Custom Tuning
Step 1 of 3

by Michael Decipha Ponthieux
Last Updated: 2020-10-14

This page ONLY applies to those whom were directed here AFTER receiving a custom tune from me.

DO NOT, continue reading this page until AFTER you have read over and verified the Pre-Tune Information and Initial Tune Instructions

If you have a quarterhorse you must use TunerPro RT. If you don't have it setup yet the Getting Started Write Up will give you all the details.

Subscribe to your Tune Progress Thread

Your tune progress thread is private, only premium members have access to the tune repository section of the forum. Be sure to subscribe to your Private Tune Progress Thread so you will receive an instant email notification when a reply (updated tune) has been posted to your thread. This can be done by scrolling down to the bottom of your thread and clicking on "Subscribe Topic". Your registered email will be notified when a reply has posted. If you would like text messages sent to your mobile phone, go to the User Control Panel and change your registered email address to your mobile phone's text message address. CLICK HERE if you do not know your mobile phone carrier's default text messaging email address.

Load Tune & Verify Tune Loaded Correctly

First and foremost load in your startup tune before doing anything.
Make sure you ALWAYS VERIFY that your tune is for you, the first letter will be the initial of your first name.
For example: MPON_191014a.bin. ----> M for Michael PON for Ponthieux, _YYMMDD and the revision for that day a,b,c,d,e,f,etc...
When receiving your tune verify it is for you. If the tune is not for you then DO NOT LOAD IT.

If using an SCT handheld then CLICK HERE for the SCT Information link with specifics on getting the SCT device and livelink configured correctly.

EEC-IV

Once you have your tune loaded and turn the key on you will hear the fuel pump prime and shut off.
IF THE FUEL PUMP DOES NOT SHUT OFF THEN THE TUNE IS CORRUPT, DO NOT TRY TO START THE ENGINE.
Then set the base fuel pressure to either what we discussed (typically 55psi if you have less than 60lb injectors).
Next verify the ignition timing is at 10 degrees btdc with the spout plug removed. This is VERY IMPORTANT otherwise you risk damaging the engine.
EEC-V
For EEC-Vs that have been converted from returnless to return style, the fuel pump may run constantly with the key on unless I have written custom code and remapped an unused output pin to control the fuel pump correctly. In all cases, verify the ecu is communicating correctly by starting the log with the key on / engine off and pumping the throttle a few times to verify the dashboard gauge shows throttle movement before starting the vehicle.

When you load the tune in and fire up the engine for the first time on the startup tune it most likely WILL NOT BE HAPPY. You will need to do EVERYTHING you can to baby the engine and keep it running until it gets in to closed loop and corrects fueling.

Don't worry about how the engine starts cold or idles since it cannot be adjusted until after the warm engine fueling and idle is dialed in. Cold enrichment compensation and startup compensation can ONLY be adjusted AFTER the base fuel, idle spark, throttle stop and idle air has been dialed in correctly.
If the engine doesn't fire up on the first crank, repeat a 2nd time, if it doesn't fire up on the second crank, then HOLD THE THROTTLE TO FLOOR == WOT to enable flood-clear mode. On all factory ecu's this will shut off the injectors during cranking. The ecu is pre-programmed to disable the injectors when the pedal is held at WOT during cranking to clear out and engine flood.

Note that flooding the engine out with excessive cranking can wash down the rings and destroy an engine. Although all decipha tunes incorporate excessive cranking fail-safes to prevent this occurrence it is not practical to do excessive cranking. If you cannot get the engine to fire off post the log for review and a revised startup tune.

DO NOT do any of the following with your startup tune:

Verify its not overly rich

If you have a wideband watch the gauge and make sure it is LEANER than 0.82 lambda after the engine has been running for at least 2 minutes, if you don't have a gauge then pay attention to the hegos. IEGO1 voltage should be reading less than 0.800 volts after the engine has been running for at least 2 minutes. If the hego voltage is stuck above 0.400 volts and is not switching (jumping above and below 0.400 volts) then the engine is rich. Shut the engine off and post the log to your private thread for review and an updated tune.

Note: If you feel up to it, you can reduce the maf flow at 400 imaf counts on down by multiplying the flow by 0.85 this will remove 15% fuel and expedite the process. As always, whenever you have EDITED your tune be sure to post your modified tune along with the datalog you created using it.

