I just got my Crane AFPR and Hypertech gauge in the mail.

2 questions.. What is a good PSI with my mods?

and.


Can I leave the gauge hooked to the pressure port and just tape it to my windshield or something?

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'92 Formula<br>
305 TPI<br>
Mods: SLP catback,SLP air foil,ported plenum,Crane AFPR,MSD6AL,homemade cold air,K&Ns,3:73s

 

first check your stock setting, then go up about 2psi. i wouldnt go past 48 psi on a 305.
the gauge you have isnt intended to be kept on the car. it is just for testing. you can tape it to your windshield but just when you test psi.

 

When you set the (ideal) fuel pressure, you are stting it for WOT runs only.

At part throttle, the ECM is in closed loop mode. The ECM is looking at the O2 sensor output along with other sensors. The ECM goes to a lookup table and selects a fuel injector pulse width. If the fuel pressure is increased by 4psi for example, the ECM will adjust the injector pulse width to a smaller value.

However, during WOT runs, the ECM is in open loop mode or enrichment mode. The ECM does not look at the O2 sensor output at all. Therefore, you will have the biggest effect on the engines performance during WOT runs by dialing in the optimum fuel pressure.

You can set the optimal fuel pressure in several ways:
1) WOT runs with a scanner reading the O2 sensor output and dialing in 850 to 875mV on the O2 sensor.
2) On a chassis dyno for max torque or HP.
3) At the dragstrip for best ET.

Even on a chassis dyno or at the dragstrip, you should have a scanner to check what the O2 sensor is putting out.


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'87 L98 TPI IROCZ, AFR190 heads, 3.70 gears, ZZ9 cam, 2400 Art Carr TC, SLP 1 3/4" headers, SLP cat-back, no cat, no AC, no MAF screens, Accel manifold base & SuperRam, Edelbrock double roller timing chain, MSD ext coil & distributor, trans cooler, 52mm TB with airfoil, TB coolant bypass, AFPR(48psi), K&N filters, Hotchkis lowering springs, Car-Pro custom chip, Lay Ind. ram air kit, 265/45R16 Kumho V700 tires.
'90 Eagle Talon AWD, no rust thru 9 winters
'99 Camaro SS, red, 6-spd, T-tops, Mcleod clutch, Pro 5.0 shifter, MAF processor, Direct Flow airlid, K&N filter.
313.7Hp & 320.6ft-lbf, 13.55sec @ 105.1mph

 

Ok guys, I just checked my pressure with the gauge and it says 42psi. The engine was off but ignition on when I did this.

However, my plenum and throttle body is off the car which means everything underneath is disconnected. Didnt it say somehwere before that my reading will differ with a vaccuum hose disconnected or something? Can someone please explain?
thanks guys.

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'92 Formula
305 TPI
Mods: SLP catback,SLP air foil,ported plenum,Crane AFPR,MSD6AL,homemade cold air,K&Ns,3:73s

 

I have been confused on this also. If your guage reads 45PSI with the vacuum line connected,isn't this the actual reading. Mine reads 45PSI, but when i plug the hose it reads 55PSI.

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92 Formula,305HO,Factory Oil cooler,Hyper-Tech Chip,Hyper-Tech Coil kit,Dual-Core Split-Fire wire set,Hyper-Tech Airfoil,Accel Fuel pressure guage mounted on fuel rail,Crane Adj Fuel Pressure Reg,March Performance Pulley set,Four Wheel Disc Brakes,WS6 Package,Dual Convertor Exhaust,3.42 Gear/w POSI,5Speed Borg Warner Tranny,Center-Force2 Clutch Set-Up,K&N Filter,ported Plenum.

 

formula92, i believe whatever it reads when the ignition is on and vacuum line is connected is the correct pressure. That's what I'm going by.

