Anybody with regulated fuel return read this!

[PTSUPERD]

Dude, you deleted the good stuff!

You were entitled to respond Dennis..just no real way to clean it up and keep some of it.

 

[Gearhead]

It is possible that with too much pressure the injectors can get fuel under the intensifier piston and cause resistance on the downstroke of the injectors.

 

[windrunner408]

Just cleaned this thread up out of respect to Adrian. Good info here. Please keep it on track and post with respect. I must say the dogpile mentality is aging.

Thank you Garrett. I agree.

 

[windrunner408]

It is possible that with too much pressure the injectors can get fuel under the intensifier piston and cause resistance on the downstroke of the injectors.

I don't know much about injector composition but this at least sounds legit, considering that I honestly can't see a difference of 10-20 psi (45-65 psi out put change) making a whole lot of difference in the grand scheme of like 2000-4000 psi.

 

[Pizza pig]

FYI, it did absolutely nothing for my truck.

 

[windrunner408]

Yea I'm sure each truck will respond differently. I noticed my gains when I dropped the fuel pressure from 63-64 psi down to about 50-52 psi and I didn't really notice any more of a difference when I dropped it down the little bit more to 46-48psi.

 

[HeavyAssault]

So it begs to ask does running a regulated return really make any difference?? If the point is to now run a low PSI why run a return system. Just feed the main pump clean fuel and get the blue spring installed.

 

[madpowerstroke]

So it begs to ask does running a regulated return really make any difference?? If the point is to now run a low PSI why run a return system. Just feed the main pump clean fuel and get the blue spring installed.

Regulated system provides fuel with no dead end in the heads, so fuel is always flowing to keep injectors happy. Also a regulated return lets you adjust what you want to run. The stock system provides pressure to the fuel rail and any addition fuel bleeds to return line.

If someone else would like to chime in, and I'm wrong feel free.

 

[HeavyAssault]

Plenty of people run a pump with PSI set, a Y to the heads with no return. Plenty of way to skin the cat.

Your post seems to reflect a lowering of the "need" of an RR compared to the "want" which retailers push.

Besides the fuel rail runs PAST the last injector, it doesn't end at the last injector. Compare the firing order of the cylinders to how the fuel would refill the rail. I don't see where any OEM fuel system working properly would "starve" the injectors.

Anyone got real world numbers of the PSI at the back of the heads?? I can't recall any accurate posts detailing a setup to show the measurements of fuel PSI taken from the two rear ports.

 

[alwil]

Anyone got real world numbers of the PSI at the back of the heads?? I can't recall any accurate posts detailing a setup to show the measurements of fuel PSI taken from the two rear ports.

I thought thats where regulated returns got their pressure reading from.

 

[HeavyAssault]

A regulated return has a built in port. Some will have a PSI gauge on the regulator..others use a sender to a gauge. Just matter how you set it up.

Since the RR is seeing what is coming thru the ports one would expect to see that PSI thru out the fuel rail.

What I was asking about is the OEM fuel system. What are the PSI numbers at the rear?? No posts I recall have ever shown REAL WORLD numbers for fuel PSI.

 

[hawgdoctor]

A regulated return has a built in port. Some will have a PSI gauge on the regulator..others use a sender to a gauge. Just matter how you set it up.

Since the RR is seeing what is coming thru the ports one would expect to see that PSI thru out the fuel rail.

What I was asking about is the OEM fuel system. What are the PSI numbers at the rear?? No posts I recall have ever shown REAL WORLD numbers for fuel PSI.

Hhmm, do I smell a Guinea pig lol?

Sent from my DROID RAZR using Tapatalk 2

 

[HeavyAssault]

I'm your huckleberry.........just say when.

 

[Strictly Diesel]

So it begs to ask does running a regulated return really make any difference?? If the point is to now run a low PSI why run a return system. Just feed the main pump clean fuel and get the blue spring installed.

The point is VOLUME/FLOW, not pressure. If you have adequate volume/flow...and proper pressure management...pressure is easy.

Take the stock system for example. The regulator is in the filter bowl. That means that the very first "drain" on the system is before the filter. As the filter gets dirty and the pressure drop across it increases, more and more fuel will be returned to the tank instead of going to the injectors.

Next in the stock system is the small fuel line size and tiny banjos with checkvalves. There is nothing good about the flow of those pieces...which represents more pressure drop.

Finally, you have the actual demand (injectors). This is where having adequate flow is critical...obviously. These represent another pressure drop in the system because they rob fuel from the rail...each injector is a drain on the rail.

