selecting the right FMU

[viper92086]

so i have tons of questions for my new build and was wondering how do i select the right FMU? i know theres adjustables out there and there are also ones with preset ratios. is there any calculations u can do to come up with what i need to proceed in my TT 1uz project?

 

[cribbj]

For all the money you'll invest in a twinturbo project, I would not skimp on the fuel system by using an FMU or any other type of rising rate regulator. These things look like a quick solution, but because they cause the pressure differential to change across the injectors, you wind up with some screwy looking fuel maps.

Do it right, and go with the proper size injectors and an adequate fuel delivery system and be done with it. If you're worried about overfueling the system at idle, there are voltage controllers out there that will help you turn down or turn up the pump flow.

 

[viper92086]

i plan on running 7psi on ct26's with 315injectors (7mge). i already have a walboro installed. this project is actually going to be a low cost setup since i have the turbos already and am doing the welding myself. what kind of fuel management would u recommend? i also will be using a maf translator basic (essentially a basic afc) from my old 7m setup. i honestly dont know anything about tuning or fuel, so any help would be greatly appreciated. i had alot of people tell 7-8psi is fine for a FMU and it would be overboard to even go any other route..


i'm not sure if this is needed to helping me select the right fuel management but my plans were to reverse the headers, and make a custom pipe to connect to each turbo. 2.5" pipe here. from each turbo there will be a custom 2.5" down pipe flowing into a 2.5" to 3" collector. then 3" exhuast straight back. both turbos will be intercooled using a 2 input IC

 

[cribbj]

Gotcha, if you're on a tight budget and are not into a full rebuild, etc. there are some people here who have fooled with the FMU's, flipping the manifolds, etc.

Hopefully someone will jump in here who's done it.

 

[viper92086]

ok so i picked up a begi fmu and i plan on running 315cc injectors from the 7mge motor. I also have a safc. i should be set to run dual stock ct-26's at stock psi(7-8psi) right?

 

[cribbj]

Not to continue to be a downer about FMU's, but here's a thread by another user who's probably wishing he had done something different, in lieu of an FMU:

http://www.lextreme.com/forums/showthread.php?t=11858

 

[speed_addict]

stay away from FMU's....

 

[stevechumo]

ok so i picked up a begi fmu and i plan on running 315cc injectors from the 7mge motor. I also have a safc. i should be set to run dual stock ct-26's at stock psi(7-8psi) right?

With 315 cc/min injectors, you don't need any FMU at all. Those injectors are good for 9 psi with a piggyback ECU. Also, you might look into an adjustable fuel pressure regulator if you want to increase the fuel pressure. I believe a member named KC95SC400 had been using those injectors at 8.5 psi makeing 340 rwhp.

 

[viper92086]

With 315 cc/min injectors, you don't need any FMU at all. Those injectors are good for 9 psi with a piggyback ECU. Also, you might look into an adjustable fuel pressure regulator if you want to increase the fuel pressure. I believe a member named KC95SC400 had been using those injectors at 8.5 psi makeing 340 rwhp.

are u sure a fmu isnt needed? everythread that i've read with low boost is using a fmu. that is some nice power for 8.5 psi. i ended up picking up a begi fmu. my plans are 7-8psi as well, but instead of kc95sc400''s maft pro i have a maft basic

 

[stevechumo]

The FMU is used when you don't have bigger fuel injectors. It raises the fuel pressure to compensate for boost. However, if you have bigger injectors, you can stay with stock fuel pressure. The bigger injectors will provide the additional fuel needed. Maft Pro or Maft Basic or SAFC can do the same job. It's used to trim down the bigger injectors at idle and max them out at full boost according to the A/F ratio.

If you only have the FMU, you'll need a fixed rising rate ratio of at least 12-1 to be safe. The adjustable FMU won't give you enough fuel; it's only 1-1 ratio.

I had used the FMU for a long time on several cars and I like it, although it's not the best setup. Keep in mind it's just for 7-8 psi most.

 

[viper92086]

well the begi unit is a rising rate regulator, so im under the assumption that it will be better not to use the injectors, just run stock injectors with the begi. i'm not sure how well the maft is going to be, i'm already having problems with it now not recognizing the maf. by using the fmu it keeps the car at its stock tune under idle and cruise. btw how hard is it to tune with a fmu? i have a wideband but i was looking at the manual and there is two adjustments for tuning.

 

[XR8tt]

Anything over 10 to1 and you'll find most injectors become nozzles and over fuel.. Most fuel regs read boost.. One issue we have had with FMU's is they tend to DUMP fuel and don't always return to std fuel pressure at idle.. Sard fuel regs are 2 to 1 and work very well..
Malpassi are the regs we had troubles with ...
In any case atleast fit a Walbro 255 intank fuel pump...
Check EMS Stinger for GOOD cheap ECU. Imo best bang for buck ecu out there..
http://www.enginemanagement.com.au/dealers.php