I'm trying to get my nos tuned with my sc, and its a b*tch. I have the bypass jet out, and my f.p. is still running up to 110 psi when i spray at 4000 rpm. So i only have a couple options from what i understand.

1. unhook the nos fmu , and put in a 8:1 fmu disk for the sc. the only problem with this is that i'll be running rich (which hopefully i can change with the s-afc), and also my f.p. is going to be over 110psi at 6500 rpm. would a fpr help me here?

2. unhook the nos fmu , and leave the 6:1 fmu disk in, and just spray at 55 psi @ 4000 rpm. Is 55 psi enough fuel to push a 30 shot? It would be up to about 90 to 95 psi @ 6500 rpm.

3. get a superfmu from vortech and go that route. I know the entire curve is adjustible with this, but its the fp at 3000 rpm i'm worried about.

4. spray it like it is, and blow my engine... dont feel like doing this.

any help is GREATLY appreciated. is anyone running the 8:1 fmu disk? if so what is your fp @6500 rpm?

 

Pm mardigras.. or try jamiecbr900.. he is not SC's.. but he had some fuel issues with his DPI.

 

I used the Fields Fuel controller which allow 3 different fuel maps.
I tuned it with the SC and the SC with NOS.

 

what kind of set up are you running? are you using the fmu for the nos along with the sc fmu? and how are you keeping your fp low enough to spray?

 

What kind of FP are you running off N2O, just the S/C? Do you have the Walbro 255 pump? I don't know much about the FMU's or the discs, but mine was drowning with the big pump and falling on it's face with the stock one. I adjusted the FP at the FPR down to like 25psi at idle to get it to run and even then it ran rich. That was with the big pump. With the stocker, the car ran ok at stock FP AFTER it got off it's face at the line. I'm still tuning as we speak and working on a different solution all together. I think maybe with you running both a disc and bypass (even though its wide open) that maybe what's causing you headaches. Is it possible to run one or the other and not both? You know that the bypass on a dry system can be taken out and run w/o one. Maybe if you are running enough FP and volume with the FMU, it may be able to support both the s/c and N2O. I'm not 100% sure on this theory but let me know what you think.

 

Thats what im thinking, but at 4000 rpm i'm at 55 psi. At 6500 rpm i'm at 90-100 psi. Is 55 psi enough to support the nos? All i'm running is a 30 shot. (.028 jet) If thats not enough fp, I could get a 8:1 disk for the fmu, and probably have 65 psi @ 4000 rpm. Im just worried about getting up to 6500 rpm. Will a fpr stop the fp from going above 90 psi? I've never used one before.

 

The FPR will stop the fuel from going up to 90, but is 55 psi enough to run both? I'm thinking that with two FP risers you're just overkill. You may be just fine with the FMU for the S/C. I know that when I was running dry setup @60 shot, they recommended around 65psi. I suspect, not 100% sure, that 55psi should be sufficient for a small shot (30), but the question is....Will it support both at the same time???? I'm not sure on that part, since I'm not up to speed on the S/C. Maybe email Jay25, he's got the S/C and has been said to know a lot about it. I'm just suggesting that since you have such a dramatic jump in FP around where WOT would be, I think maybe using two independent systems is what's killing your system. You haven't told me what kind of FP your are getting off the bottle and just running the S/C. Is 55psi what you're getting with just the S/C? What kind of pressure are you getting at WOT with just the s/c? Reason why I ask is that if you get somewhere around 65-70psi at WOT, that may be suffient to run both off the FMU and take out the bypass on the nitrous setup all together. Again I emphasize, I'm not 100% sure and I'm just throwing out ideas based on what you told me. Maybe between Jay25 and me, we can try and figure it out. We do have the same name you know....

 

Got your PM, here is some details.

This is what Steve did that I copied.

Set up your fuel pressure with an 8:1 so its very rich. With the Fields you have 3 different settings. Use one setting as a boost only tune and then use another seting as a boost and juice setting. You have to have the fuel very rich before you start tuning with the fields because when you get in the higher RPMs you will be at 100% duty cycle on the injectors and you cant add any fuel with the AFC above that point, just add pressure. So its safer to use the AFC to just lean back down to safe AFR levels. You will need to spend a few hours on a dyno with wide band O2 to get this done safely.

The only draw back of the fields is that the adjustments are all the time, not like a Apexi AFC that switches between them depending on throttle position. The way I have my fields set up is setting 2 is full race tune for all RPM points, setting 3 is full race tune or all rpm points with nitrous, setting 1 is my every day tune. On setting 1 I have zero adjustments from 1k-4k which are my daily driving rpms part throttle cruising etc., from 5k-6k I have copied the race trim adjustments. If I hit 5k-6k on I am usually at full throttle and racing the motor up. What the problem is that if you used the Fields in setting 2 with the adjustments for all the rpm ranges the ECU would learn them while you drive around the streets and over ride them. So using setting one hides the adjustments until you floor it and hit 5k. At the track, or if I have time on the street for a quick race, I switch over to setting 2. Its kinda a pain but it works.

