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difference between FMU and FPR

Old 06-04-2003, 06:14 PM
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Default 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
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Old 06-04-2003, 10:42 PM
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Default 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...
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Old 06-04-2003, 10:48 PM
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Default 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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Old 06-05-2003, 08:06 AM
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Default 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?
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Old 06-05-2003, 04:40 PM
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Default 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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Old 06-05-2003, 11:12 PM
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Default 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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Old 06-06-2003, 06:25 AM
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Default Re:difference between FMU and FPR

FYI, I ended up running 0-retard on my BTM with 6-7psi on an A6. Id say your safe w/o it at that level, run stock timing. (maybe a degree retarded from stock)
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Old 06-07-2003, 06:53 PM
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Default Re:difference between FMU and FPR

just use ghettodyne and you will be alright...thats all i got to say.

lewis
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