Here’s the challenge: design a fuel delivery system that can feed gasoline to an 800 hp engine using an in-tank pump that is stealthy quiet and does not require a return line back to the tank.
But hold off before you break out the catalogs, pen, and paper. You don’t need to design it because the work’s been done for you – mostly by the new car companies! Think about it, automakers are building cars with 500-775 hp they must feed with sufficient fuel – by a system capable of 100,000 miles worth of durability.
When Carl Casanova first decided to convert his 1968 Camaro into a road-worthy, supercharged, Pro Touring car with big power, one of the demands for his car was a rock-solid fuel delivery system.
He investigated how the OE’s were doing it, and quickly realized their returnless system was the best way to approach the problem. Even today, most aftermarket companies shy away from returnless systems. Instead, most recommend building a full-return system, because the return-style mechanical-pressure regulator is easier to control.
There’s nothing overtly wrong with a return style system, but one drawback to consider is that fuel pulls heat from the intake manifold fuel rails and delivers heated fuel to the fuel tank. This eventually raises the overall fuel temperature in the tank, especially at lower fuel levels.
According to Carl, most electric fuel pumps are only about 33-percent efficient, so anything that can be done to reduce heat means less fuel temperature increase and greater efficiency.
Plus, all aftermarket return systems require some type of reservoir or specific pickup system.
For example, the popular “pump on a stick” systems work well, but exhibit a weakness linked directly to the fuel level in the tank. First, as the fuel level drops, the pump must work harder to draw fuel into it. The second weakness comes from fuel slosh while cornering or accelerating, as it can uncover the pump inlet even under mild performance conditions. Holley’s Hydramat helps these situations, since it rests on the tank floor, but still does not cure low inlet head problems at low fuel level.
Fuel pumps are great at pushing, but less efficient at “pulling” or drawing fuel into the pump. Any design that improves inlet flow is advantageous. Ideally, the pickup to the fuel system will always be immersed in a standing level of fuel much higher than the pump inlet. This is one aspect of fuel delivery that is generally overlooked, yet absolutely critical to efficient fuel-pump performance.
The OE’s quickly determined that return systems added too much heat with higher emissions due to evaporation. The extra fuel line and connections also potentially added to both emissions and complexity to the fuel system.
Returnless systems are simpler and less expensive to build but demand a more complex fuel-pressure-management system. The better way to regulate fuel pressure is by managing pump speed through a process called pulse width modulation (PWM). In a traditional fuel-delivery system, the electric fuel pump runs continuously at maximum output. This works – unless the engine demands a very large pump to feed an 800 or 1,000 hp engine that must also run for long periods of time on hot days.
The main issue with continuously running a high output pump is that for a majority of the time, street engines operate at part throttle.
A typical, high-output fuel-injected engine might sip fuel at five percent of the total volume required at wide-open-throttle (WOT). That means that a pump running at full capacity will return 95-plus percent of the fuel at part throttle. That creates wasted effort and tends to over-heat the fuel.
The first thought would be – just feed less voltage to the pump and slow it down. Unfortunately, that doesn’t work, as all automotive fuel pumps are designed to run at 13.5 volts. Operate one at 6.5 volts and it will quickly overheat — and likely fail — but there is a solution. Pulse width modulation can accomplish the goal of running a pump at low output without damaging the motor.
Here’s how it works
Imagine you are riding a bicycle on a level-grade bike path.
To maintain a constant steady speed, you can pedal constantly with very light effort. Or, you can pedal slightly harder, but only for half the normal revolutions, and still maintain the required constant speed. So let’s say for every 10 seconds of ride time, you only pedal for half the time – or 5 seconds. That would be a duty cycle of 50 percent. A PWM-controlled fuel pump can operate the same way. When demand is low, the pump’s electronic controller will feed 13.5 volts to the pump in pulses for half of a given amount of time.
On a voltmeter, this would read 6.75 volts, but the meter is really averaging the voltage reading.
The real message to the pump can be seen on an oscilloscope where 13.5 volts is applied for a short pulse then dropped to zero and then a 13.5-volt pulse is applied again. This kind of voltage control is not harmful to the pump, because the armature is likely still spinning when the PWM signal is re-applied.
PWM control eliminates the need for a traditional external fuel-pressure regulator (there is, however, a pressure regulator built into late model fuel modules to prevent over-pressure), but does require a sensitive fuel-pressure sensor. This sensor is matched with a device that can generate a PWM signal that is commanded by the fuel-pressure in the system.
This is how the OE’s control fuel in modern high-power cars and that’s what Carl decided to create for the fuel system he calls VaporWorx.
|Description||GM PN||AC Delco PN||Source||Price|
|LS3 Camaro pump module||19208719||M100080||RockAuto||$126.79|
|ZL1 Camaro pump module||19260557||MU2101||RockAuto||$196.79|
|CTS-V pump module||19207950||M10235||RockAuto||$345.89|
|VaporWorx control kit, Camaro||N.A.||PWZL13B-23IT||Vaporworx||$429.00|
|RetroWorx tank adapter panel||N.A.||RWTAK||Vaporworx||$199.00|
|VaporWorx QD adpt. to -6AN||N.A.||FPOFGMQCAN6||VaporWorx||$13.49|
|VaporWorx Fuel Mod. plug kit||N.A.||FMPLUGKIT||VaporWorx||$13.00|
He quickly learned that GM, for example, makes an extremely well-designed fuel module that contains the fuel pump – negating the need for any kind of internal tank baffling or sump.