Email me if you need help bro.
formula@needforboost.com

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'92 Formula
305 TPI
Mods: SLP catback,SLP air foil,ported plenum,Crane AFPR,MSD6AL,homemade cold air,K&Ns,3:73s

 

hook up a fuel preesure gauge, turn the key... whatever it reads is the correct psi.. do this with everything connected(vacuum lines).

 

You can't check it without the car running. The vacuum line has to be disconnected to set the fp. If you just turn the key on the fuel pump only energizes for 2 seconds, and this usually isnt enough time to fill the line and rails with the real pressure. The most accurate way is with the car running and the vacuum line capped off. If people are setting fuel pressure with the line hooked up they are running around with high pressures. The vacuum acts kind of as a pump shot like a holley carb. With throttle tip in it gives more fp and as vacuum decreases under load it gives more pressure. If you have a mild 350 43 psi is a good number. There is an article somewhere(Ill have to look for it ) that shows how to high pressures will destroy the injectors (pressure around 55 and above), its due to the stress put on it while opening and closing.

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87z 383. mini ram tremec 5spd, funny gas, 1,3/4"headers. other stealth goodies.

 

Oh, I meant it will destroy it over an extended time. A few drag passes @ high pressure never hurt a thing.

 

So which is it guys. Is it accurate with the hose on or off? I mean if you plan to be driving with the hose on...then you should test it with the hose on. It only makes sense. I'm right ...right?

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'92 Formula
305 TPI
Mods: SLP catback,SLP air foil,ported plenum,Crane AFPR,MSD6AL,homemade cold air,K&Ns,3:73s

 

87z-ya is correct. The car must be running with the vacuum hose disconnected to check pressure.

Doc is also correct- when you disconnect that hose and adjust the pressure, you are setting it for WOT only...

For example: Let's say you disconnect the hose. Adjust your pressure to 48 psi. Then reconnect the hose. Pressure will drop about 10psi. That's normal. Now go do a WOT pass with your gage hooked up and taped to your windshield.

Your gage should read, at WOT, what it was at idle with the vacuum hose disconnected, which is- 48 PSI!

If it doesn't then you have a problem elsewhere in your fuel system. HTHs.

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1989 IROC-Z, ZZ3 shortblock with some bolt-ons.
13.20 @ 108.69, 2.2 60' on "Road Hugger" radials and dead Auburn posi.

 

When your setting your fp your setting it for WOT, thats why you need to disconnect the hose to simulate this. Try running the car with the hose on then pull on the throttle, now watch the fp climb 6 to 10 psi more, that peek reading is what were trying to change.

To set your fp you need to have your car running and the hose off just like 87Z-ya said. That way your setting for WOT, otherwise you will be running like that guy at 55psi and could be damaging your injectors.

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89 GTA 350 5-speed
(Jet hot coated) SLP headers,flowmaster force 2,no cat's,SLP cold air,MSD 6al,jet chip stage 2,march pulleys,ported plenum,air foil,B&M ripper shifter,180 stat,alston SFC,spohn LCA relocation brackets,MAT relocation kit,free mods.

G-Tech times
0-60 5.3s
E.T. 13.91@104.8MPH (2300ft)

 

doc.....what does your 87 IROC run?

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'87 L98 TPI IROCZ, AFR190 heads, 3.70 gears, ZZ9 cam, 2400 Art Carr TC, SLP 1 3/4" headers, SLP cat-back, no cat, no AC, no MAF screens, Accel manifold base & SuperRam, Edelbrock double roller timing chain, MSD ext coil & distributor, trans cooler, 52mm TB with airfoil, TB coolant bypass, AFPR(48psi), K&N filters, Hotchkis lowering springs, Car-Pro custom chip, Lay Ind. ram air kit, 265/45R16 Kumho V700 tires.
'90 Eagle Talon AWD, no rust thru 9 winters
'99 Camaro SS, red, 6-spd, T-tops, Mcleod clutch, Pro 5.0 shifter, MAF processor, Direct Flow airlid, K&N filter.
313.7Hp & 320.6ft-lbf, 13.55sec @ 105.1mph