Step colder plugs vs increase in torque?

[Stkid93]

I’ve always heard that it’s recommended you go a step colder for every 75-100 horsepower you add.

im wonder if this applies to increased torque as well? Because a ton of fist tuners highly recommend step colder plugs when doing a 93/e30. But, our car cannot gain 75-100 horsepower with the stock turbo. But it can gain 75-100 ft lbs. (obviously each platform is a little different and the 75-100 is just a very general rule of thumb)

So, are they suggesting the step colder plugs due to the increase in torque? Or is it just something we should do regardless of how much extra horsepower we add?

 

[daloonie]

I would think of it as overall load on the engine instead of specific HP/Tourqe numbers. If you increase load on the engine, it gets hotter. Hence going for a colder plug could be a good idea to avoid pre-ignition.

But talk with your tuner for recomendations, it could affect how much timing they can/will add.

 

[SteveS]

There's a lot of misunderstanding about spark plug heat range. It's really pretty basic. It has to do with temperature of the spark plug electrode and the temperature generated in the cylinder by combustion. It's worth reading something like this description from Denso:
https://www.denso.com/global/en/pro...e-parts-and-accessories/plug/basic/heatrange/

Here's an explanation from NGK which includes the power-related rule of thumb you quoted.
https://www.ngk.com/what-is-a-spark-plugs-heat-range-2

If your tuner has a lot of experience with the tunes he is supplying, then you can take his recommendation for the heat range to use. But you should also check the results and change the heat range you use based on what is really happening to the spark plugs and whether you are getting preignition.

 

[Stkid93]

Personally,

I have been using denso itv22 step colder plugs. On my fist, and I only used those on my speed 3 as well.

the only time I ran a modified car with stock plugs was when I had my srt4 neon. When I got the car protuned it start having severe blow out and my tuner gapped the stock plugs down and it seemed to work fine. It ended up making 323/387 at the wheels, which was about 85-100 horsepower more than stock at the wheels. And 150 more torque at the wheels. I didn’t have an accessport or anything to log knock so I have no idea how good or bad they were. But they didn’t have spark blow out so my tuner seemed happy with that. So In my experience gap is far more important than heat range unless you are throwing a lot more power at the car.

 

[gtx3076]

My step colders fouled last winter and the car was taking forever to start. My tuner said it would be okay to go back to stock plugs on E30. I did see a lot more larger ignition corrections on it but the car seemed to do okay. After switching back to step colders I see fewer ignition corrections. The Ruthenium step colders have not fouled up on me yet like the iridiums did.