Custom Tuning
Step 2

by Michael Decipha Ponthieux
Last Updated: 2022-03-02

This page ONLY applies to those whom were directed here AFTER receiving a custom tune from me and have FULLY completed step 1.

Throttle Stop Adjustment

Before writing the updated tune or turning the ignition key on adjust the throttle stop screw if you have been instructed to.
As always begin recording the log BEFORE starting the engine. Let the engine idle without pressing the throttle until the engine reaches warm operating temperature. DO NOT TOUCH THE THROTTLE DURING THIS TIME. Once the engine reaches stable operating temperature and has been idling for at least 10 minutes proceed with the following.

Idle in Drive for Automatic Electronic Controlled Transmissions (94+ only)

If you have a 94+ ecu with an electronically controlled automatic transmission or if I've written custom code to differentiate drive and park; Stop the and save the log. Shut the engine off and wait approx. 20 seconds then restart the engine. Immediately put the vehicle in drive while holding the brake. Include a 5 minute datalog of it idling in gear. Do not move the vehicle or take your foot off the brake. We need this to dial in the isc drive multiplier (airflow in gear) and if the vehicle moves the air correction cannot be calculated.

Once this is completed (If applicable) proceed as follows.

WOT Fuel, Spark and Load Scaling

After the throttle stop has been adjusted (if needed) now write your revised tune to the quarterhorse. After the tune has successfully written turn the ignition key on and start recording the log BEFORE you crank the engine. Let the engine idle with no throttle input until it reaches hot operating temperature. DO NOT TOUCH THE THROTTLE AT ANY POINT.

Once the engine has reach operating temperature continue on as described below.
At this point, the engine should now be at its normal operating temperature and likely has been idling for at least 10-15 minutes.
Remember, the engine has to reach fully warmed up stable idle (non surging) before dialing in fuel otherwise the datalog is going to be useless.

Now is the time to go for a WOT run, get on the interstate or some other straight highway thats safe to beat on the vehicle with no police, traffic, or wildlife around.
You will need a co-pilot to hawk-eye watch the wideband gauge during the WOT pull. Not only does your co-pilot need to be able to recall the AFRs from the gauge through-out the pull but if the wideband reports a lambda leaner than 0.85 (12.5 AFR) for boosted vehicles or 0.95 (13.9 AFR) for naturally aspirated vehicles they need to inform you to abort the pull and end it early.
After I review the logs, I'll post back with a revision so we can proceed.

Understanding Step 2 Changes
After getting the fuel close I return some values back to a sane value.
Hego Min SwitchesI usually set it between 3 to 8 switches dependent on how well the hegos respond.
BYPLESI drop it back down to 15 sec or so depending on how the hegos respond.

Return to Step 1
Continue to Step 3- Fine Tuning

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