topher01

hey yall need some help tuning my new build. I have a 98 vortec 350. enigne ha flap top pistons, zz4 cam, ls7 lifters, 1.5 rockers, ported and polished heads with over sized valves, edlebroke performer intake port matched, 1" carb spacer, ported polished tbi unit running stock 350 injectors, hooker shortie comp headers, dougs 2 1/2" y pipe to 3" mandrel bent piping to hooker aerochamber muffler. t56 trans and stock open diff rear end with 273 gears for now. heres my situation, ive been playing with the tune on the ve tables for a while now im on bin 125. i started off with a tpi pump with the fuel regulated down to around 35 psi on a vafpr. i was running rich all over it would load up when its cold and stall out. so i swapped back to stock tbi pump and regulated it to 20 psi. it runs good except when i move from a stop it leans out to around 18:1 on up. also when i stab the throttle to the floor from a roll i lean out and pop in the exhaust. please help!! im also tunning with a wide band o2. thanks for the help!!!!

RBob

iTrader: (1)

First thing to do is to verify that the fuel pressure holds under load. A stock TBI pump barely makes 20 psi so this could be an issue. For a quick test, on a warm engine glue your eyeball to the fuel pressure gauge.

Then whack the throttle wide open for a moment, don't over rev the engine.

At that time the fuel pressure should hold steady, not even a half a psi drop in pressure. If it drops, time to update the pump and/or fuel filter.

Strange that the TPI pump pushed too much fuel. They should not be doing that, was the VRFPR plumbed into the return line? Between the TBI unit and gas tank?

Once the fuel delivery is OK, set up the BPC vs VAC table in the BIN. Use the EBL Utility to create the values, then copy & paste into the BIN.

From there try some VE Learns and see how the tuning goes. Don't worry about throttle stomps quite yet. Get the vehicle drive-able and the odds & ends squared away first.

Note that the EBL will control the reverse lockout solenoid in your T56. It is the TCC output, pin A7.

RBob.

topher01

The vrfpr is in the return line between the tbi unit and tank. I'll test the fuel pressure see if it falls away. In tip in from a stop it leans out and almost stalls. Other than the hard accelerations and tip in the car runs great. I'm pretty frustrated with this situation. I'm half tempted to put a carb on her and run it. I'll play with it a bit more tell I go that route.

RBob

iTrader: (1)

Get the fuel delivery squared away and you won't be thinking of a carb again.

RBob.

topher01

so i got the fuel pressure around 35, car runs ok did about 20 ve learns. enigne sounds good kinda bogs when I step on the thorrtle just after shifting. i will try to upload screen shot of my current ve table.

topher01

heres my current bin im running on bin 145. my ve table is all over the place not sure what else to do other than keep doing ve learns. i try to smooth out the ramp of the peaks. seems to make the car run worse if i try and smooth out the map. please help! thanks!

RBob

iTrader: (1)

OK, I see some things in the BIN that should be changed. With the Vortec heads need to use different SA tables for the Main & Extended SA. Actually the extended table is OK, copy this table over from the _3000 BIN:

SA - Main Table

With the ZZ4 cam the idle should be higher, highlight this entire table and add 100 RPM to it:

IAC - Idle Speed: Drive

No need to do the park table as it is a stick shift. Always in drive.

For the bog after shifting, too much AE. Take the difference between the stock injector flow and the flow at 35 psi and we get: 61 / 100 = .61

Multiply all entries in these two tables by .61:

AE - MAP PW
AE - TPS PW

That will rough in the AE with the result being better after the shifts and on tip-in. Need to do the same with the proportional gains, this table:

PRP - Gain vs O2 Error

Then follow up with more VE Learns. You may start to run into issues with small injector PW's. If it keeps switching between sync and async injection, causing bucking or surging, zero out this table:

INJ - ASync Transition PW - TBI Only

The injector compensations may need to be increased due to the higher fuel pressure. But it would be better to see how it is first.

RBob.

DynoDave43

iTrader: (11)

I have SO much to learn.

robertfrank

iTrader: (27)

Listen to Rbob, Chris.....he is da masta!!! Lol

topher01

made the changes you talked about, car is running so much better now only thing i have now that isnt a noticable thing as far as driveablity. but when im going down hill with my foot on the throttle i let up on the throttle a little when i catch up to traffic. and the wide band shows 15.8 to 16.2 on the afr. is this something to worry about or normal?? i know when you let off the throttle complety you get dfco not sure if it happens when you have low load on the engine? thanks again!! here is a copy of my current bin

RBob

iTrader: (1)

If it isn't surging or attempting to stall you should be able to let it go. If you are lifting enough the ECM will revert to open loop decel. Can see that in a log file (closed loop and BLM lrn off).

You can un-check the open loop decel flag (Option Word 3 - Bit 5 - OpDcl) and VE Learns will then take place in those areas. However, closed loop prop gains can cause surging. If so then go back to open loop decel.

The VE Learn can also make those areas too lean, at which time go back to open loop decel along with adding some VE back into those areas.

RBob.

topher01

awesome thanks rbob!! so continue to do ve learns tell it runs good? how bout wot was told that with a wind band i can tune wot with ve learns.

topher01

hey rbob so something new is happening with the car. i drove it to work today about 10 miles mostly down hill. it drive great very happy with the way it was driving. well took it to lunch and then drove it home. every time i came to stop light or stop sign the car would stall out. it would crack and wouldnt start unless i played with the throttle. did a ve learn to work uploaded that bin into the ecm. did a ve learn home and now its stalling every time i stop. if i play with the throttle it will stay running tell i stop playing with the throttle. any ideas what might be happening??? thanks in advance!!

RBob

iTrader: (1)

Need to look at the data log of it occurring. Look at the SA, IAC steps, injector PW, whether sync or async, and so on.

It may also be just a bad IAC.

One thing to do is to check the IAC steps at a warm idle with no other loads (fan, A/C, off...). It needs to be between 5 & 10 steps. Adjust this via the idle stop screw.

RBob.

topher01

i didnt data log that drive unfortunatly. i did data log the previous drive tho and my iac steps are at 45-50 at idle with the electric fan running ill data log it again with same bin see how it goest thanks rbob

topher01

ok so after looking over everthing on the motor, found that vacuum hose to brake booster brand new had cracked and was leaking bad, distrubtor was loose and moving as it wanted to, inline fuel filter was full of rust. after fixing those issues car runs good again. still have a little lean issue on first tip in from a stop. i have to rev the engine up to around 1500 and slowly let the clutch out and it doesnt bog. if i dont it leans to about 15.6-15.8:1 then clears up and runs normally. check my iac steps it was at 85-90 at idle. adjsuted the idle stop screw and its around 10-12 now. thanks for the rbob

RBob

iTrader: (1)

There are several ways to tackle the 'going lean' when trying to pull out. Can try adding a little to the low area of the AE - TPS PW table. And/or, add a little to the IAC opening value (AE - IAC Opening Fuel).

Those changes may or may not work, what can also be done is to hide AE in the VE table. To do this need to look at what area of VE is used (RPM & MAP) while pulling out from a stop. Then add to it in that general area.

This works as the engine doesn't stay in that area for long. It is only used to transition from idle to a moving state.

RBob.