Hey Guys

After about 4000 miles on this built motor (intermediate load/intensity driving), I decided to replace the plugs (had misfire codes), and while I was at it, did a compression test as well (with fingers crossed behind my back).

OK here are the results:

Cyl 1: 170 psi
Cyl 2: 170 psi
Cyl 3: 167 psi
Cyl 4: 170 psi
Cyl 5: 175 psi
Cyl 6: 170 psi

Here is what ALL of the plugs looked like:



I used two bottled of MMT-containing octane booster (NOS Racing formula), and I think this is why there is a red residue on them (and they smelled like gas). I had pulled the plugs for an inspection right before, and they did NOT look red. This I am not worried about, more of an FYI thing.

Here is what they looked like before, each one of them:

Cyl 1


Cyl 2


Cyl 3
[url]http://www.gurgen.com/G35Pics/Spark%20Plugs/Cyl%203.jpg[/IMG]

Cyl 4


Cyl 5


Cyl 6


Here is the real question. Would the plugs look like this (any of the two cases above, before and after octane booster use) if I had a water (head gasket) leak? Last time I did, that plug looked completely "washed out", almost like bleached look.

Any comments whatsover would be appreciated. I am just tryign to see if I still have an issue with these sleeves. Thanks

 

Compression looks good! My personal opinion is the plugs look good. I would try closing the gaps a bit and indexing your plugs with the open side of the tip pointing to the exhaust valves. The top picture of the plug with booster looks like its running to cold. The before pictures of the plugs look great.
I do not see any sign's of water. Pasta

Just a quick note: Make sure your radiator cap is not holding to much pressure if your worried about a blow head gasket.

 

6 is definitely the most lean. Mine looks the same way. 1 is definitely the most rich. This is normal. The same thing happens to my plugs as your first picture when I run a methyl alcohol based octane booster. This is normal. If your motor is running 9.0 pistons your compression is a little high. If you are running 8.6 or less it is definitely high. Did they mill the head any?

 

Sorry , I forgot to mention.... my compression ratio is 9.3:1..so i think the results there are good. I was more concerned with water leakage. But I guess I am ok for now.

I am STILL gettting this really annoyinig P0300 code... random misfire. The car does NOT actually misfire..it's something else. Got the code 15 minutes after swapping the plugs... so it'sdefinitely something else..

The ting is that it happened right in front of my eyes, it came on (and this is the second time this happened in EXACTLY the same manner) as I gave it about 40% throttle coming from rest right at around 2400 rpm or. This imo lends credence to he bad cam phase sensor... will be taking those out to clean them. Any thoughts?

I gapped the plgs at 0.035-0.036 or so, by te way.. And I think i am noticing a power loss at teh present boost setting. But could just be in my head.

 

I get the same exact code. Mostly happens at idle. The only thing that I can think is the car doesn't like these cold plugs(IK22's) at idle and low loads. I get no other codes just the P0300 as well. I just live with it and carry the OBDII scanner in my car.

 

I'll bet $10 that the PO300 is from your Timing Contol device.

It comes from when the Crank signal is not cleanly altered by some piggy backs.

The ECU thinks its a misfire.

 

Okay,

I used to work as an engineer for NGK Spark Plugs for 4 years, and have worked with these plugs before.

A couple of things:
1.) The "before" plugs look good. The insulators are not fouled, and the center electrodes look good for single iridium spark plugs. One or two might be running SLIGHTLY rich or lean, but basically that is what I would expect to see from normally operating spark plugs.
2.) The one after the octane boost...yeah, that's not good. First of all, MMT contains a very high manganese content. Manganese will foul the end of a spark plug rather quickly (reduced plug life), but I would also bet that at some point you are also going to get an A/F sensor failure too. Manganese plugs the ceramic elements in O2 sensors VERY badly. So, constant use of octane boost with MMT in it will more than likely result in O2 sensor codes down the road and required sensor replacement. Not immediately, but don't be surprised if it comes up in a year or two.
The plug you showed doesn't look to be REALLY bad right now, but I would have to see it in person to tell you if it's shot or not.
3.) As for your misfire codes, they might actually be misfire codes. You see, the spark plugs you took out of the engine (NGK P/N: PLFR5A-11) were double-platinum, meaning that there is a platinum chip on both the ground electrode and the center electrode. This will ensure a long life, low-required voltage spark plug. Now, the Iridium IX you put in is a single-platinum. Albeit, initially it may have a lower required voltage due to the very small diameter center electrode (0.6mm, if I remember correctly) and the use of iridium, but the ground electrode is just Inconel, no platinum used. So, if the ground electrode becomes fouled/coated (i.e. from the octane boost), the required voltage for spark COULD go up, exceeding the output of the ignition unit sometimes, and thusly creating a misfire code. Plus, the single iridium spark plugs you put in won't last as long as the OEM ones. At best, under ideal conditions, 60k miles. The OEMs are stated to be good until 100K miles, but personally I would change them at 80~90k miles.
As a recommendation only, you may want to hunt down a set of NGK P/N: PLFR6A-11 instead of the LFR6AIX-11 that you used. They are identical to the OEM ones, except they are one heat range colder like the Iridium IX's. Or, if you're a JDM nut, a set of LFR6AIX-11P, which is "Iridium IX MAX" (iridium-platinum) sold only in Japan. Any of Those might alleviate the misfire issue, maybe. However, the PLFR6A-11 won't be cheap.
Just my $0.02. It's hard to say some of this exactly without actually seeing the plugs, and running a few tests. Hope it helps.

