines and it's done.
This makes the selection of pumps, filters and so forth simple, as the factory setup is adequate for most engines with under 650 HP. If your powerplant has more power than that, you'll need bigger pumps.
Safety is an important part of building a car and managing fuel and fuel vapors is paramount. Failure to do this properly may result in fire, injury or death. The fuel system is not difficult but it's important that you understand how it works and that you use high-quality parts. Note that in the last ten years changes in fuel chemistry and the advent of Electronic Fuel Injection (EFI) systems have created issues with rubber-core stainless hoses that we're all used to using. Additives, increased ethanol and high-volume gas recirculation which aerates the gas and transfers heat to the gas tank all accelerate hose degradation.
The configuration below will not only result in a safe and performance oriented solution, but one that doesn't leave your garage smelling like gas. Depending on your power requirements, -6 hose is adequate for all fuel lines up to around 700-800 HP. When selecting a fitting vendor, try to find one that has a long, proven history with race car plumbing, along with a wide range of fittings. Price is the last consideration.
There's a good article on HotRod here.
An excellent article about choosing the right type of hose here.
The diagram below shows how fuel flows through the system as used on the popular LS series engines. Note that a 'returnless' system is shown which means that excess fuel does not flow through the fuel rails but rather flows directly back to the gas tank, from the regulator. Each component is subsequently described in detail. Your system may vary, according to your needs, so please regard this as an example, though one that has been proven in running SL-Cs.
The kit includes a custom aluminum-baffled fuel tank with all necessary threaded fitment bungs and fuel filler inlet (note that a fuel cell can be purchased from RCR). Some builders choose to modify the fuel tank with a sump or internal surge tank, However the fuel tank as shipped, provides a proven and robust solution when used in the configuration shown in the diagram. The tank is mounted behind seats and inside the chassis per LeMans specs for improved safety and handling. Some builders mount the tanks with stainless straps as they are concerned that tanks that are mounted with welded brackets will develop cracks or even break away. In addition, the straps allow the tank some "breathing room".
A fuel shut off value is optional. It enables you to change down-stream parts such as one of the filters without draining the fuel tank. Try to design your fuel system so there is room for a fuel shut off valve. You will be glad you did this later.
The lift filter is placed before the lift pump. It typically has a 100 micron insert. The filter is mounted before the filter to catch contaminants that might hurt the pump.
The lift pump transfers fuel from the gas tank to the surge tank. Lift pumps are generally low-pressure, high-volume pumps. While a high-pressure EFI pump could be used, they don't like running dry and usually don't lift as efficiently as a proper lift pump will. Be sure to mount the pump so it doesn't have to lift fuel very far. The best case it to mount the pump so the inlet is lower than the outlet on the tank. Good LP pumps are able to lift fuel in suction, but it is safer to mount them as advised here to improve pump life.
The surge tank ensures that the inlet to the high-pressure fuel pump is never starved for fuel. This is important given the forces that the SL-C can generate when accelerating, decelerating or cornering. Some builders have opted to build a sump in the gas tank or implement an internal surge tank. A 1/2 to 3/4 gallon capacity is more than enough.
Note that the surge tank has a line to dump excess fuel back to the main tank. If this line has a restrictor, it will serve to pressurize the tank in most circumstances, and that will make it easier for the HP pump(s).
Newer kits now ship with a surge tank, saving the builder the need to fabricate or source one, as this is a universal need, regardless of the engine a builder may select.
The high-pressure filter can be placed before or after the high pressure pump, it all depends on what you're trying to protect. It is typically 5-10 microns. There are many kinds of fuel filters on the market. One kind that some builders prefer is the canister style from Canton. These filters offer very fine filtering media, and, more importantly, much easier filter changing procedures. If possible, avoid the inline style filters, as you must take apart the filter, including removing the lines to them. The canister ones permit a really fast, easy and dry filter change as only the top is removed with 4 screws. The same filters can be used for both low and high pressure fuel filters.
The high-pressure pump provides fuel to the fuel regulator. The whole point of the lift pump and surge tank is to ensure that the high-pressure pump is never starved.
The fuel pressure regulator controls the pressure of the fuel as seen at the fuel rail and injectors. It dumps excess fuel back to the fuel tank or surge tank.
A fluid-filled fuel pressure gauge on the regulator makes it easy to set and monitor the fuel pressure. This helps with potential trouble shooting later on too.
As with all fuel tanks in all cars, there is a provision for venting in the supplied tank from Superlite. This 1/2" bung should have a rollover valve installed with appropriate plumbing such that the hose or fittings run ABOVE the top of the fuel tank, then exits to an appropriate place- make sure the valve is plumbed such that any excess fuel is dumped as far back as possible.
A carbon canister should be used to contain fuel fumes. These can be obtained inexpensively at Amazon and others (search for "vapor canister"). One that has been tested and works can be found here. Run the vent line from the tank to the port marked "tank" and run a line from the "purge" port to the very back of the car. Be sure you run the vent line all the way back, as any spilled fuel should not puddle or escape near the engine, which is a potential ignition source.
You can seal the end of the hose with a small filter, like those used on valve covers as a breather.
An inertia switch is an important safety precaution and is used in almost all modern production cars. You don't want the fuel pumps to continue operating at 10-40 gallons per minute in the advent of a collision or rollover. An inertia switch has a small loose weight trapped within a spring-loaded cage. A shock in any direction will cause movement relative to the cage, and if sufficiently shocked the cage will spring open, actuating an associated switch. The switch is typically reset by pressing the cage closed through via a button that re-traps the weight. You can wire the inertia switch in-line or use it as an input to the InfinityBox system which will need to be configured to turn the pumps off. Depending on your switches sensitivity, you will to locate the inertia switch such that it can be easily reset. Some builders install them in the cockpit. Pegasus has a nice switch here.
Be sure to seal the passenger compartment from the engine compartment so that fire or fumes from the engine cannot get to the occupants of the car. This means careful attention to sealing along the top of the body, around the bulkhead, and especially in the area at the side of the tank just behind the bulkhead. Everything needs to be airtight there.
One builder's fuel system write up is here.
Fran's View: The fuel system plumbing and components are very simple really and only made complicated by the differing choices available in the aftermarket. The following are simple, reasonably inexpensive parts that we have used in dozens of builds with zero issues. We will be running the same components on the LMP as we have used them without issue on the 01 car for two seasons:
- Lift Pump: Holley HP-12-150
- Returnless fuel pressure regulator: AEI-13109
- High-Pressure Pump: Bosch-044 300lph
- We also run a fluid-filled fuel pressure gauge on the regulator making setting fuel pressure and monitoring it very easy. This helps with potential trouble shooting later on too.
- Both pumps are external in-line style pumps making changing them very easy and simple, should you have a failure..
As mentioned above, Superlite offers a complete pump and filter setup that has a low-pressure pump, a high-pressure pump, and filters mounted on a panel that can be bolted to the chassis. It makes setting up the fuel system very easy. Check with the factory for current pricing and parts list.