Hello, I'm trying to understand what all is going on under the hood during heavy towing conditions and trying to improve the performance of my 7.3l.

What would be the point of installing the fuel pressure crossover, high flow banjo bolts, and the higher-flow CVD fittings?

I've heard that the upper horsepower limit for the stock AD injectors is about 350hp.

If I install the high flow banjo/CVD fittings and install a fuel crossover with the parts from riffraff, what would the major noticeable benefit be?

I have a switchable power chip, but am looking into a PHP hydra switchable chip because it can hold more tunes and along with the minotaur software I was told that I would be able to tune the truck myself.

Trying to get a little more information before throwing money at this truck in hopes of making it stronger and capable of pulling more weight.

Any input is greatly appreciated. Thank you.

 

I'm new to the diesel world so there's my disclaimer.
I have all the parts you mentioned so I'll tell you what I know.
As we all know, parts need to work together to increase efficiency/flow and hopefully, eventually, horsepower/torque. Personally I think of all the parts you're asking about, the FRx is the only one that can standalone and make a difference. The FRx allows the internal fuel rail's flow to be "reengineered" and therefore, I think there's a benefit. The CVDs are going to increase flow, but if you can't get the fuel to them, say you need the hutch mod for example, then CVDs are useless. Same goes for the banjos.
I installed the CVDs and FRx at the same time so I can't quantify the gain of the CVDs. But the principle on why they are needed is sound. I just don't know at what level as you mod things that they hinder flow.
As for the banjos, I did those on a stock engine. All I had was the hutch, 6637, stuff like that. At first I drilled the stock banjos. This caused the truck to have a "choppy" idle with no noticeable power increase. So I bought the Riff Raff banjos and they smoothed out the idle back to stock. I still did not notice a power increase. However, clearly they did something so I would recommend them if you have drilled banjos.
Until I hit HP levels that would normally tax the stock check valves and banjos, I won't ever see the benefit. I don't know where that is and since I already have them I'll never really know. But I see these parts as building an infrastructure to support more power.

TL;DR - FRx gives benefit to all levels of HP. Banjos and CVDs probably aren't realized until higher HP levels.

 

Mine is certainly not a 'popular' opinion, but is based on extensive experience fooling around with this fuel system. There is no measurable benefit whatsoever to any of those things - but they don't hurt anything and they are sold by my favorite vendor.

The easy stuff first. Modded banjo's and CVD. The fuel flow to these parts is restricted by the kinked-up factory 1/4" fuel lines that are fed by 1/8" NPT fittings. I will buy that the CVD will have tremendously better flow characteristics than the choked-down factory CV's - but a measurable increase in power, economy or longevity is not likely. When I modify fuel systems for WVO, I replace the lines from the factory filter to heads with 3/8" PTFE-lined SS braided hoses and huge 3/8" CV's. I have yet to notice or hear of anyone else reporting a change in power/economy/etc. That includes up to 500hp 7.3's. At maximum consumption possible by our injectors, the flow rate required is still not that high and in practice - the OE parts provide adequate volume.

The FRx is much more controversial and has a history that dates back to the first Super Duty's when the hardcore PSD crowd discovered Ford did something so foolish as to go to a 'deadheaded' fuel system. Admittedly, this is a very unusual design - but so is the HEUI injection system. So, these early PSD gearheads started bashing it right away and one of the stones thrown became known as 'Cackle'. There were pages and pages of discussions and 100's of threads on the various forums debating Cackle, whether it even existed at all and most importantly - WHAT to do about it!! Keep in mind, this is when a chip added more power by making the PCM think it was -40* outside and things like the '10k mod', TAG and zoodad were popular. (wait, I think some people may still do the zoodad... ) This is when the 'Regulated Return' systems were developed and became popular with the in-crowd. Eventually, the hype over Cackle pretty much went away and everybody began to just know that RR was better than stock - of course, ESPECIALLY with bigger injectors. Some companies did extensive testing and they determined in fact, that we would benefit from using their products (that could cost upwards of $1000). Then, there was this crazy guy , FN74 (who became the Father of Vegistroke, a revolutionary VO conversion design that took advantage of the deadheaded fuel system). Part of his Vegistroke design eventually incorporated an 'air bleed orifice' (he was present for the Cackle Wars and bought into this whole trapped-air thing). He went on to develop and market what we now call FRx. The early systems were horrible with rubber hose fractions of an inch away from the up-pipes and failures were eminent. The current Riffraff version is a million times better and definitely a quality product with A LOT of satisfied customers. It's just not something I recommend.

There's my humble opinion and the history as best as I can remember it. I have taken a few hard blows to the head (seriously...) since I started this 7.3 hobby back in 2003, so feel free to correct me or say how you know it to be true - you will not hurt my feelings!!

 

I didn't take a lot of time to read the other replies but here is my $0.02.

Speaking only to the fuel crossover (FRx, CCK, or other regulated return systems), the factory design has a dead end in the fuel system at #8 and #1. This means that any air in the fuel lines will eventually end up passing through those injectors. The fuel side of our injectors is lubricated by fuel. Air=no fuel. Therefore air=no lubrication. That is always bad. Always

 

This makes sense explained as it is, although I have a question. So, when the FRx mod is installed, where does the "trapped" air go to instead of passing through the #8 and #1 injectors? Does it just get spread out throughout the head, making the "no lubrication" much less significant?

