How A Performance ECU Tune Is Developed

10 min read

How A Performance ECU Tune Is Developed

10 min read

Not all engine calibrations are created equal. Most ECU upgrades will recalibrate your engine’s computer to enable it to rev higher and deliver more power, but that often comes at the expense of the overall driving experience. Worse, if the tuner hasn’t done their homework, the gains may be inconsistent, dependent on climate or fuel, or even lead to expensive hardware failures when the moving parts fail to cope with the increased loads placed upon them.

These are all scenarios that are avoided by the meticulous approach taken by APR, which specializes in new ECU calibrations for Volkswagen Group vehicles. The process begins with the company’s team of reverse engineers, who use tools developed in-house to analyze the engine’s computer and gain a thorough understanding of how it operates.

That can be a frustratingly time-consuming process: it took three years to gain access to the current generation of Bosch ECUs used in many Volkswagen, Audi, SEAT/Cupra, Škoda, Porsche, Lamborghini, and Bentley models, and generate a new calibration. But it’s time well spent for APR’s engineers, according to lead calibrator, Tyler Wolf.

“A common pitfall when calibrating is a lack of understanding of how the factory ECU works,” he explains. “Some tuners have a limited repertoire of variables that they can change and often don’t understand how changing one thing can affect the system farther down the line. The information and resources from our software team give us a complete understanding of the consequences of our changes. Without that understanding, you’re just pushing keys and hoping for results at the end.”

Decisions on the goals for a new calibration are based on testing by a variety of drivers at APR. It’s the increased horsepower and torque figures that grab the headlines, but an APR tune might also include eliminating a throttle delay or improving drivability in other ways, raising rev limits or removing a speed limiter, enabling left-foot braking on track, providing more accurate information to the boost gauge in the digital dash or adding adrenaline boosting exhaust crackle in the appropriate driving modes. Sometimes a calibration will even include fixes for factory glitches that are later remedied by the OEM itself!

In The Lab, On The Track

APR calibration in-car

Many hours are spent with the test vehicle on the dyno and the racetrack as engineers determine the optimum calibration details for a particular model.

The process of testing a new calibration begins on one of the five dynamometers at APR’s base in Opelika, Alabama. The R&D department boasts four chassis dynos – including a hub dyno and one dedicated to emissions testing – as well as a standalone engine dyno.

“We’ll spend weeks or months on the dyno learning the system, depending on how familiar we are with the ECU, engine and drivetrain,” says Wolf, who grew up racing motorcycles and has been working with cars since he was 14 years old. “Most tuners just do a single-gear pull in fourth or fifth, whichever is closest to 1:1. We start there to learn and to find the limitations, but then we move on to dyno runs per gear and through runs of gears – fifth-sixth-seventh-eighth or second-third-fourth.

“We’ll do many kinds of testing on the dyno, from launching the cars on the dyno to performing simulations like top-speed runs or zero to 200mph acceleration, just like on the Autobahn. On top-speed runs we will look to see whether the car can push through the gear to reach that speed. Is the cooling capacity able to handle it? We’ll also do transient runs to simulate laps of a road course.”

The next stage takes the prototype tune out to the track to see how it performs in the real world, again driven by a variety of drivers to see how it responds to different

driving styles. From there, and depending on the car, the team moves into track testing: on a drag strip to get performance results for stock vs tuned, and at road courses such as Barber Motorsports Park or Road Atlanta, for torture testing.

“That’s where we get to look at longevity: how the oil holds up, how the plugs look, whether we’re causing damage,” Wolf continues. “What is the car capable of at that point? Are the cooling system, oil cooler, transmission cooler and radiator up to snuff? We also look for further areas of improvement like the transmission off-throttle to on-throttle response in corners. If we need to, we’ll come back, review the data, put the car back on the dyno with new parts and repeat the process.”

Intensive Instrumentation

APR in-cylinder pressure testing

The details that APR focuses on go far beyond simple fuel and timing changes. Engineers look at hundreds of variables from fluid temperatures to individual cylinder pressure readings to determine the perfect calibration constraints that yield power and reliability.

During the testing phase, the team gains a greater understanding of what’s happening by comprehensively instrumenting the test car with around 20-40 sensors depending on the complexity of the car and the hardware fitted. Many of these sensors would have been in place during the calibration process at the factory but are absent on production vehicles.

“We collect information from the sensors using a datalogging system,” says Wolf, who handles the Porsche calibrations at APR. “For example, in a recent track test of a Carrera Turbo at Virginia International Raceway, we were running a larger turbo at roughly double the car’s factory horsepower. For that, we were able to monitor the temperatures and pressures right through the intake and exhaust system, and through the turbocharger itself, as well as engine speed, wheel speed, clutch pressure and much more.

“We can overlay laps and combine that data with our ECU logs to ensure we prevent the car from overheating, prevent damage to the turbo and keep the catalyst at its operating temperature,” he expands. “We can also see how the changes affect the intercooler’s ability to reject the heat – to not get heat soaked on track and slow you down. We then also use a lot of that data to remodel the factory ECU.”

