420a fuel

[2qik4u]

ok so i got a 420a and i have a walbro 255 hp in the tank I have rc engineering 550cc injectors and i have a sard 1:1 im using without boost reference hooked up. im using it before the fuel rail to keep fuel pressure to 45 psi before the rail. not on the other end of the rail i have an obx 12:1 fmu. I know this isnt going to work to drive it down the road but it got it so i can drive it in the yard instead of pushing it to the garage and back. I know i need a sfmu but what side of the rail do i run that on??? the feed side or the return side?? and do i need any other means of regulating fuel mechanically once i get one??? could i improve performance with what i have already?? if so how???

 

[VelocitàPaola]

No fuel regulator, FMU or otherwise should be before the fuel rail; it's just not how they work. I recommend putting at least the AFPR after the fuel rail -- that should let you drive the car to wherever it needs to go. The FMU will allow you to boost if the AFPR is calibrated similarly to your stock FPR; otherwise scrap 'em both and get an S-FMU.

 

[2qik4u]

i am on my way to a sfmu!!! I gotta sell my greddy profec E-01 with remote switching system first!!!

 

[2qik4u]

so after the rail do I run fmu and then afpr or afpr then fmu?? just to get it to run better than it does now.

 

[rstare]

You don't necessarily need an AFPR. Those usually are also rising rate regulators, however, they only use a 1:1 rate. Whie this may seem insignificant, at 8psi that will be 8psi more fuel pressure. And with the 12:1 FMU the fuel pressure is already plenty high enough. You need to use your stock FPR, and mount the FMU after that.

 

[VelocitàPaola]

You don't necessarily need an AFPR. Those usually are also rising rate regulators, however, they only use a 1:1 rate. Whie this may seem insignificant, as 8psi that will be 8psi more fuel pressure. And ith the 12:1 FMU the fuel pressure is already plenty high enough. You need to use your stock FPR, and mount the FMU after that.

In other words... here are the acceptable combinations:

1. Stock FPR and FMU
2. Aftermarket AFPR and FMU
3. S-FMU

I wouldn't go for option two unless your stock FPR is damaged, or you really know what you're doing and you need to lower your idle fuel pressure.

 

[2qik4u]

my stock fpr is gone. the kid who owned the car before me took it off and I didnt get it with the car. but none of that matters now cause i bought a vortech sfmu from a guy on 2gnt!!!! got it for $190 and it still looks brand new in the pictures. it should be here in a few days. after i get it installed i will post and let ya know how it works with my 550cc injectors. what static pressure do you think i should run to start my tuning with?? i know what stock pressure is but my injectors are now bigger. and what rising rate do you think i should start with??? thank you guys for your input. it is very appreciated!!!

 

[VelocitàPaola]

my stock fpr is gone. the kid who owned the car before me took it off and I didnt get it with the car. but none of that matters now cause i bought a vortech sfmu from a guy on 2gnt!!!! got it for $190 and it still looks brand new in the pictures. it should be here in a few days. after i get it installed i will post and let ya know how it works with my 550cc injectors. what static pressure do you think i should run to start my tuning with?? i know what stock pressure is but my injectors are now bigger. and what rising rate do you think i should start with??? thank you guys for your input. it is very appreciated!!!

Here are a few resources to get you started:

RC Fuel Injection
https://www.vortechsuperchargers.com/download.php?dir=pdf/manuals&file=superfmuim.pdf
Team 2GNT Forum - Viewing topic #104257 - Help Tuning with SFMU

 

[2qik4u]

thanks paul!! that will help alot. i need to read more about idle and static pressure and need to sit down an study some of those formulas for fuel needs and such but i think i will soon be able to wrap my head around this thing and get my car to boost at least to 12 or so pounds till i can get a megasquirt system. now about that. there are people out there selling v1 v2 and v3 with various processors. what version do you think would run the 98 420a best??? i will need to learn fuel tuning before i get into spark at all and i know it will take some time to learn it but what version of msns do you think i should start with??

 

[VelocitàPaola]

No one sells the v1.0 board anymore. The v2.2 board is outdated, as is the MS-I processor. So... v3.0/MS-II -- but that's for another thread.

 

[2qik4u]

i wasnt meaning vendors for the msns i was talking about the used ones ive seen. I will start another thread if i need any more info about it. im probably just going to have you build me one when i get the money. i need to come up with another laptop first.

 

[VelocitàPaola]

I don't build Megasquirt systems, but I can point you in the right direction if you PM me when you're ready.

 

[2qik4u]

i thought you did symtech?????

 

[VelocitàPaola]

I'm not exactly sure what you mean by that, but I'm a moderator on DSMtuners, not a vendor. You can PM me if you have any further questions.