Why *pump-fuel rails-FPR* not *Pump-FPR-fuel rails*?
 

I have read people complaining about their fuel overheating with high HP fuel systems, and have only seen fuel lines plumbed pump to fuel rails to FPR and returned.

Why is no one running fuel first to a FPR, located out of the engine bay and heat, with the return going back from there to the tank, and then a line from the FPR to fuel rails? The fuel getting any hotter in the engine bay would be immediately burned instead of being returned to the tank. And since it's not being recirculated it wouldn't end up getting hotter then the other way around. The only thing heating the fuel in this configuration is the pump.

It seems odd to me to do it the other way around when it also takes extra line and fittings.

What am I missing? They make regulators big enough that they don't cause restriction. There's no difference in return volume. The only plausible (but still extremely unlikely) thing I can think of is when you transition from low to full HP the increased flow at the injectors could cause a momentary drop in pressure at the rail before the FPR reacts, but really for that to happen fuel would have to be compressible (which it essentially isn't)

Let me guess, this is IDRIVEAG8GT.

It has nothing to do with fuel being compressible. You can very easily have a fluid at a much lower pressure downstream of a point in the system. For example... take a tube standing straight up full of water. The water at the bottom is at a greater pressure than the water at the top. Putting the FPR before the rails allows the rails to greatly drop in pressure below what the FPR is trying to maintain. It doesn't matter how big the regulator is... if you're going through the regulator before the rails, you're introducing a sink to bleed pressure off before it gets to the injectors. I'd MUCH rather have my full flow, full pressure feed hitting the injectors before the regulator so that during changing demands, the rails are able to keep their head of pressure from full, unrestricted flow.



Here's a test you can do. Take a tube and hook it up to a hose. Now, poke a decent sized hole in it. Later down the hose, make another hole (or 8) to represent injectors. For now, cap the end of the hose with your thumb and turn it on. You'll see water bleed out of the first hole (the regulator), and then drip from the later holes. Suddenly remove your thumb from the end of the hose and watch as the little set of holes suddenly come to a drip (that may not recover). This is similar to draining the rail on a sudden demand.

Take that hose and flip it around so the eight holes are near the feed, and the single hole that acts as a regulator is after the little holes. Cap the end, turn the hose on, and let it stabilize. Now take your thumb off the end. The first set of holes should barely be phased. This is how it functions with the regulator after the rails.

Your CONTROL for pressure should be after the the rails... the injectors should be the first spot in the system where fuel bleeds out. This is why I hate returnless systems on higher horsepower setups.

Thanks for the explanation Dave. I have the tanks out of my car and planned on going to a return style system with the regulator just outside the tank in the drive train tunnel with a very short return line and connecting into the stock fuel line from there to the stock fuel rails that feed my 60# siemens. At my power levels I didn't think I needed more. Am I totally wrong on this line of thinking?

BJK

If anyone has first hand experience, feel free to reply. I simply cannot consider fluffy bunnies reply because he makes it clear he lacks understanding.


Whoa guy, first off, chill out. Second many OEMs plumb fuel the way I described, and I know of a lot of 1k HP cars that do it this way too.
Furthermore, If you bothered to read I brought up the point you are trying (rather horrendously) to make. While I'm not saying I'm an expert in fluid dynamics, you made it clear you definitely are not.

I have no idea who that is.

The point you're replying to has a lot to do with this, but I know from the rest of your reply you don't understand this point.

What you're referring to is hydrostatic pressure, hydrostatic pressure is the change in pressure over height of a column of water. It's not even a dynamic force, which is what we're talking about. It has absolutely nothing to do with what we are talking about, unless your fuel system has a vary large elevation change in relation to the fuel rail and regulator, in which case you would simply have to increase the requested fuel pressure at the regulator to effect the desired pressure at the fuel rail (which is a static change).

In theory, I agree a change is possible (that's why I mentioned it after all) but without running numbers I made a (fairly educated) guess that the change would be negligible.

You're implying the regulators going to bleed off more pressure then your set point, that's pretty fallacious.

A regulator only bleeds pressure above the set point. The only way for the regulator to get to that pressure is if the fuel rail did first or you used greatly undersized lines or introduced some gross restriction on them.

A quality FPR is not a restriction to flow, they are straight through and properly sized will have a cross section greater then your line.


http://1.bp.blogspot.com/-NzI16Bl1GL...-chan-meme.png
Is this a joke? This is wrong in so many way's I have no idea where to begin.

A pressure regulator is not an open static orifice
Capping and uncapping a hose does not replicate the increase in flow volume of the injectors. Rather it makes the system completely unrestricted and depressurizes it.

If the "first" hole was actually a pressure regulator the second you uncapped the hose it would shut completely to begin with.

I'm baffled you could even come up with a "test" like this and think it's sane.




Now look, again, I am not disagreeing about the theory you're trying to make (I did bring it up after all), I was simply inquiring (toward people who actually know one end from the other and designed these systems) If this was why they were doing it this way, and if they were just doing it based on perception of the theory or actually having had problems. Since you have made it clear you really have no understanding of fluid dynamics, I do not wish to discuss any of this with you further. Please do not bother to reply to me.

