Join Date: Oct 2007
Location: Phoenix AZ/Franklin TN
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I woud recommend calling Dennis at ITP Diesel. He's very knowledgeable on his products.
This is quoted from another site.>
The factory fuel system is designed that 100% of the fuel goes up to the fuel bowl. From there it is regulated and the extra fuel is sent to the HFCM. The pressurized fuel is then filtered and sent through the small factory fuel lines and then through the banjo bolts with check valves inside. The area around the check valves is extremely small and very restrictive. Once the fuel is in the cylinder heads, it is there until it is injected by the injectors.
Problems with the system:
On high demand situations with factory programming, the fuel rails will run low on fuel, potentially causing injector issues. When additional power adders have been added, the fuel demand is substantially higher and outside of the factory spec. Consequently, the fuel system was never meant to flow that amount and the fuel rails will run extremely low.
The factory designed the system to work within their given ranges within a budget. Feeding the front of the heads achieves this from a budgetary and a function standpoint. The cost of warranty isn’t higher than the cost of designing the system better. If they were to add lines to the back of the cylinder heads, the cost of the fuel system would easily double.
Any debris that gets past the filter has no where else to go but through the injectors or clog the injector fuel screens.
Regulating before the demand source. The way the factory system is designed, the demand is after the regulator. So, from the fuel pump to the fuel bowl, is always what the regulator is set at. But after the regulator, the fuel will fluctuate because of how far away the pressure source is. There is a static loss of flow that occurs in tubing. The longer the tubing, the more the loss is. When the engine is at high rpms under a high demand, the fuel system won’t keep up and the injectors will start to be starved.
Benefits to a Regulated Return System:
A regulated return system is designed differently. 100% of the fuel is sent to the cylinder heads and passed the injectors. That is because the regulator in the fuel bowl is capped off or removed entirely (depending on who’s system). From there, 100% of the fuel is sent to an external regulator. This regulator does two things. First, it regulates the pressure from that point all the way back to the fuel pump. So, everything in between sees that pressure. Secondly, the regulator acts like a y-block and equalizes the pressures from both cylinder heads. From there the extra fuel is sent to the HFCM or the tank depending on your system.
As long as the fuel pump can keep up with the pressure, the injectors will always see the pre-set pressure and will always be feed.
If there is a fuel pump problem and the pressures start to fall, the injectors will see whatever pressure is remaining. While the pressure is lower than what we would want, it is still better than no pressure and the chances of the injectors staying alive is extended because they are seeing some sort of pressure.
What you will see:
Trucks with a regulated fuel system will idle smoother. (There is no reason for this difference unless the factory injectors aren’t getting enough fuel)
Many trucks will show an increase in horsepower at wide open throttle.
Injector life is generally extended. (We have not been able to conduct a proper study to say how much longer.)
Generally, the throttle is more responsive.