spark plug e3

years ago when Splitfire plugs came out I tested them on many cars and they didn't make a blind bit of difference. Apart from the Rover A series and B series engines (old Mini and MGB) where they would always improve horsepower by about 3 or 4hp. on a small engine that is a lot. I swapped plugs back and forth on some engines multiple times to make sure it wasn't rolling road errors and every time the Splitfire plug gave more horsepower.

needless to say we recommended for the MGB and MINI the Splitfire plug.

never found any other four cylinder (not many V8s in the UK) engines it worked on and came to the conclusion it must be something to do with the combustion chamber shape that preferred these plugs?


as for the E3 plug there does seem to be a lot of extra metal shoved into the combustion chamber in the form of the ground electrode. not sure if I would trust that?