My rod bearings after a HPDE

[VG30DETT]

I spun rod bearing #1 and damaged #2 badly during a HPDE @ Monticello Motor Club in NY. I drive a 91' 300ZX TT with the stock engine and turbos but with roughly 17lbs of boost on stock turbos, larger injectors, safe ecu tune, K&N style cone intake, cat-back, etc. however with stock intercoolers, radiator, and oil cooler. The car handles very well with coilovers and Sumitomo HTR ZIII 275 rear and 255 front tires.

The sump takes only a measily ~4quarts of oil to lubricate the 3L V6 TT. I usually run RL 5w30 however at this event I was running GC 0w30 and overfilled about .5quart with M1 15w50 EP.

I was driving pretty agressively, and keeping RPM's high up, shifting at 7k RPM. 10 minutes into my last session, I heard rod knock and pitted. No noise at idle, only above 2k rpm depending on the load. I was able to drive home the 100miles as well.

My initial thoughts were oil starvation, knowing that oil starvation issues are common with the Z32 when tracked at higher G loads, and most serious guys tracking this car have an accusump installed to prevent this. However I doubt myself sometimes considering I was only running sticky summer tires and not slicks.

Rod bearings 1-6 are shown from left to right respectively. A thing to note is that the rod bearings were damaged at the front of the engine. I need to find out which way oil is fed through the crank for lubrication, but I would have thought the front cylinders next to the pump would be first...

I have since replaced the rod bearings with new oem nissan bearings along with cleaning up the #1 journal to drive as long as I can until the I build up a replacement engine. Is this definitely oil starvation?

Pics:

 

[ARCOgraphite]

Overfill and GC and a blend. Dont know where to point my finger first. GC wrecked the bearings on my street car. But it may just have been the luck of the draw. Did you do any UOA on the RL? Is there no room to weld another 2 litre capacity to the bottom of the sump? Any improved windage control?

 

[aquariuscsm]

Most of the guys I know who race/track their Z32s use only 20W50. I`ve read about owners spinning bearings while tracking their Z`s using M1 10W30. Too thin of an oil imo.,especially for racing.

 

[VG30DETT]

No UOA unfortunately. It is common for Z32 guys to overfill a bit in hopes of preventing starvation just that extra tiny bit..The only downside I see is perhaps blowing out seals. I can't see how adding only .5quarts of another high quality synthetic would be detrimental or cause such a problem?

If oil viscosity was the issue, wouldn't all the bearings show damage? Especially in the back where it is most hot. My #6 bearing looked to be in the best shape.

If at operating temperatures, the manufacturer specs a 10w30 weight oil, the only reason I see to run a thicker oil for racing applications is to maintain enough oil film due to reduced viscosity as a result of high temperature and shear.
However if today, premium synthetic oils have proven to remain at a stable viscosity with increased temperature, and resist shear due to its properties and minimization of VI...isn't it safe to say the GC 0W30 I used was fine, also considering it is thicker than most multigrade 30weights?

However I do admit sometimes I feel uncomfortable with the idea that the same bearing is take twice the load due to increased HP out of the same engine. But, wouldn't a thicker oil film be squished out just the same as a thinner film during a power stroke? This is obviously where the additive package comes into play.

 

[Shannow]

Synthetics still thin out with heat, and the hotter the thinner they get. They don't have a "stable" viscosity at varying temperatures.

A thicker oil will be less likely to be squeezed out for sure, but you aren't really talking squeeze films in an operating engine.

 

[FL_Rob]

Caused by wiping out the oil hole on the top half of the first bearing you could try (on your next engine)'camphering' the oil holes.

 

[IndyIan]

I'm no engine guru, but it seems kind of strange the 4 rod bearings were fine, and two at the end weren't. Were those two cylinders running lean? I used to follow the miata forum and guys running higher turbo hp found that the fuel rail was too small and letting the farthest cylinder from the fuel line go lean, causing detonation that the stock knock sensor didn't always see, a solution was to run fuel lines to both ends.
Also FWIW, I foamed the oil on my Neon running high rpms and cheap dino a bit over a half quart over full. It turned the oil light on, but seems that little damage was done.

 

[Johnny]

Well, I will say one thing, when you do something you do it first class.

 

[Kiwi_ME]

Originally Posted By: VG30DETT
Is this definitely oil starvation?
With four good bearings what else can it be?

 

[Mitch Alsup]

What was the peak oil temperature, and how long was the oil at that peak temperature?

 

[VG30DETT]

I wish I knew...I have no aftermarket gauges to monitor these things. I have no idea if pressure went to 0 either, as I wasn't looking at the stock pressure gauge. Perhaps I will be prepared next time. At what temperatures would you be concerned about with the 30weight oil?

As far as running lean due to fuel problems, this is a good point, but unlikely for this car as it hasn't been an issue with Z32's especially at these power levels with stock turbos...BTW I have 740cc injectors which can support up to 700whp, new TT Z32 pump (is regarded as one of the highest flowing stock pumps,) and I have new oem regulator & damper installed as well.

I believe the top half of bearing #4 and 5 also have some signs of wear from the same incident, gotta go to the garage and take some closer pics of them.

 

[Kiwi_ME]

I would modify the sump to remove the issue of starvation and put it back together. Air drawn in may have found it's way to the closer bearings first. Any other issues would have affected all cylinders evenly.

 

[quick_16]

did you measure the crank to see if got bent?

 

[aquariuscsm]

I know of a few TT Z32 owners who go to the race track regularly and whenever they track their cars,they use off the shelf Pennzoil yb 20W50. If I were tracking my car,I`d use a dedicated racing oil.

 

[VG30DETT]

Any idea what oil temps your Z32TT buddies are typically seeing at the track? I guess you can't really go wrong with running too thick a oil, but depending on the temps it could just be unnecessary and further elevate oil temps.

I wonder if there any documented experiments with thick vs thin weight oils in the event of oil starvation? Which would offer more protection during the short time? I would think this is debatable both ways..

quick_16, I did not measure the crank for trueness...why do you ask? So far it is running fine with the replaced bearings.

 

[mechanicx]

You got to figure a turbo engine's oil is going to get very hot and thinned when driven hard. You'd probably want at least a 40W or better a better yet a 50W like Mobil 1 15W50 for insurance.

 

[Kiwi_ME]

Originally Posted By: VG30DETT
... thick vs thin weight oils in the event of oil starvation? Which would offer more protection during the short time?
I don't see that this is a scenario you need to consider. If you have any oil starvation at all you need to correct it, not try to get around it.

 

[Mitch Alsup]

Originally Posted By: VG30DETT
At what temperatures would you be concerned about with the 30weight oil?


265dF for typical synthetics, 285dF for the synthetics with really high HTHS numbers like RedLine 10W-30.

{Where 'concern' means its OK for the oil to get this hot, but the oil must stabilize at this temperature and not inch higher. If the oil temp does not stabilize, then this is a temperature at which you begin to think about saving the engine.}

 

[aquariuscsm]

Here`s a copy and paste from Specialty Z`s site:

Oil Recommendation
We highly insist on using nothing but the best for our Zs, so we choose to use synthetic oil. If you know anything about oil you know it's the best route to take. Don't forget that genuine Nissan Oil Filter too! We like to use Mobil 1 or Royal Purple oil in our personal cars. Due to the extreme heat turbo cars make, it's not a bad idea to use thicker oil (15w50).

 

[addyguy]

Racing something THAT hard, go thick all the way - straight 40-weight racing oil, or HDEO, wouldn't be out of place here.