Sorry if this post is a bit cobbled together, I'm not in the best mood right now. Went to the track today with mike. Worked on my car til 3:30am removing radiator, fixing it, and putting it back in, new plugs, etc. I put in NGK Iridium IX BKR7EIX, gapped to .029. Previously I had been running NGK coppers BKR7E gapped to .025. They didn't work out so well, I thought at first I was getting severe spark blowout, but now I'm not so sure. More on that later.

So since the power was breaking up so badly on the way to the track, (initially with the boost a bit higher than normal, .95-1.05bar ~14-15psi) I tried turning down the boost first some, helped a bit but still breaking up, so I turned it down lower, found out I've got a .80 bar spring in the wastegate since I can't go any lower with the boost controller. That's lower than I run daily. Still breaking up. "Typical" daily boost for me has been .90 bar, with 1.00 once every few days, and 1.10 once or twice. As long as I keep the gain turned down a bit, I have no spark blowout problems (gain is how quickly the boost rises as you start to spool. Hard, quick spool is what causes spark blowout for me, not high boost levels).

So by the time I get to the track, I'm thoroughly disgusted with the performance of the Iridiums and I pull them. They look like this:



WTF is that. The ground strap is completely white. That means leanness typically, but look at the rest of the head of the plug, it's carbon black. All 6 plugs look identical at this point. They've been in the car for about 80-100 miles, and have seen a few quick boosts but as soon as the spark breakup (or perhaps detonation?) started, I let off. So I don't know what to think at this point, I'm worried that I'm running lean but I can't figure out how things would have changed overnight, with just a swap of plugs (only other change was removing and reinstalling the radiator).

As you can see, the previous plugs which have 1500 miles on them, look perfect:



So I put in a brand new set of NKG coppers, same kind as were in the car originally, and gap them to the exact same gap as before (.025). I go make a run on these, they worked great. Boosting only 11.8psi (.80 bar) I ran 13.39 @ 114.53 (don't ask about the ET, wheelspin is insane). So that shows I'm making great power at this point. I do a few more runs, one right after the first one, and then I wait like 30-45 for my next one. Everything seems fine at this point, I boosted .87bar (12.6psi) and .91 bar (13.2psi), no problems encountered. No spark breakup, no detonation, just lots of wheelspin. After these 3 runs the plugs were a little lean perhaps, but I was told by a few people it didn't look dangerously lean.

I think about calling it a day but instead I decide to run again 2 hours later. Big mistake. I turn the boost up a tiny bit more (keep in mind still lower than I see quite often on the street). I made another pass without any problem, boosting .92bar (13.3psi) and then I make my final pass. I didn't turn the boost up at all, but saw .95 bar (13.8psi) on this pass. Shift into 3rd, and I start to get what I assumed was spark breakup but stupidly I didn't let off, into 4th, more breakup for part of the gear, then it goes away, and I finish the pass ( I did check my rearview, no smoke or steam or any evidence of a blown motor/HG at all). Pull into the pits, pop the hood just to do a random plug check for my own verification that everything is fine... and everything isn't fine. Steam coming out of the front valve cover breather, and the engine is idling rough. I could see the turbo vibrating back and forth about .25" (it's not isolated from the engine). Pull the plugs, front 3 look just as they did 2 passes ago, a little lean perhaps but nothing I'm really concerned about. Then I get to the back plugs. Rear bank passenger side plug looks just like the iridiums did, very white ground strap, and very black surrounding ring. Hmm. Rear bank center plug looks like the front ones, no worries there really. Rear bank driver's side plug made me know I was in trouble though . It looks like this:



Telltale sign of detonation severe enough to melt the ground strap into slag. Crap. At this point everything starts coming together. What I thought was spark breakup, I now think was detonation/preignition. It was a little bit different than the spark breakup I experienced months before (and turned the gain down to cure). It's hard to describe, but this seemed a little more severe, noise was a little bit different, and it didnt completely go away even when I turned the boost all the way down (with the iridiums), yet it only surfaced on a single run with the brand new coppers.

So basically, something changed. Something changed drastically enough change my car from being well tuned to lean enough that I detonated and blew a head gasket. All I changed were the plugs, and the radiator and coolant. Didn't change any emanage settings. I made sure my GM 3 bar MAP sensor was plugged into emanage unit snugly as it should be, and it was (if it wasn't it wouldn't bring the 2 auxiliary 850CC injectors online).

So now I'm just wondering what the heck happened. Also wondering if it's worth it to try to change the head gasket, or just pull the motor, throw it in my collection of maxima parts, and buy a junkyard motor. Building a forged, low comp bottom end with aftermarket pistons, rods, rod studs, main studs, etc, isn't really an option at this point financially.

I'll be doing a compression test monday to check the other cylinders, but I suspect I'm going to find 4 cylinders are just fine, maybe 5, and then the rear drivers side cylinder in poor shape.