I got an email back from HOB the same time I posted this saying the location of the FPR was for convenience and doing it this way is perfectly fine. (minus the part about the stock fuel line if you're going for high HP)

Edit: And also that the systems that they installed had no issues running the way the designed and suspected installation error for those that were. Sorry I left that out.

Quote:

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Originally Posted by BoosterClub (Post 1578770290)

If anyone has first hand experience, feel free to reply. I simply cannot consider fluffy bunnies reply because he makes it clear he lacks understanding.

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My input was directed to DSTECK specifically because I do lack understanding . That's why there is a guestion at the end of the last sentence and I gave Dave a thank you for his input.

BJK

Thanks for your reply. As a person who is not very educated in this area, I appreciate any input I can get. I'm staying with my current HP levels as shown in my signature.

BJK

No no, that comment was not directed at you, sorry for the confusion.

Okay, The "fluffy bunny" thing seemed to fit my avatar.

BJK

It will work in most applications. I don't personally run them that way but I have had a couple customers that are running it back in the wheel well without issue. Take in consideration that none of them are radical builds. DSteck does make valid points though. You will have more consistent control over the entire system with the regulator being after the rails rather than controlling pressure before it reaches the engine. I still recommend running as sold in our system.

Let me jump in here and say first and foremost, DSteck is very knowledgeable about fuel system technology. He is an asset to the community and tries to help as much as possible.

Second, buy a fuel system that is designed for the power levels that you are trying to make. Bleeding the fuel pressure off and dead heading the rails will cause pulsations in the flow and simply gets worse as that flow demand increases. The installation is easy and requires a less expensive system so it makes for a great setup within reason. But if you are wanting to make big HP numbers, cutting corners on your fuel system is a big no-no.

As for heat, again if your system is setup correctly, you wont have a problem.

As I mentioned in the email and as Will reiterated. A properly installed fuel system will not have heating issues or fuel pressure variances.

He might be, but I don't know him and all I have to go off is what he posted as explanation (for the theory I already put forth) which was definitely contrived and completely without sound logic in it's explanation. There is no denying that.

I would like to hear from someone who has first hand experience with the FPR being before the rails causing issues. Preferably a builder or engineer.

Yes, the degreed engineer from the powertrain department of one of the Big 3 doesn't understand fluid dynamics. I'll go back to scribbling interpretations of the world on cave walls.

FYI, I actually work for a boiler company now. All we do is fluid dynamics. But hey, thanks for trying to sh!t on me for trying to help clear this up. God forbid I over simplify an explanation to help the average enthusiast get a generic understanding.

Friend, you're the one who started your post accusing me of being some dishonest fraud. If you really are an engineer then I'm sure you should be able to say your "experiment" would not actually demonstrate any of the dynamics we are talking about. And it would be easy for anyone to misunderstand yourself to be well...

Whoa there, I didn't call you a dishonest fraud. The only reason I asked if that's who you were is because the exact same topic came up from that poster on the HP Tuners forum. Settle down.

The "experiment" would accurately demonstrate what happens when a sudden demand is put after the regulator. Is it a completely accurate recreation? No, but it still demonstrates the general concept of draining the rail on a hard request.

But whatever, I'm wrong, hee haw. Me go drag stick on wall to show kill mammoth.

I'm done.

i can move my fpr to the rear and solve this once and for all.. i think i already have all the fittings, just need to find a long piece of vacuum line. unless you want me to test it with a solid base of 58 and not referenced.

-Carl

And I could simplify an engine into popping popcorn pushing the lid of a kettle, but I think anyone would agree that would be dumb.

Anyway for the millionth time agree in principle it's there, I just have the feeling it's a non issue. Still looking for someone who has actually encountered one. I'll probably just put the regulator after the fuel rail but monitor temps and if I run into a problem (probable even if I don't) try the regulator before and see what happens.

Personally if I do it this way I would run it out of the engine bay but not all the way in the rear. I'll probably just try it in both configurations anyway, I don't like the look of the FPR in the bay and the extra lines. It wouldn't really be conclusive unless you had an FP differential gauge setup. Not running into obvious problems doesn't mean none are there. How much power does your car make?

i think around 800whp +/- 20hp, really depends on how much boost creep i have, lol. well, i have fp tapped into my hptuners, so id just do back to back runs.

-Carl

We have run fuel systems both ways many times; sometimes on the same car. First off, while the motor does play a part in the heating of the fuel, it is not the only source of the heat. A properly set up fuel system, supplies the least amount of fuel to obtain your objective.
The guys who run around with twin pumps running full time, or massive Aeromotive pumps running full tilt when they dont have the consumption to support it, are the guys who have the heating issues. The key is to regulate (or bypass) the absolute least amount of fuel. More more pressure the pump is making, the more the regulator is bypassing. This leads to higher fuel temps. Pressure causes heat. More head pressure, more heat.

You can run the regulator before or after, its up to you. Its six to one, half dozen to the other. That is, assuming you are regulating at the motor; or at the very least, right by it.