L28et Turbo Fuel System Questions

[Challenger]

Hey, Im working on some planning for my turbo motor, right now I have a aluminum fuel rail for the stock injectors on its way. Il be running 12psi of boost on a mostly stock turbo motor and over the last week or so have been doing research regarding the fuel system and getting more fuel on boost.

 

My question is do I use the stock regulator off of the stock fuel rail? Or will the 1:1 fpr replace it. *** From what Ive read the fpr that will give me extra fuel on boost is added in addition to the regulator.

 

I feel overwelmed with all the info Ive been reading about regarding fuel pressures, fmu's, afpr, fpr, etc. and all of these being used together.

 

If I need to include any addition info just ask.

 

*** maybe not the correct term but the regulator that will give me 1 extra psi of fuel pressure for every psi of addition boost. Still researching it.

 

THANKS!

 

Edit- Thought Id include a little info on the motor, f54/p90, stock turbo cam, intercooled, stock tubo afm, ecu, harness, n42 intake, stock injectors, aluminum fuel rail, DSM BOV, external wastegate/proper downpipe.

[MJLamberson]

FMUs are the same as rrfpr (rising rate fuel pressure regulator) and its sounds like this is what you want, anywhere from 80-200$ on ebay

[Calgary280ZT]

MJ, here's a post by TonyD on zcar.com where he discusses RRFPR and how they are NOT for turbo engines. I was planning on buying one for my car but Tony burst that bubble in a hurry. http://www.zcar.com/forums/read/4/1950802/1951178#msg-1951178

[Lukaniuk]

I used the stock fuel pressure regulator on 11 lbs of boost with no problems. But I was also using megasquirt and 440cc supra injectors.

Just last week I bought and installed a new Aeromotive boost referenced fuel pressure regulator. $170 CAD. You can probably get them cheaper in the states. Car parts always seem to cost so much more up here.

[Challenger]

So do I pull the stock regulator off my fuel rail and use it wil my aluminum rail?

 

And the rrfpr, Id look for a 1:1 unit that would install along with the original fuel pressure regulator?

 

Thanks

[Lukaniuk]

Ya I pulled it off the stock rail and mounted it in front of the valve cover. I just ran hose from the front of the return on the fuel rail and through the regulator.

 

I don't think you'll need both regulators

[Tony D]

The stock fuel pressure regulator is manifold referenced---meaning the fuel pressure is spring set to be a set pressure ABOVE manifold pressure. The stock FPR IS a 1:1 fpr with a 37psi preset bias.

 

A rising rate FPR changes fuel pressure NON-Linearly. For every psi you get in the manifold, you get 2, or 3 X that change in the fuel pressure. For band-aiding a stock EFI system with STOCK sized injectors it works to give more fuel under boost.

 

With a standalone, a RRFPR is not required. With stock ECU and Stock Sized injectors it will give you more fuel flow under boost than the stock injectors would normally be capable of doing.

 

For a Turbo ECU, ANY stock regulator from a Nissan EFI system will work fine---it already has 'boost flows' compensated into the fuel mapping up to around 10psi. And yes, you can use them on the aluminum fuel rails simply by mounting them on the firewall, or wherever, and using a barbed fitting at the end of the rail.

[linchpin360]

Is it better to install this before or after the rail? (aeromotive specific)

[Challenger]

Thanks Tony, I will have stock turbo ecu and wiring but Ill be going to 12 psi. So do you think I will need to add fuel for the extra 2 psi?

 

Thanks

[woldson]

DO you have a wide band?

[Challenger]

Ill DEFINITELY be getting one when I get the motor together. Such a small price to protect a huge investment. But Id like to find out to start off what will get me in the ball park. I can to the fine tuning when the car is running.

[woldson]

Under the idea of protecting, which I agree with, stay with in the limits of the stock ecu.

 

I know you will succesfull push further,,,,,, I've just seen to many jump too far too fast and dynomite.

 

Besides you can update you drive viedo with a much bigger "bark" in second!!

[Challenger]

Thanks Tony, I will have stock turbo ecu and wiring but Ill be going to 12 psi. So do you think I will need to add fuel for the extra 2 psi?

 

Thanks

 

So any idea on what I should do for the extra 2 psi? What does the stock regulator do after 10psi?