 

wow that sucks

i cant believe is you dont have a wideband with the kind of power your making its pretty much maditory and thats the first thing i would get once you fix the motor

as far as only one cylinder being lean maybe that injector got clogged or the fuel from the 850cc injectors isnt getting evenly dispersed and that cylinder is getting no extra fuel

where is the 850cc ijectors located i assume in the mid pipe

maybe you should ditch the 850s and just upgrade all the primaries to 660cc

what size are your primary injectors

maybe send all your injectors out to get flow tested

it might cost more money in parts to replace the head gasket/s compared to a 2-300$ VQ so thats up to you plus you pretty much have to pull the motor to change them or at least i would think it would be much easier and maybe faster to do so especialy the back

 

Everything you have said are the things I have been thinking over the last few months (or this afternoon in the case of replacing the motor). I guess I figured because it was safe before it would continue to be, but obviously that theory is proved wrong. As far as injectors, I'll be running Deatschwerks 680s at some point this summer, I've got 6x 370cc and 2x 850cc right now. I too have wondered about how even the fuel distribution is, and yes they are located in the midpipe. Carpart.com has about 20 VQs within an hour of me for under $550 like 10 of them under $350. That is what I will most likely end up doing, especially since swapping the motor out of this car is cake compared to a normal stock motor. No exhaust to mess with, no emissions equipment.

 

This may be a case of uneven fuel distribution due to the flow characteristics of a dry intake manifold that is designed for air only and not an air/fuel mixture

 

Yes very likely. Another reason I need to dump the auxiliary injectors and just get some bigguns.

 

Let me know when you guys are ready to adopt my fuel system design.

 

i wish that i would have gone neal. I was looking on car part too and there are tons next to mike. head gasket on a v6 is a PITA. if you pulled it and installed a new one, you could use mardi's copper head gasket mod to lower compression on that motor while its out.

 

Neal you could always get a pair of 3.5 VQ heads like you were talking about before. This is assuming that something catastrophic didn't happen in the bottom end. I can give you a name and number of a guy whom owns a bunch of junkyards(remember the guy with the 03 Cobra Vert @ Gingerman?) and he should be able to get you some pretty reasonably I would think.

 

Why doesn't he just use the entire VQ35? I heard you can get one for as low as 650$. I have an easier time believing that a VQ35 is "low mileage" since it's been out only since late 2001 where the VQ30 has been around since late 1994. I know they have problems with rods snapping but that usually doesn't happen until 450-500whp.

 

Sorry again Neal. Don't get too ahead of yourself. Check the compression then go from there.










oh, and get a wide band and actually tune the car. That is why you got the e-manage

 

speaking of widebands...........check your phone.

 

Man, sorry to hear about that Neal. Wish I coulda made it out there today, thanks for the invite. What did the detonation feel like, was it just a hesitation, or did you actually hear a knock also?

 

Brad, some guy at the track in a red civic hatch came up to me and told me he raced a blue or black turbo maxima the night before...was that you?

 

So what is that engine number 8 for hal's car?...... I lost count.

Get a real tune and real fuel setup. That should fix this problem.

 

You can hear and feel it. What doomed me is the fact that I had problems with the spark blowing out before, and the sensation and sound are sortof similar, so I figured it was just that. To someone who has never experienced spark blowout (which is fairly benign, just annoying) you would IMMEDIATELY know something was wrong. Unfortunately I was conditioned by my experience with spark blowout to sortof ignore it, and that cost me. I'll let you guys know the results of the compression test.

 

Yeah that was me. It was a close race, I had to open my cutout to beat him. What did he end up running?

 

I never saw him run, but he told me his PB is a 13.5. Don't know the trap.

 

Neal,

First off sorry for what happend.

So the NGK Iridium are not good. Which ones should i pick up then since the Iridiums did not work out. Should i pick up some NGK coppers instead since they worked out better for you?

 

The joys of FI...sorry to hear about the situation and I hope everything gets worked out and its not too much of a hassle. Let us know what the culprit is once you find out.

Matt

 

Sorry to hear this Neal, if you need help give me a ring.

The irids worked, his fuel set up was the problem.

 

I have a question, Im not real familiar with Emanage or Nissan ECU functions. Is there no way to monitor the knock sensor using the Emanage? Will the ECU retard timing based on knock sensor readings? Can Emanage monitor knock/timing retard?

 

No, the emanage doesn't monitor/ detect knock.

However

" If the "Optional Ignition Harness" and the software are used the unit has the ability to control a 16x16 ignition timing map." - per Greddy.

Of course to tell what timing you're running, you'd have to monitor it via something like a consult.


Edit: While at it.... a unit that does what you're asking is the J&S Safeguard/Ultra Safeguard. It does indeed detect knock, and will retard timing based on it. It even allows you to retard timing based on boost pressure.