difference between FMU and FPR
06-04-2003, 06:14 PM
#1
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difference between FMU and FPR
Hello, I am wondering what is the difference between an FMU - Fuel Management Unit and an FPR - Fuel Pressure regulator, and what is the purpose of each of these? I am aiming to run about 5-6psi of boost and am wondering what to use for my fuel management? Do I need an aftermarket fuel pump, FMU, FPR, Injectors, or anything else? Any advice would help me greatfully. Thank you for all your help. ... Chris 
06-04-2003, 10:42 PM
#2
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Re:difference between FMU and FPR
you have an FPR on your car stock. it keeps your fuel pressure at a steady rate by releasing pressure in the fuel line to keep a constant flow of fuel to the injectors at a set pressure.
an FMU reads positive manifold pressure through a vacuum line, and increases fuel pressure to the injectors. this is *supposed* to be a cheap way to get your injectors to spray more fuel under boost so you dont lean out. IMO they are peices of ----. but anyways...
to tell you what you need, you need to post what motor you are boosting and what turbo you want to use...
an FMU reads positive manifold pressure through a vacuum line, and increases fuel pressure to the injectors. this is *supposed* to be a cheap way to get your injectors to spray more fuel under boost so you dont lean out. IMO they are peices of ----. but anyways...
to tell you what you need, you need to post what motor you are boosting and what turbo you want to use...
06-04-2003, 10:48 PM
#3
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Re:difference between FMU and FPR
Yeah, ---- that FMU. It should work for 5-6 psi though. As for the FPR, I think you are talking about an adjustable FPR, right? That only allows you to raises the pressure. Raising the pressure too much will make your car idle like ---- and could cause your injectors to fail.
You will most likely need some sort of check valve/missing link setup if you don't plan on using an AFC.
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You will most likely need some sort of check valve/missing link setup if you don't plan on using an AFC.
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06-05-2003, 08:06 AM
#4
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Re:difference between FMU and FPR
it wont cause his injectors to fail. can just make them idle bad. there is a way to lower fuel pressure on your stock FPR by drilling a hole in the base as a pressure release...there is a how to on endyn's site. the old one or whatever. cant remember the URL.
and im pretty sure you can raise or lower fuel pressure with an adjustable FPR...cant you?
and im pretty sure you can raise or lower fuel pressure with an adjustable FPR...cant you?
06-05-2003, 04:40 PM
#5
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Re:difference between FMU and FPR
If you have your fuel pressure set at 80+ psi for a long period of time it will eventualy destroy your injectors. I screwed up a set within a couple weeks at about 100 psi.
My adjustable FPR only goes down to about 40 psi, which is still a little higher than stock.
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My adjustable FPR only goes down to about 40 psi, which is still a little higher than stock.
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06-05-2003, 11:12 PM
#6
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Re:difference between FMU and FPR
Yeah, thank you's all for the replies and for the help, this site is the best, I am running a d16a6 or an SI on a 1988 honda CRX SI and I am wanting around 5-6psi of boost and I am attempting to do the 12:1 FMU and MSD BTM ignition. I am going to run the check valves to illiminate the MAP sensor seeing boost and going all crazy and setting off the CEL. I am running a Garrett T3 turbo, fully rebuilt and a 1989 shelby daytona shelby Z intercooler, and am still looking for that hf/cx manifold. I am still unsure if I still need to change the FPR, the injectors, etc... or just leave them for my 5-6psi of boost. Thank you all for the help, you've been really great.
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