What size injectors with a-trim @ 5 psi?

AT11 · 05-21-2007, 11:50 AM

Hey guys, I am currently running a n/a 306 with a trick flow top end kit-twisted wedge heads, stage 1 cam and trick flow intake. I was wanting to add a vortech a-trim supercharger and keep it at 5 psi but was wondering what size injectors would be good to use with this setup. I have a 255 intake pump and aeromotive adjustable fuel pressure regulator. Should I keep the 24 lb injectors and use the FMU for them or go with a bigger injector and use no FMU. This will be my first time using a supercharger and I want it to be done right. I know the 24lbers might work well with an FMU if the engine was all stock but not sure if I would need to step up having H/C/I? Also would some type of boost timing retard be necessary if I'm only running 5 psi. Maybe 30 lb injectors with an FMU would be better or 36 lb injectors without an FMU. Just looking for some opinions and to see if anyone has ran a setup close to this. Whatever way I go I plan on getting it tuned. This will be going on a stock shortblock 9.3:1 compression I think so I'm wanting to keep the boost at 5 psi for now. Thanks for reading.

96greengt · 05-21-2007, 12:17 PM

24#s will be ok for that boost, but the 30#s seem to suck. Your next option is 36# or 39#

AT11 · 05-21-2007, 04:54 PM

Yeah I plan on staying at 5 psi on boost due to the stock shortblock and since I don't have any supercharger experience. It will be a good starting point.

96greengt · 05-21-2007, 04:57 PM

24#s should do then, unless you know your a/f numbers already and at the very least SFT numbers.

**psiperformance** · 05-27-2007, 03:38 PM

if your going to buy injectors at all go ahead and get 42 pound injectors and throw away the fmu and tune the car.
you wont overfuel the motor if its tuned correctly and you have room to grow up to 500 rwhp.

311-420 · 05-30-2007, 12:06 AM

Quote:

Originally Posted by psiperformance

if your going to buy injectors at all go ahead and get 42 pound injectors and throw away the fmu and tune the car.
you wont overfuel the motor if its tuned correctly and you have room to grow up to 500 rwhp.

very true. without a tune, 42lbers would be too much. but if you have the car tuned for those injectors, it should not pose a problem.

05-21-2007, 11:50 AM	#1
AT11 Registered User Join Date: Jan 2007 Location: Rockdale, Tx Posts: 23 Trader Rating: (0)	What size injectors with a-trim @ 5 psi? Hey guys, I am currently running a n/a 306 with a trick flow top end kit-twisted wedge heads, stage 1 cam and trick flow intake. I was wanting to add a vortech a-trim supercharger and keep it at 5 psi but was wondering what size injectors would be good to use with this setup. I have a 255 intake pump and aeromotive adjustable fuel pressure regulator. Should I keep the 24 lb injectors and use the FMU for them or go with a bigger injector and use no FMU. This will be my first time using a supercharger and I want it to be done right. I know the 24lbers might work well with an FMU if the engine was all stock but not sure if I would need to step up having H/C/I? Also would some type of boost timing retard be necessary if I'm only running 5 psi. Maybe 30 lb injectors with an FMU would be better or 36 lb injectors without an FMU. Just looking for some opinions and to see if anyone has ran a setup close to this. Whatever way I go I plan on getting it tuned. This will be going on a stock shortblock 9.3:1 compression I think so I'm wanting to keep the boost at 5 psi for now. Thanks for reading.

05-21-2007, 12:17 PM	#2
96greengt LOL @ your mom Join Date: Feb 2007 Location: N.E. SA Posts: 8,680 Trader Rating: (21)	24#s will be ok for that boost, but the 30#s seem to suck. Your next option is 36# or 39# __________________ Built 00 Windsor engine, .20 over, 11.6:1cr, fully ported heads, Hardballer intake w/cooling mod, Scat rods, Probe pistons, Cobra crank, tri-metal Clevite race bearings, VT Stage 2 N/A cams, adjustable cam gears, Canton windage tray, MMR oil pump, Cobra pick up, 75MM Accufab t-body, Dragon plenum, JLT CAI, 24# injectors, Bassani mid lengths, mufflers & O/R X,255lph fuel pump, BBK FPR, Fidanza aluminum flywheel, AJE K-member, ARP hardware everywhere, X-Cal SCT custom tuned, 3.73's, Pro 5.0, polygraphite motor mounts, over 300+ RWHP & 320+ TQ

05-21-2007, 04:57 PM	#4
96greengt LOL @ your mom Join Date: Feb 2007 Location: N.E. SA Posts: 8,680 Trader Rating: (21)	24#s should do then, unless you know your a/f numbers already and at the very least SFT numbers. __________________ Built 00 Windsor engine, .20 over, 11.6:1cr, fully ported heads, Hardballer intake w/cooling mod, Scat rods, Probe pistons, Cobra crank, tri-metal Clevite race bearings, VT Stage 2 N/A cams, adjustable cam gears, Canton windage tray, MMR oil pump, Cobra pick up, 75MM Accufab t-body, Dragon plenum, JLT CAI, 24# injectors, Bassani mid lengths, mufflers & O/R X,255lph fuel pump, BBK FPR, Fidanza aluminum flywheel, AJE K-member, ARP hardware everywhere, X-Cal SCT custom tuned, 3.73's, Pro 5.0, polygraphite motor mounts, over 300+ RWHP & 320+ TQ

05-27-2007, 03:38 PM	#5
psiperformance LSS Sponsor Join Date: Mar 2006 Posts: 876 Trader Rating: (1)	if your going to buy injectors at all go ahead and get 42 pound injectors and throw away the fmu and tune the car. you wont overfuel the motor if its tuned correctly and you have room to grow up to 500 rwhp. __________________ PSI Performance Solutions 210-655-6546 10811 nacogdoches road San Antonio TX 78217 cmr tuners and full service performance shop.

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05-21-2007, 04:54 PM	#3
AT11 Registered User Join Date: Jan 2007 Location: Rockdale, Tx Posts: 23 Trader Rating: (0)	Yeah I plan on staying at 5 psi on boost due to the stock shortblock and since I don't have any supercharger experience. It will be a good starting point.