what fuel pump to get....
 

I know that if I get the Walbro 255, I have to get a adjustable FPR, but if I get the 190, I won't...how much higher flow is the 190 over our stock pump?

but if I am getting 370cc injectors, I will need an adjustable FPR anyway wouldn't I??? so might as well go for the 255? remember, I am planning on running a peak of 11psi of boost....

I put this graph together using published fuel delivery data for Walbro fuel pumps:

http://memimage.cardomain.net/member...62_77_full.jpg

The way to read it is to first look at the top axis and find the horsepower level you want to achieve at the crank. Go down to the purple line that best represents the brake specific fuel consumption your engine produces. From there go to the left axis to find what fuel delivery rate you need to achieve the desired power level. Then go to the green curve to find what fuel pressure level you need to stay below in order for the 190 lph pump to deliver the required amount of fuel.

In your case, let's assume you want at least 350 hp at the crank, and your bsfc is .6 (just to be conservative). Go down from the 350 hp hash mark on the top axis to the purple line representing fuel required at .6 bsfc. From the left axis we can see that the flow required corresponding to 350 hp at .6 bsfc is about 35 gallons per hour. Now go to the green 190 lph line and find that if your fuel pressure is less than about 50 psi, your 190 lph pump will deliver 35 gph.

Notice that your fuel pressure at 11 psi of boost is going to be at least 54 psi using a 1:1 oem rise rate. So the 190 lph pump may not be enough.

If your bsfc is .55 instead of.6 then your fuel requirement for 350 hp is less (about 32 gph), and your fuel pressure limit is raised to 60 psi, but you're still cutting it kind of close. Better to go to the 255 lph pump.

I know this has been said a million time before, but what is the difference from the GSS341 and GSS342?

BTW, tons of these are on ebay for $82ish.

what is the difference between the HP and the non-HP 255LP? I know what it stands for (high pressure), but what is the difference?

At higher pressure, it can sustain the flow rate (gph). While the non-hp, it will drop off very quickly.

Fuel management with the Stillen Supercharger kit
 

I wrote a little explanation of how the Stillen SC kit provides sufficient fuel during boosted operation. Maybe this will help answer some questions of people who are new to boosting.

As far as the stock fuel system is concerned. The Maxima uses an air flow referenced system. The mass air flow sensor (mafs, or maf) sends a voltage signal to the ecu based on how much air is flowing through it into the engine. The ecu uses that information, along with engine rpm and O2 sensor voltage to determine how long injector pulses should be to achieve stoichiometric combustion. This is for cruising and light acceleration and is called closed loop mode. Closed loop refers to the feedback loop in which fuel metering by the injectors is adjusted based on whether the O2 sensors detect combustion that is either leaner or richer than stoichiometric.

If the throttle is opened beyond a certain amount, as sensed by the throttle position sensor, the ecu goes into a mode in which it ignores O2 sensor voltage altogether and uses only the maf signal and engine rpm. This is open loop mode. Injector pulse widths are determined by a lookup table for each combination of maf voltage and engine rpm. The values in the lookup table are based on engine testing and give about a 13:1 to 13.5:1 air fuel ratio for the stock engine at wide open throttle.

When you install the supercharger kit you are significantly increasing the air flowing into the engine. This is not a problem during cruising and light acceleration because the SC does not exceed the air flow beyond what the maf is able to measure. At wide open throttle, however, it is possible to exceed what the maf can measure. Also, for boosted operation we want an air fuel ratio that is lower than what is provided by the ecu as a deterrent to detonation. The method that the Stillen kit uses to provide sufficient fuel for the additional air is to provide extra fuel pressure based on manifold pressure. This is done with the fuel management unit (fmu), which boosts fuel pressure according to a ratio that is determined by the size of the disk inside it. It is possible to have a fuel pressure to boost pressure rate as low as 3:1 and as high as 12:1. The stock Stillen kit comes with an 6:1 disk in the fmu (it might actually be 8:1, I forgot which), meaning that the fmu raises fuel pressure 6 psi for every psi of positive manifold pressure. This is a fairly crude way to tune, but it is simple and effective. In most cases it results in an overly rich afr at mid range rpm which leans out to an acceptable afr at high rpm.

