Mods: 1857cc 8.7:1 comp, B18A/VTEC, JE pistons, Eagle Rods, Ferrera SS Valves,Brent Frazier Race port & polished 2000 GSR head, Skunk2 intake manifold, cam gears, lowering springs.STR Fuel rail and sleeve saver, RC 550 injectors and 68mm Throttle body,
The Vortech FMU is fairly simple. Boost pressure is fed into it through a fitting on the top, return fuel enters from the side and exits back through the stock return on the bottom. When boost pressure is applied it pushes down on a diaphram that blocks the return fuels path. As pressure increases more fuel is blocked off. What that does is increase pressure in the rail and forces it through the injectors. You can change the total amount of fuel "blocked off" by changing the calibration of the fmu, by changing out the metal disc in the top portion of the fmu.
The SAFC or VAFC can only add or subtract 50% of fuel. On some Integra ECM's it can only take out 10% before the Check engine light comes on and at that point the Apexi unit is obsolete. The ECM does not recoginize the distortion of the map signal if it gives an engine light for MAP. The 50% deal can mess you up depending on how much power you want to make and the size of injector you want to run. So technically you can run an injector 50% LARGER and still be able to manipulate the map signal to maintian good idle and driveability. That's not going to make a bunch of power, maybe in the mid to high 200's of your lucky.
My solution is to use both. The SAFC can be bought at a local store for about $320.00 USD, the Vortech FMU is about $160.00 USD. It will allow the FMU to add extra fuel under boost and the SAFC will allow the ability to fine tune.
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No substitute for positive manifold pressure!
Mods: 1857cc 8.7:1 comp, B18A/VTEC, JE pistons, Eagle Rods, Ferrera SS Valves,Brent Frazier Race port & polished 2000 GSR head, Skunk2 intake manifold, cam gears, lowering springs.STR Fuel rail and sleeve saver, RC 550 injectors and 68mm Throttle body,
Running both is very common. If you have stock injectors there will be no way for the SAFC to add fuel under boost conditions. You can set fuel tables really high for a set boost level with no guaranty that it will supply enough fuel. And if you change your boost level, or the outside temp changes then your fuel tables are garbage. You can run just the fmu on most any car, and it changes amount of fuel by how much boost is applied. The SAFC works great as a fine tuning device. Once you have fuel, then you can adjust small dips in the fuel curve.
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I'll be investing in a used FMU, I already have a GEN1 SAFC on the way....so for the FMU, how do you calculate the optimum ratio to use?
To answer that you need to have an idea of what kind of power you will be making. Using the 12:1 calibration in the FMU, Four 450cc injectors @ 80% duty cycle with fuel rail pressure at 80psi under boost (FMU will increase rail pressure this high) with B.S.F.C. at .50 the fuel system will be capable of producing 375 hp at the Crank. Of course you will need a fuel pump capable of providing enough fuel to the rail, a Holley ( this pump is made by Walbro and can be purchased under other names but I prefer this particular pump) 255 intake pump Part# 12-916 will be more than suffencient. At this point a tuning shop can "fine tune" the fuel with the SAFC.
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No substitute for positive manifold pressure!
it also depends on the way you have the AFC is set-up with the FMU and 450cc injectors. As an example, most people do the AFC "hack" these days with the DSM 450cc injectors. That elliminates the FMU and the check valve missing link. This allows you to minupulate fuel curve per RPM while the AFC alters the actual MAP input so the ECU still does its calculation of fuel mapping. If you have the FMU, missing link, DSM 450cc, and AFC combination, your AFC will not read the actual MAP input due to the missing link. you can still tune your set-up but I can almost guarantee you that the idling on a 450cc and FMU combination will be rough. The route that I will recommend to you is the AFC "hack". Here's the link to my website: www.geocities.com/thermalfid16/VAFChack1.html
I personally do not like the FMU method of fuel enhancement. It does not give a smooth transition to boost unlike the "hack" which is pretty much like Hondata. The FMU only increases fuel flow to the cylinder only at boost condition. Hopefully you can dial in your AFC to get a better transition. I had a hard time trying to do that on mine when I had the FMU, missing link/check valve, and AFC combo.....
Originally posted by 4CFED So technically you can run an injector 50% LARGER and still be able to manipulate the map signal to maintian good idle and driveability. That's not going to make a bunch of power, maybe in the mid to high 200's of your lucky.
Actually it lets you use injectors 100% larger. Cutting 50% of the fuel from an injector twice as large will bring the flow back to stock level. A stock Civic/Integra has 240cc injectors @ stock pressure, so you could technically run 480cc and cut 50% so they flow at the same level as the 240cc.
Great information guys keep it coming. Ohh and thermal great website by the way. I built myself a custom turbo kit from scratch and don't know what to do for EMS. There's so many different routes and i never know which one to take.
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88 Crx HF sohc ZC swap with zc trans. exterior mods like shaved door handles carbon fiber hood and a bunch of other crap.
So..if I hear right klungermonger, technically...I could run the 450cc DSM injectors and set the AFC to -xx% to tweak ie lower rpm range back to stock levels....reduce the -% into the boost ranges?.
let me know if I'm on track ...or just plain wack. If I am going to start off by running low boost - 6psi...Do I really need the FMU?? If so, would a lower ratio FMU suffice ie. JRS FMU 5:1?
PS. thermalfi'd16, I'm not sure how I would perform the hack on the GEN 1S-AFC...but thanks for your input as it is much appreciated.
Yeah, that's my plan so I've been checking up on how-to, I found a very informative site they even tell you what settings to use on the AFC.
Since the DSM injectors are 45% larger than stock, you can cut fuel by 45% at the RPMs before boost kicks in, then you can decrease the cut level as boost builds. You should use an air/fuel meter while setting it so you can make sure the program you set doesn't go lean or too rich either.
This guy claims he gets no CEL/MIL and is not using an fpr or a missing link, just big injectors and the hack. Remember the resistor pack if you use DSM injectors, or use the proper saturated-type injectors.
Originally posted by aznexec2 let me know if I'm on track ...or just plain wack. If I am going to start off by running low boost - 6psi...Do I really need the FMU?? If so, would a lower ratio FMU suffice ie. JRS FMU 5:1?
Any one of the electronic FMU's basically require the same amount of work to wire in, might as well put in the good stuff that will let you re-tune later when you go for more power.
Linear Mode
