Wiki source for Fuel-System
Fuel System
Contents
1 Description of Components
1.1 Fuel Tank
1.2 Fuel Pump
1.3 Feed Line
1.4 Fuel Rail
1.5 Fuel Pressure Regulator
1.6 Fuel Return Line
1.7 Fuel Injectors
2 Injectors
2.1 RC Engineering
2.2 Cobalt LSJ
3 Fuel Pump
3.1 Walbro
3.2 MSD
4 FPR
4.1 Accel
4.2 Aeromotive
5 Fuel Rail
Description of Components
To understand the fuel system, you need to understand its parts. Here is the basic fuel system:
[Fuel Tank]--[Fuel Pump]--[Feed Line]--[Fuel Rail]--[FPR]--[Return Line]--[Fuel Tank]
Fuel Tank
The fuel tank obviously holds the fuel. In our cars (and many OBD-II cars) this tank is pressurized. This is why you hear a hiss when you open the gas cap. The computer monitors the pressure in the tank, so that when it drops below a certain point for a certain period of time, the tank or evaporative system has a leak. Usually this is caused by a loose or bad gas cap, but occasionally has other causes.
The evaporative (or evap) system is interesting in itself. If you've ever spilled gas you know that it "dries" up very fast. Its not actually drying, its evaporating. The evap system uses the evaporated gas and pipes it back into the intake manifold to improve gas mileage.
Fuel Pump
The fuel pump pulls the fuel out of the fuel tank and sends it down the rest of the system. The stock pump is not designed to handle much pressure over stock, no matter what other people have gotten with it. Do NOT trust the pump over 60 psi for any length of time. You may get away with it for a month or two, but one day the pump will burn out and fail when you really don't need it to.
You can pressure test a fuel pump to see what its maximum pressure is. First you need a gauge in the fuel system somewhere on the feed line or fuel rail. Next, start your car and let it idle. Clamp a vise-grip around the return line and wait until the pressure stabilizes, then unclamp it. That is your maximum fuel pressure. Just don't leave the line clamped very long, it will burn out your pump in a hurry.
Feed Line
This is a pressure line from the fuel pump to the fuel rail. There really is nothing special about it, other than its made for fuel injected cars (carburated fuel line is different... NEVER USE IT in an fuel injected system).
Fuel Rail
The fuel rail distributes an equal amount of fuel pressure to each of the injectors that are attached to it. The stock fuel rail holds enough fuel and fuel pressure to support well over 500hp. Aftermarket rails are really nothing more than dress up items. Fuel rails aren't really any technological wonder. Its a tube with a hole on each end, and 4 holes for the injectors. One end-hole attaches to the fuel feed line, and the other end has the fuel pressure regulator on it (FPR).
Fuel Pressure Regulator
This is a wonder of science right here. Basically, its a vacuum actuated valve. The more vacuum the FPR sees, the less it opens. If you are thinking to yourself... "well that doesn't sound right... at 0 vacuum (wide open throttle) you want more fuel, so you'd want it to open more", then you are just a bit backwards. The fuel pressure regulators job is given away by its name. It DOES NOT regulate how much fuel is in the fuel rail, but how much pressure is in it.
If you want to have a real world example of how you can understand this, get a drinking straw. Put one end in your mouth and put your fingers at the end so you can pinch the end closed. Now blow into the straw, but don't pinch the end, thats how the fuel pressure regulator is when there is full vacuum. You don't need a lot of fuel pressure going into the injectors because at full vacuum, the engine's throttle plate is fully closed (you are not accelerating).
Now, blow through the straw, but pinch the end shut (or varying degree's of shut), and blow through it. That is how the FPR is at WOT, where there is no vacuum. It increases the fuel pressure so each time the injectors open, more fuel is forced through them.
A common misconception about the fuel system is that the fuel pressure is regulated by the computer. It is not. The pump is running 100% (flow wise) all the time. The FPR chooses how much of this flow to hold in the rail (and increases fuel pressure by doing so), and how much to let back into the fuel tank (reason for the return line). The fuel pressure is completely vacuum controlled.
