max hp 42lbs injectors
#4
where:
- HPmax = flywheel HP
- lb/h = injector capacity
- Dutycycle = % as a decimal fraction (E.g 95% = 0.95)
- Cyls = # of cylinders
- BSFC = Brake Specific Fuel Consumption (0.5 hp/lb for n/a, 0.6 hp/lb for f/i)
42 * 8 * 0.95 / 0.6 = 532 at the flywheel, take out 15% drivetrain loss = 452 rwHP; pretty close to lizzyfan's 440...
Last edited by cliffyk; 08-19-2011 at 09:07 AM.
#5
where:
- HPmax = flywheel HP
- lb/h = injector capacity
- Dutycycle = % as a decimal fraction (E.g 95% = 0.95)
- Cyls = # of cylinders
- BSFC = Brake Specific Fuel Consumption (0.5 hp/lb for n/a, 0.6 hp/lb for f/i)
42 * 8 * 0.95 / 0.6 = 532 at the flywheel, take out 15% drivetrain loss = 452 rwHP; pretty close to lizzyfan's 440...
#8
Wow, i didn't realize Chris was running 39's. If he truly is then it might have something to do with the fact that he's running a built HCI 4 valve with only 12 lbs. of boost.
BTW, what does Lidio say about all this? I would just go off his recommendation. Besides you don't have a intercooler or meth right now anyways, so maybe just have it tuned to work within the capabilities of the 42's. When the time comes for meth then bump both both the injectors and psi, then get a retune.
Just a thought.
BTW, what does Lidio say about all this? I would just go off his recommendation. Besides you don't have a intercooler or meth right now anyways, so maybe just have it tuned to work within the capabilities of the 42's. When the time comes for meth then bump both both the injectors and psi, then get a retune.
Just a thought.
#9
It depends on the fuel pressure, which affects the delivery rate of the injectors--I should have been more clear about this in the formula I presented above, where lb/h represents the injector capacity when operated at the actual pressure drop across the injector.
Fuel injector capacity is normally specified at a pressure of 3 bar (43.5 psi), though as Ford runs 39.15 psi differential FRPP injectors are specified at that pressure. That is why the FRPP 24 lb/h injectors can be found listed as 26 lb/h capacity, which they would be if run at 43.5 psi.
The formula for recalculating injector capacity is:
So, 39 lb/h (FRPP spec) injectors operated at 80 psi would become:
((80.0/39.14)^0.1) * 39 = 55.7 lb/h injectors
55.7 lb/h injectors running f/i at 90% DC could support 55.7 * 8 * 0.8 / 0.6 = 594 fwHP.
On my old '90 to '93 Miatas I ran the stock 24 lb/h injectors at 115 psi to get enough fuel to support 12 psi boost, this "turned them into" 39 lb/h injectors.
Fuel injector capacity is normally specified at a pressure of 3 bar (43.5 psi), though as Ford runs 39.15 psi differential FRPP injectors are specified at that pressure. That is why the FRPP 24 lb/h injectors can be found listed as 26 lb/h capacity, which they would be if run at 43.5 psi.
The formula for recalculating injector capacity is:
So, 39 lb/h (FRPP spec) injectors operated at 80 psi would become:
((80.0/39.14)^0.1) * 39 = 55.7 lb/h injectors
55.7 lb/h injectors running f/i at 90% DC could support 55.7 * 8 * 0.8 / 0.6 = 594 fwHP.
On my old '90 to '93 Miatas I ran the stock 24 lb/h injectors at 115 psi to get enough fuel to support 12 psi boost, this "turned them into" 39 lb/h injectors.
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