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Old 08-31-2007, 12:23 PM   #1
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Default disconnect FPR?

i installed my MSPNP and noticed it would go very rich as soon as i hit any boost (WB hit 9)

i disconnected the vacuum line that connects the FPR that came with the greddy kit and have had no problems since

is this because the FPR has the wrong ratio, and i need to get one of the adjustable ones?
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Old 08-31-2007, 12:32 PM   #2
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The Vortech is technically an AFPR and from what I've read you don't need that once you start using the MSPNP and in fact it can be problematic as the MSPNP isn't setup to work with it.
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Old 08-31-2007, 12:37 PM   #3
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ok cool, like i said, i just have the vacuum disconnected right now, and it works fine
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Old 08-31-2007, 01:03 PM   #4
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It'd probably be better for you to instead of running a FPR to be running larger injectors and be controlling them with the MS. The reason why standalone ECU's like the MS are so nice is because the generally can controll any size injector. You just need to figure out how much fuel for how long with bigger injectors to meet the demands of the extra air.
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Old 08-31-2007, 01:26 PM   #5
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Quote:
Originally Posted by MX_Eva View Post
It'd probably be better for you to instead of running a FPR to be running larger injectors and be controlling them with the MS. The reason why standalone ECU's like the MS are so nice is because the generally can controll any size injector. You just need to figure out how much fuel for how long with bigger injectors to meet the demands of the extra air.


Yep-- a FPR like what comes with the Greddy references vacuum/boost, when it sees boost it raises the fuel pressure through the roof to try and force more fuel through your injectors to account for the boost. It's a bandaid.

The MSPNP can work with this bandaid if you tune the tables to do so. But ideally I prefer to run injectors sized for the application and run a standard 1:1 FPR that still references vacuum/boost, but as it's a 1:1 it only raises fule pressure 1 psi for every 1 psi of boost it sees to offset the air pressure in the intake manifold. If it didn't do this then 15psi in the intake manifold would be pushing back on the 43.5 psi in the fuel rail and you'd effectively have 28.5 psi of fuel pressure pushing fuel through the injectors. With a standard (like stock) 1:1 reference FPR it's adds that 1psi of FP per 1psi of boost, and at 15psi of boost your FP will be 43.5 + 15 = 58.5 psi, so when the 15 psi of air pressure in the intake manifold is 'pushing back' on that, you still effectively have an even 43.5 psi of FP. It's just balancing it out.


By disconnecting the vacuum source on your FPR it's doing neither, and your FP could be dropping under 43.5psi effectively when you're under boost, that's not good for atomization of the fuel. I'd suggest either running this FPR and tuning for it (which will work fine once you tune for it). Or sizing injectors for your needs and running a standard (stock maybe) 1:1 FPR.
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Old 08-31-2007, 01:55 PM   #6
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Dlaitini,
Completely remove the Vortec FMU and (when you have a high enough post count) post it in the classifieds. You don't need it anymore.

With a properly functioning fuel pump, 1.6 injectors will be good for around 140-150 rwhp, 1.8 injectors will get you 170-190 rwhp depending on exact model. Depending on your boost/power goals, you may need larger fuel injectors. See the PNP injector list in the DIY FAQ.
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