 

jamie -
all the numbers i gave were without spraying. just the sc.

 

thanks for the info.
heres another option. i talked to bryan @ atlanta chassey dyno, and he gave me a guys # that tunes a lot of imports. He said that I should get a wet system to spray my 30 shot, then i wouldnt have to worry about fp anymore. Is anyone else running a wet system in the throttle body? Sounds like its the anwser to my problem, but i dont know anything about spraying wet.

 

I'm running the FMU that comes with the SC kit(8to1). I only run an NOS jet and only add fuel via the fields.

If you run the wet kit you'll have too much fuel PSI(110 per u) for the little about of NOS that your running.

You can run it the way I did or run a separte fuel system.

 

i thought the sc kit came with the 6:1 disk.
steve what fp are you running at 3000 rpm (or whenever you start spraying)? Also how much nos are you running? would you be nice enough to tell me your afc settings or is that secret

 

Stock from Stillen is a 6:1 disc. As you add boost you need more pressure increase in the upper rpms because more boost puts you deeper into 100% injector duty cycle.

When I still had stock injectors and 10psi with an 8:1 I was at ~45psi at 3k and by shift point with peak boot I was at ~85psi.

IIRC Steve is running a .030 jet, ~40hp per NOS, but you get more on a boosted ride due to the intercooling effect, ~60hp

The settings are done like this Put the car on the dyno. Do a base run. Then turn the AFC settings way up like +15% from 3k-7k, it will run like a pig but you will see where the 100% inkector point is by comparing the two graphs. Their will be a point on the plot with the AFC cranked up that no matter how much you turn it up the AFR wont change as much, it should be obvious. Now pop in that 30 jet and run it up on the dyno. take a look at the plot and see how the AFR looks. You can either add more nitrous or lean it out to get the 30 shot to ~12:1 AFR. The problem you will run into is that in the upper rpms with nitrous you will begin to lean out, it gets really lean past the 100% injector duty cycle point. So the larger shot you use the sooner you will have to cut it off in the RPM range. I had to cut my "40" shot off at ~5800rpms. If i ran a "30" or a "20" I could run it higher in the RPM range.

And steve is absolutley right, dont do a wet system unless you get a standalone fuel system. It wont work right using a boost referenced fuel pressure riser. Or you can try what I am working towards.

What I will be doing now that I have the 370cc TT injectors installed is to try a wet system. But I should be ok because I dont have to use a large FMU disc, I use a 4:1 now and after I dyno I may use a 3:1. With this set up my fuel pressure range wont be as wide so I should be able to tune a wet shot easier with a 25psi idle to 50psi peak fuel pressure range. I will still have an issue but it wont be too bad. My choices are... 1)Run a shot set up so its tuned for 25psi, but it will get really fat as the fuel pressure rises. 2)Run a shot that is tuned for 50psi, it will be lean in the lower RPMS but on the money at peak. 3)Or some where in between and be a bit lean in the lower rpms and a bit fat in the upper rpms.

Options 2 and 3 are the most viable and are probabbly what I will test out first on the dyno. But I wont do this unless I am on a dyno.

You should consider the larger injectors because you are starting to push those stockers too much. Where Steve is and I was is about the safe limit for the factory 4th gen injectors.

 

I think he's saying what I was trying to, but better said. I think, operative word is THINK, that if you run the kind of pressures you're running, you could possibly be able to run the N2O jet alone. I think that adding the entire dry setup is causing you to drown out the entire thing and is running your injectors to the max.

As some of the guys said, you may only be able to manage both systems safely via stand alone fuel supplies. It would be so hard to make sure you have varying amounts of fuel for s/c and N2O that would make them both happy at the same time. If you are up in the 85psi+ range on the s/c and you are running good or rich on it alone, I personally don't see how that may not support a shot of the juice too. See what I mean? I mean unless you've run it on the wideband w/o the juice and it runs good or rich, it is a risky proposition to try what I'm suggesting. But if your gauges say you're running on the rich side s/c'd, then you should have enough fuel to support a small shot of juice at the same time. Maybe try running just the main jet, no bypass at all, and spraying later in the power band where you KNOW you're getting plenty of fuel.

Just throwing out ideas.

 

Yea I put in a 10 to 1 with a bleeder valve so it's about an 8 to 1.
I couldn't tell you what I'm running fp wise at 3k. I'm at 100 psi at max rpm. I'm running a .030 jet. If your running a fields it would be easy to share settings.

 

Three words:

Cartech Adjustable FMU.

 

thanks a lot for the help guys. i guess the bottom line is that i need to get to a dyno w/ an o2. i've gathered some VERY helpful info though.

 

Two words:

Wont Work

 

Two other words:

Why not?

Seriously, I'm interested to know.

IanS

 

Nitrous need a constant fuel pressure for a wet system to be tuned right. The cartech is a fancy version of the vortech fmu, but it basically does the same thing, it raises fuel pressure as boost pressure rises.

 

Ah, makes sense.

I stand (as usual) corrected.

IanS

 

very good info

mardi for maxima man of the year