 

I would run 2 step colder copper plugs and change them every 10-15k miles.

 

A basic write up on Crank Angle Signal Integrity Done by APS. Which may cause the Misfire diagnosis from the ECU..

During the development of the APS Intercooled Twin Turbo High Output System, a problem was encountered with the tuning of the engine. The problem manifested itself as ignition timing scatter under conditions that were intermittent, transient and at times occurred for only fractions of a second. In other words, the ignition timing would vary in a manner that was inconsistent with the engine RPM and engine load - and was not repeatable under identical operating conditions. In addition, due to the short period of time when the issue presented itself, very difficult to diagnose. The problem never the less did continue to appear on the APS engineering vehicle from time to time.

Tests were also conducted on a number of other 350 Z vehicles and whilst it was never encountered on those vehicles, the intermittent and erratic nature of the problem made it impossible to replicate without sustained long term testing of those vehicles. That is not to say that the problem does not occur on other vehicles, but it was an issue that did need addressing.

APS embarked on an exhaustive testing and engineering program to identify the cause of the problem and then deliver a solution that would be cost effective and practical.

After a great deal of data logging of the variety of sensor signals leading to the engine management computer, it was noticed that the signal quality from the crank angle sensor at times became erratic. The crank angle sensor is a vital component that informs the engine management computer of the exact position of the engine crankshaft and is used throughout the engine management program to control a variety of functions - in particular the ignition timing (when each spark plugs fires to ignite the air/fuel mixture inside the combustion chamber).

When the signal from the crank angle sensor becomes erratic, so does the ignition timing (in addition to other functions).

Ignition timing is a vital tuning parameter particularly in forced induction applications. If the ignition timing becomes retarded from the optimum point, the engine will produce less power and torque. However, and most alarming is when the ignition timing becomes advanced from the optimum point, pre-ignition and detonation may occur. Detonation places extremely high loads upon a variety of engine components such as pistons, conrods, bearings etc and the chance of failure of each or all of those components becomes very high.

With the intermittent and erratic behaviour of the crank angle sensor signal, either scenario was possible.

The engineering process continued at APS and the entire crank angle sensor circuit was painstakingly checked and verified using a variety of sophisticated electronic testing equipment. The circuit was found to be quite robust and electrically sound, however it did become susceptible to electromagnetic interference commonly found in a modern motor vehicle.

The solution was relatively simple (all the best solutions are!) and involved amongst other things, replacing the existing cabling from the crank angle sensor with robust shielded cable (and effectively earthed).

The entire crank angle sensor solution is included with each APS Intercooled Turbo system complete with factory connectors for a truly plug-in application.

After long term and demanding testing of the APS Intercooled Turbo system with the crank angle sensor solution installed, we are pleased to report that the timing scatter problems experienced with the APS engineering vehicle have never again occurred. Nor have they on any of the other 350Z vehicles APS has tested since.

A final point to consider is that the timing scatter problem was only ever encountered on the APS engineering vehicle. It may indeed have been a problem on that vehicle only when used with a forced induction system. The problem may not be present on other 350Z vehicles with other forced induction systems, be they turbocharged or supercharged, however due to the intermittent and transient nature of the problem, APS was not prepared to take the risk of assuming that it was a one-off occurrence - hence inclusion of the APS solution with all APS 350Z Intercooled Turbo Systems.

