92 Camaro 730 w/healthy 350

[Dave Zug]

The Iroc at E-town was running MAF, but was sprayed with a dry 70 shot. It ran a 12.44 that day, and a 12.16 later at another track. It has a 383 too. Yea the time does not reflect a sprayed 383 but the setup is very mild and there are lotsa weak drivetrain parts still on it.

I have a MAP conversion on the car now. I'm at the stage where yes I am seeing that the VE must drop compared to the stock 350 A4 cal, but only a bit (less VE at idle and less VE by about 9 decimal at 100Kpa between 3000 and max rpm) since I dialed the engine size and injector const in given the fuel pressure I run (41).  your cam will raise your idle MAP reading to the area where the stock TPI starts to want lil extra fuel. This will make the thing idle rich.

Bruce wrote tuning tips that are definetly the place to start. tuning 101. 

Reading your description, if the o2 falls that low I would check the fuel pump and pressure first, make sure it is not dropping off.  Hopefully you are not using the old version of winbin, it had a problem with calculating the injector constant correctly. It is fixed now I understand and has other enhancements I think I read a while ago. probably with your mods, the motor wants alot of fuel later in the RPM band compared to the stock TPI (torque curve moved up with the cam mods) and you need to maybe put a hump in the PE v/s RPM table. look at the scan results and increase the PE adder right where the RPM is when the o2 drops, and keep increasing the later entries until the RPM where the 02 comes back. Its hard to do this without driving the car and seeing the results ;-)

make sure ignition is good (I'm sure you have, tuning buicks for the number of years you have)

First start with a stock a4 (if you have an a4) 350 cal. set the injector constant considering any fuel pressure changes and the pressure at which the new injectors are rated. get it to idle with IAC counts at 10-20, not 80. the cam will raise the idle MAP reading, I shifted my VE lower table values rightward (move the lower map values into the next higher cell) so it wasn't so fat at idle and it worked well to stop the hunting and near stalling. With cam mods you will see your torque peak higher, therefore the fuel "hump" in the ve table in a stock cal will be in too low a rpm range, it needs moved upward in RPM. 

The VE is more accurate if you get the injector const right and the AFR desired is not set wierd to manually compensate ahed of time.  in other words, you should not go straight to adjusting VE entries in a pig rich or lean car cause you may end up with 40's at WOT before the thing runs well, and you KNOW the engine is more efficient than that. make sure the engine size and injector const is right first, tunetips recommends attacking idle, then cruise first (BLM's), then WOT. If in the coarse of tuning cruise ranges, you discover that you have to make massive changes in VE, you probably will be changing the rest of the VE stuff radically as well... depends on the combo. (and I *only* have actual experience with a 350NA, 350SC, and 350NOS using MAF, and part of a 350NA MAP (so grain-o-salt)

the up down changing of the VE entries will move the o2 sensor readings up and down DRAMATICALLY ONLY when the o2 is near stoich. (because the sensor is so not linear).. at 1000 mv, a change of 10 may move the WOT reading to 0.970's, but another change of 10 may put it at 0.800's. just gotta change it some, then 'feel the force' to guess how much to change it next time. It might take a pro 3 attempts to nail 0.870's and an amateur 15 tries. not too bad, and a bit fun!

VE is the "shape" of the motor's efficiency, PE is the adition of fuel when more serious levels of power are requested. If you did cam changes, intake mods, exhaust mods, head work then the shape isnt going to follow a stock 350, and you should work in VE. If the motor is a stock almost 350 with maybe only intake/exh mods, you *can* work directly in PE to make the WOT o2 sensor reading flat and near 0.880v during a run. (then raise or lower it until you get the best E.T. cause the stock o2 isnt that acurate) I think bruce said something similar plenty of times, Tune for power and E.T, (or economy if thats your gig) not for knock fringe and o2 millivolts.

geeze I wrote a book. SNIP when replying I think.

  ----- Original Message ----- 
  From: JTesta1966 at aol.com 
  To: gmecm at diy-efi.org 
  Sent: Thursday, January 18, 2001 5:29 AM
  Subject: 92 Camaro 730 w/healthy 350


  Looking for tips/suggestions on where to start with fuel mods in this puppy. 
  A friend of mine owns the car and converted from a stock 305 to a pretty 
  healthy 350,,cam, edelbrock heads etc. Had a bucking ~35-3600 RPM which when 
  viewed on a scanner shows REAL lean (like .019mV) so I'm pretty sure the 
  problem is arising when touching PE but not WOT (car runs well at WOT, but 
  I'm sure theres more to be had). My question is kinda along the lines of 
  having a 350 program would it be more productive to work in the VE tables, or 
  PE tables? If I understand right, the VE tables (high and low) are similar in 
  effect to MAF tables on a MAF car. Only thing is the cal he has now, the VE 
  tables approach 85% in some areas and I cant imaging the car is much more 
  efficiient than that. Does each up/down value have as dramatic effect as it 
  seems? 

  Are there any bins of note on the FTP site so I can look and see how 
  different people approach modified airflow situations? Or does anyone have 
  experience they'd like to share? Dave Zug? I remember you having a healthy 
  camaro at etown last season...care to share the wealth of knowledge? 

  ================================================ 
  Jim (FA) Testa                                 Type86 on buick.fiendish.net 
  ASE Cert Master Tech                                 jtesta1966 at aol.com 
  L1 Adv Engine Performance                     http://www.turbojim.com 
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