So what is the actual pressure at the injectors under load with a stock system? I've never measured after the rails with a stock regulator because I already knew it wouldn't be better than taking the measurement at the bowl. I have seen pressure drop across a stock filter of 2-5psi (depending on the condition of the filter). Add to that the drop from fittings, resistance of the fuel flowing against the walls of the tubing and fuel rail, fuel used by the fuel injectors (particularly with a hot tune...and even more with larger than stock injectors) and you can count on several more PSI of pressure drop to the rear of the rail. If you've measured pressure at the bowl and assume between 5-10psi of drop through the filter and rails...that's probably pretty safe.

Way back when I first designed my 6.0L kit, my personal truck had an Edge Juice with Attitude (long before SCT). Stock injectors and a stock pump, with the J/A on kill and a bone stock fuel system...20psi+ of pressure drop at the bowl! There is NO way I should have ever had that much drop, and it wasn't the fault of the pump. There was plenty of flow, but piss poor pressure management. The stock pressure at idle was about 52psi (at the bowl, pre-filter), the stock regulator spring should have had no problem maintaining that pressure were it not for the fact that the stock regulator design sucks and makes it's job really hard. With NO other changes except installing my complete RR kit, 65psi...rock steady...same stock pump...and it held that pressure later with larger injectors and SCT tunes too boot.

What changed? First, no longer had a leak at the front end of the fuel system (stock regulator poppet valve). The pump was always moving enough volume, but leaking it back to the tank before it even got to the injectors didn't help with trying to maintain pressure. Second...we reduced the pressure drop by making the feed lines larger in diameter, switching to larger high flowing banjo bolts and banjo fittings and getting rid of the checkvalves. Now all of the fuel was flowing to the fuel rails all of the time, and doing it with less resistance/pressure drop...which makes it much easier to maintain pressure. Even if I'd set the regulator to the same 52psi, the injectors were seeing an increased flow of fuel and the pressure was being managed AFTER all of the pressure drop instead of before it...this is why we do a regulated return!

You mentioned doing a "set pressure pump" and doing a Y to the heads with no return. This can work if done better than the stock setup, but I still disagree with doing pressure management before the system pressure drop and before the demand. By the time the fuel makes it through whatever filters and through the rails, the pressure at the end of the circuit won't be the same as at the regulator in the pump. You can turn the pump up (run the pump at 70psi hoping for a final of 65psi in the rail)...but regulating the pressure before all of the drop and demand just isn't ideal in my opinion.

Just my thoughts...for whatever they might be worth.

 

[HeavyAssault]

Based on that post the OEM pump provides enough volume and pressure correct??

 

[Strictly Diesel]

For stock to moderate injectors...yes. We've seen the OEM pump support up to about 190s. That seems to be about the tipping point, depending on the particular set of injectors, particular tuning and condition of the stock pump.

 

[strokin6L]

I ran stock pump with my 190/75's for a while. However i ran the stock pump piggy backed with a FASS low pressure pump. fuel pressure never dropped on with ID's race tune.

 

[HeavyAssault]

So now we move to the banjos and pressure spring. The tension on the poppet is key. ONLY when pressure/volume pushes the poppet open is there any return to the tank.
With normal driving the poppet will be shut, no fuel returning to the tank. With the larger 6.4 banjos this will provide PLENTY of fuel to the injectors.

Even with filters installed the OEM setup is doing it's job given the minor mods that should be done.

Once again no one has shown a "lack of PSI" to the rear injectors.

I run a sump, AD100, blue spring, 6.4 banjos and larger front lines. Truck runs great and NO issues. I don't even use a FP gauge. All this on a truck running 220k on the original injectors,

 

[windrunner408]

Based on that post the OEM pump provides enough volume and pressure correct??

Yes it does for at least stock injectors. I'm sure Dennis can tell us more about how big of an injector the stock fuel pump can feed with his RR kit.

It is as he said. All of the restrictions in the stock fuel system need to be addressed so the right amount of flow is provided to all of the injectors. With a regulator on a RR kit set to 60+ psi, the pressure of the fuel inside the rails is greater than 60 psi because the point at which the pressure is being controlled is after the fuel leaves the rails. So if 44 psi is the bare minimum that is needed to safely run the injectors and I set the regulator on my RR kit to 44 psi, then I can easily assume that I have at least that and probably 2+ more psi in the rails them selves. Furthermore, if I set my pressure to 65psi at idle and then do a WOT run and my pressure drops to 50 psi, then that is what the capability of my fuel system is with whatever injectors are in my truck and if I lower my regulator so that I have 50 psi at idle and then do another WOT run, I should now still see 50 psi of fuel delivery because I have set it up for worse case and there is still more than that inside the heads due to the fittings at the back of the heads slowing it down some and the length of line and bends in the line making the pressure drop as the fuel flows through it. Hope this helps.

EDIT: you all posted before I could get this out.

 

[09stroker]

The tension on the poppet is key. ONLY when pressure/volume pushes the poppet open is there any return to the tank.
With normal driving the poppet will be shut, no fuel returning to the tank.

You got that backwards.
Less fuel usage=more return flow