Frequently Asked Questions:
AirDog®/Fuel Preporator® for Class 8 and Commercial Applications
Why is this product important?
Diesel engines have long been known to lose power, increase fuel consumption and have increased exhaust emissions as the fuel filter plugs with use, when operating at higher altitudes, and especially when air vapor is present in the engine’s fuel system. Air and vapor are compressible. Their presence in the injector delays the pressure buildup and the injection, which results in Retarded Injection Timing and increased fuel consumption, increased exhaust emissions and low power.
The AirDog® Fuel Preporator® is the only system in the world that is third party verified to remove entrained air and maintain positive pressure head to the pump eliminating cavitation and vapor, eliminating the above issues and restoring correct injection timing!
What benefits are to be gained with the use of this product?
- Increased fuel economy of 8%-12%: Depending on the particular engine make, model, year, and application. Testimonials repeatedly show a minimum of .5 mpg, upwards to over 1.0 mpg. Heavy haulers and others hauling high resistance OD loads, show even greater gains.
- Maintains peak power: Sustaining net positive pressure flow to the transfer pump eliminates the normal drop off from peak torque at the 1400-1500 rpm levels. Engine idle is much smoother. Plus much better throttle response.
- Easier starts, especially in colder weather. Self priming after filter changes.
- Extends engine life: Air/Vapor in the injector can result in GALLING of the barrel & plunger, PITTING of the barrel and TIP erosion. A cleaner burning engine leads to longer life and lower maintenance costs.
- Reduced exhaust emissions. 29.9% documented reduction in unburned hydro-carbons in Series 60 Detroit; 76% reduction in 3406B Cat; 70% reduction in an Isuzu. Documented Nox reduction of 46% on Cat 3208. CO reduction documented 54% on same 3208.
What is a vacuum feed system and what are it’s deficiencies that contribute to the problems?
A fuel pump is a mechanical means to move liquids. It does not “suck” fuel in, it only pumps what is pushed into its mechanism by an outside force. This force, as in the case of the “vacuum feed” system on your engine, with a tank positioned below the pump, is the force of atmospheric pressure pressing on the surface of the fuel in the tank attempting to equalize to the low pressure or vacuum at the pump inlet. As the pump operates, there is insufficient pressure flow available to completely fill the pump. This condition creates a void or cavity within the transfer pump. The effect of this cavity allows the vapor pressure of the fuel to become greater than the liquid pressure and results in the vaporization of the fuel and vapor. This is termed cavitation or pump cavitation.
As the speed of the engine increases, there is less time for the fuel to enter the pump. However, fuel flow into the pump does not increase. The result is increased cavitation and increased fuel vapor. The installation of a fuel filter in the line creates restriction. As the filter becomes more restricted, cavitation and air/vapor increases. Other restrictions such as water separators and fuel heaters, coolers, etc. compound the problem. The greater the presence of air/vapor in the fuel, the more retarded injection timing and poor engine performance become.
The use of the inadequate vacuum feed fuel supply system on diesel engines which does not remove the entrained air/vapors and does not address cavitation and the production of fuel vapor is the predominant source of performance and emission problems in the diesel engine. The vacuum fuel supply concept is the root cause of the inconsistencies and performance problems.
How does the product work?
In the most simple summation, the AirDog®/Fuel Preporator® removes the entrained air and maintains a positive pressure to the engine’s transfer pump. This net positive pressure prevents pump cavitation. The removal of entrained air and vapor from the fuel flow to the engine results in correct injection timing in unit and injector pump engines. It also eliminates spray pattern disruption and low fuel pressures in common rail engines. Air and vapor, being compressible, delay the pressure buildup in the injector which delays the injection resulting in retarded injection timing. Remove the air/vapor and restore correct injection timing and engine efficiency.
However, the best explanation is by watching. You can see the video by visiting the link: www.pureflowtechnologies.com On the home page hover or click on the top tab: “Technical” and from the resulting drop down menu click on “How it Works” for the short but demonstrative video to better visualize the functioning device.
How is the product sold or justified in the eyes of the purchaser?
There are two approaches: a) solution to mechanical ailments; and, (b) fuel savings.
The fuel savings is frequently the easiest way to justify a purchase. We consistently see a minimum of 0.5 mpg improvement across the board, with gains of 0.6-1.0+ on some engines and use applications. The variance can be explained by certain engines having greater inefficiencies, such as Caterpillar Acerts, C-15’s, Volvo, and the Cummins ISX as the more notable ones seeing improvement on the higher ends.
However, we all know that a conservative approach is best when estimating savings and payback. If an average trucker is driving 2500 miles a week, and his current mileage is 6.0 mpg, that is 417 gallons of fuel. A 0.5 mpg savings reduces fuel consumption to 385 gallons. At an average price of $3.85 gal equates to $123 per week.
This is a typical scenario, and generally we find ROI to be between 2-3 months, depending on the three variables of: 1) mileage driven, 2) fuel saved, and 3) price of fuel. After that, the trucker is essentially putting $500-$750 a month in his pocket. Over a year that is $6000-8000; and for a fleet of 100 trucks that is $600,000+.
Another way to justify purchase is that we have consistently shown the AirDog® can solve a variety of symptoms resulting from air in fuel as recounted earlier. Maybe it is an engine that is hard to start; maybe it is excessive injector wear; maybe it is a lack of power, and maybe a combination of things that together say: This engine just doesn’t run right. The smoothness of the idle, the responsiveness of the engine, improved power to get up hills, the reduced unburned hydro carbons resulting in a cleaner engine, longer injector life and lower maintenance costs also provide great user benefit beyond those pure fuel savings numbers.
But combined, if we can offer a solution that solves many other problems and provides a fuel savings together, the combination is a win-win. The service professional who recommends it gains the trucker’s trust and allegiance and the product gains another proud advocate.
