New Idea for Regulated Fuel System
 

There's been so much work done to the fuel systems here lately, and I maybe about to throw a kink onto some of it. But, given the working knowledge some of us have, I would like some feedback. I've been emailing Aeromotive about some of their fuel pumps, and in talking to them the question of the regulated fuel system came up. They had a different suggestion of the way the fuel is routed, which they claim will both provide a better fuel supply to the heads and increase fuel pump life.

In the way it's setup now, they said that there are potential issues for fuel pump durability. I'll parahprase what they said: The fuel rail in the heads has plubing that is flow restrictive to the point that as the pump attempt to force fuel through at a much increased rate of flow, pressure builds on the inlet side of the head to a very high level. REports indicate an excess of 90 psi at the inlet with the regulated pressure of 55-60 psi at the outlet. This "pressure drop" across the fuel rail loads the fuel pump excessively for continous operation, creating high current draw, wearing out the brushes and commutator prematurely, and decreasing pump clearances, which basically drives the roller vanes into the outlet plate.

Their solution is what I find interesting. Again, paraphrased: Feed the cylinder heads from both ends, the front and the rear. This would be done by placing the regulator before the cylinder head. You would feed the line from the pump into one side of the regulator, still have the bottom return line going back to the tank, then taking the other side of the regulator to a T or Y to split it for each head, then another T or Y to feed the front and rear of each head.

I want to get some opinions on this one. I've never heard, or even though about doing it like that. It does make some sense though. If it was to be done that way, I would try to find a regulator with at least 3 outlets on it though. One for the feed line, and the other two to feed each side of the heads seperately. What do you guys think?

JT

It does not make sense to me. Do they know that folks are running an orifice? How does this play into their equation? I could definitley see a pressure drop using some principle of fluid flow I cannot recall right now if the inlet to the head is smaller than the fuel rail diameter in the head itself and just continued in that manner. Now even so, I think that is alleviated by the same restriction at the opposite side of the head where the law applies in reverse as it exits in a more restricted path. I can see a percieved difference based on volume within the rail and along a line on the other end where the regulator is. My opinion is that pressure is pressure along the same line as long as there is no air present anywhere. That increased volume in the rail will become repressurized at the opposite end, maybe not to the exact extent but could be compensated for at the regulator. Also, what they are describing smacks of another dead end fuel supply system if I understant the concept. How would we eliminate air in that kind of a setup? Maybe through the injectors until it's gone and then all good until the next filter change. Having said all of that, if they've done testing, I would like to see it because they must know a little something about fluids and flow. JMO.

If yall can provide a simple schematic with the tubing diameters, and initial flow rates and pressures, I can tell you what the pressure drop is, where it is and possibly what effect air will have on the system.

*This is from an engineering stand point. I am a petroleum engineer from A&M

I would love to see something like that, but I have no idea what the fuel rail inside the head looks like or specs out at. I believe the air will be hard to calculate because it would be an unknown volume in an unknown location of an unknown duration. Since air compresses and fluids do not like to, that could be a huge variable in any equation. Also in the equation should be the possible pressure drop inside any regulator diaphram body since this too might be a volume change in the flow if we are going to concern ourselves with these things. How to test/measure these things?http://images.ford-trucks.com/forums...s/confused.gif

On Edit: I forget to mention the pressure temperature volume variable of gases when I talked about air.

This is because the aftermarket systems regulate the pressure after flowing through the heads. Thus the flow through the heads is the quantity burned plus the quantity through the return line. This forces the pump to work harder. The stock system regulates the pressure before the heads. Add to that everone is running higher than stock pressures, and bumping up the power (therefore the fuel burned) and this further increases the pressure at the pump outlet. If I were to plumb in an aftermarket regulator, I would plumb into the same location as the stock one. Replace the FPR cover with a NPT plate and connect that into a regulator that would bleed back to the stock return line. Their suggestion of feeding both ends of the head will reduce pressures at the pump because you're not constantly flowing the return fuel through the rails. It is now a dead headed system with two feed locations, and all excess is bled off at the regulator like the stock system.

Check this out.....