Next, he needed a fuel-pressure sensor, something that GM has built for years. The last piece required for his VaporWorx kit was a stand-alone controller that would take fuel-pressure readings from the sensor and feed high-power commands to the fuel module.
This demanded the only major non-OE component, a PWM controller that Carl had designed by a wizard electronics expert. Now, with 7 years of durability testing of his own, along with hundreds of kits sold, the system works.
Besides the PWM controller, the heart of any fuel delivery system is the fuel module. Carl specifies three different GM modules for nearly any requirement from very low horsepower (Carl has plumbed a VaporWorx system into a four-cylinder MG with aftermarket EFI using a Gen5 V6 pump) all the way up to over 1,000 hp.
The included chart indicates which of these GM pumps is recommended based on your horsepower requirements.
OE Fuel Pump Recommendations
|HP Rating||Fuel Pressure||GM Pump|
|Under 600 HP||60 psi||LS3 Camaro|
|Under 775 HP||60 psi||ZL1 Camaro|
|Under 950 HP||60 psi||CTS-V|
|Under 650 HP||60 psi||ZL1 Camaro|
|Under 810 HP||60 psi||CTS-V|
|Over 810 HP||60 psi||Custom twin modules and/or DW300 pumps.|
The beauty of this system is that the pump(s) are contained within the module body and are always fully immersed in fuel even when the fuel level is near empty.
How the module accomplishes this is both innovative and incredibly simple.
Let’s say we load a module into a new, dry fuel tank. As you can see from the photos, these modules are designed to operate within a height of 5.5 to 7-inches in height and are spring loaded, which ensures the module seats firmly on the fuel tank floor. Adding a couple of gallons of fuel to the tank and a small, one-way foot valve, allows fuel to enter the module reservoir.
Once the pump is energized and begins making pressure, a small amount of high-pressure fuel is internally bypassed and used like a siphon pump to fill the reservoir from the fuel in the tank. Even with a very low liquid level, this jet-pump assembly pulls fuel from the tank and fills the reservoir to overflowing, ensuring the pump inlet is always covered as if the fuel tank was full. This also maintains a vertical load of fuel over the pump inlet which improves pump efficiency and minimizes cavitation.
The module also uses a mounting ring which is standardized throughout GM, Ford, and Chrysler fuel modules. This mounting ring locates the module in the tank, which is then locked into place using a standardized OEM cam-locking ring.
There are several companies that make fuel tanks for popular performance cars like the first and second-generation Camaros and other cars that will accommodate these fuel modules, making it very easy to convert to a VaporWorx system.
The above description applies to all the fuel modules except the 2009-14 CTS-V, which uses a twin-pump design which increases its capacity. This module was intended to feed the supercharged 6.2L CTS-V engine, rated very conservatively at 556 hp. It is designed so that both pumps run simultaneously. Though it has the highest-flow rating of any GM fuel module, with PWM control its service life is extremely long.
Gen5 and Gen6 ZL1 Fuel Module Performance Data
Performed by RC Engineering in Torrance, CA
|PSIG||Amps||Lbs/Hr||Gal/Hr.||Ltr/Hr||CC/Min||BHP at 0.5 BSFC||BHP at 0.6 BSFC|
PSIG – gauge pressure
Amps – amperage required to run the pump
Lbs/hr – pounds-per-hour of fuel delivered by the pump
Gal/Hr – gallons of gasoline per hour
Ltr/Hr – liters of gasoline per hour
CC/Min – cubic centimeters of gasoline delivered per minute
BSFC – Brake Specific Fuel Consumption. This is the amount of fuel, in pounds, required to produce one horsepower for one hour. Naturally aspirated engines = (0.5lbs/hp)/hr, Supercharged up to 800hp typically (0.6lbs/hp)/hr.
BHP at 0.5 BSFC – brake-horsepower potential at a brake-specific fuel consumption of 0.5
BHP at 0.6 BSFC – brake-horsepower potential at a brake-specific fuel consumption of 0.6 used for supercharged engines
For even a daily-driven performance street car, this pump module would last near a lifetime of driving. Carl says this OE pump will easily feed up to 75-supercharged-horsepower on gasoline. Above that level, the OE pumps could be upgraded or a custom twin-module system could be created.
The only other major component you would need, besides the fuel module and the VaporWorx electronic-control system, would be a fuel tank. Most ‘60s -‘70s muscle car tanks are usually not quite deep enough to accommodate the fuel-pump module height requirement, which starts at roughly 6.5- inches.
Several aftermarket companies like Rick’s Tanks, Rock Valley, and even Detroit Speed offer tanks for specific vehicles such as early Camaros, Chevelles, and other cars. A stock tank could also be modified to accommodate a late-model module by using a VaporWorx weld-in mounting ring.
There’s far more to returnless PWM systems than we can fully detail in this story, but VaporWorx offers more details and information on its website. Carl encourages potential customers to do their research with regard to other systems to compare the benefits of a VaporWorx system. That was exactly the effort we made that led us to this story.
The VaporWorx approach is not the least expensive so it probably isn’t for everyone. But for the discerning builder, long-distance hauler, and autocross/track day enthusiast, there are certain benefits you won’t find anywhere else.