Fuel Return Line
This brings fuel back into the fuel tank. It is important to note that the fuel return line IS NOT a pressurized line. Don't use the return line to feed your extra injector's, or whatever else needs fuel. This line simply takes fuel from the fuel pressure regulator and drops it back into the fuel tank.
Fuel Injectors
Your fuel injectors sit under the fuel rail and inject fuel at the back of one of the valves, which, when open, suck fuel into the combustion chamber.
Fuel injectors are electronically controlled valves. They operate on a square wave signal from the ECU. Basically this means that the valve opens when the signal is high, and closes when the signal is low. The length of time that the signal is high (and the valve is open) is called the pulsewidth. The pulsewidth, as a definition, is the length (in time) of the pulse that opens the injectors.
Now injectors have a duty cycle. This is the amount of time they spend open. When an injector is open, it generates heat (electricity turns to kinetic energy in the form of heat, physics stuff). The longer the valve is open, the more heat it generates, and therefore the more prone it is to failure. When an injector fails, it will either stick open, or stick closed, both are very bad. When sizing injectors, you don't want to have the injectors working with more than an 80% duty cycle under the very worst conditions, and even then, not for very long.
Fuel injectors are sized at a certain pressure, usually 45 PSI. They are then tested at that pressure and rated for a certain flow (lbs/hr or cc/min). The more fuel that the injector can let through it at one time, the bigger the injector is. You can effectively change the size of the fuel injectors by changing the fuel pressure that is going through them. Obviously if the injector is rated at 45 PSI, and you push 60 PSI through it, then you will get a higher flow rate. Many times, this is desirable since you can get a lower duty cycle on smaller injectors and increase the fuel atomization.
There is a downside to just increasing the fuel pressure though. Actually, there are 2 downsides. The first is the fuel pump. Backing up the fuel in the rail causes the pump to try to push more fuel into the line (which increases pressure), but causes the pump to heat up and eventually fail. The second downside is called clipping. Clipping occurs when you try to push too much fuel pressure into the injector. The high fuel pressure can actually hold the injector closed, causing it to clip, or miss that pulse. When this happens often enough, it causes misfires and possibly engine damage.
Injectors
Bigger injectors are required to add more fuel in any upgraded engine. Tuning is required for the optimum performance when you replace your stock injectors for aftermarket, higher flowing ones.
RC Engineering
RC manufactures injectors that work with the Alero. RC Engineering is the world's leading supplier of made-to-order, high-performance, electronic fuel injectors. Resistance is 12-16 ohms and flow rates are measured at 43 PSIg. These are also known as saturated injectors. Harness Clips are required for 99-02 2.4L High Impedance injectors. Sizes available at CarCustoms: 270cc, 310cc, 440cc, 550cc.
In order to utilize RC Engineering injectors with the stock wire harness you will need adapter clips, also available at CarCustoms.
Cobalt LSJ
The stock injectors from the Chevrolet Cobalt SS Supercharged (36lb, 378cc) will work with the LD9 engine. They plug right into the stock connectors. The only issue is that since the LSJ injectors are shorter, so the bolt holes on the fuel rail must be slotted a little bit, as seen in the image.
You can pick these up anywhere from junkyards, CobaltSS.net classifieds, or even buy the upgraded Stage 2 (42lb, 440cc) and 3 (60lb) injectors from a Cobalt performance parts retailer. Be sure to get the wiring harness for the upgraded Stage injectors. The stock 36lb do not require this and plug right in.
Fuel Pump
When running larger injectors you may want to get a higher flowing pump, however, many have used 550+ cc injectors without issue on the stock system. Any bigger, an advanced pump is required.
Walbro
This upgraded fuel pump increased the fuel delivery required for high horsepower applications. This pump flows 255 liters/hour.