In order to supply the additional fuel, either the Vortech auxiliary inline pump should be used, or the stock intank pump should be replaced with the Walbro 255 lph pump. The stock pump can not deliver enough fuel at a sufficiently high pressure to provide a rich enough afr to prevent detonation.

this needs to be stickied.

if we are going to talk about fuel. I think that the 370cc injector "how to" needs to be writeen up as well, as well as some of the other fuel injector threads, such as the z32 maf, scotts redesigned fuel set up, a ss line how to, and maybe some of the fuel settings for the safc and emanage (like jaime's for instance)

just my .02
steve

So if I have the Stillen Kit with everything the same except a 3.25' pulley, then it's recommended to get the Walbro pump? If you get the pump, then do you still need the blue FMU disc that came with the kit?

You need more fuel than what the oem fuel pump can supply. You have two options. You can use the Vortech T-Rex auxiliary inline fuel pump (that comes with the Stillen kit) along with the oem intank pump, or you can replace the intank pump with a Walbro 255 lph pump. If you go with the Walbro pump you do not need the Vortech aux pump.

In either case, you still need the fmu to raise fuel pressure when you are boosting. The only thing that would change that is if you installed larger fuel injectors that could supply an adequate amount of fuel at oem fuel pressure.

Prepping before Turbo install (fuel)
 

Ok, before I start in a couple weeks, im going to relocate the battery and get a 255 walbro fuel pump. I was wondering if the stock FPR would still regulate the right amount of fuel with the 255 pump.

Also, once I boost with the SAFC, will it control my pressures, or do i still need to get a FMU on top of the electronic management system.

Im just curious if I need to get a (non-stock) FPR and/or a FMU.

Thanks a lot,
Jeff


This post was a good one and a common one. So I tossed it in here and gave my answer below... Bags

What amount of boost are you going to run?

Your FP, with the walbro, will be ~46 PSI at WOT. Not enough fuel if your boosting more than 4 PSI, IMHO.

Again, if your using stock injectors and boosting more than 4 psi, the SAFC will only be able to correct so much. You may be able to do 5 psi with the SAFC safely. You can use ONLY an FMU, but that is a broad adjustment. See the thread below this one for more info

The SAFC CAN'T control fuel pressure. It changes the amount of air the MAF thinks it's seeing. See below thread for more info if needed.

You NEED an FMU or bigger injectors. You can keep your stock FPR and slap an FMU on there and boost 8 psi without any real problems.

I'm borrowing Stephen's post and changing it slightly for TURBO'S...

This applies to Turbos and Supercharged maxima's using a MAF refferenced fuel system. I just stuck it down here as well.

As far as the stock fuel system is concerned. The Maxima uses an air flow referenced system. The mass air flow sensor (mafs, or maf) sends a voltage signal to the ecu based on how much air is flowing through it into the engine. The ecu uses that information, along with engine rpm and O2 sensor voltage to determine how long injector pulses should be to achieve stoichiometric combustion. This is for cruising and light acceleration and is called closed loop mode. Closed loop refers to the feedback loop in which fuel metering by the injectors is adjusted based on whether the O2 sensors detect combustion that is either leaner or richer than stoichiometric.

If the throttle is opened beyond a certain amount, as sensed by the throttle position sensor, the ecu goes into a mode in which it ignores O2 sensor voltage altogether and uses only the maf signal and engine rpm. This is open loop mode. Injector pulse widths are determined by a lookup table for each combination of maf voltage and engine rpm. The values in the lookup table are based on engine testing and give about a 13:1 to 13.5:1 air fuel ratio for the stock engine at wide open throttle.....


Also, for boosted operation we want an air fuel ratio that is lower than what is provided by the ecu as a deterrent to detonation. The "standard" varies from 11:1 - 12.5:1. It really depends on who you talk to. If your tuning in the summer, you may want to aim for the 11:1, so when it gets cold, if you pick up a 1-2 psi, your fuel system has a little more room for error. If your tuning in the winter, I'd go with 12:1. These are MY choices, NOT the RULE.

