will the hotter/colder plugs change the a/f mixture needed? i had to change my plugs from bp6es cause i broke one and found champion wadc in my other motor and the plugs have gone black and the bp6es were a dark brown

Up untill recently i had been using BP6ES and BP5ES and had been getting 1 or 2 "dead" ones in the pack or run the car turn it off, let it sit for a while, start it again and it would have a miss fire (didnt matter if the engine was well used or freshly rebuilt), so have changed to BP6EY & BP5EY and am yet to have any of the same problems with these spark plugs.

So, if I were to change the plugs to NGK BP5ES should I get a small but measurable increase (5-10%???)?

My Turbo 1132 is running BP5ES but looks like they may be fouling a little (its running a bit richer due to turbo, etc)
Hmmm, I cant run BP4ES as they are too hot and even with the 5ES I am getting some burning/pitting on the electrode.

Might try some bosch or Champion plugs ay.

Peter.

With modified engines (those engines that have increased their compression) more heat is a by-product of the added power that normally comes with increased compression. In short, select one heat range colder for every 75-100 hp you add, or when you significantly raise compression. Also remember to retard the timing a little and to increase fuel enrichment and octane. These tips are critical when adding forced induction (turbos, superchargers or nitrous kits), and failure to address ALL of these areas will virtually guarantee engine damage.

An engine that has poor oil control can sometimes mask the symptom temporarily by running a slightly hotter spark plug. While this is a "Band-Aid" approach, it is one of the only examples of when and why one would select a hotter spark plug.

Heat range selection is vital to ensure optimum performance of spark plugs.

A spark plug's optimum operating temperature is between 450 degrees C and 870 degrees C. Spark plug tip temperatures outside this range can occur when an incorrect heat rating is selected. Viz:

When the heat rating is too high:

The spark plug temperature remains too low and causes deposits to build up on the firing end; the deposits offer an electrical leakage path that gives rise to loss of sparks.

When the heat rating is too low:

The spark plug temperature rises too high and induces abnormal combustion (pre-ignition): this leads to melting of the spark plug electrodes as well as piston seizure and erosion.

NGK Spark Plugs pioneered the use of a copper cored electrode in 1958, which enables a spark plug to heat up quickly and also dissipate heat quickly giving an ultra wide heat range. It is essential to use a spark plug that fits a specific engine and its conditions of use.

What spark plugs should i use if i have a Mk1 G13B gti engine, Mk1 Head?

are these ok?

Usually how much HP or torque sees increasing for a good set of spark plugs?

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What do the 'S' & 'Y' signify? - What is the difference between the two?

I've just figured it out -- the 'Y' plug has a 'v' groove in the electrode. Mystery solvered