 

Thanks

[Six_Shooter]

The regulator won't raise the pressure proprotinally to the boost pressure after 10 PSI manifold pressure. That is if the stock FRP indeed does have a 10 PSI limit, sounds plausible since other OEM FPRs I've seen seem to have about the same limit.

 

The 1:1 rise in fuel presusre is really just keeping the differntial pressure the same.

 

A little education:

 

Fluid will flow from high pressure to low pressure.

 

In this case the fuel rail has the high pressure and the intake manifold is low pressure, thus fuel flows from the rail through the injector and into the intake tract.

 

Now fuel mapping is generally done with a a set pressure differential. From tony's post it sounds like this pressure differential is 37 PSIG. Now you will notice that when there is manifold vacuum, the fuel rail pressure will go down. This keeps that same or close pressure differential of 37 PSIG between the rail and the intake, even though the rail pressure is less than 37 PSIG. N

Now once you go above 0PSI (~100KPA) intake manifold pressure, you now need to raise the fuel pressure in a 1:1 ratio to maintain that 37 PSIG differential, to keep mapping the same, or linear.

 

you would need to increase the fuel rail pressure in a ratio greater than 1:1 to have "additional fuel", when in boost.

 

You may find that you might run a bit rich in boost pressures below the factory 10 PSI, and then taper off a bit above that if you use an FMU, due to the ECM already being calibrated to deleiver adiquate fuel in that range.

Using a Cartech FMU is supposed to reduce this, since it is supposed to be adjustable at the point in which fuel pressure starts to rise.

I have a Cartech FMU that I will likely in my swap initially, to basically make the injectors seem larger than they are, to get enough fuel to the engine at higher boost pressures. I will be using a GM ECM that I will tune myself, but all injector calculations indicate that my injectors are about 10 lbs/hr too small for my end goal. I don't plan to run it this way long, but I may not find large enough injectors before I get to the point of running higher boost pressures, and I have this FMU kicking around from when I was going to put a turbo on my '98 Malibu, that never came to fruition, just didn't find the time to do it.

[MJLamberson]

did you see how big phil hit his on a certain spot to raise the fuel pressure? Its in one of his earlier vids whe h e converted his NA to turbo I believe

[Challenger]

The regulator won't raise the pressure proprotinally to the boost pressure after 10 PSI manifold pressure. That is if the stock FRP indeed does have a 10 PSI limit, sounds plausible since other OEM FPRs I've seen seem to have about the same limit.

 

The 1:1 rise in fuel presusre is really just keeping the differntial pressure the same.

 

A little education:

 

Fluid will flow from high pressure to low pressure.

 

In this case the fuel rail has the high pressure and the intake manifold is low pressure, thus fuel flows from the rail through the injector and into the intake tract.

 

Now fuel mapping is generally done with a a set pressure differential. From tony's post it sounds like this pressure differential is 37 PSIG. Now you will notice that when there is manifold vacuum, the fuel rail pressure will go down. This keeps that same or close pressure differential of 37 PSIG between the rail and the intake, even though the rail pressure is less than 37 PSIG. N

Now once you go above 0PSI (~100KPA) intake manifold pressure, you now need to raise the fuel pressure in a 1:1 ratio to maintain that 37 PSIG differential, to keep mapping the same, or linear.

 

you would need to increase the fuel rail pressure in a ratio greater than 1:1 to have "additional fuel", when in boost.

 

You may find that you might run a bit rich in boost pressures below the factory 10 PSI, and then taper off a bit above that if you use an FMU, due to the ECM already being calibrated to deleiver adiquate fuel in that range.

Using a Cartech FMU is supposed to reduce this, since it is supposed to be adjustable at the point in which fuel pressure starts to rise.

I have a Cartech FMU that I will likely in my swap initially, to basically make the injectors seem larger than they are, to get enough fuel to the engine at higher boost pressures. I will be using a GM ECM that I will tune myself, but all injector calculations indicate that my injectors are about 10 lbs/hr too small for my end goal. I don't plan to run it this way long, but I may not find large enough injectors before I get to the point of running higher boost pressures, and I have this FMU kicking around from when I was going to put a turbo on my '98 Malibu, that never came to fruition, just didn't find the time to do it.

 

Ok that helped, thanks. So I looked at prices for the cartech and their nearly $300. Is there another brand that I could look at, like the ebay models. But Id still need to look for a 1:1 rising rate fuel pressure regulator.

