Just got the car back on the road just woundering what you guys are running. I'm at 46 right now.

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87 Z28 305 TPI, Auto, LT-1 cam (peanut is history), roller timing set, 2.73, Gutted air boxes, K & N fillters, Dyno Max 3" cat back, 8.8 mm spirals, rapid fires, and 170* Stat.
Old Best 15.414 @ 87.47.

 

I've got mine set at 48 psi.
Darrell
1991 GTA
Canada

 

with the 19#'s it was like 52 psi

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Brandon
"ScreaminDeamin 360"
350 60 over, TRW forged 9.83:1 pistons,Hooker Comp headers, crane cam 216/228 .484/.512, crane 1.6 RR's, ported plenum, home made ram air, 19 lb SVO injectors, crane AFPR, all going through 3 inch mandrel pipe and a flowmaster.
New project-89 IROC
http://users.argolink.net/bvana
http://ScreaminDeamin.cz28.com

 

Though I haven't experimented much, I am very happy with 45 psi. I do have a Thermomaster chip which I understand richens the mixture.

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87 Formula 350 13.94@96.67
98 Z28 1LE 13.15@107.59
1LE Owners Association

 

43#s. You want to be as lean as possible without detonation. Anything above 45psi for a NA stock LB9/L98 is WAY to rich.

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91 Formula
305 TPI 5speed
1LE/G92/WS6

Paxton SN92 polished kit, SLP airfoil, ported/polished plenum, March pulleys, Crane AFPR(43psi),Crane Gold 1.6rrs,MSD coil,MSD6AL,MSD boost-master,Holley 9mm wires,Ac delco R43ts plugs,custom chip,Ford SVO 24# injectors,Bosch O2sensor, Bosch in-line pump(w/stock pump), SLP 1 5/8" headers,SLP catback,short shifter,3:73s w/Auburn posi,170* t-stat,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.

 

Theformula is right. This "cranking up" the fuel pressure on a basically stock engine is one of the best ways to lose power.

The stock GM (and virtually all of the "off-the-shelf" eproms) are far too rich as they are. When I got into eprom burning, I found I had to remove a ton of fuel to get my engine to the be "optimized". I ended up cutting my injector pulse width by almost 25%.

High fuel pressure DOES have benefits, but only if you optimze the eprom to shorten the pulse width so you do not add too much fuel. Personally, I think on a basically stock L98 that 19# injectors are a better match than the 22# injectors. You want less fuel not more.

Also, you don't want to go too high on the fuel pressure or you will shorten the life of your fuel pump and/or injectors.

When it comes to power, always remember the saying "Lean is mean". But, if you enjoy going slower and wasting gas, by all means give your engine more fuel. I swear this increasing fuel pressure on a basically stock engine rumor was started by Ford to make our cars slower.

[This message has been edited by Glenn91L98GTA (edited February 22, 2001).]

 

I believe that its in my sig.


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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(58psi), K&N filters, Hotchkis lowering springs, Car-Pro custom chip, Lay Ind. ram air kit, 265/45R16 Kumho V700 tires.
ET 13.39sec @ 107.21mph
'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, ET 13.55sec @ 105.1mph
next mod: 4.10 rear gears

 

What factors should you consider when you adjust your pressure? I mean, dont just jam it up to 50psi, tune it to your engines specs. What specs should I consider before settin it?

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'83 Firebird 2.8
'89 Firebird Formula 350
2nd owner, red/grey, t-tops, dual cats, and a 3.27:1 rear
K&N, TB bypass, No MAF screens, CAI, full Accel ignition

 

Glenn is right. When I was testing on my stock L98 everytime I bumped up the pressure I would lose about a .1 at the track. Turn it back down and went quicker.

Sparks a flyin'

 

i have my AFPR ready to put on now but soon i also plan on getting headers, underdrive pulleys and removing my AC. taking that into account and the stuff in my signature, what would b the best pressure? i read somewhere that 50 psi was good

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89' Firebird Formula WS6 L98, MSD 6AL MSD Blaster, Hypertech chip, K/N filter cone,flowmaster 80 series, hypertech air foil, koni shocks, edelbrock trailing arms

 

Get a scan tool and note the BLM/INT when you are cruising around. 128/128 is the desired number. Numbers below 128 indicate an overly rich situation and you should reduce. Numbers above 128 indicate a lean condition and you should add.

Ultimately, you should adjust the %Fuel Add when in PE mode. There is not WOT inside the eprom, it is called Power Enrichment.

Always remember, "lean is mean".

 

I run 24# svo's @ 51 psi. I think I'll need to bump the pressure up a hair more because I'm still a hair lean when cold. I had TPIS burn a chip for my combo and told them to trim the fuel curve so I could run higher pressures with larger injectors for better atomization. There was a limit though for a stock motor and the minimum pulse-width @ idle. I'll goto 53 psi tomarrow and see. I don't even 'smell' rich when I cold start-up in 10 degree wheather and have a slight lean pop while cold in open-loop but mpg's are pretty good.

 

52 psi

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We need Perry Mason

 

I have my pressure at 48 psi, but don't rely on what I say, or anybody else for that matter. Everybody pretty much a different setup, and each responds differently to different pressures. 48 works for me, and thats with 22# injectors on a 305. HOWEVER, I have spent several hours "tuning" my engine via computer to make it work successfully. If you don't have PROM burning equipment at your disposal, your eninge will run miserable if you try to duplicate what I did.

Your best bet is to install the AFPR, set it at the stock setting, make some runs, bump it up in 2 psi increments. When you start running slower, you need to go back down. This is where local tracks get the term "test and tune". The local track here has "test and tune" nights on Wednsday. You do some tuning, and then you test it. There is no better way.

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If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors, Whatever chip I feel like burning,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

 

Ok I took the pressure back to 42 psi the car seems to like it a little better. Track opens March 31 I'll find the right setting then.

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87 Z28 305 TPI, Auto, LT-1 cam (peanut is history), roller timing set, 2.73, Gutted air boxes, K & N fillters, Dyno Max 3" cat back, 8.8 mm spirals, rapid fires, and 170* Stat.
Old Best 15.414 @ 87.47.

“Fallen But Not Forgotten”

 

Glen, explain this to me please.
How and from what does the computer get info to show a 128/128 or lower/higher values. Are this numbers coming from the O2 Sensor? If so, this would be wrong because I've heard people saying that a stock O2 sensor is not reliable when it comes to telling the truth about fuel ratio due to the fact that is not a wide band O2 sensor. Can you please clarify this for me?
Rick