MSD
Multiport EFI systems require a stable fuel supply to maintain the best performance throughout the engine's rpm range. This high pressure and high flow fuel pump features a roller vane pump mechanism which is extremely resistant to clogging and jamming. The pump mounts in-line (out of the tank) with two supplied cushioned clamps for a quick and sturdy installation. The nipple inlet is 3/8 in. with a 5/16 in. outlet and the wire terminals feature brass studs for secure connections. Made in the USA, the pump is ideal for use as a booster for nitrous oxide applications, or as a stand alone pump for multiport EFI systems on engines up to approximately 500 HP. Available at TurboTechRacing.
FPR
Normally the best option for increasing your fuel input is by obtaining bigger injectors and using tuning software to control them. However, some use the "band-aid" method of installing an aftermarket fuel pressure regulator that is adjustable, to increase or lower fuel rail pressure to push the right amount of fuel in.
Accel
These premium quality pressure regulators provide stable fuel pressure under the most demanding conditions. Adjustable fuel pressure regulators allow adjustments for increased fuel volume and superior fuel atomization. Available at TurboTechRacing.
Aeromotive
Aeromotive regulators beat the competition with the best of all worlds: Outstanding, consistent performance from equipment that’s built to last. Aeromotive delivers more flow than similar regulators thanks to a custom, convoluted diaphragm that maximizes piston stroke while minimizing stress. Every model uses a poppet designed specifically for that regulator, and a diaphragm fabricated from a proprietary elastomer material. The standard vacuum boost port delivers perfect 1:1 boost reference and makes these regulators ideal for turbo-charged and supercharged engines. Available at Jeg's.
Fuel Rail
A polished or anodized "high flow" fuel rail is typically only a visual modification. The fuel rail distributes an equal amount of fuel pressure to each of the injectors that are attached to it. The stock fuel rail holds enough fuel and fuel pressure to support well over 500hp. Aftermarket rails are really nothing more than dress up items. Fuel rails aren't really any technological wonder. Its a tube with a hole on each end, and 4 holes for the injectors. One end-hole attaches to the fuel feed line, and the other end has the fuel pressure regulator on it (FPR). One of the most popular choices is one by Venom, which can be purchased at Summit Racing, Andy's Auto Sport, and many other retailers.
Contents
1 Description of Components
1.1 Fuel Tank
1.2 Fuel Pump
1.3 Feed Line
1.4 Fuel Rail
1.5 Fuel Pressure Regulator
1.6 Fuel Return Line
1.7 Fuel Injectors
2 Injectors
2.1 RC Engineering
2.2 Cobalt LSJ
3 Fuel Pump
3.1 Walbro
3.2 MSD
4 FPR
4.1 Accel
4.2 Aeromotive
5 Fuel Rail
Description of Components
To understand the fuel system, you need to understand its parts. Here is the basic fuel system:
[Fuel Tank]--[Fuel Pump]--[Feed Line]--[Fuel Rail]--[FPR]--[Return Line]--[Fuel Tank]
Fuel Tank
The fuel tank obviously holds the fuel. In our cars (and many OBD-II cars) this tank is pressurized. This is why you hear a hiss when you open the gas cap. The computer monitors the pressure in the tank, so that when it drops below a certain point for a certain period of time, the tank or evaporative system has a leak. Usually this is caused by a loose or bad gas cap, but occasionally has other causes.
The evaporative (or evap) system is interesting in itself. If you've ever spilled gas you know that it "dries" up very fast. Its not actually drying, its evaporating. The evap system uses the evaporated gas and pipes it back into the intake manifold to improve gas mileage.
Fuel Pump
The fuel pump pulls the fuel out of the fuel tank and sends it down the rest of the system. The stock pump is not designed to handle much pressure over stock, no matter what other people have gotten with it. Do NOT trust the pump over 60 psi for any length of time. You may get away with it for a month or two, but one day the pump will burn out and fail when you really don't need it to.
You can pressure test a fuel pump to see what its maximum pressure is. First you need a gauge in the fuel system somewhere on the feed line or fuel rail. Next, start your car and let it idle. Clamp a vise-grip around the return line and wait until the pressure stabilizes, then unclamp it. That is your maximum fuel pressure. Just don't leave the line clamped very long, it will burn out your pump in a hurry.
