Hey Guys.....

You may have cought the hint in the NorCal thread about today's Meet up here.... well... here is the rest

We were on a great drive through the Skyline Blvd twisties (one of the best I've been to, an appropriate name as well), when my engine spilled some of it's guts on the road. I heard a hard thump or two, as if i ran over a boulder and it hit the underside of my car.... There were no "explosions" (nothing was seen from behind either) or anything of the kind... in fact i didn't hear any significant sounds from the engine (in front of me), but only the underside of the car.

For the first fraction of second, i thought that i did in fact hit something... Until of course i came to my senses, saw a plume of smoke that completely covered up the road. Andy and the rest of the guys behind me reported 3-5 foot visibility, form what i gather. Once I knew that the engine went, and realised the hazard of that much smoke, I just starting hoping that everyone will emerge out of the cloud alright (and guys... it was seriosuly a HUUUGGGEEEEEE cloud). I was relieved to see Andy come out of it ok with his hazard lights blinking...

So, we park, look at the car.. once i see the trail of oil that I left behind... it's pretty darn clear what happened, a rod broke and flew THROUGH the block. We later found pieces of the block on the road (took pics of this too). Andy wll post some pics soon. After we parked and called for a tow truck, we saw how much oil the car was hemorrhaging.... a few quarts there, and a few quarts on the bed of the truck itself, after we drove into S.F.

Here is technical aspect of things:

Boost: 5.7 psi (+- .2)

RPM: I hit the rpm in 4th gear at around 4000, and ~2 seconds later, it blew. So, about 4300 rpm.

Timing: I was retarding about 0.9 degrees per psi, so my total retard was about 5 degrees. The g35AT sedan timing is about 21-22 degrees BTDC, 3-4 degrees less aggressive than the MT's and the Z's. So, I was at about 16-17 deg BTDC. Which is pretty safe. Aside from that, I do after all have a J&S that indicates knock, and it was NOT going off. Also, I was NOT hearing any audible pinging. So, I am pretty confident saying that it is is not a detonation-related failure. Then again, it's hard to say.

A/F: I did NOT catch a glimpse of my AEM right before it blew... sorry. But, the A/F was ALWAYS, WITHOUT exception over the last few weeks in the low 11 range at this PSI setting (and sometimes below 11).

So, no detonation (audible or knock sensor-detected), 4300 rpm (torque peak)... It's got to be a stress-related failure... the rod was probably just fatigued, or it was a weak one from the start who knows. It sucks that it happened now... b/c I was ready to put in a full data-logging solution in my car next week, that would've logged everything.. and we would know much more.

Oh well..... I was planning to build a new motor anyway. But I just hate saying this... as this just shouldn't have happened. Any thoughts guys?

Gurgen

 

Wow !

That REALL Y REALLY SUCKS MAN !!!


Sorry to hear that.

Now I'm really going to get forged rods and new pistons !


But I too have an auto (coupe), so I'm still not 100% sure about going TT .


Hopefully by next spring there will be more info on an auto TT.

Good luck on the new engine !




Tasso-

 

Tasso

By then I should have pretty good longevity data on the PE with AT (being a test mule yet again)

 

sorry to hear about your loss. at least everyone came out ok. hope all works out with you and your rebuilt motor. damn this sucks.

 

Well that's really bad luck................I really feel for you................that's not a nice experience.

I suspect that your diagnosis is correct..................if the engine failure was around peak torque (extremely high cylinder pressures) I'd guess that the con rod was either under spec or fatigued as you stated...............more likely a faulty con rod.

I'd really like to see some pics of the engine..............maybe you spun a big end bearing and the rest is history.

Sounds like it's now time for forged con rods and pistons .................crank the power up for an even bigger buzz.

Look foward to seeing some pics of the engine if possible and good luck with the new engine.

Peter

APS

 

Thanks Damen, Peter

I will document this as much as possible.

Do you think it would be likely (more or less than the presumed cause as discussed above) for detonation to take out the engine without any warning (i.e. no audible pinging, and nothing being picked up by the J&S).

Gurgen

 

P.S. The NorCal meet I am referencing is for the G35 site.. sorry this was a cut'n paste.
G

 

I doubt that this failure is detonation related though it's possible................sounds much more like a con rod failure (most likely a faulty con rod) though I would l like to see a picture of the crankshaft and big end bearings.

