6 Things an ECU Won’t Do
1. IT WON’T MAKE POWER
An ECU cannot make power, it’s a tuning tool.
We often receive questions from people asking how many horsepower an ECU make – an ECU does not make power, an engine makes power. The only way you can make power by putting an ECU on a factory engine is if they left power on the table. Generally, this is not done but there are some manufacturers who do this on cars that needs to be detuned so that it makes less power than the more expensive model.
On turbocharged engines, you can crank up the boost to have more power but then you’ll be eating into the safety margin the manufacturer put there, and will reduce the life of your engine. Eventually, it will need support modifications – bigger fuel injectors, stronger ignition system, and a stronger bottom end of your engine.
In order to have more power, you need to have more air through the engine. Your engine is an air pump; naturally, the more air it can pump, the more power it can make. Your ECU will help you make these modifications to make sure you get the right amount of fuel in to the engine and set fire to it at the right time.
2. IT WON’T TUNE ITSELF FOR YOU
Adaptive tuning is a tool for tuning – it’s a machine that can make the task easier for you. Aside from the limitations we would like to point out, there is also one problem a lot of people encounter when working with an ECU. Some people often think that because they have an ECU, they can avoid the responsibility of tuning and assume it will do the job for you. You cannot leave the task of tuning your engine on a piece of hardware and take control of the process.
Also, your tuning tool has its limitations. There are 3 limitations we like to point out:
- It can only adjust the current cell the engine is operating at. So, if you’re at 50 kPa at 2000 RPM and the mixture is a bit off, the ECU has no knowledge to adjust the adjacent cells. To be able to use it, you need to visit every cell in the adaptive tuning function.
- It can only act when it’s had a consistent mixture for a decent amount of time. This is a particular issue on high power to weight ratio engines, you can’t hold it at a high load position long enough at street legal speeds for the ECU to settle on the target mixture. Even on a dyno, you don’t want to hold it at full power for the several seconds it will take to stabilize at the target.
- It only does fuel adjustments. Measuring the lambda and feeding back through the fuel map won’t change the ignition timing, which has an impact on torque. To get the best results, you need to get on a dyno to tune both the fuel and the ignition timing.
3. IT WON’T FIX ANY UNDERLYING PROBLEMS IN THE CAR
Your ECU can only get the fuel in your engine and set fire to it. If you made modifications to your car and your factory ECU cannot keep up with your modifications, that’s when you need an ECU. An aftermarket ECU will normally give you more ability to control than with a factory ECU but it won’t fix any underlying problems. This include volumetric problems, fuel pressure problems, ignition system problems, etc. If you have an unstable fuel pressure, then you still need to fix that before you can tune it.
4. YOU CAN’T RELY ON CLOSED LOOP FUEL TO SAVE A LEANOUT
Running your engine on a closed loop fuel mode does not necessarily save you from a leanout condition. The ECU can be set with different gains to make it more or less responsive but the fact remains that there will be some delay, and it does not take long to destroy a highly strung engine. In addition, a lot of really high strung engines can be quite fragile, rotary engines in particular. One of our customers had a situation at the race track where the driver ran the engine out of fuel when he was at full throttle. According to the logs, it went lean for 1.5 seconds before the fuel pressure ran out. In that time, it melt an electrode off a spark plug which caused some impact damage.
5. YOU CAN’T RELY ON CLOSED LOOP IGNITION TO SAVE FROM KNOCK
Another thing your ECU cannot do for you is it can’t save you from detonation by being on closed loop ignition mode. Closed loop ignition control only works by detecting knock then delay the timing. It means that knock actually has to occur before your ECU can take action. This is another example where you cannot rely your tuning completely on a piece of hardware – on a highly strung engine or a fragile engine like a rotary, it won’t take long before this cause lasting damage. It’s always advisable to properly tune your engine and put the right fuel in. Keep in mind that it can be difficult to detect knock. Many factory ECUs don’t even use knock detection above about 4000RPM because the mechanical noise from the engine is so high that it drowns out the sounds of knocking. Humans are really good at detecting knock which is why all Adaptronic ECUs have earphones to assist you with it.
Until more recently, with the invention of DSP technology that it has become good enough to properly detect knock reliably above mid-RPM range. The proper way to do knock detection is with crank angle windowing. Only a few ECUs do this and among the Adaptronic ECUs, the e1280s is currently the only ECU that supports this function.
6. BE CAREFUL HOW YOU SET UP RPM / BOOST LIMITS
Plenty of tuners have said that they don’t like to use fuel cuts for a rev limit because of the possibility of the fuel delivery being split between intake strokes, ending up with two lean strokes rather than one complete stroke and one with no fuel. As a result, they prefer using ignition cut as it’s “safer” than fuel cuts. Although it introduce other potential problems, like allowing fresh, unburnt charge to exit the engine – where it can combust in the exhaust system or turbocharger. On a street driven car, it will also kill the catalytic converter if you do this too often. This is why on factory cars, they do fuel cut – but clearly, they have a much bigger R+D budget than your tuner to ensure that the fuel cut is safe on your particular engine with this particular tune and these modifications.
A note also about boost limits: the ECU can only see the boost that’s coming to it from the sensor. So there are lots of things you can do to stop this from functioning; for example, if the boost hose comes off, or if the boost limit setting is higher than the sensor is calibrated for.