Feed Line
This is a pressure line from the fuel pump to the fuel rail. There really is nothing special about it, other than its made for fuel injected cars (carburated fuel line is different... NEVER USE IT in an fuel injected system).
Fuel Rail
The fuel rail distributes an equal amount of fuel pressure to each of the injectors that are attached to it. The stock fuel rail holds enough fuel and fuel pressure to support well over 500hp. Aftermarket rails are really nothing more than dress up items. Fuel rails aren't really any technological wonder. Its a tube with a hole on each end, and 4 holes for the injectors. One end-hole attaches to the fuel feed line, and the other end has the fuel pressure regulator on it (FPR).
Fuel Pressure Regulator
This is a wonder of science right here. Basically, its a vacuum actuated valve. The more vacuum the FPR sees, the less it opens. If you are thinking to yourself... "well that doesn't sound right... at 0 vacuum (wide open throttle) you want more fuel, so you'd want it to open more", then you are just a bit backwards. The fuel pressure regulators job is given away by its name. It DOES NOT regulate how much fuel is in the fuel rail, but how much pressure is in it.
If you want to have a real world example of how you can understand this, get a drinking straw. Put one end in your mouth and put your fingers at the end so you can pinch the end closed. Now blow into the straw, but don't pinch the end, thats how the fuel pressure regulator is when there is full vacuum. You don't need a lot of fuel pressure going into the injectors because at full vacuum, the engine's throttle plate is fully closed (you are not accelerating).
Now, blow through the straw, but pinch the end shut (or varying degree's of shut), and blow through it. That is how the FPR is at WOT, where there is no vacuum. It increases the fuel pressure so each time the injectors open, more fuel is forced through them.
A common misconception about the fuel system is that the fuel pressure is regulated by the computer. It is not. The pump is running 100% (flow wise) all the time. The FPR chooses how much of this flow to hold in the rail (and increases fuel pressure by doing so), and how much to let back into the fuel tank (reason for the return line). The fuel pressure is completely vacuum controlled.
Fuel Return Line
This brings fuel back into the fuel tank. It is important to note that the fuel return line IS NOT a pressurized line. Don't use the return line to feed your extra injector's, or whatever else needs fuel. This line simply takes fuel from the fuel pressure regulator and drops it back into the fuel tank.
Fuel Injectors
Your fuel injectors sit under the fuel rail and inject fuel at the back of one of the valves, which, when open, suck fuel into the combustion chamber.
Fuel injectors are electronically controlled valves. They operate on a square wave signal from the ECU. Basically this means that the valve opens when the signal is high, and closes when the signal is low. The length of time that the signal is high (and the valve is open) is called the pulsewidth. The pulsewidth, as a definition, is the length (in time) of the pulse that opens the injectors.
Now injectors have a duty cycle. This is the amount of time they spend open. When an injector is open, it generates heat (electricity turns to kinetic energy in the form of heat, physics stuff). The longer the valve is open, the more heat it generates, and therefore the more prone it is to failure. When an injector fails, it will either stick open, or stick closed, both are very bad. When sizing injectors, you don't want to have the injectors working with more than an 80% duty cycle under the very worst conditions, and even then, not for very long.
Fuel injectors are sized at a certain pressure, usually 45 PSI. They are then tested at that pressure and rated for a certain flow (lbs/hr or cc/min). The more fuel that the injector can let through it at one time, the bigger the injector is. You can effectively change the size of the fuel injectors by changing the fuel pressure that is going through them. Obviously if the injector is rated at 45 PSI, and you push 60 PSI through it, then you will get a higher flow rate. Many times, this is desirable since you can get a lower duty cycle on smaller injectors and increase the fuel atomization.
There is a downside to just increasing the fuel pressure though. Actually, there are 2 downsides. The first is the fuel pump. Backing up the fuel in the rail causes the pump to try to push more fuel into the line (which increases pressure), but causes the pump to heat up and eventually fail. The second downside is called clipping. Clipping occurs when you try to push too much fuel pressure into the injector. The high fuel pressure can actually hold the injector closed, causing it to clip, or miss that pulse. When this happens often enough, it causes misfires and possibly engine damage.