 

Gurg, the way I understand it is:

White chauky color means your running lean and dark caramel color means you're running rich...you want in between...light caramel color...

 

Darth,

Fabulous write-up from APS. Thanks for posting. That would make complete sense. Approximately 2 years ago, Nissan did a HUGE recall of a lot of VG, VQ, and QR motors due to bad crank angle sensors. Now, that's not to say that this one is bad, but it certainly lends credit to a potential problem with either the crank angle sensor itself, or its output signal.

It may be something else to investigate

Randy,
You are correct. You're basically looking for a light tan color on the insulator. That usually means a properly running engine. I believe that the plugs above were still white because they did not have many miles on them (relatively speaking).
The one that was red is fouled (of course), but is red instead of black due to the high manganese content of the fuel, I would guess.
The manganese plugs the ceramic insulator, which lowers its insulation resistance, which can lead to misfiring as well. Basically, the spark can "leak" through the carbon deposits on the insulator and ground to the metal shell where the two meet, instead of jumping the gap. Remember, electricity always follows the path of least resistance, so if it's easier to ground to the metal shell through carbon deposits on the insulator, instead of through jumping the gap (thusly sparking), it will.

 

Only in my case I am NOT running a any kind of piggyback..stock ecu with a reflash. no other devices. In fact from MY testing, I am POSITIVE it's not an actual misfire (i.e. by a plug), as I wouild likely get a p0301-0306 code along with the 0300 code. There is no miusfire 'felt' AT ALL. It's gotta be a sensor issue. Crank sensor is ALL new, and I have teh crank sensor shielded wire mo das well (but thos problem presented before the wir mod - so that can't be it).

 

The code back on these brand spanking new plugs after only 10 miles of driving...

 

What great advice...thanks.

But the code came back in about 15 minutes of driving on the brand new plugs... Are the plfr6a-11 also of 0.6mm tip variety? What is the advantrage of running iridiums, just that (at least initial) low voltage requirement? Should I jsut use the platinums(i will be running about 16 lbs of boost)? Also, and sorry for the questions, what gap should I run. All these plugs were left at the stock .043" gap, while I gapped down the current ones to 0.036". Your htought would be greately appreciated, thanks.

 

GurgenB,
Hmmm, interesting, the codes came back after only 15 minutes of use, huh? Well, first of all, let's answer your questions:
1.) The PLFR6A-11 are not 0.6mm tip. They are (I think) a 1.0 or 1.2mm platinum-tipped plug (can't clearly remember). Only the Iridium IX are 0.6mm, as only iridium could have such a small center electrode diameter and last any respectable amount of time (Iridium is VERY durable).
2.) Yes, you are correct, The smaller the center electrode diameter, the less required voltage to jump the gap. Plus, Iridium is a much better conductor than standard nickel center electrodes. So, the two combined make for a lower required voltage to jump the gap (assuming identical operating conditions within a cylinder compared to stock).
A question before the gap answer:
1.) Are you running any kind of aftermarket ignition module (MSD, etc.)? If so, I highly recommend NOT using iridium or platinum spark plugs. Just run standard nickel spark plugs and change them every 15k miles. An MSD-like system erodes the tips of platinum/iridium spark plugs so fast that it makes the investment in them pointless.
I am wondering now if your ignition system is up to the task. Standared OEM ignition systems typically can't generate any more than about 30-34kV of power, and a standard ignition system usually only draws about 19-24kV per spark. If the system occasionally cannot provide enough power (due to high boost levels), you may be getting a misfire code....But, based on what you've said, the codes you would think would show up are NOT....

Now, as for the gap...Sorry guys, I talk in millimeters. The standard gap on both the OEM and Iridium IX is 1.1mm (thusly PLFR5A-11 and LFR5AIX-11 )
So, decreasing the gap size from 1.1mm to 0.9mm should reduce the required voltage by about 15% or so. This may solve the issue. If you are not using an MSD system, I would recommend changing the gap on the IX's to 0.9mm and then trying them out. If you are using an ignition system, then 0.9mm on standard nickel (LFR6A-11 would be good) should help as well.
The main advantage to the IX's is not only the lower required voltage, but also that, due to the smaller center electrode size, flame front expansion upon ignition is faster. With a smaller gap of 0.9mm, the burn may not be as clean, which means faster flame front movement will help alleviate that somewhat.
I hope this answered some of your questions. Good luck!