The method that most of us use to provide more fuel is pressure based on manifold pressure. This is done with the fuel management unit (fmu), which boosts fuel pressure according to a ratio that is determined by the size of the disc (icy) inside it. It is possible to have a fuel pressure to boost pressure rate as low as 3:1 and as high as 12:1.

The size of the disc will be detremined by the amount of boost your running and the size of your injectors. This can be determined by either dyno tuning with a Wide Band o2 or "street" tuning with a wide band o2. For example if using a 6:1 disc in the fmu, meaning that the fmu raises fuel pressure 6 psi for every psi of positive manifold pressure.

This is a fairly crude way to tune, but it is simple and effective. In most cases it results in an overly rich afr at mid range rpm which leans out to an acceptable afr at high rpm. Using a SAFC or piggy back like e-manage, you can get a FLAT A/F ratio from 2500rpm-7200rpm.

In order to supply the additional fuel, either the Vortech auxiliary inline pump should be used, or the stock intank pump should be replaced with the Walbro 255 lph pump. The stock pump can not deliver enough fuel at a sufficiently high pressure to provide a rich enough afr to prevent detonation.THIS IS A MUST.

Again, credit goes to Stephenmax for putting this together, I just added a word here or there.

Fuel Pressure Under Boost
 

If anyone out there could please tell me what I should be looking for as far fuel pressure with this setup.

3.125 pully, T-Rex Pump, Cartech FMU

I am curious if anyone has logged their Fuel Pressure at given RPM in Third Gear.

If I am in Third at 2500 RPM, and then go to WOT my pressure jumps from about 40 psi to 62 psi and then climbs to around 80 psi at 6200 Rpm's

I'm thinking that the center screw may be in too far, because it seems like I have less torque when I'm at WOT (open loop) than I do at 3/4 pedal in closed loop.
I will be purchasing a wideband O2 at some point in the future, all I have right now is a millivolt readout for my stock O2. Any info or suggestions would be appreicated, Thanks Much.

Im running the stock fuel pump and fmu that comes with the stillen kit, I have stock injectors and im running the 3.33 pulley and all I have done is some tunning on the dyno to get a rich air/fuel mixture (12.1 to 1) and I have had no fuel problems after 2 years.

iv done some reading on here and wanted to verify something that i am confused about. I have walbro 255 high pressure pump, along with 370's and afpr and vafc2. for under 8 psi, do you guys think i will need an fmu? (this is for turbo)

I posted this in the supercharged discusson but ill try here as well for some advice.

i just bought a '98 I30 with a stillen SC. The previous owner said he also had a walbro 255 installed. I have gone through my first tank of gas and noticed when the fuel light came on, less than a mile down the road, the car began to sputter and run out of gas. Lucky i was at an intersection with a gas station. When i filled the car up it only took 16.5 gallons on an 18.5 gallon tank. Does anyone know why this may have occurred? Is the walbro pump have a shorter fuel pickup that leaves 2 gallons in the tank? Is there anything i can do to correct this problem to eliminate the problem?

Crazyred

Your fuel pump sits in a dust collector plastic housing about 9"x5"x1.5" dimensions. When the fuel level is low enough, your fuel pump sucks all the fuel out of that housing while the rest of the 2 gallons aren't high enough to seep into it, thus causing an out-of-gas sputter to kill your car. (Basically, 2 gallons of gasoline spread evenly at the bottom of the tank is less than 1" high, not even close enough to get into the fuel pump housing.) If you can jerk your car hard enough like a hulk can, you may manage to spill a little more gasoline into it, and be able to start the car again till it runs out. But that's not humanly possible; what we do is "pump the gas when it's pretty low".

-Peter-

Walbro Fuel Pump Fix
 

Myself and Ptatohed came to realize that there's a remedy to this problem. The stock fuel pump has its strainer parallel to the bottom of the gas tank and is able to suck up pretty much all the gas in the tank. The strainer that comes with the Walbro points upward at about a 30 degree angle and is not capable of sucking as much gas up (when it gets below approximately 1/8th of a tank) as the stock strainer.