I recently did the Hutch/Harpoon mod and this made a noticeable difference in my engine noise. So, in an effort to get rid of all air in the system, the FRx is on my list of mods to do, but I need to be clear about why I am doing this mod.

 

So my understanding is, that once purged, there is no trapped air. Since fuel can travel through the rail all the way, then exit and get spit back into the tank, there's no way to trap air. If air did get in, it would travel that same path and end up back in the tank.

 

I have heard this before as well....however, the FPR does bleed air back to the tank on a stock system. So, air that is introduced into the fuel flow from the tank to the filter housing has a very good (if not 100% chance of returning to the tank). If for some reason air made it to the fuel rails in the cylinder heads then it has no other place to go except for through the injectors. If you don't run your truck out of fuel, then that situation shouldn't ever occur since the FPR is the highest point of the fuel system. (actually a pretty good design IMO....).

I had the FRX on all three of my trucks and I ended up removing them because one of my trucks sprung a leak. For my use, the dangers of modifying the fuel system outweighed the perceived benefits.

As for the high-flow banjo bolts.....total waste of time and money in my opinion. I can't see how they would make any difference in performance or economy on a stock vehicle.

I don't even know what CVD is....

 

This is the CVD fitting (the black fitting with white sealer on it). In the head where the fuel line attaches to it.




The left one is stock. The right one is the high flow CVD.

 

FRx explained:

The stock system supplies fuel to one end of each head. The FRx opens up the other end of the heads and allows some fuel to flow all the way thru the head. This fuel is introduced into the return-to-tank line after the FPR on the filter housing. The theory is any air that gets as far as the heads will be returned to the tank with the fuel that is constantly flowing through.

It sounds really important. We really don't want to send 'air' through our injectors. Obviously, that reduces lubrication and that's gotta be bad - right? And as Peter pointed out, #1 and #8 are at the ends of the fuel rails in the heads - so we don't wanna damage them. One company even did extensive testing measuring individual cylinder CP's (cylinder pressures) and found that #8 actually did have lower CP than the others - proof that we needed to buy their product (regulated return/'fuel system mods').

Here's the problem. #1 and #8 don't have any higher failure rate than the other cylinders... Furthermore, there are LOTS of totally stock trucks out there with 100's of 1000's of miles on stock injectors and no fancy mods...

Now, let's talk about the rest of the stock fuel system and it's legitimate shortcomings. The pick-up in the tank is tempered with return fuel in a mixing chamber. This chamber has mesh screen 'strainers' in it. Fresh fuel is brought in to the mixing chamber via an 'umbrella' that also has a screen, but more importantly, it's job is to suck fuel right off the bottom of the tank.

From here, the fuel is pulled to the electric fuel pump on the frame rail. The fuel is now pressurized and sent up to the filter on top of engine.

Fuel enters thru the bottom of the filter on the drivers-side. The pump is capable of 110psi and moves a multitude more fuel than the engine is ever capable of using. There is a FPR (fuel pressure regulator) built into the top of the filter on the drivers-side. This valve opens at a set psi (usually about 55psi) and relieves the extra fuel back to the tank (mixing chamber).

Now, fuel flows through the 2-stage filter 7mic media and exits the very bottom of the filter housing on the pass-side and out to each head.

You can see the mixing chamber would make it easier for any air in this part of the system to continue to be recycled in this loop. The filters are also considered not serviceable and require entering the tank to replace. THIS is what the in-tank mods fix and why everybody needs to do them eventually.

I want to point out the filter/FPR system was designed to remove air from the fuel and mitigate it's ability to get to the injectors.

That's all I have time for now. I have pics of all these parts if anyone would like to see them.

 

I know I can't wait to get my FRx installed. My truck chatters like marbles in a can. I also have the HPx coming too. From what I read it should make a big difference. Then I just need to do the hutch mod and everything should be good Providing my turbo rebuild goes as planned. Figured it was a good time to do it while I had the turbo out.

 

Does anyone know if the fuel rails maintain pressure when the truck is shut off. I'm pretty sure the pressure bleeds off, otherwise when you removed the fuel filter you'd have 60psi of pressure spraying fuel everywhere. Now, if they do not maintain pressure, where does it bleed off to and if it bleeds off then there has to be air introduced every time the engine is shut off.

 

The FPR and fittings in the heads are vented, so pressure is relieved by allowing fuel to return to the tank. No air is introduced when that happens.

 

I have the FRx and the Banjo bolts installed on my truck. I don't have the CVD's as I have 3/8 fuel lines from the OEM bowl to the heads. The FRx is pretty much known for what it does and that is solving the poorly designed "dead head" condition. It allows any air that "may" enter the system a path (besides the injectors) to exit the head (by returning to the tank).

The idea behind the CVD's and the Banjo bolt is to increase flow. Flow increase does not effect horsepower or torque until you get the flow increased at the injectors. As mentioned above it's a "system" approach where everything works together.

Just like the intake systems we install on our trucks, they increase the air flow! The CVD and Banjo's increase the fuel flow to the heads. It's simple as that .

 

I have enjoyed reading all the information in this thread. Thanks to all who are contributing!

 

quick question, since i've replaced my stock hard lines with braided SS lines, would i see any benefit or cause any harm to route the driver side line to the back of the head? I'm working towards a full regulated return and this will be the proper route once i'm fully RR. I'd like to route that side to the back now if i can.