In order to increase an engines performance we typically install items such as higher flowing intake and exhausts systems, camshafts and cylinder heads as well as supercharging and turbocharger systems. These increases change the volumetric efficiency of the engine. If the engine management system does not know of these changes you will have a poorly running combination. This would include start up, cruising and part throttle as wall as peak performance at wide open throttle. The byproduct of this will also effect the total emission output which we aggressively try to comply.
The calibrating process requires that you be able to keep the engine at a steady state. In order to do this we uses a state of the art Eddy current load control chassis dynamometer. This gives us the ability to log many parameters within the PCM as well as information on the dyno acquisition system such as the air fuel ratio (or Lambda) during all conditions. The two main items that require initial calibrating are the MAF (Mass Air Flow Sensor) and the Volumetric Efficiency Tables. These two areas are responsible for reporting to the PCM how many grams/sec of air are entering the engine. If you have every heard the saying “garbage in….garbage out”, it would also apply here. The PCM is a glorified calculator. Once it knows the exact mass of the air entering the engine it can then calculate the exact amount of fuel delivery needed for complete combustion. Of course this in turns dictates peak performance and clean emission output.
This is a timely process when done correctly. Many shops claim to tune your car and just do several Wide Open Throttle pulls. WOT calibrating is the considered the easiest part of calibrating as airflow at that point becomes very linear. What makes a great street vehicle is one that feels like stock until power is commanded with your foot!
With technology changing every day we try to stay active with updated training on calibrating.
Today’s transmission’s are also computer controlled and require the same depth of knowledge to properly calibrate. The transmissions we currently support are the four speed 4L60E, 4L80E and the 6 speed automatic 6L80E/6L90E (used in the CTSV and ZL1 Camaro’s. These transmissions are controlled by the several controllers including the T42 and T43.
The most complicated of the four transmissions is the 6 speed automatics. The following is an overview of how it works and the reason why you need a shop experienced in its operation.
“The A6 transmission is a torque based transmission. This means that it needs to know the estimated torque that the engine is outputting in order for the A6 transmission to work properly.The transmission controller determines the proper amount of shift pressure and shift times as needed depending on driver demand. This becomes more critical after a large increase in power like a supercharger or larger motor. It is imperative that the engine calibration be done first before any changes are made to the A6 trans controller (T43).The trans controller (T43) receives critical estimated torque values from the ECM (E38). Any engine that produces 600 ft/lbs vs. 400 ft/lbs will require more pressure and typically a faster shift to avoid slip…..which inevitably will kill a transmission!!
Estimated torque is derived from the MAF and coefficients (or VE table) within the engine controller. If these values are not correct then the information that is sent to the trans controller WILL be incorrect and will cause the transmission to slip. This can be a big problem on earlier ECM’s where the MAF tables have a hard limit of 512 gs/sec (pre 2008). Once a MAF has maxxed out, the reported load will actually go backwards reporting less load even though the engine continues to make power. What this means is the T43 will command less applied clutch pressure, and shift times, yet the engines torque is increasing. Common sense will dictate that this IS going to cause a trans failure!
Many shops feel the need to kill all the Torque Management and cut shift times to zero. We have found this not to be required especially if the process noted above is performed properly. Not too mention the engine will also respond with better drivability when the engine is properly “air modeled”. Trans shifting is like a baton race….the same way runner one (lets call that 1st gear!) tries to hand off the baton to runner two (or 2nd gear!), there has to be a smooth but properly timed hand off. If one gear is still engaged fully while the other is trying to grab you can destroy the transmission. Torque Management when “properly” calibrated will enabled a firm yet smooth shift.