Fuel Injector Size
12-19-2004, 06:23 PM
#1
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Fuel Injector Size I had my car dyno'd at just over 390 at the wheels with an auto trans. I've got Z06 injectors which are only slightly larger than stock. I did a 1/4 mile run 12.5 @118 but it felt like it was cutting out slightly starting at 5,800 rpm. I thought maybe the injectors are too small. Any thoughts on this?
Last edited by Silver02; 12-20-2004 at 02:11 PM.
12-20-2004, 05:28 PM
#3
Mine dyno'd 392 and ran 12.1 at 113. I'm running stock (28.8) injectors for now.
You may have been touching the rev limiter. The tach lags a bit and you were probably a little higher than it appeared. Was the limiter raised by A&A?
The only way to be sure about the injectors is to log your injector pulse widths and see if the duty cycle is too high.
Your fuel pressure may have been dropping off too. Maybe you can borrow a fuel pressure gauge and monitor a run, to confirm or disprove this as a potential problem.
You may have been touching the rev limiter. The tach lags a bit and you were probably a little higher than it appeared. Was the limiter raised by A&A?
The only way to be sure about the injectors is to log your injector pulse widths and see if the duty cycle is too high.
Your fuel pressure may have been dropping off too. Maybe you can borrow a fuel pressure gauge and monitor a run, to confirm or disprove this as a potential problem.
12-22-2004, 08:19 AM
#4
Originally Posted by Silver02
I had my car dyno'd at just over 390 at the wheels with an auto trans. I've got Z06 injectors which are only slightly larger than stock. I did a 1/4 mile run 12.5 @118 but it felt like it was cutting out slightly starting at 5,800 rpm. I thought maybe the injectors are too small. Any thoughts on this?
FWHP X BSFC
____________ = Inj size in #/hr.
# inj's X duty cycle, [85%]
Note: Injectors are usually rated at 3 bar.
HTH,
12-24-2004, 02:18 AM
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Originally Posted by Old Geezer
Do the math...
FWHP X BSFC
____________ = Inj size in #/hr.
# inj's X duty cycle, [85%]
Note: Injectors are usually rated at 3 bar.
HTH,
FWHP X BSFC
____________ = Inj size in #/hr.
# inj's X duty cycle, [85%]
Note: Injectors are usually rated at 3 bar.
HTH,
I am guessing that this formula is independent of fuel pressure. By that I mean that the result needs to be the flow rate of the injector at the fuel rail pressure being used. So if I want 50 lb/hr I need injectors that flow that rate at my own fuel pressure. I don't really care what pressure they were rated at, except to calculate their flow rate at my fuel rail pressure.
And aren't SVO injectors rated at 39 or 39.5 psi not 43.5? In fact most Ford injectors are rated at rather odd pressures in the mid 2 bar range.
Perry
