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Bit of a major hijack here Dean, don't worry dude I'm still focused on your AFM dramas mate :P

Tim, there are a few basic rules when it comes to plugs and modifying. Here's a short bust from the NGK web site (with a few additions from me); it'll give you a bit more of an idea:

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.

When it comes to plug gap those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability in these denser air/fuel mixtures). As a rule, the more power you are making the smaller the gap you will need.

A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximises burn efficiency. It is for this reason that most racers add high power ignition systems. The added power allows them to open the gap yet still provide a strong spark.

With this mind, many think the larger the gap the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think.

Be cautious! In reality, most "racing" spark plugs are just colder heat ranges of the street versions of the spark plug. They don't provide any more voltage to the spark plug tip! Their internal construction is no different (in NGK's case, as all of our spark plugs must conform to the same level of quality controls) than most standard spark plugs.

NGK as a company tries to stay clear of saying that a racing spark plug (or ANY spark plug) will give you large gains in horsepower. While certain spark plugs are better suited to certain applications (and we're happy to counsel you in the right direction) we try to tell people that are looking to "screw in" some cheap horsepower that, in most cases, spark plugs are not the answer.

To be blunt, when experienced tuners build race motors, they select their spark plugs for different reasons: to remove heat more efficiently, provide sufficient spark to completely light all the air/fuel mixture, to survive the added stresses placed upon a high performance engine's spark plugs, and to achieve optimum piston-to-plug clearance.

Some of these "specialised racing plugs" are made with precious metal alloy centre/ground electrodes or fine wire tips or retracted-nose insulators. Again, these features do not necessarily mean that the spark plug will allow the engine to make more power, but these features are what allow the spark plug to survive in these tortuous conditions. Most racers know screwing in a new set of spark plugs will not magically "unlock" hidden horsepower.

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.

This is where cold starts can become a problem. The plug tip is obviously at it coldest when the engine is first cranked over. A very cold plug (8 and higher) will take some time to get heat into it and can foul due to low initial plug temp, and the small plug gap normally run in an engine with large horsepower. You can even add the larger injector sizes normally found in large horsepower engines to the potential cause of fouling cold plugs. This is very dependent on the choice of ECU and how well it controls the injectors at idle – small millisecond openings.

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.

no probs with the 8s at all Matt, all good.

Enrico, sounds like its time for a power fc and z32 AFM. Also, have you upgraded your fuel pump yet? about time for that too. If you fit it when you do the AFM, you can get one retune for both at the same time - save you a few $$$

I got this email from Air power systems, the makers of unichip:

Dean,

Even if the MAF is max’d out, there are a number of solutions. – We deal with this issue on WRX’s all the time. - John / David should know how to handle this.

Best Regards,

David

APS

hmmm alex thats weird, cos i just spoke to John today and he was very apologetic about everything, he knew exactly what i was talking about, and told me that he would retune the car for nothing.

I feel better now, except now uve got me worried!? :D

John is really good, he definitely knows his stuff about almost all cars. He used to do heaps of tuning of Supercars etc when he was at DAT. I'd take my car to him except I refuse to go to that workshop after hearing so many bad reports.

Mrman, he did used to have a beard a few years ago so you may be thinking of him from back then.

Hey Enrico, sorry to hear about yet another person getting ripped off in the import scene! I myself have been majorly bitten before also. Could you PM me and let me know where ur car was done? If its where i think it may be im sure we'll have a very interesting conversation over it!

:sadam:

is APS the same company that do the wrx kits? Cos when I went down to melbourne to tune the wrx a couple of yrs ago, they had a really bad rep. They even had a WRX in the showroom on display with their APS kits with a blown motor!

Haha...

Hey dean, U SHOULDA gotten a FC mayyyyyyyyyyyyte....

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