Fuel Management Unit (FMU)

[schamsy]

I am very close to finishing my turbo setup and I was wondering if I need a different FPR or a FMU. I have looked at past threads but couldn't find what I was looking for. I am only running 7 lbs. of boost. I didn't know if anyone else with a turbo got a new FPR. And I don't quite understand a "FMU" and if it takes the place of the FPR. Is there a good one to get?

Any information is appreciated.
Thanks

[sharkey]

an fmu (fuel managment unit) is the same thing as a rrfpr (rising rate fuel pressure regulator). what it does is raise the fuel pressure as a function of boost. a 12:1 regulator would raise fuel pressure 12 psi for every pound of boost. basicly what these things are is a band-aid for not being able to tune the pcm. they get you close and may be able to keep the motor alive, but you will never see the maximum potential out of the motor without proper pcm tuning.

that being said, what vehicle is it in??? if its obd1, then you can have chips burned. if its obd2 thre likley is hp tuners or dhp tuners avalible for it. if you have a 94-95 with the dreaded obd 1.5, you arent able to tune, and in this case, id recomend retro fitting an obd 2 system or going back to obd 1, or if you dont have emmissions testing or stand alone fuel managment is allowed, id recomend going full stand alone.

[schamsy]

I have a 2001 Grand Am GT. I am getting a tune sooner or later I just didn't know if I needed a FMU or different FPR.

[sharkey]

the stock fpr will work as long as your able to tune the thing

[ForcedFirebird]

Good advice Sharky, I would also like to add that the GM ECM's (from N/A cars) pull out fuel for rev limiting and will toast your engine if hit (speaking from experience).

[IsaacHayes]

Get a DHP and larger injectors and you can tune it right. You might need a larger fuel pump possibly, I don't know for sure on that application.

[schamsy]

The fuel pump shouldn't be an issue. I have a basic mail tune done for my car for 7 lbs. of boost. I have 30 lb injectors.

Forcedbird- I'm not quite sure what you mean by what you said. Are you saying if I hit the rev limiter without a tune I will blow my engine?

[ForcedFirebird]

Forcedbird- I'm not quite sure what you mean by what you said. Are you saying if I hit the rev limiter without a tune I will blow my engine?

More than likely. Most people change the rev limiter to 10k rpm and just don't over rev. (effectively removing the limiter) I haven't talked to anyone with OBD1 that has been able to use spark to limit rev, and am not sure it can be done. I believe you have OBD2 and would have to ask someone with experience with your system, but in the end GM favors fuel cut to slow the engine back down in naturally asperated ECMs.

[IsaacHayes]

Certain things need to be edited out or modified from the stock ECM. Such as torque management and rev limitters as these pull fuel to keep the motor from making power or reving too high. This causes a lean condition while under boost and can pop a piston. There is one guy on here that blew his motor when he hit the top speed limiter with a stock ECM tune and supercharger. The top speed limiter does the same thing, pulls fuel.

[sharkey]

interesting, the 7747/7749 ecm for the turbo 2.0l and typhoon trucks does the same thing, cuts the fuel for overboost, rev limit and speed limit. the difference may be that they are programeed to wait till boost, rpm or speed must drop more before it turns the fuel back on, instead doing it quickly. i know when you hit boost cut, you had to wait till it dropped back into vacume before the fuel would come back on. i beleive the rpm had to come belore 4500 when you hit the lmiter. it may be possible to do this with your ecm. if your not and have to up the rev limiter to 10k, id recomend another form of over rev protection, such as an msd box with rev limiter.

[schamsy]

Dang I dont like that idea.

[timg]

If you skip the tune, get the FMU. It will run in series with the stock FPR. I would recommend getting the tune and larger injectors though. That's the right way to do it.

Fuel cuts for overboost or overrev are common. They seem to be very popular on almost all stock vehicles. If you cut spark then fuel, you wind up with some pretty loud bangs/pops from the fuel exploding once it hits your exhaust.

Tim

[schamsy]

I got 30 lbs injectors and I sent my computer out for a basic mail tune. I will be getting a full tune soon, but just want to get it running for now. So will I be able to run it with the stock FPR or will I NEED to get a different one? I can't find anyone who has a better FPR that will bolt on the 01 Grand Am 3.4L in stock.

[SappySE107]

Get the stainless fuel adapters and run -6AN hose to an aftermarket FPR. Not the cheapest route but really nice.

[IsaacHayes]

What does this "basic" tune include? Are they just adjusting the tables for the 30# injectors or are they going to estimate what fuel demand will be when under boost and edit the MAF values for that?