ok i plan on rebuilding soon and funning like 18 psi and iam starting to get the fuel part all set up do you think 440ccs are good for this and the safc ......but if the 440cc are good what do you guys think of buying a used ste for like 100.00 is that good deal and are used injectors ok if they look good on the outside?

bump

If the 440's are in good shape, $100 is a steal. As far as how to define good shape, I have no idea. You might ask rceng.com if no one else here knows.

w/ the star system, you'll max out your pump capacity before you reach 18psi. You'll probably need 550's.

w/ the 255lph pump (which comes w/ the star kit), you should max out the pump @ ~14psi or so. if you get the 255 hp pump, you can go a little higher, but the easiest thing to do is just get bigger injectors and run the pump you already have.

99GS MT | Star Stage 2 | GC coilovers | HurriganeGS tie bars | Tokico Illuminas | 17x7 Enkei RS5 | Baer track brakes |+

Only way to know if injectors are good is to send them to be tested.

Dave
05 Ford F150 SuperCrew FX4

what size do you recamend withe the star kit?

Boost pressure isn't what maxes out the pump, it's fuel pressure. If you are running say a 3:1 rising rate FPR and 18psi boost then you you are way closer to maxing out the pump than if you run a 1:1 reg and run 18psi boost.

iam confused now i dont now what injector size to go with i have a star stag1 right now and iam going to go to a stage 3 soon and i can get some used injectos 440cc for 100.00 iam going to change my fpr disk so what should i do go with bigger injectors or what?

Here spend some time using these formulas and figure out what kind of fuel system you need. You can use the 440's but you need to figure out at what pressure to run them at and if your fuel pump can keep up. Use a BSFC of .6 instead of the .525 in the formulas.

http://www.2gnt.com/www/corbin/example.html

"Boost pressure isn't what maxes out the pump, it's fuel pressure. If you are running say a 3:1 rising rate FPR and 18psi boost then you you are way closer to maxing out the pump than if you run a 1:1 reg and run 18psi boost."


True....and with 440's and a 2.5-3:1 rise rate, you will max out your injectors at about 13-14 psi. I've done the math and I didn't think it would be understood in this post, so I didn't bother. Actually the combo of fuel pressure and flow rate are needed to find the max of the pump. From what I've calculated, w/ 440's and star kit, I should theoretically max out the injectors at about 13.75 psi. Take that for what it's worth.

and if you haven't rebuilt your engine to have different compression, your BSFC should stay the same (~.525)
However, if you have rebuilt, BSFC should drop as engine efficiency drops (w/ lower compression).

99GS MT | Star Stage 2 | GC coilovers | HurriganeGS tie bars | Tokico Illuminas | 17x7 Enkei RS5 | Baer track brakes |+

There is no way that you are going to max out 440's at 13-14psi. Even the 4G63's can get 16psi out of the stock 440's and they use a 1:1 reg. Even if you ran 15psi w/ a 3:1 reg and a static of 30psi the you have a max pressure of 75psi. That Walbro flows about 45GPH at that pressure. You don't need anywhere close to 45GPH to support the HP made from 15psi. Also since he said he plans to be stage 3 I just assumed he'd lower compression. So since it's less efficient he'll need more fuel so I suggested .60 BSFC.

Regardless of rise rate, injector, and/or fuel base pressure, your engine at XX psi needs a set amount of fuel. I have my numbers set at 40psi for static. At that pressure(as seen below), you need 76 psi and 28gph from the fuel pump which is maxing it out as seen in the chart below the numbers.

If you want to change to 440's and 30 psi base pressure, then your rise rate required will change to 3.38:1 and you will still need 76psi fuel and 28 GPH which maxes out the fuel pump. Or at least this is as close as I'm willing to push it. Feel free to go on up if you want. I won't with this setup.

These numbers match the stock fuel curve w/ 12:1 rise as close as possible. It may be slightly rich, but it's a starting point from which to tune.
Desired HP (est) 325
Injector Size Chosen (cc/min) 440
Static Fuel Pressure 40
PSI (boost setting) 13.6
BSFC 0.525
Maximum Duty Cycle 0.85

Fuel Vol Per Injector (cc/min) 447.89
Injector size needed (cc/min)527
Injector Flow Rate (cc/min) 421.93
Fuel Pressure Needed (psi) 76.00
Fuel Pump Needed (GPH) 28.44
Disk Ratio needed 2.64
AFC Offset Needed (at idle) -36.2%





If you run 15psi boost w/ a 3:1 rise rate, according to my graphs, you'll deliver less fuel than desired, starting at about 11psi.

99GS MT | Star Stage 2 | GC coilovers | HurriganeGS tie bars | Tokico Illuminas | 17x7 Enkei RS5 | Baer track brakes |+

Are you using the LOW PRESSURE Walbro or something? Even if you are then you're still flowing 30GPH @76psi. And 255HP does not max out anywhere near 28GPH at 76psi fuel pressure.

>Are you using the LOW PRESSURE Walbro or something? Even if
>you are then you're still flowing 30GPH @76psi. And 255HP
>does not max out anywhere near 28GPH at 76psi fuel pressure.

You're right, the 255HP does not max out at that. That's why I suggested above that if you wanted to go past these levels, you'd have to get that. The star kit (at least mine) comes with the 255 low pressure. So, yes, I'm running the low pressure walbro which is the blue line and it does max out there. Look at the graph. I might give you 30gph @ 76psi, but not much more. You're right the HP pump does max out well above 30gph (somewhere near 45gph), but I don't have that and I don't believe qwad does either.

Do you have the star kit? If so, did yours come w/ the HP pump? I wish mine did, but unfortunately I have the LP pump.

99GS MT | Star Stage 2 | GC coilovers | HurriganeGS tie bars | Tokico Illuminas | 17x7 Enkei RS5 | Baer track brakes |+

No I don't have a turbo kit but I do have the HP pump. I don't know why the Star wouldn't come w/ the HP pump since it's made to run on stock injectors. So yeah the LP is really close but I thought for sure that the Star had to come w/ the HP. My bad.