Thursday, December 13, 2018
Since the introduction of the GM crate engine package, wortec have been supplying custom calibrations to small manufactures and individual owners. Cars ranging from RX7 to Nissan drift cars have had V8 engines fitted by customers and tuned by wortec.
The GM engine, gearbox and electronics package are advertised as plug and play. This as mentioned on other pages of our web site is not the complete picture. The kits as supplied rely on an instillation that is identical to that GM intended. This is almost impossible in the varied range of cars the engine has been fitted to. Restrictions in intake position, exhaust manifold shape and size and the addition of power adders like superchargers means that a new calibration is required.
The GM PCM is capable of adapting to allow for some variations in the installation. But the further away from optimum the less happy the car runs. A variation of 5-7% is the most that is acceptable and even then it is best to have the car data logged to make sure there is no consequence to this error. After 10% error the car will feel less than perfect, it will run and drive but it will feel "soft". At 20% error the PCM is out of range and cannot make further adjustments.
As GM supply the kit as one size fits all and have no variation for the type of car or use it is intended for the calibration is deemed a good starting place. This is where wortec start to change the calibration to suite the car it is fitted in.
First stage is to correct the monitoring of airflow into the engine. Modern cars use a "Mass Airflow Meter" to read the airflow into the engine. The calibration of this sensor is vital to the running of the car and amounts to 50-60% of all running problems on "Run Kits". In some installations this sensor is removed but that is dependant on many things and if removed necessitates an extensive re calibration to get perfect results.
Once air flow is corrected we move on to fuel and timing. Both these items need to be adapted hand in hand as one effects the other. Timing is also dependant on the vehicle weight, or more importantly the "inertia" which changes how much timing is required under some load conditions.
Now that the car is running to the correct level we turn our attention to driveability. This covers the feel of the car, areas like low speed smoothness, throttle response, and off throttle airflow are worked on to give the owner the best possible drive. A well calibrated GM PCM will give a far better driving car than any aftermarket system and has proven to have no limiting factors.
All the calibration is produced on the road and test track as this is where the car will be used. Meaning the car must be road legal or able to be transported to the test track. If the car is a none runner wortec can supply a base tune which fixes known calibration problems and enables the customer to get the car road legal or at least get the car to a test circuit for a "shake down" before calibration work starts.
If required the car is dyno tested after completion to supply a finished power figure. We don't make changes to the tune on the dyno as this is not the environment the car is used in and changes made here can effect the quality of the tune. If any areas for concern are found we will re-data log the car and make changes and re-test if required.
Due to drive train differences and dyno calibration it is not recommended to use a calculated fly wheel figure generated from the dyno, it is best to quote power at the wheels as this is more reliable (but still effected by operator, conditions etc).
As wortec data log all parameters of the engine and have engine dyno information for GM engines we are able to know when the engine is at its optimum state of tune as we have recorded airflow, rpm, fuel and spark advance which gives a very good gauge of power when compared to known engine dyno data.
A custom tune on a simple GM run kit is achievable in one day and approximately 100-150 miles driving time. More involved tunes will take a number of days and will require over night brakes for the car to have "Cold Start" tuning applied.
Please contact your wortec dealer for more
information and possible costs.
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