Injectors
Bigger injectors are required to add more fuel in any upgraded engine. Tuning is required for the optimum performance when you replace your stock injectors for aftermarket, higher flowing ones.
RC Engineering
RC manufactures injectors that work with the Alero. RC Engineering is the world's leading supplier of made-to-order, high-performance, electronic fuel injectors. Resistance is 12-16 ohms and flow rates are measured at 43 PSIg. These are also known as saturated injectors. Harness Clips are required for 99-02 2.4L High Impedance injectors. Sizes available at CarCustoms: 270cc, 310cc, 440cc, 550cc.
In order to utilize RC Engineering injectors with the stock wire harness you will need adapter clips, also available at CarCustoms.
Cobalt LSJ
The stock injectors from the Chevrolet Cobalt SS Supercharged (36lb, 378cc) will work with the LD9 engine. They plug right into the stock connectors. The only issue is that since the LSJ injectors are shorter, so the bolt holes on the fuel rail must be slotted a little bit, as seen in the image.
You can pick these up anywhere from junkyards, CobaltSS.net classifieds, or even buy the upgraded Stage 2 (42lb, 440cc) and 3 (60lb) injectors from a Cobalt performance parts retailer. Be sure to get the wiring harness for the upgraded Stage injectors. The stock 36lb do not require this and plug right in.
Fuel Pump
When running larger injectors you may want to get a higher flowing pump, however, many have used 550+ cc injectors without issue on the stock system. Any bigger, an advanced pump is required.
Walbro
This upgraded fuel pump increased the fuel delivery required for high horsepower applications. This pump flows 255 liters/hour.
MSD
Multiport EFI systems require a stable fuel supply to maintain the best performance throughout the engine's rpm range. This high pressure and high flow fuel pump features a roller vane pump mechanism which is extremely resistant to clogging and jamming. The pump mounts in-line (out of the tank) with two supplied cushioned clamps for a quick and sturdy installation. The nipple inlet is 3/8 in. with a 5/16 in. outlet and the wire terminals feature brass studs for secure connections. Made in the USA, the pump is ideal for use as a booster for nitrous oxide applications, or as a stand alone pump for multiport EFI systems on engines up to approximately 500 HP. Available at TurboTechRacing.
FPR
Normally the best option for increasing your fuel input is by obtaining bigger injectors and using tuning software to control them. However, some use the "band-aid" method of installing an aftermarket fuel pressure regulator that is adjustable, to increase or lower fuel rail pressure to push the right amount of fuel in.
Accel
These premium quality pressure regulators provide stable fuel pressure under the most demanding conditions. Adjustable fuel pressure regulators allow adjustments for increased fuel volume and superior fuel atomization. Available at TurboTechRacing.
Aeromotive
Aeromotive regulators beat the competition with the best of all worlds: Outstanding, consistent performance from equipment that’s built to last. Aeromotive delivers more flow than similar regulators thanks to a custom, convoluted diaphragm that maximizes piston stroke while minimizing stress. Every model uses a poppet designed specifically for that regulator, and a diaphragm fabricated from a proprietary elastomer material. The standard vacuum boost port delivers perfect 1:1 boost reference and makes these regulators ideal for turbo-charged and supercharged engines. Available at Jeg's.
Fuel Rail
A polished or anodized "high flow" fuel rail is typically only a visual modification. The fuel rail distributes an equal amount of fuel pressure to each of the injectors that are attached to it. The stock fuel rail holds enough fuel and fuel pressure to support well over 500hp. Aftermarket rails are really nothing more than dress up items. Fuel rails aren't really any technological wonder. Its a tube with a hole on each end, and 4 holes for the injectors. One end-hole attaches to the fuel feed line, and the other end has the fuel pressure regulator on it (FPR). One of the most popular choices is one by Venom, which can be purchased at Summit Racing, Andy's Auto Sport, and many other retailers.
