legacycentral bbs

Ok, quick question:

When running tire-pressure-like boost, what direction do I go with my plugs?

I got a new set of plugs off of a WRX guy for free when I bought some suspension parts from him.

They are NGK copper plugs (my favorite plug, by coincidence), and part number BKE7ES-11.

I've seen it posted that our Part number is BKE7E-11 (for 1 step colder than stock).

So my questions rise as what direction do I want to go, hotter or colder. I live in Maryland, so we get ALL kinds of weather (sub zero temps, and 100+).

And, will the BKE7ES-11 plugs work?

You plan on running above 30 psi of boost?

I don't know what the S designation stands for....so you may want to find out what that means.

What sort of engine management do you have?

I think people try to swap plugs around too much, and it ends causing a loss in power, rather then helping. A friend with a very lightly modified RS decided to put colder plugs in, and it ran worse, and got worse fuel mileage.

The only reason I can see to put colder plugs in is if you're getting pre-ignition/detonation due to the plug not having enough time to cool between firings, or if your plug life is really short or electrodes are burning up.

I wouldn't go with a hotter plug if you're running high boost, that'll just make any pre-ignition/detonation worse.

If your plug life is fine, and don't have any detonation issues, I'd just leave what plugs you have in there. You could try the colder plugs and see if it helps....if it doesn't, put the stock ones back in.

dzx - Not quite 30.

Josh - Engine management is still up in the air, really. It will be figured out soon enough. Just gotta hammer out the final details of it all. Of course I need to get fuel controlled, and then tune.

Do you have any present driveability issues? Check the old plugs and look for signs of hot running; like blisters, prematurely eroded electrodes, or insulator damage. If they're a nice tan on the insulator and they run fine I'd stay at that range. As Josh said, going too cold would be detrimental to performance.

Steve

You definitely don't want to go hotter. The two changes you might have to make are a) switching to a colder heat range, and/or b) reducing spark gap.

From what I understand, you should go to a colder range only if your plugs do show signs of glazing due to overheating, or if you're getting knock that you believe to be due to extremely hot spark plug electrodes. Generally, if you do switch to a colder range on a daily driver, you'll have to replace your plugs more often because they'll foul up when you're driving off-boost around town and stuff.

The recommended NGK coppers for our car are BKR6E-11.

The S in plugs like BKR7ES means "standard," as opposed to V-Power. The V-Power design has been pretty conclusively proven, so I would stick to that.

Before you start monkeying with the gap, I'd do some upgrades to the ignition system first. An MSD DIS-2 will help keep the spark strong under higher cylinder pressures, for example. Good quality wires, like Magnecors, help too.

I used to run BKR7E-11s on my car. But I ended up having to use the BKR6E-11s because Autozone didn't have any of the BKR7E-11s in stock. After 5000-7000 miles they showned normal wear for the plugs. No unusual lean run condition or eroding of the electrodes.

But that was at 16-18psi with your setup. Not exactly "tire-pressure-boost."

Never had any cold-weather problems with the 7Es, so I would say just stick with the stock range until you turn up the boost.