safc and fmu???

[VeloceDrift]

So you may laugh at me but thats ok it seems to work really well. So a couple years ago when i first went ka-t i put an fmu in for fuel and about a year ago i came across a safc for like 50 bucks and i through that in with a z32 maf. my question is do a lot of people run both of these at the same time. If i unhook the fmu my afr's go much leaner so i just left it their and i seem to be getting plenty of fuel out of my stock injectors. Just wanted to know if this is a good idea or not.

[Doya]

I don't see why it would hurt anything, as long as you have a wideband to confirm that you aren't running too lean.

[VeloceDrift]

yeah i have an innovate lc1. just woundering because i have never seen anyone else run one but my theory was the safc is going to add more fuel and what better way to get the fuel their faster then having an fmu their to make some pressure.

[96NismoZ]

What exactly does the FMU do?

[egan]

What exactly does the FMU do?

FMU - fuel management unit shortened from rrfmu or rrfpr - rising rate fuel pressure regulator. ups X psi of fuel for each 1 pound of boost. iifc ka wants around 6-8:1 ???? no more than like 7 psi if you really wanna push it

i do however like the idea of rrfpr + safc as cheap tuning. never thought of that. interesting combo

[neverlift]

I myself just put in an afc with my fmu and love it, I had some rich spots I wanted to play with , but then today my w/g blew off so I will probably be looking at retuning it cause it had some nasty leaks. I am thinking abou 370cc with the fmu/afc that would get me into the 300whp range easily with reasonable fuel pressure.

[Doya]

I myself just put in an afc with my fmu and love it, I had some rich spots I wanted to play with , but then today my w/g blew off so I will probably be looking at retuning it cause it had some nasty leaks. I am thinking abou 370cc with the fmu/afc that would get me into the 300whp range easily with reasonable fuel pressure.

See, I'm kinda new when it comes to tuning. I've turbocharged two cars before and I've always just used an fmu and left it at that. Right now I have a 10:1 fmu and it causes me to have some rich spots. Could I just get a AFC and lean out those certaint spots?

[C-Kwik]

yeah i have an innovate lc1. just woundering because i have never seen anyone else run one but my theory was the safc is going to add more fuel and what better way to get the fuel their faster then having an fmu their to make some pressure.

If you are looking at this from a standpoint of trying to increase duty cycle to allow for more boost, look elsewhere. The simple fact is that with stock injectors at about 7 psi of boost, are already at 100% duty cycle pretty quickly as the MAF will detect a much larger rate of flow and try to compensate (IIRC, from the datalogs on my emanage before I upgraded injectors, the duty cycle was maxed well before redline at 6.5 psi of boost with a 8:1 FMU). This is why an FMU is used in the first place (by bumping up pressure, more fuel can be delivered for a given duty cycle). But the FMU's ability to increase fuel flow is limited by the fuel pump's ability to provide enough pressure and flow. As pressure and flow have an inverse relationship, trying to do both at the same time requires a very robust pump.

About the only thing I see you doing with this is trying to trim some of the rich spots, but with an FMU in place, tuning isn't quite as linear since the duty cycle requirement will be based on 2 parameters instead of one (airflow and fuel pressure). Traditionally, when tuning an ECU, standalone or piggyback, the fuel pressure, relative to manifold pressure, is kept constant so that tuning is linear. Not sure how much resolution the SAFC has, but part throttle tuning in particular will likely be a pain in the butt to get right short of coming up with an accurate equation for the relationship between airflow, boost pressure and fuel pressure, or spending a ton of time on a dyno incrementally optimizing each cell on the tuning map.

I myself just put in an afc with my fmu and love it, I had some rich spots I wanted to play with , but then today my w/g blew off so I will probably be looking at retuning it cause it had some nasty leaks. I am thinking abou 370cc with the fmu/afc that would get me into the 300whp range easily with reasonable fuel pressure.

Frankly, if I were going to upgrade my injectors, I'd just get the proper size and work with a system that is easier to tune overall than to run larger injectors and an FMU. Or, if you only need a small boost in fuel flow to reach your goal, I'd probably look into an adjustable 1:1 FPR and bump up the pressure only moderately. This will keep the tuning linear and probably be less apt to hit the limits of the fuel pump.

[neverlift]

thread jack in progress

not sure what limit the pump would have, I pinched the line and it hits 120psi. The 370cc and fmu shouldn't be too hard to get a rough running tune on, the fmu can be manipulated pretty easy, if the 370's can handle 7~8psi safely without much tuning involved , install a one way that will hold 7psi, then with the fmu(in my case 7:1) you can add another 7psi and still be under 90psi fuel pressure. And that would leave room for the ballsy fellow out there not scared to hit 100 plus psi fuel pressure.(a local guy a couple years ago ran an 8:1fmu with walbro and made like 320IIRC on 12psi, I'll look and see if it was transferred to the new board but I was impressed. That's 14~15psi and about my total max goal for this little t3(.42/.48). I did 12psi on 73psi(IIRC) fuel pressure with stock ecu/maf/injectors on only a afpr accident it was but it was in the 11:1 afr, I'd like a little richer as I don't have timing under control except 5* knocked off base timing.

However with that said Running a set of 550 would be better on a tuned ecu, but and its the big one, I am on limited funds these days, I have no budget except what I have laying around or can get for a steal. But it still doesnt seem very hard from my POV

[C-Kwik]

thread jack in progress

not sure what limit the pump would have, I pinched the line and it hits 120psi.

Since the pressure and flow are inversely related (an unrestricted pump can flow more fuel than one that is restricted; a restricted pump will have higher line pressure than an unrestricted pump), the more pressure you try to run, the less it can flow. If you reach the pump's max flow/pressure, then at the given flow rate, the pump will not be able to provide enough flow to sustain that pressure. You'll know this is the case if the pressure drops at the max boost as the injectors approach full open. That said, if you are maxing out the pump with a set of stock injectors, then with larger injectors, it will be trying to flow even more fuel. The pressure will be even lower. This is contingent on if you are maxing out the pump or not. If the pump you use is capable of sustaining enough pressure at the necessary flow rate, then you are fine. But as I explained, be weary that larger injectors increases the flowrate which brings the pump pressure closer to or potentially beyond its ability to maintain a the desired pressure level.

[neverlift]

I see

[WDRacing]

I would use the FMU by itself. If I was upgrading the MAF or anything else I'd use the proper fuel management, like a rom tune or standalone. The SAFC is "ok" for fine tuning. But it changes your ignition maps so you have to be careful.

WD

[neverlift]

yeah I have been very careful , I have a thread wd hop on in

[WDRacing]

You could have linked me

[neverlift]

zer...stionend thread jack

[VeloceDrift]

zer...stionend thread jack

get off my thread fool!!!!!!

[neverlift]

hell na

[coupe240sxguy]

lol looks like u been jacked foo