Just copy and paste if it doesn't link.
Put in an electric fuel pump instead of the mechanical pump in the diagram.

http://www.nav-international.com.br/...oke/cap_n2.asp

Cody

Very well put sc93f. I have been toiling over this regulated return system for some time, I know Jeremy. I've often wondered why OEM was the way it was minus the dead end part. I was wanting to put my regulator just off of the stock return/regulator location but am concerned about over pressurizing the Orings in the filter. I know that this is where any air in the system can escape as it will go straight to the top of the filter housing. But I also want to be able to eliminate any air entering the rails too. I've got several ideas but not knowing what the stock filter assembly can handle, I would be "experimenting". Perhaps it is time to get off of the porch.

So, if I read that correctly, a helper pump to the filter with an orifice to return and supply to actual pump, then into head, then a regulator? So either replace the stock filter or add one afterwards to feed the heads?

Also, I would expect the volumetric efficiency of the pump to get worse at higher pressures, which will put even more strain on the electric motor that spins it over and above just the load increase due to higher pressure. You could look into alternate pumps with higher pressure ratings once your stock pump goes. Kwik found a nice replacement, but don't know what the pressure rating of the original application is.

This is another reason that Kwik's bleed system is a better solution in my opinion. Much less difference in the operating conditions of the pump and filter assembly compared to stock. :)

I have a question on this, I actually have been thinking about this for a couple of days. But is there a reason we have to keep the stock filter? I haven't looked to see if there is a sensor in there that is needed for the engine but I have been thinking that you could run a GOOD filter after the pump mounted either under the truck or on the fire wall and then to your regulated fuel system which ever type you want to run. I was thinking of basically what aeromotive is suggesting for myself with the exception of only going to one side of the rail and then running a crossover orifice setup similar to Kwik's setup he came up with to eliminate air but using a return style multi port regulator.

I have the schematic from the link.... now all i need is a rough estimate of hose and tubing sizes, a pressure range (65-70psi @ filter, and how much on the rails??), and flow rates.

Pressure on the rails??
Fuel flow rate??

I agree with the end of Tenn01PSD350's post, sounds like you are back to a dead-head system. I have always thought the primary goal of the regulated return is to eliminate the dead-head fuel system. May as well just shim the stock regulator. Kwikk's system would be far superior to aeromotive's suggestion in my opinion.

It's pretty well acknowledged that the regulated return may limit fuel pump life especially at higher pressures. But I didn't think the stock fuel filter housing would take 90 psi.

Seems like the guy at aeromotive is thinking like a gasser mechanic.

There is absoutley no reason to keep the stock filter or filter bowl. The only electrical part in there is a heating element, which rarely comes on. In fact, when I go with a dual HPOP setup, I will be eliminating my fuel bowl all together. The Dahl 150 I use has a 2 micron filter, and that is plenty of filtering. If any type of quality pre or post pump filter is used, you can ditch the stock fuel bowl. I came to this decision after talking to Zane at Wide Open Performance. He's got several cases where they have eliminated the stock fuel bowl, and have no ill side effects.

Monsterbaby and jtharvey I agree. There is no good reason to keep the factory fuel filter.
In fact, the filters that I work with every day are very similar in design to the toilet paper roll filters that are so popular. I sawed one open today and I was struck with the similarities. A rolled filter media within an aluminum container. And the container is able to be installed post fuel pump without worries of over pressuring the housing. They are designed to operate at 73 psi fuel pressure.
Ideas thinking...........

Someone brought up a good point that I had thought about but forgot to mention, when discussing Aeromotive's suggested system, that will basically have me keeping my regulated system that I have in place on the engine now. That is, if you were to feed the heads from the front and rear, you basically still have a dead head fuel rail.

With that said, I've decided on what I'll do for my fuel supply. To start with, I'll put in a 5/8" fuel pickup tube. From there, I'll have a cleanable screen type filter with a rating of 100 microns. Then onto a low pressure/high volume fuel pump, to act as a lift pump. The screen filter and lift pump will be mounted as close to the tank as possible. After that, it will go into the Dahl 150 (talked to Dalh today, it'll work fine under the low pressure of the lift pump) for water seperation and 2 micron final filtration. Out of the Dalh and into an Aeromotive A1000, and then straight to the engine compartment where the fuel will split going to each head, and thus completely eliminating the factory fuel filter and bowl.