xr4tic

There's been a few posts lately on the A4 forums about different types of spark plugs.

This is the one that got me thinking: <a href="https://forums.audiworld.com/a4gen2/msgs/263262.phtml">https://forums.audiworld.com/a4gen2/msgs/263262.phtml</a>

Right now, I'm running the stock Bosch 3-prong plugs. I prefer these over the gee-whiz platinum and iridium plugs since they're cheaper (~$4 each), work just as well, and I don't feel bad when I foul a set out when running super-rich

The question is, now that I have a bigger motor and turbo, should I start running a colder plug?

The NGK website recommends one range colder for every 75-100hp increase over stock.

Jeff (from the link) recommends NGK BKR6E or BKR7E (aka 6097 - one heat range cooler)

The NGK BKR7E/6097 seems to be popular with the Supra guys (but I don't have a Supra motor)

Are there any better copper plugs out there?

The multi-prong plugs might last longer, but I'm thinking a single prong plug would be easier to experiment with gap, so I'm thinking that's the direction I want to take.

My XR4Ti runs $1 Autolite plugs, and they work great, just need to be changed every 5k or so, so I have no problem swapping plugs out earlier than the factory 30k recommendation.

What are you big turbo guys running? Stock?

WYSIWYG

nah, just experimenting

Shano

The tuning shop I talk to does not care for the multiple prong plugs, they said over time one prong tends to spark better than the other and the other one or ones get left out of the hole sparking process, so they saw no benefits.

I mentioned this here once before, but just to add confirmation to coppers as the plug of choice. I know place that dyno'd a half dozen plugs. The NGK copper plug dyno'd 6hp higher than any other plug, it was the only copper one they tested in the group.

xr4tic

would be that if one prong starts to wear, it could hit another one. But if the prong is worn, more than likely the electrode is too, and it should probably be replaced.

Catfish

What I read was they recommend going one heat range colder if you add a turbocharger or supercharger. They recommend reducing the stock plug gap .004" for every 50-75 horsepower increase over stock. I have followed this advice with my installation of the G2 supercharger. Since you were turbocharged stock, I suggest you stay with the stock heat range, but use a single ground electrode plug so you can decrease the plug gap IAW the above recommendation. I could tell a difference just by changing the gap .004". This applies only if you have the stock ignition.

hurricanesteve

couldn't find the autolite 3922's locally.

RCY9 somthing or other. so far, REALLY happy (couple hundred miles on em)...the iridiums (IK22) were fouling non-stop as were the bosch plats that APR sends and recommends. Cleaning them didn't help this last time. Kenne Bell always advised me to run copper plugs on the s/c kit I bought from him..."better conductor, just replace em every 10K"

so I'll watch these carefully and see how they do. Smoother accel. and better idle so far.

hurricanesteve

gapped at .032 currently

hurricanesteve

YGM...

xr4tic

"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."

Theoretically, increasing the boost is the same as raising the compression, your cylinder pressure will go up. This is what causes the extra heat, not to mention the fact that the turbo air is pretty hot to start with.

My interpretation is it goes three ways:
1. compression increase
2. adding a turbo/supercharger
3. increasing boost

Catfish

How much have you increased your compression?