Bruce
03-02-2004, 12:41 PM
There seems to be alot of folks trying to give pat answers to some complex subjects. And it really doesn't work that way. For alot of items you have to know the specifics of the matter, to give an accurate answer.
When do you need a double pumper?.
How much injector do you need?.
I'm reading 82 mv on the O2 so I know I have enough fuel.
If you have a low restriction intake TRACT, and exhaust with 55's you might need a double pumper. While your friend might be running a cool air kit, a quiet exhaust, might be rich with 55s, and have an excess of fuel. The difference?, restriction. For ever 1% restriction in the intake tract can cost you 2% in HP. While these number might seem small, they do in fact add up.
It doesn't take much work to get a GN to really start flowing some big numbers. And thus, with not much difference in combos, one might bet by with a 340, and one might need a double pumper.
For injector sizing, well, any issues you've heard about large injectors not working on street cars, is just dated. 60s, and even 72s, with the proper tune with run just fine on the street. Thou, the bigger the injector the more precise the calibration has to be. It kind of seperates the real chip guys, from the hacs when you get to the big injectors. With the smaller injectors, you could just run them static, and there was no real talent involved. With the big injectors you have the fuel to run alot of boost, and that means having the lower end of the load areas correct, or the engine is just sloppy rich.
Not to mention the start up routine, and getting that right.
And if your running a chip with a fuel curve, then 50s are limited in the amount of boost they will support. In just a mild combo, if you're running a 90% DC, with them, you'll probably need water/alky injection to run much boost. Or run a very limited amount of timing.
It's always safer to have an excess of fuel available then not having enough. A goof up going rich means fouling a plug, lean, and you knock the corners off the piston, or pop a headgasket.
When do you need a double pumper?.
How much injector do you need?.
I'm reading 82 mv on the O2 so I know I have enough fuel.
If you have a low restriction intake TRACT, and exhaust with 55's you might need a double pumper. While your friend might be running a cool air kit, a quiet exhaust, might be rich with 55s, and have an excess of fuel. The difference?, restriction. For ever 1% restriction in the intake tract can cost you 2% in HP. While these number might seem small, they do in fact add up.
It doesn't take much work to get a GN to really start flowing some big numbers. And thus, with not much difference in combos, one might bet by with a 340, and one might need a double pumper.
For injector sizing, well, any issues you've heard about large injectors not working on street cars, is just dated. 60s, and even 72s, with the proper tune with run just fine on the street. Thou, the bigger the injector the more precise the calibration has to be. It kind of seperates the real chip guys, from the hacs when you get to the big injectors. With the smaller injectors, you could just run them static, and there was no real talent involved. With the big injectors you have the fuel to run alot of boost, and that means having the lower end of the load areas correct, or the engine is just sloppy rich.
Not to mention the start up routine, and getting that right.
And if your running a chip with a fuel curve, then 50s are limited in the amount of boost they will support. In just a mild combo, if you're running a 90% DC, with them, you'll probably need water/alky injection to run much boost. Or run a very limited amount of timing.
It's always safer to have an excess of fuel available then not having enough. A goof up going rich means fouling a plug, lean, and you knock the corners off the piston, or pop a headgasket.