LT1 Editor FAQ

( A work in progress )

 

Updated 10/15/001 by Christian Millard ( cmillard@crutchfield.com )

Questions, Comments, or Suggestions ? Email me, feedback is appreciated.

Current home of this FAQ : http://cmillard.freeservers.com/Z28/PCM/FAQ/LT1_Editor_FAQ.htm

 

( Formatting note: I’m writing this on my old Compaq laptop used for programming, so I’m writing in bold RichText for easy Html or PlainText conversion.)

 

I. System Configuration and General Setup (discusses hardware, cables, and OS issues )

To be discussed later, I’m jumping to the tuning tips first, due to demand.

 

II. Initial Settings

  1. What are the first basic setting changes?

A.      Fan turn on settings:

If you’ve changed to a 160 thermostat the factory fan settings up at 225 degrees aren’t ideal anymore.  I personally run 170 and 180 for my fan setting.

B.      Idle speed:

If you’ve changed to a bigger camshaft you may find a higher rpm idle is necessary for the engine to run smoother.  A common setting is 900 rpm, versus the usual 800 rpm for an M6. Idle speed is regulated by the IAC (Idle Air Control) valve and the throttle body stop screw (not usually adjusted.)

C.      Skip Shift (CAGS) disable

For emission purposes the M6 transmission will force shift from 1st to 4th gear. This occurs as low throttle position and low speeds. CAGs can easily be disabled by setting the enable temp to something outrageous like 255F.

    D.  Gear and tire size changes
          Straight forward here, if you’ve changed your gears or overall tire size, change these settings.

    E.  Speed limiter settings
          Don’t want a limiter? – raise the speed to 255 mph

    F.  Rev limiter settings
            The factory rev limiter cuts off fuel at WOT, this causes a lean condition, which could crack pistons on high power setups. Set this values high and get a soft touch rev limiter.

    G.  VATS disable
            Don’t like the factory anti-theft setup, you can disable it here. Also good for street rods, or engine swaps.

    H.  EGR disable
            If you’ve removed the EGR (cams with higher overlap create self-EGR, os the valve is not needed.) You can set the values so the value is never energized.

     I.  Speed density - for street rods without MAF
            Pushing more than 471 gm/s into the motor for an extended period of time?) then you might consider ditching the MAF and running speed density (airflow calculated my the MAP.)

     J.  DTC disable
            Various Diagnostic Trouble Codes can be disabled here, so you don’t see the check engine light.

    K.  Engine size
            The engine displacement is used in lots of calculations, set the value to the true engine size.

    L.  Injector size
            Something important to realize is that injectors are rated at different pressures by the manufacturers.

GM Multecs are rated at 43.5 psi (3 bar = 3 atmospheres)
            Bosch/ SVOs are rated at 39 psi (other Bosch may vary)

Lucas injectors are rated at 37.5 psi (may vary with application as well)/


            To calculate the new injector constant use this formula:

RatingNew = (sqrt (PressureNew/ PressureOld)) * RatingOld

 

So say we put 30# Ford SVO injectors (rated at 39 psi) in a LT1 (which uses 43.5 as a pressure.)

RatingNew = (sqrt ( 43.5 psi/ 39 psi)) * 30#

RatingNew = (sqrt 1.115 ) * 30#

RatingNew = 1.056 * 30#

RatingNew = 31.683 #

 

This same formula can be used if an adjustable fuel pressure regulator is being used to increase fuel pressure (which shouldn’t be necessary having LT1Editor.)

 

    M.  Knock retard settings
            The tables involved here are:

            Max Retard vs RPM- This the table most people lower to prevent excess timing from being pulled

    N.  Closed Loop engagement settings

 

III.  Sensors (are your friend)

  1.  What sensors and solenoids affect our tuning?

       Note: Sensors - input for the PCM. Solenoids, Motors - controlled by the PCM

    A.  IAT sensor

    B.  MAF  sensor

    C.  MAP  sensor

    E.  IAC solenoid

    F.  TPS sensor

    G.  CCP solenoid

    H.  EGR solenoid

    I.   O2 sensors

    J.  Air Pump motor

    K.  Crankshaft angle sensor

    L.  Coolant sensor

    M.  VSS sensor

    N,  Oil level sensor

    O.  Knock sensor

    P.  CAGS solenoid

    Q.  Reverse Lockout

    R.  Fuel Injectors

 

IV.  Menus and Tables

    A.  Engine

      1. Idle Speed

      2. Idle Air Control

      3.  IAC follower vs. Mph

      4.  Cylinder Balance

      5.  EGR on/off

      6.  DTC enable/disable

      7.  DTC 32 test parameters

 

    B.  Fuel

      1.  Open Loop temp vs. Load

      2.  Injector Offset vs. Load

      3.  IAT scaling

      4.  Power Enrichment Temp

      5.  Power Enrichment Rpm

      6.  MAF calibrate

      7.  WOT table

      8.  Closed Loop enable temp

      9.  Volumetric Efficiency

        a.  0 - 340 RPM

        b.  400 - 2000 RPM

        c.  2000 - 7000 RPM

      10. Cylinder size

      11.  Injector size

 

    C.  Ignition

      1.  Load vs Advance

        a.  RPM 400 - 4000

        b.  RPM 4000 - 7000

        c.  Load Offset

      2.  Temp vs Advance

        a.  Load vs Temp

        b.  Cranking Advance

        c.  Offset

      3.  Closed throttle spark advance

      4.  Minimum spark advance

      5.  Minimum spark advance offset

      6.  Max Retard RPM

      7.  Max Retard MAP

      8.  Knock Retard

        a. Attack vs RPM

        b. Decay vs RPM

        c. Minimum coolant temp degree C

      9.  Burst Knock

        a.  Enable Temp

        b.  Lo Octane Retard

        c.  Knock Count to Enable

      10.  Traction Control Retard

     

    D.  M6 Transmission (out of time – start here)

    E.  A4 Transmission

    F.  Checksums

    G.  Gear/ Tire

    H.  Chassis

 

V.   Engine operation

    A.  Air to Fuel relationship

    B.  Timing (spark advance)

 

VI.  Event Tuning

    A.  Cranking

    B.  Idle tuning

    C.  Cruise timing

    D.  Wide Open Throttle tuning

 

VII.  Data Loggers
    A.  PcmComm

B.      B.      Datamaster

C.      C.      FreeScan

 

VIII.  WWW resources

 

IX.  Suggested Reading