injector size help again

[BigRand]

Injector size help again.

Okay so I'm currently in the middle of a rebuild, and just had a few questions about the amount of boost I'm running with the injectors I have or how much more power or boost I could run with the right size injectors.

Okay I basically have got the same howell bottomend kit except with Weisco 8:8:1 pistions, along with some light port work and a 3 angle valve grind, I'll be boost with the star stage 2 kit, with the SFMU instead. Now I have an SAFC2 for fine tuning, and currently have 370cc RC injectors.

1) How much boost should I be able to run for a good daily drivien built motor?
2) what should the fuel pressure be at?
3) What size injectors should I upgrade too and how much boost with those.
4) What should the fuel pressure be at for this set-up?

Now I've read corbrin's fuel set-up guide, but I get confused using the formula because I have no idea how much power I should be expecting to put out. My goal was 250whp or close to 300bhp, but I really don't know how possible that is?

 

[xxthayxx]

not sure if it will help but i'm using the sfmu,400cc injectors and no safc..i kinda maxes out at 15lb of boost,my idel fuel pressure is set at 16-17 with the 400cc injectors my fuel pressure is a lil over 100psi at full boost but i use 2 fuel pumps to back me up though.if u plan on boosting more then go with 440cc injectors,sfmu, and safc..that prob be good for 15-17lbs of boost...i plan on getting the mega squirt soon.

 

[siueclipse]

Injector size help again.

Okay so I'm currently in the middle of a rebuild, and just had a few questions about the amount of boost I'm running with the injectors I have or how much more power or boost I could run with the right size injectors.

Okay I basically have got the same howell bottomend kit except with Weisco 8:8:1 pistions, along with some light port work and a 3 angle valve grind, I'll be boost with the star stage 2 kit, with the SFMU instead. Now I have an SAFC2 for fine tuning, and currently have 370cc RC injectors.

1) How much boost should I be able to run for a good daily drivien built motor?
2) what should the fuel pressure be at?
3) What size injectors should I upgrade too and how much boost with those.
4) What should the fuel pressure be at for this set-up?

Now I've read corbrin's fuel set-up guide, but I get confused using the formula because I have no idea how much power I should be expecting to put out. My goal was 250whp or close to 300bhp, but I really don't know how possible that is?

1) At most 14lbs. Watch out for injector duty cycle.
2) Idle pressure should be at about 30, full booost.. not sure
3) 440cc injectors can run 20 to 21lbs of boost. Granted the injectors are screaming but they can do it.
4) 440cc injectors should idle at about 15 to 20. Full boost (21lbs) you should see like 98psi of fuel. (if i remember correctly.)

 

[siueclipse]

not sure if it will help but i'm using the sfmu,400cc injectors and no safc..i kinda maxes out at 15lb of boost,my idel fuel pressure is set at 16-17 with the 400cc injectors my fuel pressure is a lil over 100psi at full boost but i use 2 fuel pumps to back me up though.if u plan on boosting more then go with 440cc injectors,sfmu, and safc..that prob be good for 15-17lbs of boost...i plan on getting the mega squirt soon.

your setup is ####ered.

over 100psi of fuel at 16lbs of boost? .

 

[BigRand]

1) At most 14lbs. Watch out for injector duty cycle.
2) Idle pressure should be at about 30, full booost.. not sure
3) 440cc injectors can run 20 to 21lbs of boost. Granted the injectors are screaming but they can do it.
4) 440cc injectors should idle at about 15 to 20. Full boost (21lbs) you should see like 98psi of fuel. (if i remember correctly.)

So If I jump up to about 550's I shouldn't have any problems, and can run a lower duty cycle with less fuel pressure under boost?

 

[xxthayxx]

your setup is ####ered.

over 100psi of fuel at 16lbs of boost? .

dude how u get 16lbs...sounds like ur reading skills is kinda ####ered..i said i max out at 15lbs of boost and fuel pressure is a lil over 100psi..

 

[siueclipse]

So If I jump up to about 550's I shouldn't have any problems, and can run a lower duty cycle with less fuel pressure under boost?

550cc injectors are too big. they wont work

 

[BigRand]

550cc injectors are too big. they wont work

Your shi*ting me right?
I just ordered em from slowboy last night.
Can't I just turn the static fuel pressure on the SFMU down. Not to mention I'm still runing the fuel pump from the STAR kit (190)??

 

[siueclipse]

you can't turn down the fuel pressure low enough. with 440cc injectors you can go down to like 15psi.. which is too low as it is for the motor.

 

[BigRand]

you can't turn down the fuel pressure low enough. with 440cc injectors you can go down to like 15psi.. which is too low as it is for the motor.

I'm so confused, right now. So I called up slowboy to cancel my 550cc injector order, and I got into this convorsation about what kind of injectors I should be using.
And he said with the stuff I had on my car and fuel management, and me wanting to run boost in the 15-20lbs range, I should be using at least 650cc.

