Something interesting about spark plugs!

[WydRyd]

I just read something interesting about spark plug heat range selection.

It seems, for every 75-100HP you add to your motor, you should go one range/step colder when selecting spark plugs.

I never knew this to be honest! There you go, you learn something new every day

[wcc]

Where did you read that? Not trying to doubt you, but curious. Do you have a link or the whole article. Sometimes, not all the time, things are taken out of context. If you can believe that..

[DRV2FST]

It may not be that simple. I am not an expert just a 930 owner/addict.

I have 505 rwhp. So that is what ...about 594 at the motor? I was running cold (NGK 7 range) spark plugs and they kept getting fouled. I swapped them out for some hotter ones and it is better so far. Only more time (and miles) will tell.

[WydRyd]

I read it in a tech section on the NGK.com WEB site.

If you add significant HP gains to your motor with more boost, you will need a colder plug in order to remove heat from the combustion chamber more efficiently.

If you run a plug that is too hot for your motor, you risk detonation under heavy loads (which is BAD). If you run a colder plug for your motor, the only risk is that the plug will foul quicker.

I personally would rather be changing fouled plugs more frequently, than running the risk of severe engine damage by running a plug that is borderline

I'm currently running W3CS plugs and they seem to be performing better in my motor than the W4CS plugs I had in there previously.

[GO DAWG GO]

What about the DPO's? Does the W3CS work better or just cheaper? will the W3CS work on a stock engine..and what did you pay for them?

Thanks

Bob

[WydRyd]

DPO's are Platinum plugs and have a longer lifespan than the CS's. The DPO's also fire more reliably on stock ignitions at higher than stock boost levels, but since I run a CDI, that's not really an issue for me. W3CS would work fine on a stock motor at stock boost levels. Certainly a cheaper alternative to the DPO's, at the same heat range as recommended by the factory.

I suspect the factory specified a 3 heat range because they knew their customers would be thrashing their cars on/off the track, so they wanted the extra insurance of running a colder plug.

At the end of the day, cost was the factor for me. I was quoted AUD$50 for each DPO plug , whereas I sourced the W3CS's for USD$2ea NEW So I purchased a dozen of them. Might pick up another 18 or so and just have them as spares, since I typically change my spark plugs every 5,000-7500km's.

EDIT: I know a warmer plug will stay cleaner longer, but I'm not risking pinging/detonation in my motor, especially at the boost levels I run. $50 on a set of plugs every 7,500k's is more cost effective than an engine rebuild

[NathanUK]

Merv, maybe you could get the W3DPO's sent to you from the USA at a reasonable cost.

[WydRyd]

Yeh, I looked into that, but it was still cost prohibitive, especially since I'll soon require 12 plugs The W3CS work very well and are significantly cheaper. My source is selling them at $2ea (excess stock), so I'm stocking up on those whilst I can