To fix the problem, take the stock fuel pump strainer and put it on the Walbro fuel pump. This has been tested and proven to work during the course of installing Mike's (VIP Maxima) supercharger. With this mod, you can now drive your car like normal and not worry about running out of gas/poor performance at 1/8th of a tank.

I want to add to this (since i think this would be the more correct Sticky for this, move if necessary).

RC injectors that you buy and do not include the pigtail connectors-

NAPA P/N 2-17427. They were ~$6 each

Just have to trim off the edge at the tip and they will sit flush and clean (wont snap in and lock into place, BUT there's no reason for them to come off unless you pull on them).

I wanted to add this little gem to this sticky. Ever wish you didn't have to deal with both an external ajustable fuel pressure regulator, and then adjust the disks for your FMU when you mess with boost settings? I happened to stumble across this looking for a BOV of all things, but the functionality is amazing (just judging from what i have read).

Synapse Rail Mounted Synchronic Fully Adjustable FPR/FMU
http://www.hpautoworks.com/images/sc001_7.jpg

Taken from the website:
Synapse Synchronic Fuel Pressure Regulator is a bolt-on all in one solution for all motor, nitrous or forced induction engines. Allows for infinitely adjustable boost dependent ratio from 1:1 to 12:1 and adjustable static fuel pressure from 16 to 80 psi. Its solid piston design with no diaphragm will prevent from rupture or failure. Maintains full fuel pressure when vehicle is powered off, for immediate ignition at next cycle. Potential application to maintain no-return conditions in return less fuel system while compensating for the fuel delivery required for boost. Direct bolt-on installation, requiring no additional plumbing or hoses that introduce leaks and additional points of failure.
Key Features:
# Direct bolt-on to the fuel rail
# Absolutely no additional fuel lines to re-work from stock
# Guaranteed 1:1 off-boost ratio for a proper air/fuel ratio at idle
# Infinitely adjustable from 1:1 to 12:1 boost indexed fuel pressure ratio
# Interchangeable adapters for various applications
# Adjustable static fuel pressure
# Absolutely no diaphragms to fail, easily rebuildable with new seals
# Tough enough for direct applications of Nitrous
# Patent 6,863,260

Just thought I would share this.

Anyone try this item??

Can an after market FPR like this be used instead of expensive electronics to do fuel management under boost??

I'll be installing mine here in about 2 weeks. Got it for $125 off eBay last week. The patents for Synapse got bought out by Vibrant, so be on the lookout for manufacturer change. Looks like direct rail mounting might be a bit tight, can't be sure untill I take the stock FPR off. Also not sure if the included rail fitting adapter will work or not. Those with phenolic spacers or PF throttlebodies shouldn't have much of an issue with fitment as the TB looks to be the only obstacle in the way of fitment. Remote mounting may be an option as well, though I'll have to look into just how to accomplish that with like 2 fuel rail adapters and some fuel hose...

MarcL, as far as tuning goes, having a fuel pressure regulator / fuel management unit like this allows to get your fuel pressures really close to what is necessary for your particular AFR tuning goals.

Say, for instance, you boost your car and install a walbro 255. Well, with this FPR/FMU you can adjust your base fuel pressure back to near the stock level for idle/vacuum running - save gas. Then, because as you boost you need more fuel, you can adjust the boost referenced rise rate ratio to compensate for the needed fuel consumption to keep the car from running lean. Well lets fast forward and say now you've installed 370cc injectors since you've up'ed the boost or just decided to lower you overall fuel pressure necessities. Now you have the ability to simply turn a knob to decrease your rising rate ratio and a screw to lower base FP if needed (since you won't need to boost the FP near as much as before per pound; thanks to the increased flow from the new injectors).

Now having said that, this has nothing to do with fine tuning. I you want a rough tune that will "work" - though not optimally well, then yes this could handle the "tuning" for boost. You still will need some sort of piggy-back computer like a S/V-AFC or Emanage to do the fine tuning to hit your target AFR and keep it there; but having the adjustabilty of a unit such as this will allow for much simpler tuning (less correction +/-).

