gtchow

Just received 16 Denso spark plugs and it turns out they are the wrong length. I called tech support at Denso first before ordering and was told to use the IK16 plugs. The original OEM plugs are the NGK ILFR6A, with the L stands for long. The difference between the two are pretty big, about 8mm. Why would Denso use a plug that is 8mm shorter than the OEM ones? Would that not decrease the compression ratio with the increased volume inside the combustion chamber?

alx

Yes. What you got are slr plugs. A friend of mine with a cl55 did the same thing as you and ended up with the wrong plugs too. He did not know that at the time and put them in. Got misfires so took the car to the dealer and they told him his plugs were wrong...