Since you are using a fmu, the fuel pressure will increase with boost unlike if you just had a normal fpr that remains constant which you could see fuel pressure with the car just idling.

If you can dump the fmu and just tune the injectors, i would go that route personally. Just keep the a/f between 11.5 and 12:1 and you will be fine. Also, you may want to put back in a normal head gasket to bring the c/r back up since it will give you more power throughout the rpms since you arent out there running 20+ psi

 

I read in "theshortbus " build thread the he had trouble with the 440cc injectors with the fmu. Since it is boost sensitive wouldn't it make you run very rich under boost?

 

well it is a daily driver so i wanted to be on the safe side with the lower compression ratio, even if it meant a loss in power...

as for getting rid of the fmu, you think i'll get enough fuel pressure to comp with the injectors with just the walbro and the ecu???

 

Pretty agree. You are chasing fuel cause of the FMU. Either run less boost with FMU or run 550cc injectors and no FMU. Then tune from there.

ROAD/RACE

 

^ isn't the problem with running a fmu, an overly rich condition?? would the fmu make her run lean also?

 

You cant control the fmu as well as leaving the fp constant and tuning the injectors. Plus 550cc is way overkill for what you are running. People with vw/audi's are making 325+ with 440cc injectors @3bar (45psi) fp. If you ever need more, you can increase base fp to 3.5-4bar (440@4bar ~= 550cc@3bar)

 

okay so i rescaled the injectors and still have the same lean condition... so im gonna remove the fmu and try see where it will get me. i jus dont get how the same fuel pressure(stock) will be enough pressure to feed gthe 440s???

 

its not the fuel pressure that feeds the injectors, thats the pumps job. Changing the fp will change the rating of the injectors as i stated above.

 

the specs of 440cc injectors mean thats what they flow at ~45psi. but as far as your lean condition idk. i have stock injectors with a 12:1 fmu and its kinda exhibiting the same problem... it will reach 12.5 afr at about 7.5 to 8 psi of boost. but i have a stock engine with no airflow mods so it will overboost after about 5000rpm to 9-11 psi and cause it to lean out too much(13-13.5).

 

^ you need better boost control. What are you using?

 

oh ok. kinda had a brain fart there. fpr regulates fuel pressure seen at the rail. im gonna just run the stock fpr and see how it changes the afr then.... i should be okay as long as i dont boost too much right? cuz wont i be even leaner without the fmu?

 

I havent used the ecuflash. When i had my lancer it was basically rrm piggy or a fmu and i used the fmu. How does it let you control fuel, by rpms or just overall adjustments?

 

internal actuator with 8 psi spring.

 

can control fuel by injector scaling, latency, and also rpm vs. load tables...

 

oh yeah and i got a hallman mbc to control boost.....