Thanks for the great info..

I may try to pick one of these up too. It sounds like it will get the car running in a reliable and safe manor without the need for expensive electronics. That may come later, but I need to crawl before I walk. :)

Which model FPR did you get? On the Synapse web site it lists 2 of them for "nissan". I think I have the space to mount direct to the fuel rail because I am going to be using a modified Kenetix intake.

My fuel pump is rated at 2.5 lpm, Do you think that is enough? I am not sure my fuel lines can handle much more than that! (This is not in a Nissan body car)

The model I got is the SC001. I might be able to tell you whether or not it fits/works here in a hour or two. The stock bolts are too short to screw into the rail through the new FPR. I do have some concerns that the seal won't work. There might be another adapter available that will make it work, but I won't know if it's an issue till I go get some longer bolts.

I'll edit this post with more information here in the next couple hours (time stamp: 6:38pm EST).

Edit: (Time Stamp: 10:31pm) 4 Hours and 5 trips to Home depot later (2 were unrelated...) she's up and running! Adjusted Idle/base fuel pressure to 35-36psi, which is a long way screwed in on the center screw... much more than I thought it would take to get a positive response on the FP gauge... Just need to get the car boosted now :thumbsup:

Edit#2: Car is boosted now and I can honestly say this FPR/FMU has got to be designed for boosted applications. It used to give me fits (constantly fluctuating and actually dropping pressure instead of increasing it), but now it's running beautifully.
Pictures of it it installed:
http://i167.photobucket.com/albums/u...MAXSE/FPR2.jpg
http://i167.photobucket.com/albums/u...MAXSE/FPR1.jpg

Just to bump this back up with some new information about the synapse FMU/FPR. A couple months back I ran into an issue where the fuel pressure regulator just simply stopped rising the fuel pressure under boost and if I was driving for an extended period (100miles or more) the fuel pressure would gradually lower over the course of the trip. I thought it was an issue with my fuel pump, but it wasn't. What had happened is that because I had exceeded 80psi, there was fuel blow-by occurring. This had caused there to be buildup of some sticky crap along the inside of the chamber of the FPR, keeping it from cycling and increasing/decreasing the fuel pressure.

I would recommend, if you are running fuel pressures in the upper limit of the FPR's range to check it when you do your oil changes and lube it with a little bit of oil on your finger.

BTW, this FPR will work on 4th and 5th gen maxima's and is a much less complicated and easier to dial in than a combination of an external FPR and FMU in boosted applications. I will be transferring it to my new motor (which I installed a 2k2 fuel rail on).

Are you running stock 3.0 de injectors casue if so switching to the dek injectors when you swap the motor will allow you to run less fuel psi.

and I have said DEK injectors for sale...:D

I'm guessing you don't realize I'm going to be swapping in a 3.5 here in a couple weeks. If you are, then I'm not sure I understand. Are the DE-K injectors higher flow than 6th gen 3.5 injectors (cause the part numbers are the same from 2000-2009+ according to Courtesy Nissan's parts listings).

Right now my base pressure is about 37psi. I was being very conservative on my fuel (rise rate is set pretty high to give about 11.0:1 AFR near redline - though it's really fat in the mid range that dip into the 9's). The weather around here has been hot and humid for forever, so I haven't leaned it back out yet, and i likely won't before I'm ready to do my swap to pre-ballpark my fuel pressure and rise rate.

do i still need the vortech fmu when adding larger injectors (dw 555) and tuning with the emanage ultimate?

Nope, sure don't.

Thanks! One thing less to worry about in the install! =)

Keep in mind, that with such big injectors, your car will have a very hard time starting and idling. Once I dropped off my car and had it professionally tuned, only then did I have OEM-like cold and warm starts etc etc.

That is exactly where I am at with my 555s, Vortech FMU, and NEO to dyno-tune. I was hoping to correct it some with better tuning gear, maybe a AEM f/ic. Still so up in the air over tuning gear, seems no one in MD wants to touch the Greddy. Any suggestions appreciated!