Density Tuning using Wideband O2 Input by William Henn,
Application: GM V8 based vehicles
Hopefully you’ve already worked out your idle & set your ifr
table. If not start there & come back to this when that’s
If you are running a 1999 or 2000 operating system, you should
consider upgrading to a 2001 or later operating system or splurge
for the 1 bar speed density license, as they will really simplify
the process in the end. If you’re unfortunate enough to own a 1998
operating system at this time, my sincere condolences. You’ll still
be able to do SD tuning but you have no way to update to a later
operating system without major work involving a PCM swap and major
First things first…determine what the car is going to be used for
mainly. This tuning guide is for semi mild setups as in the end we
will be putting the car back in closed loop. If you plan on having
a complete racecar that rarely or never sees the street an open
loop speed density tune might be the answer. I’ll get to that in my
next write-up since there are a few differences in how things will
- Open the HPT Scanner.
- Open the Table portion to set up
- The default config is a good
starting point, from there just add:
Wideband Input ie LM1, LC1, PLX, etc…
Air Fuel Ratio Commanded Hi Resolution
Just keep in mind that the more PIDs you have the less frames per
second of data it will gather so make sure you keep it under 24
- Save the PID file as SD tuning.cfg
by clicking on the Save Config file button
It should look something like this
- Read your PCM & Save as
- Open the saved file with the
- Open both Primary & Secondary VE
Tables if applicable and multiply these tables by 1.15…this is just
to add extra fuel in so you run safer while in SD mode.
It should look like this
- Under Fuel Cutoff/DFCO set DFCO
enable normal to 284°F this is so deceleration fueling wont effect
the tuning process. Under normal conditions the computer leans out
the a/f mixture when you let off the gas which can skew the numbers
you gather for tuning your VE table.
It should look like this
- Under Power Enrichment set the EQ
ratio vs. RPM to your desired a/f across the board. This will keep
your engine safe & make for one less step once you go back into
It should look like this
- Under Fuel Control-Open & Closed
loop open “Open Loop EQ Ratio” and set it to 1.00 all the way
across. This will set all cells to a 14.7:1 air fuel ratio.
- Next set Short Term Fuel Trims &
Long Term Fuel Trims to Disabled or set their limits
- Then set All Closed Loop Enable Temp
cells to 284°F this will ensure you go into open loop.
- Under COT, Lean Cruise set COT to
Disabled. This is mainly to simplify the fuel tuning…the less
adders & multipliers involved the better.
Caution: This can damage catalytic converters if you still have
them on your car.
- Under Spark control open both your
high & low octane tables then copy you’re your high octane
table to the low octane table using the copy & paste
buttons…this because once in SD mode it falls to the low octane
- Set MAF fail frequency to 0.
The PCM will detect a MAF fault as soon as you key on and thus
revert to speed density mode.
The PCM requires a MAF DTC to be set to revert into speed density
mode. If you set all of your MAF DTCs (101, 102, 103) to no error
reported the PCM will not revert to speed density.
The factory settings will work but if you are concerned about an
SES light, set the DTC's to No MIL Light. The PCM will still set
the code for a MAF fault and thus still revert to speed
- Pop the hood and unplug the MAF
sensor. This step is a precautionary step to make certain that your
vehicle does not use the MAF sensor to calculate fueling while
tuning in speed density. It is not required on all vehicles.
Note: If your MAF has a 5-pin plug, your IAT sensor is built into
You will need to make provisions to get the IAT signal into the
Various write-up’s on this can be found at www.ls1tech.com
- Save this tune as SDStarter1.hpt and
perform a calibration only reflash of this file into your PCM.
- Prepare your wideband for use with
the usual preheating procedure.
- Start the engine and let it come up
to full operating temperature.
- While the engine is warming up,
start the HPT Scanner, connect to the vehicle and start monitoring
your data (do not log at this time).
- Once the engine is warm (160 °F or
higher), start your drive and start Data logging. Your driving
style should be very calm. Avoid sudden throttle changes. The
smoother you can make your driving style while covering as much of
the histogram as you can, the better your results will be.
- It helps to have a passenger viewing
the AFR Error Histogram while it is displaying the cell count. You
want to hit as many cells as you can, as many times as you can. Try
to get a cell count of 50+ per cell.
- After you have finished logging
data, save the log file as SDtune1.hpl
- Start the HPT Editor & open
- Start the HPT Scanner & open and
- Open your pre-configured AFR error %
histogram & set cell his required to 50, click average &
load all data.
- Next highlight & copy all
- Switch to the SDStarter1.hpt file
& open your main & secondary VE tables & paste
special-multiply by % to the main & hand blend the surrounding
unaffected cells. Then copy each line to the secondary.
- Now Save your tune as: SDtune1.hpt
& perform a calibration only reflash to the PCM
- If necessary repeat the until the
average cell values in your AFR error map(s) are close to 0 (aim
for +/- 1%).
- At this point if you have completely
removed your MAF & have made the decision to never use it again
you are done and can go about your way. If you are going to put
your MAF back on keep reading.
- To re-enable the MAF simply plug it
back in (if you previously unplugged it) and set your MAF Fail
requency back to its original value and write it to the
- Load the MAF - AFR Error.hst
- Make sure you log MAF in Hz in the
table and go for a drive.
- Hit as many of the higher frequency
cells as possible as many times as possible
- Copy & paste special-multiply %
to your MAF airflow vs. frequency table & smooth
- Save & load new calibration
- Repeat if necessary
- Again the cells in the histogram
should get closer & closer to 0% indicating 0% difference
between actual AFR and commanded AFR.
- Open your Stock file
- Copy & paste your new, verified,
VE primary & secondary, PE, & MAF tables in.
- Save & load the new file
- Start the HPT Scanner and open the
default config file also scan for the w/b & commanded a/f
- Start your engine and the Scan Tool
and go for a drive
- Monitor Commanded AFR and WBO2 AF,
they should be extremely close.
- Long-term fuel trims should
eventually settle in the range –4 to 0
- You should also look over &
evaluate your injector duty cycle…if your running over 90% you
might want to consider stepping up in injector size.
- After all this you’re ready to start
with Spark tuning
Thanks To All That Helped Put This Together