This should tell the entire story...................I suspect that the engine spun a big end bearing and then broke the con rod at the big end of the rod.

Peter

APS

 

Sorry to hear the sh*tty news Gurgen.

Once I hit the rev limiter while under WOT and some how flatened the tip of my #5 cylinder spark plug. Nothing broke off, the tip of the spark plug simply was bent to the diode and therefore giving no spark. Up to now ppl have told me it could have need rod stretch. I'll know for sure when my motor is completely apart and i'll post the pics. These connecting rods seem to have some crappy consistency in their build quality.

 

Peter, Enron

Yeah I agree... These rods are of relatively bad quality.... It sucks for us that got the "bad ones" of the bunch.

APS,

The detonation though WOULD ALMOST CERTAINLY give a sign, like continued pinging. that's the only way I know of for detonation to bring down an engine, right? (Unless of course there was a weak rod in the picture or smth).

THe big end bearing sounds like an explanation... There will be some pics of the broken off pieces posted soon (of the block, did not find any piece of the rod)

G

 

Gurgen,

That's awful man, I'm really sorry to hear it. Makes me think twice about pushing my engine at 9psi everyday :-/

Hope you sort everything out, you've been a big help to everyone here. Please keep posting, we count on you.

 

Slay... i'll tr to document everything as much as I can....

If it is in fact mechanical, and not tuning related (which honestly I do not see how), just prey that your engine components are good. Good luck man

Gurgen

 

Wow, I'm away from the forums for a couple of days and *this* happens?!? Yikes!

--Steve

 

Sorry man. Bigger and better next time

 

damn gurgen.. that's sucks.

good luck in getting everything figured out, it really sounds like you had a lot of angles covered and that you shouldn't have had any issues; especially at 5.7psi. did it all happen right after your 3-4 shift? a ton of automatic maxima owners had related problems as this because they would boost through the shift and put a ton of stress on the motor and eventually blow it. silly vq's.

nows the time to iron out that 6-spd swap we talked about, hah.

jason

 

It would be nice to believe that the cause is just a bad batch of rods but that would be wishful thinking. It is becoming increasingly clear that the stock rods are not suited for these HP levels. Don’t be misled by the fact that only a small percentage of engines have broken rods because mechanical failures are never 100% unless the part is grossly under designed for the task.

 

horrible news!!!

hope you get it all sorted out soon. Like slay2k said it makes me really wonder about my engine and how hard i push it. I am currently in the middle of changing the plugs and then getting on the dyno to try 10psi. Why as my engine held up to so much abuse when others are so unlucky? Very wierd... maybe the track edition got some xray tested rods or something and the ones that failed the test went into the other models?? i think not... i have no idea why my rods are holding still... especially this kind of mileage of abuse..

 

Sorry to hear about everything man hope you get it all sorted out soon. Rods are definitely the weakest link in this motor and it seems more and more that most of the failures are attributed to fatigue rather then improper tuning.

 

Gurgen, just saw this thread. Sorry to hear about your motor and hopefully you will have more information when more analysis has been done. Hope you get this sorted out and back on the road again. Most likely with bigger and better parts..

 

Hey Gurgen..just wanted to put my thoughts and hopes that everything works out ok..even though we already talked on the phone.

Given the history of failures with the TT kirt and rods snapping, I am 100% convinced that our rods are not capable of producing reliable F/I power...even at low boost levels. Your car is a particularly telling case, becuase you are very knowledgable, and do things in a thorough fashion. Car was tuned to perfection, timing retard, J&S as safeguard, low 11's in A/F...it cant really be anything else. If you look at the thread where I posted the stock rod vs. Pauter, you'll see that Nissan intentionally cast the stock rod to be very lightweight. This is fine for N/A applications, and actually gives you more power. But with F/I..you need a beefier, thicker, and heavier rod to take those types of power levels.

Given 6 or 7 examples of TT's breaking rods, I am convinced that TT's and our stock rods do not mix. SC's are another story. Since the power is more linear in nature, I imagine the SC's are significantly gentler on the rods than the TT's. However, the SC's are blowing rings...so there arent entirely safe either.

Thanks for sharing your story....and helping us learn from this.