The Short History of Saab Trionic
When it comes to engine management, there are a number of ways to cook the goose. When the IC engine was first produced, several huge hurdles had to be overcome just to get it running right. The science behind using venturi currents to feed fuel based on airflow (how a carburetor works) was a huge breakthrough, and in many cases is still used today as a simple and effective device to control how an engine works. As time progressed, we realized that the more control we had, the better our engines would run. The biggest hurdle to overcome was how to provide the best performance, without allowing the air/fuel mixture from pre-detonating, also known as knocking or pinging.
A big moment happened when knock sensors began to be installed on engines. However far from sentient, this allowed the car to know when the timing is too far advanced past top dead center and pre-detonation is occurring before the spark plugs go off. The computer could use this data to retard timing, reigning in the performance but with it, damaging pinging.
How Ionization Sensing Works
When engineers realized they could go further, the gears at SAAB were turning. As early as the mid 80’s, the technology that Saab Trionic is built on was being developed, a system that wins the engine management 1-up game handily. Here’s why:
The knock sensor cannot tell what cylinder is knocking. When it registers a knock, it signals to retard timing and the entire engine is effected. Because of the way consumer grade engines work, no two combustion cycles will be exactly the same. Trionic does things fundamentally differently. In combination with a critical component called a Direct Ignition Cassette (oh, you’ve heard of it?), the computer is able to very precisely control everything that is going on with each individual cylinder and spark plug. The critical difference from a knock sensor is the system’s ability to detect the ionization in each cylinder and relay that info back to the computer individually.
To do this, the computer uses the DIC to send a signal between the spark plug electrodes to measure the electrical resistance of the air in between. Depending on how well the flame envelope is burned, and what is left over after the main combustion, the computer can deduce a lot. It’s like the DIC is telling the ECU “On the sensing phase of that last firing in cylinder number 3, I got 734.2 ohms, and on this one I got 729.8 ohms” Then the ECU can return with, “I’d prefer a range in the 600s, for the next combustion I will retard timing by .5 deg, let’s see where that gets us”*.
This happens many times a second, for almost the entire time the engine is running. This way, no matter what quality or octane fuel you use, no matter the altitude, humidity, or temperature of air…. the system will always be able to dial in exactly the turbo pressure, spark timing, and fuel injection timing.
The only time that this active timing doesn’t take place is when you just start the engine. Upon initial startup on a Saab Trionic engine, all spark plugs are firing at the same time, using a much older process called “wasted spark“. That just means on cylinders that aren’t combusting (exhaust stroke), the spark is ‘wasted’. During this phase, Saab Trionic is getting it’s bearings. Soon after, the process switches to sequential ignition and the process above starts. The fuel injection system and turbo pressure is also controlled with this information, hence TRIonic, but that is a discussion for later. Additionally, when the engine is shut off, the computer sends a hefty dose of high powered spark across all the plugs for a second or two in Saab Trionic 5 cars. This cleans the plugs to prepare for the next cold start.
Differences between Trionic 5, Trionic 7, and Trionic 8
Trionic 5 engines use a MAP (Manifold Absolute Pressure) sensor to assume approximate airflow, and feature a RED direct ignition cassette. Trionic 7 cars switched over to use a MAF (Mass Air Flow sensor), and feature a BLACK ignition cassette. If you are wondering if the DIC’s are interchangeable, think again.
This argument comes up, as they basically do the same thing and the prices are different. However, make no assumptions; the coils are different, the inductance is different, the knock (ion) sensing is calibrated differently, and they use completely different charge and discharge circuits. These are different families of technology, when shopping get the one that fits your car.
On Trionic 8 cars, which include the new gen 03+ 9-3 and 2010+ 9-5 cars, the ionization sensing is moved into its own unit. These cars feature individual ignition coils and a separate ionization module that controls the process of retrieving and sending ionization data.
Lately, most new cars are coming with this type of ionization sensing hardware, due to its effectiveness.
When the car cannot detect proper ionization, or is getting false readings, it will cause your engine to run poorly, have bad fuel mileage, and throw engine code. These codes will typically signal misfires, and often come back with cam sensor or knock sensor errors. Of course these cars do not have cam sensors or knock sensors, the ionization takes care of all of this. That’s when you have to look at your ignition system.
- Start with spark plugs, because if they are in bad condition it’s hard for the ionization module to understand what’s going on.
- If that doesn’t fix it, you may want to take a look at your ignition coils next (or DIC).
- On Trionic 8 cars, if you’ve replaced all spark plugs and coils and are still having these engine codes, the ionization module will be a likely candidate.
I hope this was easy to understand, as it is a fairly complicated process, but the ability of these engines to run well and adapt instantly and correctly to changing conditions rely on you for regular maintenance. Don’t go too long on spark plugs, make sure your PCV system is burning off too much oil, and make sure you use dielectric grease whenever you change plugs in order to get the clearest possible ionization signal for the computer to work with!
*All data made up for sake of explanation, I couldn’t find specifics, but if you have a good source I’d be interested to know.