taejin11

i'm sorry...i kno this topic has been dealt with before...

so in a nutshell...can some please explain to me the difference between an fpr and fmu?

i thought with bigger injectors, pump, and v-afc hack...ppl don't need fpr and fmus...

but now i see that some ppl run the afc hack AND and an fmu...

not only that...some ppl run fmu and fpr...

problem is, i always thought both were the same thing....

so can someone please enlighten this newb with knowledge??...what is their main difference, and how exactly do each of them operate? also, how does a rising-rate fpr work?

thanx!!

91civicDXdude

the only reason to run both an FMU and a VAFC hack is if you are making too much power for 450cc injectors, so you bump up the fuel pressure.

FMU raises fuel pressure from stock based on boost, while an FPR sets the stock fuel pressure. so you use the FPR To set your stock fuel pressure, then use the FMU to rasie that stock fuel pressure a set amount.

TurboBumblBee

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 91civicDXdude &raquo;</TD></TR><TR><TD CLASS="quote">the only reason to run both an FMU and a VAFC hack is if you are making too much power for 450cc injectors, so you bump up the fuel pressure.

</TD></TR></TABLE>

what is considered too much power for 440-450cc injectors???

Inline pro tuned the car last year w/ a vafc, fuel rail, fpr, fmu and check valves..

car put down 303whp i dont think that is too much for the vafc hack..

why would they tune it like that? they know there stuff but risk lots at tuning i think to get the max whp out of a motor..

chronodyne28

Very informative. Bump.

Boltz

FPR - fuel pressure regulator - 1:1 i believe it raises fuel pressure 1psi per pound of boost.
regulates your fuel pressure for the entire powerband.

FMU - fuel managment unit, aka rising rate fuel pressure regulator most come 12:1, but some use 8:1 with bigger injectors (raises the fuel pressure 12psi per pound of boost, (or 8psi per lb of boost if using the 8:1))
add's gobs of fuel under boost conditions

fmu +'s multiplies fuel output of your injectors by dramatically raising your fuel pressure....

fmu -'s because of all the extra pressure through the injector and the extra amount of fuel that must go through the small injector in a small amount of time, it can cause injector failure from overheating. beware of heavy sustained boosting, this is where your injectors will most likely fail.

also since it is adding fuel per pound of boost, its harder to get the fuel table dialed in perfectly.

I personally wouldn't run an FMU in any car of mine.


Modified by Boltz at 7:17 PM 6/21/2004

0BoostedJeff

good info