Daihatsu's KF series engine was introduced in November of 2005 replacing the old EF series engine. From it's introduction in November 2005 to the present day it has brought forward many changes, some small or big. From pistons (increasing compression ratios), electronic throttle, injector differences and various other changes. In this thread I'll be discussing the differences between the Ignition coils for the KF-VE, KF-DET and KF-VET engines.
KF-VE and KF-DET (2006- MAY 2010)
Both turbo and non-turbo variants used the first variation of the ignition coil with a clear top that showed the circuitry and are circular in shape which I refer to as the green top coils. DE DIAMOND or Diamond Electrical manufacture these coils in Japan with the part number 19500-B2040.
KF-VE and KF-DET (MAY 2010-2011)
Now these ignition coils lasted for a small amount of time and have differences to the earlier ones. They are more angular in shape and have a clear top that shows the circuitry. From the side you can see there is a rib going down to the bottom of the coil and the base is thicker. I presume this was done to combat spark leakage which the earlier coils were more susceptible too and often had to wrapped in electrical tape as a temporary Jugaar. I refer to these coils as the grey top coils. They have the part number 19500-B2050.
KF-VE and KF-DET (2012-present)
The latest coil as of date. It has no differences other than the blackening of the top. Although info is limited on their internal changes if they have any. It shares the same part number 19500-B2050 as the silver top coils. I named these coils the black top coils.
KF-VET uses blacktop coils
So, are they interchangeable? Yes and no. All these coils have the same plug so yes they can be plugged in and run on a 2006- May 2010 engine. They have the same mounting locations as the valve cover hasn't been changed in every variation of the KF series engine, but the problem arises on high speeds such as 80km/h + is when you'll see the check engine light on and the engine jerks. Now why is this can due to many reasons. My theory is that the ECU freaks out as it comes to the conclusion that it doesn't know what it's sending signals too. This is vice versa. Using old 2006 - May 2010 green top coils on a new Mira/move/Hijet will give the same issue. This can be resolved through an ECU flash but would depend on what kind of a car you have and it's transmission. That is if the ECU supports the newer tune.
I would like the experts @Xulfiqar and @Hassan1991 give their opinion onto why this happens in more detail. I'm just a A Levels graduate who will go to uni soon and, I'm no expert here.