[Brad-ManQ45]

The terms 1:1 and risiing rate are mutually exclusive....

[Tony D]

The regulator won't raise the pressure proprotinally to the boost pressure after 10 PSI manifold pressure. That is if the stock FRP indeed does have a 10 PSI limit, sounds plausible since other OEM FPRs I've seen seem to have about the same limit.

 

The 10psi limit is imposed by ECU mapping, not because the FPR stops working.

 

A fuel pressure regulator works as a balanced unit of spring pressure against a seat. If you have a spring pressure set to 37psi, against a seat presure of 37psi, it doesn't open. If you see more pressure on the seat than the spring provides, then the spring pressure is overcome, and the seat cracks open, bleeding pressure (to the return line).

 

Follow that so far?

 

Now, you add manifold referencing. Put a hose to a sealed chamber where your spring resides, and connect it to your intake manifold. Now you will have TWO forces working to hold the seat closed. Still only fuel pressure working against the seat, though.

 

So you're at idle, and have 18" of Hg vacuum in the manifold. Offhand conversions say 1psi=2"Hg of Mercury. So that works out to be roughly -9 psi of pressure, working against your spring pressure of 37psi meaning the effective pressure on the seat is 37-9=28psi. Under high vacuum, you could have 28"Hg in the manifold, or -14psi, and fuel pressure would drop to 37-14=23psi. This is how the old Bosch EFI systems used the injectors they did to run the horsepower. It allows larger injectors to run as 'smaller' injectors under light load, letting you run an increased pulsewidth because the older systems didn't have a lot of resolution...but I digress.

 

NOW...

 

Lets go into boost. You throw 10psi at it, and your effective seat pressure is 37+10=37psi. Put 20 psi at it and 37+20=57psi.

 

It is irrelevant how much boost you throw at the regulator. It simply is a dumb device that uses spring pressure plus referencing pressue to determine ultimate fuel pressure. Stock regulators have been run to 30psi of boost (I used stock FPRs from a BMW to run 25psi+ on a VW I built some loooooong time ago...)

 

THE LIMITATION IS THE PULSEWIDTH PROGRAMMED INTO THE STOCK ECU!

 

The same FPR works GREAT at 17psi on my Megasquirt system with 440cc Supra Injectors.

 

The limitation is not the FPR. It's programming of the ECU for 'standard conditions---which is to say, they programmed the system to run with a failed wastegate running the popoff valve wide open under all rpm conditions. I know, I did that experiment on an 84 Turbo Skyline. Wired the wastegate shut and ran with the pop valve whistling dixie...

 

The regulator raises on a 1:1 porportional pressure rise. The limit on the stock pump will be around 20psi of boost as the stock internal relief valve lifts and starts bypassing around or just before 60psi (if you are lucky).

 

The limit on the FPR is the burst pressure on the casing. I have put 100psi to them and haven't blown the casing yet...so to say it stops working above 10psi is incorrect.

 

Does it provide enough fuel above 10psi? If you have adjustable pulsewidth, yes. If you are using the stock EFI system and ECU...No. That is the ECU's fault, not the FPR's.

 

Some people will run a solenoid to close the bypass line and run the pump to full pressure when it hits 11 or 12psi...you get a jump from 47 to around 57psi and that is a non-linear fuel delivery which is what the RRFPR's do. Do you 'need' that much fuel at 12psi? Who knows. The only way to know is try. This is a hack-style approach to making it work.

 

If money is the prime concern, I'd stick to 10psi till I had the money for a Megasquirt, and THEN start upping the boost. Drop your requirement for '12 psi'---I mean what is the magic behind 12psi? You end up spending money for interim patches that you end up throwing away when you up the ante further and go with a proper fueling solution. If you don't have the money to do it right now, when will you have the money to do it over?

 

Just stick to 10psi until you have the MS and some 370 or 440cc injectors to install as a set, you will be money ahead, trust me!

[Challenger]

Thanks, that helped.

 

Thats why I started this thread, I new 10 psi would be easy but thought Id do some research into what it would take to raise it a few more. Obviously doesnt look like it will be of any benefit to pass the 10psi mark.

[lifegrddude]

In case you do decide to buy an adjustable fpr, I got mine from Sard for about 90 bucks and it's 1:1, and you'll be able to set the base pressure anywhere from 25-60 psi.