What happens if the product suddenly quits operating and the engine goes back to vacuum feed?
The unit goes on by-pass and the fuel system works on a vacuum feed system just as it did in the past. One must remember, however, that a vacuum feed system is limited to a maximum of 10-12” Hg restriction. If the filter, which had previously been working under pressure has greater restriction than this maximum, say 25,000 miles for example, it may require that the filter may need to be changed for it to operate. A driver should always carry an extra filter.
Can the product be sold and used in California?
AirDog® Fuel Preporator® has met the necessary requirements through CARB to obtain a CARB Exemption number so that it can be sold, installed and used legally in the State of California.
Does this product replace or complement the existing filtration arrangement?
The AirDog® Fuel Preporator® is a replacement for the primary filter. Any secondary filters are retained. By virtue of the micro-processor which measures the amp draw on the motor, we can precisely determine through increased load on the motor when the filter needs changing, thus avoiding premature filter changes and unnecessary expense. The dash mounted multi-colored indicator light will give a solid red color when the filter is near full and a flashing red light when it has reached full capacity.
Additionally, the wire screen water separator needs servicing, not replaced unless physically damaged. The micro-processor indicates with a flashing green indicator light on the dash when it needs servicing.
What is the life of your filters?
Our filters are micro-glass, 6 micron nominal, 10 micron absolute, long life filters, similar in construction to those used on fuel islands. We have a multi-pass filtration process. The longer life, approximately twice that of normal filters, is from both the expanded filter capacity and the ability of the net positive system pressure as opposed to the easily restricted filter of the vacuum feed system.
Does a customer have to use your filters?
No, there are several cross-over filters available. However, we recommend our filters because of the improved quality and longer life. Nevertheless, should a customer find himself on the road without a replacement, there are choices.
How much time is required for a typical installation?
We estimate normal installation to require 3-4 hours; even with the upgrades required of certain engines. A person specialized in the process could probably reduce it to 2 hours; and someone not experienced and doing the most complicated system might take 4-4.5 hours.
Are additional fuel return lines required?
No additional return lines are required. Our unit is demand flow; which means we only draw from the tank the amount of fuel the engine requires. The excess flow is recirculated within the unit for multi-pass filtration avoiding the need for separate (and costly) return lines. The return line only carries the separated air/vapor and a small amount of fuel back to the tank through the existing return line.
Do I need to adjust fuel pressure, or what pressure is the unit set at?
Pressure is pre-set engine specific.
What is the product life?
The new 4G motor/pump assembly, designed to specifically address longevity concerns of the Class 8 and Commercial operations, have passed extensive testing and been found to have an anticipated motor life to be over 18,000 hours. Two important features add to the longevity. The first and the most important point is to avoid premature seal wear. Additionally, the seal bore “EVAC” groove was redesigned to further prevent seal leakage. To prove its effectiveness, we tested the system with no seal installed for over 700 hours without any seepage or leaks. In conclusion, system longevity is not an issue of concern.
Can a motor be replaced?
However rare, in the event that a motor would fail, it can be easily changed in a matter of minutes with the removal and replacement of 3 allen screws. The alignment of the motor to the pump in replacement is not any type of challenge because of the “butterfly” soft drive socket. This arrangement also contributes to quiet operation.
Will the product affect a vehicle/engine warranty?
We have never had any warranty issues and in fact, have had several OEM facilities install the units.
Intuition and logic show that the current system (vacuum feed) passes entrained air onto the engine (Cummins® 1965 Service Topic 5-135, 1965). Also, as the filter plugs with use, increased pump cavitation and vapor develop, all of which can potentially create permanent fuel system damage. The AirDog® Fuel Preporator® eliminates these issues which help rather than hurt the engine, the AirDog® increases engine longevity.
What is the warranty period?
Units carry a 2 year limited warranty.
PureFlow® Technologies, Inc.
5508 Business 50 West
Jefferson City, MO 65109
Toll Free:1.877.GO DIESEL
Hours of Operation
8:00 AM-4:30 PM
Saturday & Sunday
How Does Air Become Entrained In Diesel Fuel?
As in all liquids, air becomes entrained in diesel fuel from sloshing and agitation! Air can be on the surface of the fuel in the form of foam or it can be in the bulk fluid in the form of tiny bubbles. Entrained Air is an issue of an "in use" engine in operating equipment!
What is Pump Cavitation?
Pump cavitation, simply put, is the pump not having enough pressure flow, or "Net Positive Pressure Head" of fuel coming into the inlet to completely fill the vacuum chamber of the pump.
Diesel fuel, as is true with all petroleum base liquids, will give off vapor when subjected to a vacuum. The amount of vapor depends upon the level of vacuum and temperature.
How Does Fuel Filter "Restriction" Effect Cavitation?
In the diesel engine industry, "fuel filter restriction" is a term that refers to the vacuum level at the inlet to the transfer or lift pump. It is measured in inches of mercury (in hg).
As the filter plugs with use, it further restricts the flow and increases the vacuum level in the pump.
The amount of vapor produced depends upon the level of vacuum.
What Else Increases Cavitation and Vapor?
As the fuel levels in the tank(s) goes down as the fuel is burned, the "Dry Suction Lift" increases. This reduces the flow, increasing the vacuum.
Operating at higher altitudes, where atmospheric pressure is less, reduces the fuel flow and increases vacuum. For example, at Denver, atmospheric pressure is about 17% less than at sea level and at Eisenhower Tunnel, it is approximately 32% less. Having less pressure to drive the fuel from the tank to the transfer pump, reduces the flow and increases the vacuum levels.
Higher fuel temperatures cause more vapor to form than cooler fuel under the same vacuum!