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Would you be interested in this kit?

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Discussion Starter · #1 ·
So, anyone who is running an upgraded in-tank pump will see a VERY high base fuel pressure. Personally, mine was a whopping 72psi (where it should have been 38psi).

With some modifications to restrictions in the return system in the tank, I only managed to get my idle pressure down to about 64psi.

With this protype kit, I got my base pressure down to 38-40psi (from 64psi).

I'm thinking of releasing this as a SpeedCircuit FPR kit.

It would come with the following:


  • Your choice of either a 190* U-Bend (for a boomba style rail) OR an adapter to go from the stock FPR to -6AN.
  • -6AN SS braided line.
  • All necessary anodized fittings
  • AEM adjustible FPR
  • Heavy duty FPR mounting bracket powder coated wrinkle black.
  • OPTIONAL fuel pressure gauge
We'd like to price this for around $290 shipped.


Pics:


Adapters and line:






Regulator and bracket:





Is there interest for this item?

EDIT:

Group Buy on now!


http://www.evoxforums.com/forums/showthread.php?t=59482
 

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I'm not to the the point where I need to supply more fuel yet, but it's one of the things I've been trying to plan out, so I'm interested! I have a couple questions, but to get some theory out of the way, let me know if my understanding is right or not. disclaimer: I have 0 hand-on experience with injector scaling yet, just studying so I can deal with it in the near future.

Injectors have a fuel flow rating at a specific fuel rail pressure. For example, ID1000's are rated at 1000cc/min @ 3bar (or 43.5 psi) of fuel rail pressure. However, the actual flow rate of the injectors will be different as that pressure changes.

Actual flow rate = rated flow rate * sqrt(actual rail pressure / rated rail pressure)
and yes, i had to look that up ;)

So in your example with 72psi of rail pressure, if you were running ID1000's, you'd actually be running them as if they were 1285cc/min injectors! ... at least until they max out. You can try to tune it out by adjust injector scaling and latency, but you lose some resolution that way. It's better to correct the pressure the right way via regulation, and just scale to fine-tune.

Am I on base so far?

If so, then I'm confused by how you were able to reduce rail pressure by regulating the return. Can you explain restricting the return side (post-rail) drops rail pressure? Or am I misunderstanding and the regulator is before the rail? Can't really tell form the photo. Thanks!
 

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In for one in if it includes a gauge At that price.
 

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Discussion Starter · #13 ·
I'm not to the the point where I need to supply more fuel yet, but it's one of the things I've been trying to plan out, so I'm interested! I have a couple questions, but to get some theory out of the way, let me know if my understanding is right or not. disclaimer: I have 0 hand-on experience with injector scaling yet, just studying so I can deal with it in the near future.

Injectors have a fuel flow rating at a specific fuel rail pressure. For example, ID1000's are rated at 1000cc/min @ 3bar (or 43.5 psi) of fuel rail pressure. However, the actual flow rate of the injectors will be different as that pressure changes.

Actual flow rate = rated flow rate * sqrt(actual rail pressure / rated rail pressure)
and yes, i had to look that up ;)

So in your example with 72psi of rail pressure, if you were running ID1000's, you'd actually be running them as if they were 1285cc/min injectors! ... at least until they max out. You can try to tune it out by adjust injector scaling and latency, but you lose some resolution that way. It's better to correct the pressure the right way via regulation, and just scale to fine-tune.

Am I on base so far?
More or less, yes.

In a nutshell, you want to get your base pressure to about what a stock base pressure is. From there, you need to ensure that the rising rate of the regulator matches the rising rate of the stock FPR (which is 1:1 in our case - that is, 1psi of fuel pressure is gained for every psi or air in the motor).

If so, then I'm confused by how you were able to reduce rail pressure by regulating the return. Can you explain restricting the return side (post-rail) drops rail pressure? Or am I misunderstanding and the regulator is before the rail? Can't really tell form the photo. Thanks!
Well, all FPRs I've ever seen were on the return side of the fuel system - including your stock setup. An FPR is just a fancy clamp that restricts the return of fuel back into the tank which in turn backs up the pressure on the feed side since it can't return quickly enough.

Restricting fuel on the feed side could be dangerous and could possibly lean you out during high demand. I've never done it, but that's just a guess.

Anyway, when you start running a big-boy fuel pump, you'll see your base pressure at idle rise to 60-80psi instead of the 38-40 it should be. As I'm sure you understand, this isn't good for anything, and would throw off your tune to say the least.

This regulator solves that issue by allowing you to set your base pressure and avoid a whole series of problems.

And since we're offering this as a kit, you'll be able to install it all in an hour or two instead of taking the time to research a bunch of fittings and taking all day to make your own setup.
 

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cool, thanks for the explanation. I still don't understand how restricting the return affects the feed pressure unless the pump is is a closed system or something, but at the end of the day, it doesn't matter :) If it gets the job done, that's all that matters.
 

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Best I can think of as an explanation right now is blowing into a straw. If you would squeeze it with your fingers, it will take more pressure to push air through the system. FPR basically allows you to throttle the restriction to vary the pressure feeding, like you squeezing more or less on the straw with your fingers. Putting my engineering degree to work :)
 

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nah, i figured it out. A fuel pressure regulator pretty much works in the opposite direction as most other types of pressure regulators. That's why I was getting confused. I'll try to explain in case anyone else was confused.

So think of an air pressure regulator on an air compressor or any tank of compressed gas. The tank might have up to 2000PSI stored inside it, but you only what 90psi to operate your impact wrench. If you hook a hose up to the tank, it'll blow up your wrench. You need to regulate the flow of gas FROM the tank TO the tool. so the regulator works by regulating the stream after the regulator in the direction of flow. Like this:

(tank) --> gas @ variable --> (regulator) --> gas @ 90psi --> (tool)

if you think of putting this type of a regulator on a car, it would look like this:
(fuel pump) --> fuel @ 90 psi --> (fuel rail & injectors) --> fuel @ variable psi based on IDC --> (regulator) --> fuel @ 40psi --> (tank)

Well that wont work! You could move the regulator before the fuel rail, which was what I had in mind:
(fuel pump) --> fuel @ 90 psi --> (regulator) --> fuel @ 40psi --> (fuel rail & injectors) --> fuel @ variable psi based on IDC --> (tank)

But a fuel pressure regulator doesnt work like this. It works in the opposite direction. It regulates the pressure BEFORE the regulator, not after. It does this by bypassing/bleeding excess, instead of limiting flow. Like a wastegate does with exhaust gas when you already have enough boost. Think of it more like a river dam. The higher the river water, the more water the dam flows, thus lowering the river level. It's goal is to keep the river level constant. Same thing with the FPR - the higher the fuel pressure, the more fuel the regulator passes through the return, thus lowering the pressure before the regulator.

make sense? probably not... that was a horrible explanation :)
 
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