difference between FMU and SFMU

[speed127]

I am planning my turbo install and someone on hear did an install for under $1000 (awesome write up) and used a FMU. Then everywhere else on hear and on 2gnt.com says to use a SFMU. What is the difference between the 2? Thanx

 

[the_red_pooch]

I'm assuming you can do more with the SFMU since its probley the "Super" Fuel Management Unit. Like the AFC compared to the Super Air Flow Converter. I would say you'll probley be fine using the FMU but having a SFMU may have been a bit easier and more adequate. Good luck...

 

[speed127]

WOW that was helpful.. I kinda figured that but was hoping for a little more insight, like what the SFMU does more than the FMU and if it justifies the price.

 

[l6u9k6e9]

Anyone tho? ive been looking for almost 1 hr and i cant figure out the diferrence between the 2! also there is non on ebay, i type in sfmu and noting! plenty of fmu's tho. also would i need an fpr if i have an fmu?

 

[VelocitàPaola]

FMU's provide extra fuel while under boost by restricting fuel flow along the return line according to manifold pressure (boost). They do this in a linear fashion, which isn't very efficient.

SFMU's allow the user to adjust that fuel curve to be just that... a curve. They use a small adjustable bleeder valve to release some of the higher pressures creating more of a sigmoidal curve - in other words, they don't indefinitely add fuel pressure (and thus more fuel).
Also, SFMU's are expensive which is why they're harder to come by. Just keep your eye out and one will pop up; either in the classifieds or eBay.

The shape of an SFMU fuel curve is close to this...

 

[l6u9k6e9]

so the sfmu just lets you tune where as teh fmu does not? also in order to tune this u need a wideband o2 and a safcII?

 

[VelocitàPaola]

so the sfmu just lets you tune where as teh fmu does not?

More or less... neither are ideal for high HP, but that's the gist of it.

also in order to tune this u need a wideband o2 and a safcII?

Not necessarily, but they can't hurt. A datlogger should be sufficient to tune the SFMU.