I am using Octane 95 in my 230E (EURO) and my EZL-KAT Dial is set at S.

I want to try Octane 98 someday to compare performance, do I have to change the settings on the EZL-Kat Dial when I use Octate 98? if so then what is the setting?

The "S" position is 750 ohms. The most aggresive advance map is (I believe) position 1, which is infinite resistance (open circuit), but the difference is not great. Check the dial resistances to determine which one is open circuit.

I doubt that you will find any noticeable improvement in performance. My US car has a 750 ohm fixed resistor - equivalent to your "S" position - and my engine does not detonate on fuel equivalent to a European rating of 90-91 octane (87 in the US) as long as the weather is cool. In warmer weather it will detonate at low revs/high load, such as upshifting at low revs. I currently have the resistor removed, and really can't notice any improvement performance (or increase in detonation tendency) and a check with a timing light didn't show any signficant change in the ignition map.

Suggest you change the dial to the infinite resistance position using 95 octane and see if you can detect any difference in performance or any detonation. I don't think you will. Then you can try 98 octane, and I expect the results will be the same.

On my car there is no detonation as long as the ambient temperature is below about 65 degrees F (about 16C) and coolant temperature is below 90. At about 70 degrees (19C) I begin to pick up some light transient detonation if I short shift and load up the engine below about 2500, but there is no detoantion above about 3000.

The EEU uses Research Octane Number, which is about 4-5 points higher than US posted octane numbers, which are the arithmetic average of RON and Motor Octane Number (MON). US octane numbers are usually called the Pump Octane Number (PON) since it is the number posted of fuel pumps.

Make sure you test with the coolant temperature below 95C as the EZL module will reduce timing if the coolant temperature climbs to 95C or greater.

Duke