Don't be worried if the wideband reads lean at idle. Its safer to be leaner than richer below half throttle. Ideally we want it at 1.000 lambda but if it idles at 1.23 lambda thats perfectly fine as well and will not cause any harm so do not be alarmed. A lean mix can only harm the engine when your at or greater than half throttle. Below half throttle being lean is perfectly fine and cannot hurt anything.

WARNING: The check engine light should not be on while tuning! If the check engine light comes on at any time while the engine is running then SHUT THE ENGINE OFF IMMEDIATELY and pull codes. The check engine light will only be illuminated on a tuned engine when the ecu has detected a MAJOR PROBLEM that could potentially cause catastrophic engine damage. If the check engine light comes on at any time while the engine is running immediately shut the engine off and pull codes.

Note: The CEL will be on at key-on while the engine is not running and will turn off during cranking as-is normal operation signifying the ecu is powered up and the engine is not running.


Once the engine gets up to warm operating temperature it should go into closed loop and adjust fueling.
If for any reason it doesn't you may need to rev the throttle a few times in order to get the hegos to switch and allow closed loop.

The OL/CL indicator on the dash will inform you when you are in open or closed loop. You can also easily tell if your in closed loop by LAMBSE jump up and down increasing and decreasing its value.
if LAMBSE stays at a single locked value then you are in open loop.

Warm Stable Idle

Once the engine reaches a operating temperature approximately 15 minutes of running, let it idle on its own (if it can). If the engine is capable of idling on its own let it idle for at least 75 seconds with the engine at a stable warm idle with no throttle input.

During this time I highly recommend checking for any coolant, oil, powersteering, or any other leaks underneath the vehicle. Pop the hood and make sure nothing has come loose. Give everything a good double over as you will need to drive it. Double check the brakes and lug nuts are intact and that the brake fluid reservoir isn't empty. Continue to
LEAVE the datalog recording and proceed to do 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.
Remember, the engine has to reach a warm stable idle (not surging) before dialing in fuel otherwise the datalog is useless.


If the vehicle has been sitting a while or if you hadn't put fresh fuel in the tank recently then now is the time to do so. Your first trip should be to the gas station to fill up with fresh premium fuel (low grade fuel can only be used if discussed and the tune is setup for it). Now that you have fresh fuel drive to a nearby patch of road you and your comrades use for testing and tuning. Most of you will know what im talkin' bout! Go ahead and cruise on out there to perform the step 2 log. If you don't have an area you play around in you can drive on the highway where you have a straight patch that you can safely do some testing.

Logging for Fuel Errors

Half Throttle / 0 vac / 0 boost PERLOAD

After completing the above imaf or mapope increments you will need to do an idle to shift rpm HALF throttle pull for PERLOAD calculations. If you have a boosted setup its imperative that you try to maintain 0 vac and 0 boost as closely as you can through-out the rpm range.

NOTE THAT THIS IS NOT A WOT PULL. DO NOT EXCEED HALF THROTTLE FOR ANY REASON.
With the engine idling on the road pointing in the direction you plan on going quickly HOLD half throttle until you get to your shift rpm (6k or so). Let the vehicle coast back down to speed in order to pull over safely to stop and save the log.
Post the logs in your Private Tune Progress Thread.

After I review the datalogs I'll post back with an updated revised tune with specific instructions to proceed.

If you have any issues along the way don't hesitate to shoot me a text or buzz my tele at: five zero four six zero six zero five three two

DO NOT Continue to Step 2 until you are specifically instructed to do so.


Understanding the Step 1 Changes - FYI
I usually start all my custom tunes from my base tunes, I then typically apply the following changes for starters.
Base Fuel TableI null ==1.000 so interpolated lambses don't skew my corrections
WOT Multiplierassign all 1500+ rpm to wot lambda (just in case someone goes WOT its not commanding lean)
FN320AI max it out so open loop is forced only by tprel while i dial it in since fn035 won't be dialed in yet
WOT BreakpointI kick it up along with the OL breakpoint scalar so i can see how the fuel trims up top
Hego Min SwitchesI set it to 1 switch so it goes into closed loop quickly
BYPLESI kick it up to 60 sec for initial tuning so the hegos have 60 sec to fail if the fuel is too far out and it can't switch in a shorter period of time



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