Today at Atelier Kaz - ex-Honda R&D, F1, Indy/CART engineer

One of the most common question that I receive is the difference between the Front and Rear IG coil.

The IG coil itself is different due to the misfire detection rule and thus, there are 2pin style as well as the 3pin one.


Most of you already know that Front and Rear ones have different parts no. and also they are stamped as ‘FR’ and ‘RR’ at the head respectively.



From engine and electronics point of view, they are exactly the same and you can actually install and run the engine with Front and Rear ones swapped.


Some of the engines that I looked at were running under this condition for more than 5 years without any issues.


I prefer to keep the same IG coil and spark plugs at the specific cyl so I normally place them back in their original position but I know other people won’t do this and it didn’t cause any problem in running the engine.



For many years, I was also under the impression that there is no difference at all between the Front and Rear IG coil.

Even my master told me the same.


However, after looking at many IG coils, it seems that there is a possibility of a small difference between the two.

This could be just a coincidence and I could be wrong but the direction of the tiny hole at the rubber seal just below the head of the IG coil is different between the Front and Rear.


On some of the IG coils that I looked at, the rubber seal seemed to be shifted/rotated in the past and didn’t follow the same story so again, I could be wrong.

For the Front IG coils, the hole tends to be at the non-connector side whereas for the Rear ones, it tends to be on the connector side.


When they are installed, the hole will be facing upwards on both the Front and Rear ones.


Don’t know the feature of this hole once the seal has been compressed…

Air channel for cold/hot engine condition???

Kaz