MAF and FPR independent from injectors?

Nixon1 · 02-28-2003, 03:05 PM

I'm looking to push some decent power down the road and was wondering.. My car just got brand new Motorsport 19 lb/hr injectors thrown in.. First question, they're titled as high flow..but how can they be high flow but push the same lb/hr rating? Is that just BS?

My main question is...I really don't want to have to get new injectors again later, and I assume these injectors will support decent power #'s....is it possible to find a high flowing MAF that's calibrated for only 19 lb injectors? If I were to run 19 lb injectors with a large MAF calibrated for them, and perhaps an adjustable FPR to up the fuel pressure a little...would this work?

Just an idea..thanks.

95mustanggt · 02-28-2003, 08:41 PM

I have a 75mm MAF that is calibrated for 19# injectors. You can increase fuel pressure to squeeze more fuel out of them, but only so far. 19#'s should be good for a while though, unless your considering some bigger changes (Head/cam/intake or Supercharger)

Nixon1 · 02-28-2003, 09:13 PM

Only mods I'm looking at right now, short of a motor rebuild, are underdrive pulleys and a dry-type nitrous system. Course all of this probably wont be for another year..I'm in debt right now cause of just repairs.

Hethj7 · 02-28-2003, 10:00 PM

Those 19 # injectors will be good up to about the 300 hp level. The adjustable FPR is a good idea too, but keep in mind that you may not always have to increase fuel pressure to get the most power. My first trip to the dyno we actually decreased my pressure a little and picked up about 10 hp at the wheels.

Technick · 03-01-2003, 02:00 AM

If possible use a bigger injector. The larger the injector the less fuel pressure required, the less fuel pressure required the more control the injector has (PCM) over the pulse width. The processor can always lower the pulse width and control air fuel ratio eaiser at lower pressures than it can at higher pressures where the nozzle can lose control of the spray pattern and volume. Also little known fact--- the higher the pressure the LOWER the volume from the pump. The lower the pressure the HIGHER the volume from the pump. Its true! I have built 600 rwhp 4.6 Cobra's with 50 lb/hr injectors and used only 40 psi of pressure! Mind you this is with 1/2" feed line and 3/8 return and a Aeromotive A-1000 pump. And this was on a supercharged car with 18 psi boost! No FMU! Just a 1:1 regulator! Stock Processor!
It is much eaiser for the PCM to trim injector pulse width down (in time in milliseconds)than it is to controll pulse width up (open longer in milliseconds) with higher pressure to boot.

02-28-2003, 03:05 PM	#1
Nixon1 Registered Member Join Date: Jan 2003 Location: Palm Bay, FL Posts: 432	MAF and FPR independent from injectors? I'm looking to push some decent power down the road and was wondering.. My car just got brand new Motorsport 19 lb/hr injectors thrown in.. First question, they're titled as high flow..but how can they be high flow but push the same lb/hr rating? Is that just BS? My main question is...I really don't want to have to get new injectors again later, and I assume these injectors will support decent power #'s....is it possible to find a high flowing MAF that's calibrated for only 19 lb injectors? If I were to run 19 lb injectors with a large MAF calibrated for them, and perhaps an adjustable FPR to up the fuel pressure a little...would this work? Just an idea..thanks. __________________ '91 Mustang GT 5.0 AOD Daily Driver Current stats: NEW 302 short block, E-303 cam (@.050, 220/220, .498/.498, 110 degrees), 1.6 roller rockers, Performer RPM heads (aluminum, 1.9/1.6, 60cc chambers), Cobra intake, Granatelli 75mm MAF, Billet AFPR, Equal-Length Shorty Headers, Off-Road X Pipe, Flowmasters, 4.10 POSI 13.73 at 103.8, ~2.2 60'

02-28-2003, 08:41 PM	#2
95mustanggt Registered Member Join Date: May 2000 Location: Kamloops, BC Posts: 2,875	I have a 75mm MAF that is calibrated for 19# injectors. You can increase fuel pressure to squeeze more fuel out of them, but only so far. 19#'s should be good for a while though, unless your considering some bigger changes (Head/cam/intake or Supercharger) __________________ 1995 Mustang GT 20016 F150 Lariat Super Crew

02-28-2003, 09:13 PM	#3
Nixon1 Registered Member Join Date: Jan 2003 Location: Palm Bay, FL Posts: 432	Only mods I'm looking at right now, short of a motor rebuild, are underdrive pulleys and a dry-type nitrous system. Course all of this probably wont be for another year..I'm in debt right now cause of just repairs. __________________ '91 Mustang GT 5.0 AOD Daily Driver Current stats: NEW 302 short block, E-303 cam (@.050, 220/220, .498/.498, 110 degrees), 1.6 roller rockers, Performer RPM heads (aluminum, 1.9/1.6, 60cc chambers), Cobra intake, Granatelli 75mm MAF, Billet AFPR, Equal-Length Shorty Headers, Off-Road X Pipe, Flowmasters, 4.10 POSI 13.73 at 103.8, ~2.2 60'

02-28-2003, 10:00 PM	#4
Hethj7 Mizzou Tigers Join Date: Apr 1999 Location: weston, MO United States Posts: 1,455	Those 19 # injectors will be good up to about the 300 hp level. The adjustable FPR is a good idea too, but keep in mind that you may not always have to increase fuel pressure to get the most power. My first trip to the dyno we actually decreased my pressure a little and picked up about 10 hp at the wheels. __________________ 2006 Mustang GT 1990 LX GT-40 motor 262 horsepower, 307ft-lbs (sold but forever loved) 1998 Contour SVT Rice Haters Club Member #244

03-01-2003, 02:00 AM	#5
Technick Registered Member Join Date: Feb 2003 Location: Seattle, Wa. Posts: 175	If possible use a bigger injector. The larger the injector the less fuel pressure required, the less fuel pressure required the more control the injector has (PCM) over the pulse width. The processor can always lower the pulse width and control air fuel ratio eaiser at lower pressures than it can at higher pressures where the nozzle can lose control of the spray pattern and volume. Also little known fact--- the higher the pressure the LOWER the volume from the pump. The lower the pressure the HIGHER the volume from the pump. Its true! I have built 600 rwhp 4.6 Cobra's with 50 lb/hr injectors and used only 40 psi of pressure! Mind you this is with 1/2" feed line and 3/8 return and a Aeromotive A-1000 pump. And this was on a supercharged car with 18 psi boost! No FMU! Just a 1:1 regulator! Stock Processor! It is much eaiser for the PCM to trim injector pulse width down (in time in milliseconds)than it is to controll pulse width up (open longer in milliseconds) with higher pressure to boot. __________________ No matter how much you spend, or how much you prepare, there is ALWAYS someone else faster or quicker than YOU!!!!!!!!!!