Vehicles use more than 1,000 semiconductors today. These small components control everything, from how the airbags deploy during a collision to the acceleration speed you receive when stomping on the accelerator.
The latest models can have more than 3,000 chips installed, with up to 100 different computers operating different components.
Although these items operate independently, they’re also supervised by the Electronic Control Unit (ECU).
When you modify a vehicle to improve its speed, handling, or other attributes, the ECU doesn’t know that a parts swap occurred. Until you let the computer know that changes are necessary, it’ll stay in the stock setup.
You have two common ways to update how your vehicle functions in this area. It can be done with a flash tune or by piggyback.
ECU Flash Tune vs. Piggyback
An ECU flash tune delivers zero boost leaks. The piggyback option relies on the factory boost control system for changes, resulting in a higher risk of leak development. If this outcome occurs, a safe tune is not possible. Engine damage may occur, even if the wastegate spring is set correctly.
When you want more power to come from your vehicle, there will come a time when you’ll need to tune the computer to match the aftermarket modifications. The original programming is based on the stock setup that comes straight from the factory floor.
Although most drivers are satisfied with the control offered by the factory setup, it’s not always an option to create the necessary modifications. Several automakers set the ECU coding to disable tuning changes.
That means the only way to access the code is to crack it to alter the programming.
Flash tuning offers an advantage when available because you can quickly alter the vehicle’s software to support the new setup. If this option isn’t available, the next best solution is to piggyback it.
You have a third option to consider, which is to replace the factory Electronic Control Unit with a standalone ECU.
| Pros of Using a Flash Tune/Independent ECU | Cons of Using a Flash Tune/Independent ECU |
| The flash tuning process provides an outcome that has infinite adjustments. You can keep modifying the results to fit your setup to whatever standards you prefer because you can change, control, or add items on the fly. | Vehicles using an OBD-II port to read codes will likely no longer communicate with it when using a new standalone ECU. Any gauges that run from that port don’t function in that scenario, and emissions systems malfunctions may occur. |
| It gives you a way to fine-tune the results based on your engine. Even if you compare two of the same engine designs together in an equitable make and model, there are always little quirks in the build that require attention. | The flash tuning process or installation of a standalone ECU requires you to provide parameters for everything the car does. This work takes a long time to complete, and it must be completed to ensure safe operations. |
| You have the option of adding future mods, which can be tuned for at the time of their addition. There is no ceiling to the power and acceleration levels to which the ECU accommodates. | Depending on the factory configurations, some drivers could encounter issues communicating with dashboard gauges or sensors. The tachometer and temperature gauge may not work, while others require tuning updates. |
The best way to flash tune or update firmware is to use a tool built for that work. Standalone updaters can connect via Bluetooth® in some vehicles to work with the interface for later programming.
If you drive a BMW, you’ll need to verify compatibility with your tool or firmware update product to ensure the results meet your expectations.
What About Using the Piggyback Option for an Update?
A piggyback ECU wires into the vehicle to work with the factory one. You’re adding a second control unit into the mix.
This option works in one of two ways. It can either intercept the signal from the vehicle’s sensors before reaching the factory ECU, then modify them, or communicate incorrect information to have the car perform as expected.
The goal is to make the ECU think that something is happening to encourage an increase in performance specs.
You can also manipulate the ECU after the initial data is received and analyzed. You could piggyback the code to have the fuel injectors add or remove gasoline by raising or lowering their operating time. Since the factory control unit doesn’t see the change, it can’t try to stop what happens.
