420A Fuel Pressure System for a 420a Turbo??

[SpdrVenom9]

I've got a 99 eclipse RS. I just got a used Hahn stage II turbo system, with the intercooler, installed. I also got a walbro 255L fuel pump and greddy blow off valve installed. Now while the mechanic at the shop was installing the turbo, he told me I'd need something to manage the fuel. He told me to get a fuel pressure regulator, so I got a universal comptech fuel pressure regulator, which he said was fine. The turbo system, the intercooler, and the fuel pump all went in fine, along with a boost gauge, but he told me that the FPR I had bought would not work because the engine's stock fuel pressure regulator "is past the fuel rail, so the FPR wouldn't be able to change the pressure because the return and feed line are both before the fuel rail." Honestly, I don't really understand what that means. He said I'd need to buy the portfueler system from Hahn in order to manage my fuel system. This seems like a very expensive option for me, all I want is a little boost, doesn't even have to be as much boost as the stock GS-Ts and GS-Xs run. I just wanted my car to be a little quicker. So as of right now, I can only drive my car with minimal throttle, keeping it in vacuum, because if I go even slightly into boost, boost is added to the cylinders without an adequate supply of fuel, and we know what happens then. Is there a simple, cheap solution to my problem or do I have to go the portfueler route? Thank you for your time and any suggestions. I appreciate it.

 

[Shadow98]

Just get a FMU. You can find them on ebay and maybe even on the classifieds on here. I'm perping my fuel system right now so I can finally put my turbo in. I just need the fuel pump. I got a Vortech FMU (12:1), AFPR for fuel and waiting on my 225 hp pump. Hope this helps.

 

[VelocitàPaola]

Your mechanic is an idiot.

Hahn provides perfectly clear instructions and tech support for situations like these. Furthermore, they didn't half ass engineer this kit; everything has been accounted for, tested, and known to work.

You shouldn't have needed to buy an FPR either: the Hahn kit comes with one.

Check out "configuration #2" in my diagram for an idea of where the FPR should be mounted. DO NOT use whatever FPR you bought. For these low boost applications, you need a 12:1 rising rate FPR (i.e. Vortech FMU, or the Hahn supplied FPR).

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Sorry if any of that sounded a little rough, but I suggest taking your car, and your turbo kit to another mechanic with more experience in this area. It's ignorance like this that can cause major damage to your car.

 

[SpdrVenom9]

This was a used Hahn turbo kit I bought off of ebay, and the mechanic told me it didn't come with anything to regulate the fuel pressure. So the universal comptech fuel pressure regulator I have is not good? I shouldn't use that? I saw your diagrams on another thread of yours and downloaded the picture to my computer for future reference. I don't have much more money to spend on this project, about how much should it cost to install the vortech FMU you are suggesting?

 

[Shadow98]

Check out "configuration #2" in my diagram for an idea of where the FPR should be mounted. DO NOT use whatever FPR you bought. For these low boost applications, you need a 12:1 rising rate FPR (i.e. Vortech FMU, or the Hahn supplied FPR).

So would it be a bad idea to use my AFPR with my Vortech FMU if i'm going to be running 7 PSI of boost?

 

[VelocitàPaola]

It would probably work, but... why? Just use the stock FPR and the FMU.

The AFPR comes in handy when you're ready to slap on larger injectors, and screw with the idle fuel pressure. At 7psi, you don't need any of that...

 

[JDT]

It would probably work, but... why? Just use the stock FPR and the FMU.

The AFPR comes in handy when you're ready to slap on larger injectors, and screw with the idle fuel pressure. At 7psi, you don't need any of that...

I have 450cc injectors that I will be running with a stage 2 Hahn setup. Would it be wiser to run an SFMU or run an FMU with an AFPR with the vac line disconnected? An SFMU is about $350+ new, I can't justify spending that much on a fuel pressure regulator. I'm just trying to explore all my options.

I know an FMU is the crappiest and oldest way to raise fuel pressure on a boosted 420a, but there has to be some way to run it reliably. Right? Vortech FMU's are a dime a dozen, but I'm not entirely sure which ratio to get. A 12:1 diaphragm maxes out the stock injectors, and I wouldn't feel safe running it like that, hence the 450's. But surely a 12:1 would flood my engine with 450cc injectors, so which ratio would be best? 6:1?

The car is my DD, just trying to keep it moderately reliable.


Thanks.

 

[LeeSD1]

This was a used Hahn turbo kit I bought off of ebay, and the mechanic told me it didn't come with anything to regulate the fuel pressure. So the universal comptech fuel pressure regulator I have is not good? I shouldn't use that? I saw your diagrams on another thread of yours and downloaded the picture to my computer for future reference. I don't have much more money to spend on this project, about how much should it cost to install the vortech FMU you are suggesting?

the FMU route is the simplest/easiest one, it splices inbetween the fuel return line from the stock fpr to the tank, NOW if you used the new fpr you would have to remove the stock one.

So would it be a bad idea to use my AFPR with my Vortech FMU if i'm going to be running 7 PSI of boost?

no, but leaving the stock one in will save you time and money. and like i mentioned above you will need to remove the stock one to use the new one.

I have 450cc injectors that I will be running with a stage 2 Hahn setup. Would it be wiser to run an SFMU or run an FMU with an AFPR with the vac line disconnected? An SFMU is about $350+ new, I can't justify spending that much on a fuel pressure regulator. I'm just trying to explore all my options.

I know an FMU is the crappiest and oldest way to raise fuel pressure on a boosted 420a, but there has to be some way to run it reliably. Right? Vortech FMU's are a dime a dozen, but I'm not entirely sure which ratio to get. A 12:1 diaphragm maxes out the stock injectors, and I wouldn't feel safe running it like that, hence the 450's. But surely a 12:1 would flood my engine with 450cc injectors, so which ratio would be best? 6:1?

using an sfmu takes some playing around messing with different sized rings and discs but the sfmu definitely adjusts fuel smoother than an fmu. What some people do when running an fmu is get slightly larger than stock injectors and use a 8:1 or 10:1 fmu. if i remember correctly the stock injectors were 190cc while some people will use 210-220. You do this so the stock ecu will control them as the stock injectors but will flow the extra fuel youll need while in boost but may be richer at idle and in vac.
If your willing to spend 350+ on an sfmu then why not just get a used Megasquirt unit and control FUEL ONLY with it, that way you can use the 450cc injectors and you can actually tune your fuel afr's as to what they should be.

 

[JDT]

using an sfmu takes some playing around messing with different sized rings and discs but the sfmu definitely adjusts fuel smoother than an fmu. What some people do when running an fmu is get slightly larger than stock injectors and use a 8:1 or 10:1 fmu. if i remember correctly the stock injectors were 190cc while some people will use 210-220. You do this so the stock ecu will control them as the stock injectors but will flow the extra fuel youll need while in boost but may be richer at idle and in vac.
If your willing to spend 350+ on an sfmu then why not just get a used Megasquirt unit and control FUEL ONLY with it, that way you can use the 450cc injectors and you can actually tune your fuel afr's as to what they should be.

As far as I know the stock injectors are 235cc, for a m/t anyway.

I don't have the cash to dish out for a new SFMU, I am however picking up a BEGi fmu. Don't know much about these other than that they came with the hahn kit. I'm not sure if ill keep the stock injectors when using it or run the 450's.

 

[LeeSD1]

If your using a rising rate fmu you'll have better results with bigger injectors but with 450s most people then need an SAFC to get a steady idle. But if your running no more then 8psi might as well just go with a set fmu