Model Answers

APR sensors

APR ECUs often use corrected models that will account for changes that are made elsewhere on a vehicle. This allows the ECU to keep the engine system in a safe setting regardless of where the vehicle is at or what it is being used for.

Models are central to modern ECUs because OEMs use them to replace the more costly sensors. The ECU then uses the models as reference points in the absence of real-time data from a sensor. For example, a turbo controller will use model-derived figures for pressure and flow through the turbine when it is trying to determine a correct wastegate position setpoint. Once a tuner begins to modify the car, the factory models may no longer work correctly, so APR ensures that they too are modified to account for changes elsewhere. That way, every component remains under control, all of the time.

“The models are also important for factory protection,” adds Wolf. “Factory safety features are sometimes not turned on in the computer because they’re not needed for the performance at factory output. Once we’re making more horsepower and running the engine a lot harder, we’ll often enable the safety features and map them. If I have an accurate turbo-speed model, compressor-efficiency model or whatever it is, I can enable that in the car and make sure that no matter whether the owner is on track here in Alabama or in the heat in Dubai, the car will protect itself and ensure it’s not going past its limitations.”

On the Porsche platform, APR enables factory protections not generally used by its competitors, for example for shaft speed, compressor outlet temperature, or injection window and duration.

Turbo Tuning


The goal of an APR tune isn't solely to create an impressive horsepower number on the dyno, but to create a real-world performance improvement that is far more intricately developed than an average dyno tuner can provide.

Sensor data also provides measurable reasons for APR to develop engine hardware. Tuning parts don’t always have the impact that their makers claim, but APR’s calibration team uses data to determine which upgrades will make the biggest difference. Staying with the Porsche example, Wolf found proof that a new turbo inlet would make a dramatic difference to performance – not by adding horsepower, but by increasing turbocharger efficiency. That dropped the outlet temperatures so that the intercoolers didn’t have to work as hard, making the car’s performance on track more sustainable. “It saves customers money when they’re tuning because they’re buying parts that actually make a difference,” he says.

The company’s calibrations come in different levels. The popular Stage 1 tunes, for example, are designed to run with factory hardware and, Wolf assures us, work within the headroom that the OEMs have left on the cars. In this case, hardware inspections during testing are less critical than for more aggressive turbocharger upgrade calibrations.

For the more potent tunes, which often work hand-in-hand with tuning parts to support the power, APR won’t just rely on data to be sure that all is well with a modified engine. “We investigate where the weak links are,” says Wolf. “We’ll tear down motors to see how things are holding up – can the piston rings handle it, for example? We’ll look at the spark plugs, scope the cylinders and go through the oil. We try to make every single failure happen if we can. That doesn’t always make the boss happy, but it enables us to find the limits and create a safe, reliable calibration.

“For Stage 3 turbo upgrade tuning, we even have an in-cylinder pressure transducer, a tool that OEMs use, in addition to our regular sensors. The information we have learned from it and applied to our understanding of how a direct-injection engine works, has been fundamental in us being able to push to the next levels with the [direct injection] motor.”

Wolf adds that such resources are not available to many aftermarket tuners, nor is the time afforded to him and his colleagues to ensure a new calibration is done right. Depending on the complexity of the project, it might take up to six months to complete at APR, whereas other tuners might be under pressure to complete their calibration in a matter of hours, working from the same base that they’ve used before.

Anytime, Anywhere

APR trackday

APR’s worldwide network of dealers is a further resource to tap into during the testing phase. This can be particularly valuable when accounting for different climates, different fuel grades or different factory calibrations on the same model of car when sold in a different market, for example to meet local emissions regulations. Beta software can be tested in-market by the local dealers, or by APR’s own engineers, who travel there for the purpose.

“We want to make sure that the same tune will work in summer, winter, in the northern hemisphere or the southern, at the top of a mountain or at sea level,” says Wolf. “What we make in the US is typically good for everywhere, but the fuel quality in Europe means you can often tweak the files to get a little more performance.”

APR’s thorough approach to calibration development and testing, not to mention that ‘headroom’ of unexploited performance left by OEMs – particularly for a Porsche or Audi RS vehicle – gives the company total confidence that the engine will retain its longevity and reliability, despite the additional performance. That confidence is backed by the APR Plus warranty program in the US, which mirrors the OEM engine warranty, or the APR Garantie in Germany.

“Everybody tries to be aggressive, everybody wants high horsepower numbers,” Wolf concludes. “But without the instrumentation that we add to the engine, tuners don’t know how close they may be to the edge. We’re able to be very aggressive in our tuning, but we’re not being risky. We monitor the temperature of everything we’re doing. We can see if the turbo is spinning too fast. We understand that if we add too much ignition advance, the engine’s going to knock, and we’ll break a piston. Unless you have the tools that we have, and invest the time, you’re not going to know that. You can’t make a tune based on what you think is right.”


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