He said he's built a couple of 420a's with the same fuel management and ran 650cc for around 15-20lbs of boost.
He said something about using a smaller disc like 6:1, having the fuel pressure around 38psi, and taking some fuel off with the SAFC.

Doing the math he said, 440cc would only cover 11lbs of boost. (no obviously that has some errors in that.)

Now I'm going to be getting my motor back in about a week, and I really can't afford to screw up by buying the wrong things at this point, because I will literally have no money after this is done.

Now call me a newbie again, but could someone just explain exactly what size injectors I need and why using math if they can. (I'm not good with math anymore)

 

[siueclipse]

Im not going to bother with the math.. but instead.. ill do personal experience.

440cc injectors, topped them out at 21lbs of boost. i hit like 287whp on the dyno like that.

afr's were like 11.9

 

[BigRand]

Well a lot more research on the formula for choosing the injector size, I decided to try it out for myself doing the math, using "Corbrin's" HOW to choose injectors off of the 2gnt.com website, When I finished that calculation, it said I needed a flow rate of 602cc to sustain what fuel set up I had for a 300bhp motor. This didn't quite look right, so after looking in a magazine I found the website for RC enginering, www.rceng.com and they have the calculator their set up for you.

I did the calculations and my flow rate came up to 427cc, which should be right for the 440cc injectors that James was telling me to get (thank you ) And it so I'll be ordering those from wherever I can get them cheapest, anyone have any ideas??

 

[siueclipse]

ebay

 

[BigRand]

Okay, back again with another question reltating to injector choice. James you've been really helpful so take another crack at this one as well.

If I run a seperate Fuel return line to a Areomotive Fuel Pressure Regulator, Could I then use 550cc injectors? Just wondering if that had any play into the situation?

 

[siueclipse]

nope, wont work.

 

[Livid]

As long as ur running some sort of Stand Alone EMS or Fuel Management System with your 660cc injectors it should be fine.. Did you eprom your ecu / upgrade map sensors?

 

[GVR4592]

I'm not doubting you guys know what you are talking about, I have no experience with a 420a. What is the reason he cant use 550 or larger injectors?

 

[BigRand]

I'm not doubting you guys know what you are talking about, I have no experience with a 420a. What is the reason he cant use 550 or larger injectors?

It has something to do with not being able to adjust the SFMU down low enough to where they motor isn't being flooded by fuel. HOwever there is a way around this. if you run a seprerate return line with a fuel pressure regulator on that the guy at my shop says that should work.
either way it doesn't matter to me anymore because I"m going with e-manage now and have a whole different set of problems.

 

[Livid]

440cc injectors are close to the stock Mistsu's 450cc injectors. Which the ecu is programmed for. Larger injectors can't be toned low enough and accurately enough without an emanage or another stand alone. So yes it'll be flooded. May be possible to do this using a flashed/ eprommed ecu or stand alone but i dont know about just using a FPR unless you're always using a constant boost.

 

[selmerguy]

i am in the same boat as big rand was so my question is: will this fuel system work? 440cc injectors, sfmu, safc2 and a stand alone wide band to tune with.

also what other injector options do i have?

what will my everyday gas mileage be around if i run 15 psi?

right now i get 330 a tank with a 12:1 fmu and a walbro 255 pump?

 

[siueclipse]

440cc injectors are close to the stock Mistsu's 450cc injectors. Which the ecu is programmed for. Larger injectors can't be toned low enough and accurately enough without an emanage or another stand alone. So yes it'll be flooded. May be possible to do this using a flashed/ eprommed ecu or stand alone but i dont know about just using a FPR unless you're always using a constant boost.

You are completely wrong. The 4g63 motors have a completely different ECU with different programming than the 420a motor. Hell, even different years of the 420a have different ECUs and Im sure the 4g63 is the same way.

 

[siueclipse]

i am in the same boat as big rand was so my question is: will this fuel system work? 440cc injectors, sfmu, safc2 and a stand alone wide band to tune with.

also what other injector options do i have?

what will my everyday gas mileage be around if i run 15 psi?

right now i get 330 a tank with a 12:1 fmu and a walbro 255 pump?

Yes that fuel system will work, but I didn't see the need for the safc.

You have no other injector options unless you run with a portfueler, megasquirt, emanage, etc.

Your gas milage will go down... how far down depends on how heavy your foot is.

 

[selmerguy]

Yes that fuel system will work, but I didn't see the need for the safc.

You have no other injector options unless you run with a portfueler, megasquirt, emanage, etc.

Your gas milage will go down... how far down depends on how heavy your foot is.

cool i will get the safc last then.
thanks sui you da man

 

[siueclipse]

no worries

 

[selmerguy]

so i was looking on ebay for injectors and all i found for the 420a eclipse was 36 lbs.(375cc) can i use neon injectors or am i searching wrong? what specific 440cc injectors would i need with my setup?