Spark Plug Question

[carlo]

Hey all,

I changed my spark plugs to NGK iridium (.8 gap), and am finding that at idle and down low the car seems lumpy.. Almost like I have put a new cam in it, also I have noticed the exhaust note seems to have more definition (for lack of a better word)..

The car seems to be running well, its just down low and off boost it feels weird.

Any suggetsions as to what this could be.. Is it just the new plugs (the old ones where very old a shitty), maybe a timing thing??

Cheers

[Guest RedLineGTR]

how was the car, before you changed the plugs. Do you run higher than average boost if not why gapping them so small. Did you screw the new spark plugs in properly, were all connnections cliped in properly?

[Doctor]

Try turning the top of the plug so it faces the injector.

[rb25]

This is like a misfire at idle and is ok. My 33 does the same on a .76 gap 6heat copper plug - not burning fuel as well as it could at idle but never misses a beat on full boost @ high rpm. Running a cold plug doesnt help the idle either.

[Doctor]

I changed from 7's to 6's yesterday and my god what a difference. Better start up, idle as smooth as power delivery more linear.

[rb25]

6 are better for street use IMO. They run warmer and burn fuel more efficiently.

[carlo]

The car was fine before the change, but it seems more responsive post change..

the car runs about 9psi of boost.

[Zahos]

Originally posted by Doctor

I changed from 7's to 6's yesterday and my god what a difference. Better start up, idle as smooth as power delivery more linear.

Then try going to 5's. I just went from a heat range of 5 to 6 and I dont like it!

I'll be going back down to a heat range of 5 again, so much smoother....

[JL]

What spark plugs are the best to buy and what should I get 5's 6's or 7's. I have a 32 gts-t lightly modded,

Cheers

JL

[Zahos]

lightly moded = BCPR5E

I am guestimating I am sitting at around the 170 - 180rwkw mark, and my car runs best with these for street use.

[JL]

What brand of plugs are BCPR5E Zahos?

[Zahos]

NGK

Do a search, you'll find this is topic is covered extensively....

[Doctor]

Zahos do you find that its threshold to detonate has lowered? Do temps run a little higher?

[Zahos]

I found that once the car warmed up, idle was smoother, and that the plug didnt foul as quickly. It also significantly reduced the misfire at the 5000rpm mark seen by R33's with VVT (not that it applies to you ).

So in answer to your question, yes!

Temps were just the same, noticed no difference.

[JL]

Thanks for your help Zahos,

Cheers

JL