Blownz28man

iTrader: (2)

Ok...I'm running a ati procharger at approx 12-14lbs boost. This is on a 383 stroker. I'm running the fmu that came with the kit and 24lbs/hr injectors. Does fine with fuel under boost. But the fuel pressure spikes up there pretty high. Can i get larger injectors a ditch the fmu??would i be stupid to do this. I know 24's are pretty small for my combo. I think i should be running 38-42 based off of the formula. HELP!

87IROC350

You need a boost sensing ECM in order to get rid of the FMU and also so you can regulate your fuel under boost.

grover85

iTrader: (1)

Go 42's. And the stock ecu should be able to be tuned for it.

D's89IROCZ

I also see that you can pick a different diaphram .... so it will " spike" less. So bigger injectors ...with a softer diaphram ... ( like maybe 6:1)????Might be in your best interests ???

grover85

iTrader: (1)

Why would you keep the FMU. All that does is add a crutch to your fuel system.

askulte

The stock fuel pressure regulator is just a 1:1 FMU... Get some bigger injectors, change the tune for a 2 bar MAP sensor, and enjoy. Your fuel pump will thank you.

A.

Blownz28man

iTrader: (2)

allright THANKS! Just need to figure out now the best ecm to go with. Make another posting. I know a lot of people are using 749 ecms. Or go stand alone? Thanks guys!

AC

iTrader: (3)

I was going to ask the same thing as the original post. I have a 383 and 60# injectors and a 14lb P1SC blower. I was going to go 749 but being compeltely new to tuning I only wanted to jog and not try it out of the gate running you know. My plan was to use the FMU that came with my blower still and tuning the 730.

AC

iTrader: (3)

Any comment on my question (see above)? I don't want to go $58,$59 or $60 code & 2 bar map right now. Do I still need the FMU if I'm using 60# injectors, Procharger's inline secondary fuel pump and a walbro 255 intank pump?

87IROC350

For the amount of boost you are running you will need either the FMU or something like the 749. FMU will work but it is just a bandage.

junkcltr

iTrader: (1)

What ECM do you have in it now?

The stock 730 ECM with stock code will have a problem even with 60#/hr injectors without an FMU. The problem is the fact that it will try to achieve stoich when not in PE mode. You will have boost when not in PE mode so that is a problem. The ECM will try to pull fuel. The way around it is to allow it to enter PE mode for lower TPS settings (modify the bin). You need the FMU even with the big injectors only because the ECM can't see boost. If you were running small boost amounts you could fudge the 100 KPA area on the rich side, but wanting 14PSI puts you way out of the fudge range.

The $58 code will work fine after lots and lots of tuning to get it exactly right at all driving conditions. You can get it decent pretty quick but to get it really good it takes a long time. Much longer than I wanted to deal with so I gave up on the $58 code.

askulte

I don't have experience with the GM ECM's, but I have been running the DFI6 for a good 9 years now. Used, they are very inexpensive, and pretty easy to tune if you have an old DOS laptop and the Calmap cable (I've seen plans for the cable floating around too, if it's no longer available). It's a bit harder to dial in compared to the new systems, but overall pretty straight forward. I'm running it with a 2 bar MAP, the 55 lb Siemens low impedence injectors & an Acceleronics injector driver box.

Edit - You'll need more than a single Walbro if you plan on running 14 psi on an engine with decent heads/cam. I'm running about a 50 psi base fuel pressure, an Aeromotive 1:1 FPR, and a Walbro GSS307 fuel pump (engine is 399 CID, AFR 210's, single plane intake). At 8 psi of boost, the fuel pressure plunges, and I make up for it with more injector duty cycle. It's not nearly enough pump even at that HP level (480 rwhp @ 4 psi is fine, big pressure drop with more boost at 550 rwhp), so it would never work with a rising rate FPR (FMU).

AC

iTrader: (3)

Thanks for more input everyone. Skulte, I'm interested in your setup now even more (want to see the tuning capability of the DFI6). Here's my setup to get a sense of where my car is components harmony wise:

4bolt 1pc rear seal 350 block .030 over
Eagle Forged / Internally balanced 383 assembly
H-Beam Rods
-16cc Forged SRP Pistons
Moroso Oil Pan
Miloden Water Pump
TPIS Bigmouth Intake
SLP Siamesed Runners
Holley 58mm throttle Body
Siemens 60lb injectors
MSD 6AL
Dart Iron Eagle Heads (215cc / 72cc)
Harland Sharp 1.5 RR's
Custom Grind Comp Cam
Int: .520 / Exh .540
Duration Int.236 Exh.248
LSA: 113
Hooker 2210 LT Headers
Blower: ATI P1SC / 14lb pulley (lucky if I can build 10lbs with 383)
looking at custom prom of course....
TKO600 Transmission
Denny's Nitrous Driveshaft
SPEC Stage3 Clutch
Forenza Steel Flywheel
Strange 12 Bolt Rear
Stock 1LE Front 12" brakes w/ vented cross drilled rotors
96 SS Rear brakes w/ vented cross drilled rotors
SPOHN Rear lower control arms
SPOHN Sub-frame connectors
SPOHN Adjustable Torque Arm
SPOHN Trans-xmember w/ Driveshaft safety loop
Edelbrock Adjustable Panhard Bar

AC

iTrader: (3)

bump for a reply?

askulte

I didn't realize there were any more questions to reply to! First step is deciding what your max boost/hp will be, so you can figure out what injectors to run. If you need low impedence injectors, then decide on a high impedence ECM with an injector driver box, or an ECM that can handle low impedence injectors directly (any sequential or non-batch fire box should be able to do it). Then it's a matter of budget, picking what you want for the ECM. The new generation is easiest to learn/tune with windows software, widebands, logging, self-tuning, and more bells and whistles, but is quite a bit more expensive than a DFI6 from Ebay or using a GM ECM (both of which can handle anything, just a bit steeper learning curve). At the heart of an ECM is the fuel map, or VE table, which will be similar no matter what system you run. Where it gets more interesting is how the ECM handles tough situations, like idling with a big cam, and things like that. Any system will run your engine at WOT and cruise, it's just how difficult is it to get the last 5% of driveability for throttle response. AC - You're welcome to stop by to check out the DFI6 - send me a PM or call.

Andris