Spark Plugs Problem

[Shoryuken]

Just changed the spark plugs on my stock standard R33 GTR and now the car is running rich and there's a popping sound coming from the exhaust.

The spark plugs I used are BCPR7ES and the gap is at 0.8mm.

What do you guys reckon is the problem?

Edited August 10, 2010 by Shoryuken

[GTRPowa]

With a stock standard R33 GTR, shouldnt you be using 1.1mm gap? And possibly 6 heat range?

From what I've learned, unless you have ignition problems, or running more power than stock, you run 6 series plugs and 1.1mm gap.

I believe the 1.1mm gap ignites the fuel better, combusting all the fuel properly.

I'd have to get a +1 on that though, but it's what I've learned.

[Shoryuken]

Hmm...

I've searched these forums and lots of people recommend going 1 heat range colder and a gap of 0.8mm for a standard RB26DETT?

[GTRPowa]

Yeah opinions differ and it makes it a confusing topic.

On the other hand lots are using 0.8mm gap and 7's and haven't had the problem you described.

Some use 6 series 1.1mm gap, no problems.

Someone else said that stock they are 5's

ARGH!

But if all you honestly did was change plugs and nothing else, I'm trying to see what else could have caused it.

Do you have the old plugs still?

[GTRPowa]

http://www.skylinesaustralia.com/forums/Sp...&hl=bcpr7es

I have heard of gaps from 0.8 to 1.1

I have learnt that the gap depends on the boost you are running, for stock the gap is 1.1mm if you are running 12psi or above 0.8 is recomended, as for plugs there is no perfomance gain to be gained from any but the life of the plug is greatly increased with platinum (80,000ks) and better still with iridium (100,000-160,000ks) compared to coppers which are recomended to change at 5,000ks although some say they last to 10,000 upto 40,000, if you can change them yourself go the coppers recomended below, I am using iridiums and they have been in there for 100,000k now and still good, I know because I keep pulling them out when something else stuffs up. Price wise they arent worth it really, I have been told that they are good in motors where changing the plugs are an absolute pain.

Generally speaking if a plug has a higher number than another it runs a colder heat range. eg. BCPR6ES ..... BCPR7ES colder plugs are good for preignition troubles.

Boost effects spark gap at 12 psi and above, the gap narrows down to 0.8.

Big thread that one.

[Shoryuken]

Yup, the old plugs are BCPR6EIX. They are so worn.

[GTRPowa]

Well if they weren't causing a problem, and you want to eliminate other possibilities, I'd simply put them back in, takes all but 10-20 mins, start her up, see if this new problem goes away.

From reading a few random threads again, I've gathered it's the general consensus to go for as larger gap you can. Some threads even mention using splitfire coils and raising the plug gap.

At the same time I haven't seen many posts about 0.8mm sizes causing any problems on light load (which is when a 1.1mm gap would be preferable). Assuming this happens on light load/idle too.

[Shoryuken]

I'll try put the originals in today. I think the popping from the exhaust is "misfire". If the original spark plugs work, I'm gonna regap the BCPR7ES to 1.1mm.

[mad082]

ok going colder plugs may make the misfire worse (colder plugs don't ignite fuel as well as hotter plugs), as will making the gap bigger (if the missfire is caused by weak coils).

secondly just to point out something in your first post, changing spark plugs doesn't make a car run more rich. they have zero effect on fuel settings.