Spark Plugs Again

[ashpilot]

I am thinking of getting some more plugs for my standard IS300 but can't make my mind up.

The US Denso web site suggest the IK16, yet the car is fitted with SK20R-P11, I know the 16 refers to the amount of heat the plug removes from the cylinder. So why are the US cars running around with colder plugs and the European sites suggest the use of the warmer IK20's??

When I was on Holiday I purchased some IK16's which I dont want to fit until I get to the bottom of this.

Help!

[aido]

To be honest I thought the Denso plugs worked the other way around, ie the IK20's are colder than the IK16's and so on.

The Supra guys are running IK24's with mildly uprated boost all the way up to IK27's for serious modifications so I'm assuming that the lower the number, the warmer the plug?

[ashpilot]

To be honest I thought the Denso plugs worked the other way around, ie the IK20's are colder than the IK16's and so on.

The Supra guys are running IK24's with mildly uprated boost all the way up to IK27's for serious modifications so I'm assuming that the lower the number, the warmer the plug?

Yes you are right, the question is why are the yanks running on IK16 (warmer plug, but removes less heat from the cylinder) and we are advised to use IK20 (Colder plug, but removes more heat from the cylinder).

[ashpilot]

Anyway fitted the IK20's today, took 2 hrs including putting my tools away. Will try them tomorrow. If they are ok I will have a set of IK16's for sale brand new, cost me £35.

[MacRS200]

Yes you are right, the question is why are the yanks running on IK16 (warmer plug, but removes less heat from the cylinder) and we are advised to use IK20 (Colder plug, but removes more heat from the cylinder).

It's nothing to do with removing heat from the cylinder, it's all about the temperature of the electrodes on the plug. A cold plug conducts more heat to the cylinder head than a hot one does.

If you use a plug that is too cold for the engine and the way it is generally run it can get coated in carbon deposits and "foul" this cause mis-fires, too hot and the electrodes will corrode faster than they should.

Edited October 27, 2006 by MacRS200