Fueling & Injection - Questions about stock fuel line and 50 lb injectors
Lost & Found2
01-03-2003, 06:04 PM
I'm just wondering how much RWHP can 50lb injectors handle?
How much RWHP can the stock fuel lines handle before needing to be replaced?
Would an after market regulator help on a feul system without a return line?
99 Trans Am Vert
D&M Blockshop 383CID, MMS StageIII Heads/Blower Cam, GWP StageII Procharger D-1. G2 Suspension & BMR Trak pak. ProYankExtreme Stall. Grott Lt & Borla
Also, how much rwhp can the stock pump handle? I have 36 lb svo's inj. and still the stock pump and lines but we were just going to test the car out before we changed to the new fuel system. I did manage to get the 36lb's inj. on and the computer re-done for them....we will be pulling off the stock stuff soon but just wanted to check....
Lost & Found2
01-03-2003, 06:28 PM
I believe a stock pump is right around 425 RWHP.
Anyone else? Hell I was at 439 rwhp with just my heads and cam (ls6 intake) and it ran fine....
01-04-2003, 11:07 AM
While you guys are on the injector subject. What are the stock injectors rated at? 2000 SS Camaro with the LS1.....
Depends on what yr you have..
01-04-2003, 03:33 PM
Ok, I'll talk about what CAN be done and you can decide for yourself what you think is safe enough for you.
Injectors can support 18 RWHP per lb under some circumstances. This is pushing it right to the ragged edge and is NOT what I would recommend. This means that 26.4 lb injectors (like '99-'00s came with) can pull 475 RWHP. Can they really? Yes, it's been done many times. I pulled 480 RWHP with them, btw. Again, this was COMPLETELY maxed out and NOT at high RPM!
So, for most people running NA, 450 RWHP is safe enough for 26.4 lb injectors if you're turning stock or near stock RPMs, IMO.
You also must consider the RPM at which the power is being made. The higher the RPM, the less power the injector will support. Why? Because the faster you're turning the engine, the less time the injector has to spray the required amount of fuel.
So, a true 50 lb injector (is this rated at 43.5 psi or at the LS1's 58 psi? If it's 50 lb at 43.5 psi it would be about 60 lb at 58 psi.) might be able to max out at about 900 RWHP in some applications if the RPMs were low enough. More rpms, less power supported. I think it's safe to say that for most applications these injectors would easily support 650 RWHP.
A stock '99-'00 pump will handle about 470 RWHP. That's where I maxed mine out. '98s will handle better than 500 RWHP.
'98s, '01-02s have 28.6 lb/hr injectors. '99-'00s have 26.4 lb/hr injectors.
01-04-2003, 03:38 PM
BTW, to figure maximum injector pulse width in milliseconds, calculate it like this...60000/rpm X 2
For example...60000/5300rpm = 11.32 x 2 = 22.64 milliseconds. This is your maximum available pulsewidth or 100% duty cycle at 5300rpm.
You can monitor injector pulse widths with a diagnostic scanner such as Autotap.
Thanks Stephen... <img border="0" title="" alt="[Cool]" src="gr_images/icons/cool.gif" />
01-04-2003, 07:17 PM
Found this online.... Hope it helps some.
Electronic fuel injectors have two masters to satisfy. They must accurately match the fuel demands of an engine while meeting the electronic commands of the engine management computer. Obtaining the correct fuel flow amount from a group of injectors in an EFI system is similar to determining the right size jets for a carbureted engine. The fuel flow of both systems must be matched to the airflow requirements of the engine over a broad rpm operating range. The injectors must be able to supply a small amount of fuel to support engine idle, a large amount at wide-open throttle to prevent high rpm lean out, and transitional amounts to cover all of the operating conditions in between. Turbo/superchrged engines in particular place even more rigorous demands on an injectors range because of their increased airflow capability. Just as the wrong-sized jets in a carb can cause driveablity problems such as rough idle, surging, poor throttle response or even high-rpm lean-out causing scattered engine parts, so can incorrectly sized injectors. The following is a guideline equation for approximating fuel flow per injector based on estimates on engine Horsepower (HP) and Brake Specific Fuel Consumption (BSFC).
Engine HP must be a realistic estimate of engine output.
BSFC is determined from engine dynamometer measurements. It typically ranges from 0.4-0.6 for gasoline powered engines. A BSFC of 0.5 is a reasonable initial estimate for most engines.
The 0.8 multiplier of the "Number of Injectors" helps us derive a practical, maximum "Injector Flow Rate" for each injector based on an effective real world injector operating pulse time and fuel flow. It's unrealistic to establish the fuel flow to the engine based on an injector operating pulse time of 100% (wide open all the time). This formula uses an injector operating cycle based on 80%. Some full race engine management systems may operate at 85-95% duty cycle, but doing so for some time increases the likelihood of overheating the injectors which may cause irregular fuel rates or a decrease in low rpm operation.
Injector Flow Rate (lb/hr) = Engine HP x BSFC
Number of Injectors x 0.8
For example, to calculate the individual injector size for a 650 HP V8 using 8 injectors and assuming a BSFC of 0.5:
Injector Flow Rate (lb/hr) = 650 x 0.5
8 x 0.8 = 50.78 lb/hr
Using the formula above injectors with a flow rating of 50 lb/hr static flow at 43.5 psi (3bar) fuel system pressure would be the correct injectors.
If you have a known injector fuel flow rate you can solve the above equation for a rough estimate of fuel system capacity like this:
For example, using the same estimated values from above:
Engine HP = 50 x 8 x 0.8
0.5 = 640HP