I've read where some people are using #9 spark plugs (normally Trailing plugs) in both positions, Leading & Trailing.
The theory is they are colder plugs & less prone to detonation under boost.
I was gonna give it a shot when I dyno my car tomorrow.
Any thoughts or experiences? Good or bad? Benifits?

 

The 9's are a colder plug, so I guess they'll be less prone to heating up, maybe that'll decrease detonation during hard runs. I think one of the real benefits is that the plug doesn't overheat.

I run 9's all the way around in my 93 R1 because I auto-x and drag race sometimes.

I've had project 93 RX-7's that were completely stock with the 7's and 9's. The stock plug set-up allows a smoother start and cold idle.

With the 9's it will stumble a little more during cold idle etc. Nothing dramatic just very slight vibrations.

Jeff

 

Just like Jeff said, the car will be a little rough while running 9s all around. Most people usually don't run all 9s unless they are at the track running hard. A few runs on the dyno shouldn't make a difference unless your EGTs are getting high or if you are having preigntion problems.

Best of luck.

 

so running all 9's is actaully a little safer then the stock setup? Running all 9's is completely streetable right?

 

yes they are completely streetable. basically, they will help prevent detonation, but on other han dthey will load up with carbon faster becaseu they retain less heat. so if you drive your car through traffic all day, etc, may not be good. But if you are running hard all the time, they will keep themselves clean.

just run them for a bit, and then check to see the carbon deposits, if too high, switch back. but you shoudl eb okay with them. I run them with about 13lbs boost, and have relatively no build up,

 

so If I run them on the street. Could I just push my car every once in a while to keep them clean?

 

If you're babying it enough that you'll get lots of carbon on the plugs, 9s aren't for you. I run all 9s, but I redline it a dozen times every time i drive it. Also depends on your mods, you probably won't benefit from running 9s on a highly modified car, but you definitely will need 'em with street port, single turbo, big intercooler....or probably even 11s with that setup.
~Tom

 

I don't exactly baby it. Normal driving I shift around 4-5k. I redline it maybe one time everytime I drive. My mods are in my sig and in the next month or two I plan to add a MP, IC, and PFC. So you really think all 9's isn't for me?

 

Yeah, i'd probably stay with stock plugs. Lot of people will say use all 9s even with a completely stock car, but I disagree. My mods, i used stock plugs for a while, then just recently changed to all 9s.
~Tom
PFS- DP, MP, CB, IC
Remapped ECU
Profec B @ 13psi

 

damn you guys must drive slow! 7's are meant to scream! i run 10's and 11's on the street with no problems