ive been told that i dont need to run the fmu if im running the 440cc injectors. and i just read on vortech's website that the fmu's made to utilize stock injectors. just thought id check with youz guys cuz i ive heard lots of bad things about those fmu's and i really dont wanna run it if i dont need to.

 

I have read every forum in the forced induction thread you do not need the fmu if you using 440cc injectors

 

ok thanks.. 440's all day! FTW!!!

 

the fmu increases fuel pressure to increase the cc output when it sees pressure. Running both will provide way more fuel than needed since 440's will supply 300whp worth of fuel

 

Like everyone else has stated, both are not needed. I ran a fmu for about 8-9 months without issues. I'm on 440s now and I couldn't be happier.

 

when you switched to 440's did you get a tune or did you just drop them in and go?

 

u do need a tune!

 

I did a self tune. I used the values that senate posted up a while ago and worked my way through it with ecuflash.

 

FMU - increases fuel pressure by the proportion of the FMU (12:1, 11:1) per every pound of boost it sees. It gets around the limitation of stock injectors by forcing more fuel out of them instead of their actual flow rate. Its a crude way of getting more fuel during boost. Its not precise, and FMU's can take a dump leaving you very very lean. I however ran an FMU with my first kit for almost 8 months without an issue, and the very first RRM kits used an FMU and theres still plenty of people out there using them. Just be careful

upgraded injectors - you NEED a tune. The ecu is set to the default of the stock injectors, so when it sprays X amount of fuel at 240cc flow rate, with 440cc injectors you'll be actually spraying close to double that even tho the ecu still thinks its only 240cc. You need to get a tune so it modifies the fuel tables accordingly.

 

FMU sucks. You'll see 9 AFR going uphill

do the right thing

 

Mine really wasnt too bad, AFRs were in the high 10.5-11 range most of the time at 7.5psi