The setup gets a bit complicated since most require some signal intercepts before the ECU and more after it. Some models work better using one method more than the other, which means finding the best option can feel like a never-ending series of adjustments.
| List of the Pros of Using Piggyback | List of the Cons of Using Piggyback |
| This option tends to be a bit easier to set up and tune. Instead of reprogramming an existing ECU or swapping another one out, you can create the specific circumstances needed to support vehicle mods while leaving the factory product intact. | Some factory ECUs don’t permit a piggybacking process to occur. They can’t be tricked into thinking something else happens because of their adaptability or sensitivity. It is not uncommon for the check engine light to illuminate. |
| It retains OBD-II compliance, allowing communication to occur through the port so that the vehicle passes emission tests. You can still scan for problems or codes and run scanning gauges. | The piggyback process only lets you control a certain amount of the mods you’ve made. It can give you efficiency or horsepower increases, but it might not maximize the full potential of your engine. |
| Using a piggyback ECU requires less time and expense to program and operate than a standalone unit. | Switching to a piggyback option for tuning could cause the vehicle to fail its emissions test. |
| Drivers receive full compliance with the gauges and sensors in the dashboard, ensuring legal operations while reducing the need to make additional modifications. | It requires drivers to modify the factory engine harness. This issue is due to the need to intercept ECU or signal wires. If you want to move to a standalone modifiable ECU at a later time, you could run into some trouble. |
When a vehicle won’t accept a standalone ECU or keeps its coding locked, the piggyback approach is better than nothing. You’ll get some improvements from the modifications you’ve made.
Does a Car Warranty Cover Aftermarket Modifications?
If you’ve just purchased a vehicle that you want to modify, it’s important to review the terms and conditions of the agreement.
Modifications won’t void a warranty unless the dealer or automaker can prove your updates were responsible for the necessary repairs. If you add a new intake and your fuel line starts leaking vapors, you should still be covered.
When you add a few aftermarket parts or tinker with the ECU, is there a definitive way to say that your actions were responsible for the repair need? Not really – and the same can be expressed in reverse.
What you’ll find is that most dealerships and automakers won’t want to pay for an entirely new setup if there’s a chance that failure occurred.
Some updates are safer than others to consider if you’re thinking about modifying your vehicle. Upgraded wheels, manufacturer-recommended changes, or aftermarket items supplied by the automaker are typically allowed.
If your dealership is willing to make ECU updates for the outcomes you want, you’re typically in good shape.
It’s when you’re piggybacking or swapping the ECU for another that things get a little sticky. If your automaker locks the software so that it can’t be reprogrammed without hacking into it, there could be a voided warranty in that circumstance.
This issue depends on what you want to accomplish, the engine’s age, the condition of the vehicle, and how much risk you’re willing to take on to achieve the outcomes you want.
What If I Just Want a First-Stage Mapping Change?
If your goal of changing the ECU is to update your programming to a dual cone intake, you can see gains of 10 to 20 HP without making any changes. If that’s enough for your needs, no further alterations are necessary.
You might squeak a little more out of it by increasing the octane number of the fuel you use.
When more equipment changes happen, it becomes necessary to update the DME. Even then, you’ll max out the horsepower availability until you find the right combination with a software upgrade.
If you want to push the envelope a little more, consider adding Catless downpipes or a performance FMIC to the mix. You can boost the horsepower by another 10%, especially with ECU or piggybacking options.
Since March 2019, BMW has updated firmware to prevent flash tuning. That includes a firewall to stop future modifications. You’ll need to look at piggybacking or replacing the ECU to get the updates you want for a late-model option.
Is It Necessary to Flash Tune or Piggyback My ECU?
Altering the ECU software for your engine ensures that it performs at or close to its maximum capabilities. The outcomes rise above factory specs for efficiency, creating significant improvements to torque and horsepower by remapping its commands. If the unit can’t be reprogrammed, piggybacking is the next best option.
For the life of me, I couldn’t figure out why my vehicle wasn’t accelerating better. It was getting more air, the compression ratio was great, and there weren’t any noticeable codes or errors popping up on the dash or screen. What was I doing wrong?
After a few days of investigating, I discovered that my ECU was learning about the changes I was making through the piggybacking process. Each time I’d run an update, it would shift the map.
That’s when I decided to route intercepts in the front and the back of the signal chain. Once I did that, it was easier to see efficiency and horsepower boosts.
Every car is a little different, so it helps to stay on your toes. Make adjustments on the fly if you can, or work with your intercepts to create a map that makes sense for your setup.