Well, I've had my Vortech SC installed for a while and lately noticed it didn't seem as potent as it was originally. As long time my350z members will recall, I dynoed 425rwhp after tuning and it felt fast as hell! Recently, it has felt not quite as strong. So I figured it was about time to do some tweaking and for some regular maintanence.

I had already addressed some belt issues last week. So, yesterday I drop some fresh spark plugs into the car (iridium NGKs). The plugs originally installed with the SC looked bad, but not horrible. Definitely a good amount of carbon on the plugs and some very small metal deposits at the base of the hooked metal piece. If I think of it, I'll snap a pic or two of a pretty worn one and add it to this thread later.

I've got a little more than 10K miles on the car since installing the SC and these plugs definitely look like they have led a longer life. It was time to replace them.

This simple maintenance made a very notable improvement in low RPM power! With the new plugs, I could feel the motor pulling much stronger at launch. Mid to high RPM felt about the same, but smoother. I think at higher revs the boost was overcoming a lot of the inadequacies of the old plugs, but the motor was struggling a bit in the lower power band. I know butt dynos are terribly inaccurate, but based on same day before and after driving, I think it is safe to say that I recovered at least 20rwhp across the lower power band and probably a good bit more than that. Most certainly, a Sunday afternoon well spent!

Bottomline for all you FI-ers out there, plug life appears to be (at best) 10K miles. I plan to pull one or two after 5K to see how bad they are at that point.

 

t just changed out my plugs as well... that was really a pain in the a@% to get to...someone on this board claimed it took them 15 minutes... that for sure is an exaggeration.... my stock plugs had some wear, they weren.t too bad, but then again, i've only had the tt setup for a little over a month.

 

I can do it in 10 minutes. Plugs foul out quicker with FI because of the rich mixture. Even if your at 11.8:1, which is a good tune for a FI car your going to foul them quicker because a NA motor would never see a mix that rich. Change your oil and your turbos will spool quicker, that's just how it works.

 

2003 g35 with ati procharger what spark plug would be best?

 

I'm running NGK Iridiums and the motor seems very happy with them. I can post the part number tonight if gq_626 doesn't see this thread and beat me to it.

BTW, props to GQ for having an extra set of plugs on hand! Parts store sold me the wrong ones and as I was working on my car on Sunday would have had to leave my car apart an extra day or two had he not come to the rescue.

 

I am running the NGK Iridiums LFR6AIX-11

 

Yup...thats the ones. They come pregapped at .45, but they are virtually impossible to narrow without breaking something. So I left them at .45

Car picked up 40whp and TRQ across the board. I did a before and after dyno with new plugs and a Crawford Plenum. You can decide which mod created what portion of the WHP gain...but it was pretty tremendous!

McDuck..I bet your butt dyno is pretty accurate.

I'm glad I could help out a fellow 350Z owner with the plugs.

 

ETX:
not meaning to argue, nut how can you possibly change out plugs that quick??? im asking, not to be an a$% but to gain some insight... i had to take off the intake piping, maneuver all the wires out of the way by removing the brackets around them, then contort the coil/plug wires out... that process to type just took me more than ten minutes =-)

and im usingt some power tools to boot!
prolly really took like an hour and a half...thats with pausing to try figuring out the easiest way to complete the job

 

It takes 15 minutes to do all your plugs, and that's not rushing. You must be really slow.

 

I am in the 30min camp. Probably, the most time consuming part is lining up the bolts that hold the coil packs in place. They are in a difficult position at times...and I like to go slow so I dont drop anything.

Also, I noticed McDuck unpluged the coil packs and removed them completely...I think that might be faster, so you dont have to bend the coil pack tube in weird posiitions.

Really...whoc cares how long it takes..lets just say 15mins to 1 hour...that should cover the entire spectrum of mechanical accumen.

 

Well, if you discount the delay I had because of having the wrong style of plugs initially, the overall job probably took me about an hour.

Most of that time was getting the Vortech intake tube out of the way and remounted. Actual plug swap (including removing coil packs) probably took me about 15 minutes.

Oh, and if there are any 350Z owners in Charlotte that don't want to do this themself, I'd be happy to do it for you for a small fee. Nissan charges 3hrs on labor for new plugs!

 

btw... Sharif,

those gains are huge!!! I know that's not all plenum (Sorry, Doug). I've estimated that the Crawford plenum under FI picks up about 15hp at peak and bunches after peak... basically about 50% more than under NA application... and very small torque gains. (if you more torque, but Crawford's headers! )

I wish I could have resourced a dyno for before and after on just the plugs. I find it hard to believe just switching from standard (or old) plugs to iridiums could give you 25-30hp & tq, but based on my butt dyno and gq's actual dyno figures it seems possible.

Guess I'll find out for sure when I get back to the 1/4mile and see how much my speed improves.

 

So are these the recommended ones to run. I will be boosting about 7.5 PSI.

 

gq:
well said... you guys are plug changing gods!!! ohhh so fast!!!

i know, really ..who the hell cares... i was just curious if i was doing something unecessary, i think i was just paranoid of dropping a bolt in the deep dark crammed engine bay of doom!

 

Here is the before and after....upon further examination...the gains were even BIGGER! I swear...you guys will think I did some tuning or ran more boost or something. But I made no changes...same air temp on both days...or at least very close. And I was boosting roughly 8.5psi on both runs....given or take a tenth.

So you guys can judge what part of the gains are plenum and what part are fresh plugs. Oh, and the plugs I removed were iintact

http://www.savepic.com/is.php?i=1956...after_jpeg.jpg

 

Again, that's awesome, Sharif!

On my side, I further verified that my car is running stronger. Stopped by to see my friend who has done much of the mechanical work on my Z. He is very familiar with my car and how it runs. I actually encourage him to drive it when I drop it with him to ensure there is nothing going on that I might be missing.

He drove it this afternoon and said there is a very noticeable increase in power since my last visit. He said its pulling very strong and that he had trouble keeping it from getting sideways when he hit 2nd and 3rd!

Good enough for me. Now I get to see how much of a difference this will make in my 1/4 mile times and speeds.

 

Intresting thing I saw on TV today . I had the NHRA on ESPN on the TV while sitting at the puter .Wasnt paying that much attention . But they started talking about a drag racer that has been using the same Denso Iridium plugs for 2 years , and even won the championship in his class the second year on the same plugs . Just thought I would share what I saw

 

Sharif, your Z is pimp. Oh, and so is your job.

 

Are they a step colder than stock?

 

Fresh plugs can make all the difference. I had an HKS stage VI Eclipse turbo some years back and it developed a miss fire. I tried all kinds of things with the programmed fuel computer, etc., and FINALLY...I put in some new plugs and presto, the thing ran great. Sheesh! I had tried the old STP octane booster (which is no good anyway) and I had put in too much for the amount of fuel I had and it quickly fouled the plugs with a reddish residue. Live and learn...