Caterham 170 spark plugs

TL;DR it's factory fitted with NGK ILKR7J8

I finally placed an order to Nengun, straight from Japan on Feb 21st. A set of 6 spark plugs did cost me the same as 3 at the local Suzuki dealership.

With the car reaching the 2 years mark and 24 000 km, the spark plugs are due for replacement. The service schedule does mention 2 years or 12 000 miles (20 000 km).

I did order a set based on the information found on the Denso website, but the dimensions of the model they specify for the Suzuki R06A engine are not suited to the Caterham 170. Note that there is no information and no part available for the 170 on caterhamparts.co.uk EDIT from May 2025, they now list is as "new" product.

The car came equipped with NGK ILKR7J8 spark plugs, from the NGK IR product line
Suzuki OEM reference seems to be 09482-00634-000

Replacing them (on Feb 15th) with a set of Denso IXUH22FTT sold as a match for ILKR7J8 granted me with the immense joy of having my Seven towed back to Liège and a 100km taxi ride back home 24 hours later, on a Sunday afternoon. Take this last sentence with the caveat that I cannot totally rule out an early effect of a mis-behaved new wideband oxygen sensor that had to be replaced mid-April, 4000km later.

To remove the spark plugs :

remove the engine cover, it is attached with a pair of 4mm allen screws - tilt it in order to have it follow the breather hose then lift it free
disconnect the ignition coils by pressing the clips and pulling the connectors gently
remove the 10mm bolts that keep the coils in place
use a standard 16mm spark plug socket on your ratchet, you'll probably need to use an extension

As the spark plugs were still in great condition, there was no rush for replacement (as of November...).

Having no clear documentation regarding torques, I did match the torque from an other spark plug to re-fit the one I had removed. The spark plug I checked was around 30 Nm (I've since found documentation that states 15-25 Nm for 12 mm threads in aluminium cylinder heads). The 10mm bolt of the coil was torqued to ca 17 Nm.

(top of the engine with no cover; grinding the engine cover leaves dust on the left coil)