Recently I had a engine fail at a track day. After tearing it down and checking in to the cause I'm still not 100% percent sure what caused the failure.

When pulling the bottom end apart I found the bearings in varying shape. Some were OK while others spun in the rods. The machinist told me that the crank was slightly bent so I'm assuming that was the start of the problems. The bearing blocks and the crank don't show more than a mild black/gold discoloration where the the bearings spun into the crank so I don't think it was oil starvation (no blue discoloration). The car had 100,000 miles on it and 1800 mile old oil in it (possible issue). I also put in some gas treatment/octane booster prior because I wanted to burn off some cheap gas I put in on the way to the track (less than a 1/4 tank) before switching to track's race gas.

The last three items together seem like alot stacked up in hind-sight and I wanted to ask if you guys thought those oversights could have lead to the problem? Prior to the motor letting go it was running very strong and hard and didn't show problems with heat until after the bearings and crank was beat up. The car was fairly stock with no major mods (K&N filter), and gave up 3 laps into the second session of the day at the end of the main straight at WSIR. Also the pisons, valves and heads were undamaged.

 

the crank bending is likely the result, not the cause

bearings fail....bearings that are subject to lots of stress are more prone to it, so I would just chaulk it up to one of those things

 

not a cause , but why would you run race gas?

 

What's the octane rating ("ROZ/RON") in race fuel? Maybe it's way too high for the 3.5L Nissan engine. I'm no mechanic, but it sounds kinda risky to put it in your beaZt. Good luck, dude!

 

Thanks folks, I wanted to find something more definitive but I'm thinking Adam is right and the bearings just gave up.

Terra and J. Arnaldo, The race gas is all they have at the track and I pretty much wanted to run no more than a 1/4 tank at any one time. However, I never got a chance to put any of the 110 octane stuff in because the engine failed so early into the day.

Thanks for the suggestions.

 

What kind of race gas did you put in there?

 

Is it bad to have too high of an octane level in your fuel?
And what's too high?

 

The do have 91 octane available at the pumps at WSIR, also why 1/4 tank? My car fuel starves on long corners once it hits 1/4 tank.

 

but if the car ran lean, or worse, starved, it would be plainly visible in the piston and it likely would have bent, or altogether spit up a rod

 

I would also go with oil starvation/bearing failure. It had 100k on it and you were running the **** out of it I am sure. I have also noticed on my car oil temps are what I consider high 230+ and that is on a 90+ degree day running through two gears. Your car is fairly stock so you know the oil temps are going to be high. Take a motor with 100k + oil temp 230 degrees plus and run it on a track at WOT.

 

The issue is: Can the 3.5L engine take it?

 

Here's a quick look at the failed bearings and the damage they did to the other bearings after they contaminated the oil. I also attached a sample of the pistons which look very similar.






Here is a look at the discoloration, I don't think it was starved but it obviously heated up after the bearings let go.

 

Spun rod bearing. On a factory motor that indicates to me oil flow, oil temp, or oil condition. That cap got hot!!!
And to answer to your other question I think the vq is a great motor. I have seen very high horsepower cars with hardly a problem. I do think if you are going to run it on the track I would invest in an oil cooler. I am not going to run my car on the track and I am going to get an oil cooler!

 

My 2006 with 29K miles blew up this weekend at at track day....fresh Mobil1 and Nissan filter, oil filter safety wired on, no mods...Kablam-O

No mods, stock tires, mild temps(for the south) about 85 deg air temps, no over-rev on down-shirts...WTF?

Oil checked before each session, no noticeable oil usage in two days (blew up last session of 2nd day)

 

Thanks for the insight Turbotoy, I'm thinking the temps may have been too much for it to take. An Oil cooler doesn't sound like a bad idea.

Laze1 sorry to hear about that... Was it a Rev Up motor? I hear 2006 was a bad year for the VQ-RevUps. A lot of blown motors. Maybe someone on the thread knows a little more about the blow by issues and why they let go so soon in the life cycles.