Ok, last night I set the fuel pressure at 52 (hose on) and went to bed. Woke up this morning and checked it on my digital gauges and it read "37". I was like WTF. Disconnected the Vacuum hose and it still read "37". TPIS recommended running between 49-60psi and I'm in that range.

Anyway, I connected it to a analog gauge and it read 56psi. I disconnected the vacuum hose and it still read 56psi. What went wrong? I have a crane AFPR and it's only a week old.

thanks



[This message has been edited by theformula (edited October 22, 2000).]

 

Jesus H Christ thats alot of PSI for you. I would recomend 46PSI with vacume tube unplugged

 

Dude trust me. TPIS recommends anywhere from 40-60psi on stock engines speed density.

I have an air/fuel ratio gauge and it was showing lean. The car was also sputtering at high RPMs. Raised the pressure to 59 with the hose off at Englishtown and the car was so much more responsive. Faster also. Sputtering went away. Car is running a little on the rich side (what you want ).

 

Uhh..don't drive next to me..I think your fuel pump may explode..since when does TPiS suggest up to 60?? They told me don't go above 52 or all kinds of crap will go wrong..they said 47-49 should hit the spot.

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-Red '88 IROC 5 Speed TPI
-Dual Friction Centerforce Clutch
-Accel 300+ Racing Ignition
-Accel 300+ Pro Sleeve Plug Wires
-Accel U-Grove Plugs
-Flowmaster Force II 3 Chamber Cat Back Exhaust
-Hypertech Chip
-Hypertech Airfoil
-Removed MAF Screens
-Gutted Air Box
-Best E/T 14.90, 60 ft. 2.17, 1/8th mile 9.61(bald tires, SES light on)
-Best MPH 92.7(bald tires)

 

i think it depends on how modded your car is. I am running 50PSI, and am only getting about 860mV on my O2 readings. But who knows? Maybe it does mean i need a bigger fuel pump. formula, are you running the stock pump? Also, are you questioning the difference in readings from your analog gauge to your digital one? Cuz i just installed an analog autometer gauge, but with the electronic sender. I am reading a consistent 10PSI lower than my analog gauge hooked up at the schraeder valve. Has anyone else had any probs like these? Also, and most importantly, what are your O2 readings, formula?

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1989 IROC-Z 5.7L

 

Omar, what brand/type gauge are you using? I am using the Intellitronix air fuel ratio and FP guage. Yarnboy, a friend of mine told me TPIS recommended anywhere from 40-60 on SPEED DENSITY systems. I also called a tech personally yesterday afternoon and asked him if 59psi can do damage on my stock parts. He said absolutely not. Call them for yourself.

Omar,i have not had a volt connected yet. Hopefully I'm around 850@wot. we'll see.

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'92 Formula
305 TPI
Mods: SLP catback,SLP air foil,ported plenum,Crane AFPR (49psi),MSD6AL,homemade cold air,K&Ns,3:73s,JET fan switch...SLP 1 5/8ths are coming...oh yes

 

i know some very experienced tuners who set up TPI's ..they tell me the stock injectors 22lbrs in a 350,flow less at higher pressures because the higher pressures impede the opening of injector.

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87GTA,350,Auto,MAF screens removed,195 thermostat,cold start injector UNPLUGED,K&N,modified air intake,ADSchip,3:70s,3inch cat back Flowmaster single outlet,TPS.54,Bosch Plat plugs,base timing 6BTDC,22 MPG and runs like a bear,Bilstiens in the rear....,don't let yer meat loaf

 

I have TPIS Insiders hint and it WAS NOT 60 psi. Around 50 max as the other are saying.

But, as performance goes, every car is different. My best performance for my L98 (mildly modded) was 44 psi. At 50 psi, I had GREAT THROTTLE response, but my top end performance suffered. I lost almost 1 full second in the 1/4. At 60 psi, my engine would be far too rich and my performance would suffer even more. Remember, lean is mean when it comes to power.

If you NEED 60 psi, I would suggest that you probably need bigger injectors.

[This message has been edited by Glenn91L98GTA (edited October 26, 2000).]

 

Thanks for all the replies guys. Can anyone give me any hints to fine tune so I can increase low end and top end? Rather than increasing one and watching the other decrease? I find it difficult to tune. I'm ordering a GTECH pro to further assist me :b

[This message has been edited by theformula (edited October 27, 2000).]

 

Unfortunately, you can't get both. When I ran higher fuel pressure (50 psi), my throttle response was great along with better fuel economy and lower emissions.

When I played with it and optimized it for the best e.t.'s, I sacrificed some part throttle response, fuel economy and emissions. The closest tool I found to get the best performance was using a scan tool to monitor the O2 readings. Roughly 900mV O2 readings @ WOT seemed to give the best performance.

Using your GTech will allow you to find the fuel pressure that gives your the best performance, but you need to do a full 1/4. I found the fuel pressure differences were most noticeable in the last half.