Bosch spark plugs

[brocluno]

I understand that these cars have "sensitive" ignition systems. But, is there a Bosch spark plug like an Iridium Fine Wire that might help improve combustion ignition with motors over 100,000 miles?

[Mike Brennan]

No

[photousa]

No

+1 No, No, No Stick with Stock Plug Recommendations and you won't have to buy a new DIC, or try to pick broken pieces of ceramic out of your piston bores.

[rpiereck]

NGK factory recommended only, unless your SAAB has no turbo.

[brocluno]

OK, I get the basic recommendation. But you mean this is a one-off custom plug just for one Saab model made by only one MFG? What to do if NGK goes belly up?

[Tweek's Turbos]

They wont. NGK only.

[Rognmoe]

I suppose you can try and see what happens...

But I wouldn't.

[SaabScott]

People have gone down this road before ... with poor results.

Is there some reason you don't want to use NGK?

[brocluno]

I'm asking to see if I can figure out what the unique properties are? Why is this plug so different than some others? I thought by getting some alternative recommendations, I could work through the physical properties that make it go.

This is my first Saab. But I have been playing with Euro cars and race cars (and boats, and motorcycles) for more than 40 years. In that time I have learned a lot about tuning and ignition performance and I want to know what makes the Saab so unique and touchy?

If it is corona resistance, that's one thing. If it's pre-event resistance, that's another?

Has anyone sawed apart a failed DIC to see what makes it tick? What is the component that most often fails within the DIC?

I'm intrigued, puzzled and slightly annoyed by the absolute requirement for this one plug ...

[nordwulf]

I don't know what makes the NGK plugs special or different from other brands, if at all. I just always read there is no need to try any other brand. That doesn't answer you question though.

Here is a thread with more information about rebuilding a DIC: http://saabworld.net/f15/rebuilding-...ssettes-24895/

The DIC and Trionic T7 uses the spark plugs for knock control. Even the WIS is very specific in listing NGK plugs as the only ones to use. Info from the WIS:

A high compression ratio is favourable for engine efficiency and thereby fuel consumption. The tendency of the engine to knock increases with the compression ratio, however, so a compression ratio is selected that is as high as possible with regard to the knock resistance of the engine's recommended fuel. Knock control in modern engines is not a safety function but a normal one. Therefore, there is nothing wrong with knock control being active during normal operation.

Trionic T7 does not have a conventional knock sensor. Instead, the ignition discharge module analyses the ionization current across the spark plug gap on all cylinders and sends a knock signal from each cylinder to control module pin 38.

From the combustion signals, the control module will be aware of which cylinder has fired and if a knock signal above a certain level is registered at the same time by the control module, it will gradually retard the ignition for the cylinder in question until the knocking ceases. Timing correction then returns slowly to zero.

Note
To ensure optimal engine performance, the correct spark plug should be used for each respective engine type. See Technical data, Spark plugs (157).

Knock control on modern engines is not a safety function but a normal function. Consequently, it is considered normal when knock control reduces engine torque in certain cases. The engine knock control increases for e.g. high intake air temperatures or high coolant temperatures. Further influencing factors are driving at high altitudes and low octane fuel. Certain engine variants require petrol with an octane rating of 98 RON in order to provide the specified engine torque/power.

If the mean value of the ignition retardation on all cylinder exceeds a certain level, fuel enrichment will take place. If the mean value of the ignition retardation on all cylinders increases further despite fuel enrichment, the maximum permissible air mass/combustion will be limited.
The control module expects the knock signal to be at a certain level as the spark is produced, so it will therefore start the actual knock detection in the respective cylinder only after the spark has been produced.