fuel management help

[crazys14mexican]

Ive read many threads and I still cant decide on what to Do. My 2 goals are to reach about 280whp and run about 8psi daily driving and about 12-13psi @ the track. I already have lightned crank pully, JWT cams, AFCII, and Stage2 clutch. I am about to order Boost Designs Stage 1 kit but Im still unsure about fuel management. Im thinking about just getting an fmu which i was told is good up till about 10psi and later on get a walbro fuel pump and some injectors. I just dont want to waste any money on something I will need later on or somethin i would replace soon afterwards. Some help would be very appreciated

[Craving4Boost]

u jus said u have an AFC II..thats ur fuel management right there

[sil80drifter]

It seems liek you have/got a bunch of parts that you heard were good, or got the setup up made by someone else and don't really know abotu the mechanics of engine workings. Please research fuel injection and the functions of all the components you already have to figure out what you need to do/would like to do. Any single/simple answer to your above question would lead to a bigger headache in the future, as you wouldn't know why or where to find the reasoning behind the advice.

http://www.howstuffworks.comfor fuel injection/timing basics and F/I bascs. Then research what your individual componets do.

then you'll see why your question was a bit like "I have some bread, now where do I get food so I don't stay hungry later on?"Good luck, and please don't get offended, I just wanna point you in the right direction. If you have specific questions don't hestitate to ask, and I'll provide more specific answers or places where to get an understanding of the subjects from.

sil80

[Nismo_Freak]

Ive read many threads and I still cant decide on what to Do. My 2 goals are to reach about 280whp and run about 8psi daily driving and about 12-13psi @ the track. I already have lightned crank pully, JWT cams, AFCII, and Stage2 clutch. I am about to order Boost Designs Stage 1 kit but Im still unsure about fuel management. Im thinking about just getting an fmu which i was told is good up till about 10psi and later on get a walbro fuel pump and some injectors. I just dont want to waste any money on something I will need later on or somethin i would replace soon afterwards. Some help would be very appreciated

You need 52# (~550cc) injectors and a Z32 MAF... plain and simple.

[DammitBobby]

Quote "and later on get a walbro fuel pump"

I would recommend you replace the fuel pump first. You will need it no matter which route you go. It is a very simple and inexpensive swap.

[sil80drifter]

If you keep throwing random parts suggestions at him, he'll never learn. Then again maybe it's not my job to care about who does what.

(Those were good suggestions except you didn't tell hm why he needs them and where to get more info about what they do, you don't want him to just randomly buy parts, which he already seems to have done, do you?)

sil80

[96240SX41]

fuel managment= MoTec. Plain and simple, really easy to access on laptop, and to tune your car with.

[ILikeMy240sx]

You need 52# (~550cc) injectors and a Z32 MAF... plain and simple.

This + Enthalpy Tuned ECU. The ECU is just plug n play. That is the setup that I am going with.

Although I will be running low boost for daily driving (6~8 psi) and 10~12 psi for track days I want to make SURE that I do not skimp out on fuel system/management. Not only that but timing as well which Enthalpy ECU takes care of.

Your alternate route would be JWT ECU which might be a better route for you wince you already have a SAFC and can find tune the ECU with it.

[crazys14mexican]

thanks for the input, i think for now im just gonna get an fmu. run low boost for awhile and see how i like it.

[DammitBobby]

I am running the BD Stage I kit with the 12:1 FMU, walbro 255 and boosting at 10 PSI with the help of a MBC.

[IvanAtSPRacing]

I am running the BD Stage I kit with the 12:1 FMU, walbro 255 and boosting at 10 PSI with the help of a MBC.

Please, for the sake of not providing wrong advice, can you test your FMU to see what is really happening? Check your base fuel pressure with the vac line off the factory FPR and the FMU (plug them so you dont have a vac leak) and your motor running at idle. Use your Mitivac to put pressure on the FMU one psi at a time and see how much it goes up for every psi. If the first psi of pressure you put on the FMU nets you 12 psi, and then again on the second psi, then the FMU is 12:1 Eventually, your fuel pressure will not go up any further no matter how much boost you put to the FMU. This is the pressure limit for the pump minus what the injectors are bleeing off. You will find that at WOT where your injectors are bleeding off more fuel pressure, the peak fuel pressure you can make will be less.

IMO a 12:1 FMU is WAY too much. 4:1 or 6:1 would be much more reasonable for your application (not that I recomend FMUs) and would work better for your target boost with the fuel pump your using. The way your running it now (if you really do have a 12:1 FMU) at 4 psi, you will have 93 psi fuel pressure. I believe I read in one of your posts, you maxed out at 100 psi? If that the case, then your fueling is the same from 4 psi to 10 psi and will probably be the same for your intended 12 psi. With a 4:1 FMU, at 4 psi, your pressure would be 61 psi, 5 would be 65, 6 would be 69, 7 would be 73.... etc etc.. Obviously, this setup would have to be verified to work well on a dyno with a WB O2 sensor.

I believe you also stated that your AF was extreamly rich. With the lower rate of gain FMU, this would certainly help at lower boost levels. The load on your injectors and pump would also be less. And as you should know, as fuel pressure goes up, the ability of the pump to be able to flow fuel goes down. At some point, your risking going lean and melting your motor from lack of flow from too much FP.

[nissanfanatic]

IIRC an 8:1 forces our injectors to flow 400cc at 6psi which has gotta be extremely rich. I'm getting my wideband in soon so I'll let you guys know what kind of AFs I'm running with my 8:1.

[KATwo40]

Ivan's my hero.

[DammitBobby]

[QUOTE=IvanAtSPRacing]

Please, for the sake of not providing wrong advice, can you test your FMU to see what is really happening? Check your base fuel pressure with the vac line off the factory FPR and the FMU (plug them so you dont have a vac leak) and your motor running at idle. Use your Mitivac to put pressure on the FMU one psi at a time and see how much it goes up for every psi.

Ok Ivan problem with using the Mitivac. It is only a hand pump it does not apply constant pressure. All the actuated pressure devices that are used in the turbo kit require constant pressure. Including the FMU. I only used the Mitivac for a quick test to see if the fuel pressure would go past 55 PSI. If I had such a device that could apply constant pressure to the FMU 1 PSI at a time I would have all ready recorded for everybody`s info.Now if you would like to ship me some device that will allow me to test the FMU I would be glad to do it and pay yet another 60 bucks at the Dyno.

IMO a 12:1 FMU is WAY too much. Well according to the Blake at Walker Dyno he said " That the fuel curve looked good!"

[hannibal]

Crazy S14, you already have the SAFC (the expensive part), now go all the way and buy injectors. The 50lbs + JWT/Enthalpy ECU is a good option. Or if you dont want spend all that right now, just find some used 370cc injectors from an SR ($100). Your SAFC will be able to control them. And Ive heard too many people recommend replacing the fuel pump for me not to. A Walbro 255 is under $100 on Ebay.

An FMU is gonna cost about $100.

Your SAFC + 370cc injectors + fuel pump should be good for almost 240-250whp. The injectors and MAF max out around there. (but I dont know which maxes out first)

[crazys14mexican]

I really appreciate your guys advice and im now currently buying a fuel pump, and boost controller. The only injectors ive seen for sale on forums is 550's but those would be to big now wouldnt they? Because Instead of buying an Fmu im just gonna buy the stage 1 kit. Ive heard of getting something for timing..will that be that big of a problem? Anything else i need for my setup? BTW i will be running open downpipe for a week or two untill i can afford the rest.

[Jookmasta]

u can retard base timing if ur planning on not upgrading the ecu