I love this thread. I love this board. It's nice to see guys like Jeff taking time to help others along. Mr. Chambers, have a cookie.
Somebody mentioned running plugs 2 ranges colder than stock. Personally, I recommend against it. I have found it is hard to get accurate plug readings with plugs that cold. I recommend staying with one range colder than stock. Like I said, this is based on personal preference. Of course, I sell and install nitrous systems, so most of my experience with plugs is on the bottle. If you guys have different experiences, sound off. I always like to learn new stuff.
As for injectors, here is the rule of thumb I learned from a guy at Siemens, an OE supplier of injectors.
lb/hr (fuel) = (Max. HP x BFSC) / (# of injectors)
Max. HP is a realistic estimate or a known value from dyno testing
BSFC is
Brake Specific Fuel Consumption. Typically, BSFC for a normally aspirated or nitrous engine will be 0.45. For a turbocharged or supercharged application, use BSFC=0.55. Dyno testing can provide exact BSFC data. For a safety margin, you can use .5 for n/a engines, and .6 for supercharged/turbo combos.
# of injectors should be one per cylinder, if possible. For some applications, additional injectors are utilized.
Once a value (lb/hr) is obtained, use the closest injector size
above that value.
Example: 302 c.i. Ford 8 cylinder, naturally aspirated, 350 horsepower:
lb/hr (fuel) = (350 x .45) / 8
lb/hr (fuel) = 19.6875
This engine has exceeded 19 lb/hr, so it's time to use 24 lb/hr injectors.
You can insert injector rates into the equation, and solve for max. HP level of a given injector:
19 lb/hr= (Max. HP x .45)/8
152= Max. HP x .45
337.78= Max. HP
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Moxie Racing
The Nitrous Oxide Information Site