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Discussion Starter #1
Hi All,

I have properly upgraded my setup: V2-SCi w/8 rib pulley upgrade, Walbro 255 in-tank pump, Accel 36# injectors, Anderson 4" PP (with bypass valve), 1.7 roller rockers and TrickFlow upgraded valve spring kit and an Accufab 70mm TB. I am currently running a stock Vortech FMU. I've been searching the net, not just here, regarding whether I need the FMU or not. I found out the FMUs come standard for 19# injectors (I didn't know this but I knew you can upgrade them). I have an adjustable FPR but I'm currently running the stock non-adjustable FPR. Looking online for advice is confusing me to a degree. It would appear I should be able to ditch the FMU, button the hoses back up to stock and just run the adjustable FPR? However, I've seen some folks still running an FMU AND an adjustable FPR?

Any insight would be appreciated,

Thanks....
 

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The fuel pressure regulator alone isn't enough to support boost. You need the FMU to supply ADDITIONAL fuel over the stock fuel table in order to maintain a rich enough AFR in boost. The Regulator doesn't do this and you may be wondering why, since it is seeing a boost reference..

The reason is because the injector tip sees boost in the intake manifold as it is firing fuel into the air stream. The boost seen at the tip counteracts the initial fuel pressure (pressure behind the injector), so we pressurize the regulator to counteract the boost seen at the tip, making the injector feel like it's in an unboosted/unvacuumed environment in order to supply the stock fuel flow. If it wasn't referencing boost, a 39psi fuel pressure would look like 29psi at the injector when making 10lbs of boost, killing flow when you need it most.

Best thing to do when you have an FMU is throw a wideband sensor and gauge in the car so you can monitor your air fuel ratio. If you don't want to get into tuning the ECU, you can find adjustable FMU's that allow you to somewhat dial in the WOT AFR if your current one isn't correct.
 

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Discussion Starter #3
Thank you kindly for the in-depth information. So I'm safe with the FMU still. My other question is this: should I be purchasing a recalibration kit to change the disc in the FMU? I see them on Summit but I don't see a disc for 36# (24s and 38s/42s).

Thanks!
 

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Thank you kindly for the in-depth information. So I'm safe with the FMU still. My other question is this: should I be purchasing a recalibration kit to change the disc in the FMU? I see them on Summit but I don't see a disc for 36# (24s and 38s/42s).

Thanks!
12:1 19# inj's 2.72" diameter disc, 10:1 24# inj's 2.47" disc(cobras), 24's Non cobras 8:1 2.22" disc, 6:1 1.85" disc, 30's & 36's, 4:1 1.59" 42's......If U have any ?'s Ref these PM me.
 

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Discussion Starter #5
12:1 19# inj's 2.72" diameter disc, 10:1 24# inj's 2.47" disc(cobras), 24's Non cobras 8:1 2.22" disc, 6:1 1.85" disc, 30's & 36's, 4:1 1.59" 42's......If U have any ?'s Ref these PM me.
!! Thank you midnightrider!! I didn't see the 36lb injector listed in the Vortech FMU recal kit. Going to look again.
 

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Discussion Starter #6
12:1 19# inj's 2.72" diameter disc, 10:1 24# inj's 2.47" disc(cobras), 24's Non cobras 8:1 2.22" disc, 6:1 1.85" disc, 30's & 36's, 4:1 1.59" 42's......If U have any ?'s Ref these PM me.
Forgot to mention but thanks again midnight, I ordered the re-cal kit from Summit yesterday and it does indeed contain the disc you mentioned.
 
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