Potential issues for hot upcoming track day?

threeseventy

Mine did. Yours could. More would if this place wasn't a haven for hardparkers.

[QUOTE=Why would you tune for 100 octane for the track given the fuel starvation issue of the 370. You better hope you have a gas pump at the track.[/QUOTE]

I said tune for 95. At least add some 100. There is 91 and 100 at the pump at all of our tracks. Helps a lot with these hot-running motherf*cking VQ's that we love.

clintfocus

my bad steve, but my input still stands.

ALWAYS run higher effective octane on track then what you are tuned for no matter the weather (unless its raining)

threeseventy

cossie1600

I don't doubt you one bit that the rod bearings might be soft, but I highly doubt it is as critical as you make it sound. More people suffered from fuel starvation/clutch,ps,brake fade than rod bearings failure. I am guessing 50 cars on this forum had gone to the track more than once, the failure rate is less than 5 cars?!? I will take that odd anytime.

threeseventy, mine might fail, but it hasn't after 2000+ miles on the track and 500 autocross runs. I will keep going back at it unless something proves otherwise. I have never hit things at the track either, but it doesn't mean I won't. I hope it doesn't happen, but you don't know.

You guys with modified cars/engines have different requirements than the guys with stock cars. What's to say the failure was caused by the rod bearing and not your mods or tunes. Track conditions are rough on the engines, but most modern cars are smart enough to prevent itself from blowing up.

Rusty

Just go out and have fun. Learn the car and make changes when needed. But know when to stop before anything bad happens.

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clintfocus

I snagged this from a write up my good friend Mike Kojima wrote, since he explains it better then i do regarding Nissan's engine bearings because of his race engineering backround. He used to work for Nissan and has tons of motorsports experience with Nissan platforms.

Also, mine and threeseventy's cars are no more modified then most of the people here. Simple bolt on power mods on stock motors.

"The most oil temperature susceptible parts are the engines crank and rod bearings. The engines bearings are made of soft metals, such as aluminum, tin and zinc with other trace alloying agents such as indium which refines the metals grain for better mechanical properties. The reason why soft metals are used is that they offer good embedability. If hard contaminates are present in the engines oil such as casting sand, metallic particles, hard carbon bits and dirt, a soft bearing surface will allow the particles to become embedded into the surface of the bearing where the damage to the bearing and crankshaft can be limited. The contaminating particle will be soaked up by the soft bearing instead of being ground into the hard steel journal surface of the crank with damaging effect.

Soft metals can be used as engine bearings because under normal conditions, the crankshafts journals never touch the bearings surface. Since the liquid oil layer is not compressible, the crank rides on a pressurized hydrodynamic film of oil a few thousands of an inch thick that is maintained on the bearings surface by the engines oil pump. The oil pump must maintain pressure (this varies for as low as 5 psi at hot idle to more than 60 psi at higher rpm) and continually replenish the oil because the oil leaks out at the edges of the bearing and is flung out by the centrifugal pumping action of the rotating rod journals. This circulation is necessary because the shearing action of the oil in the boundary layer between the rotating crank journal and the static bearing surface creates heat and this heat must be dissipated. Most of the heat is removed by the oil as it passes though the interface between the bearing and crank.

The bearings, although soft still have to bear a heavy load because the incompressible liquid oil film transfers the forces acting upon the engines reciprocating parts to the bearings, thus the bearings have to withstand thousands of pounds of force even though direct contact does not happen. The best engine bearing have high embedability with a high load bearing capacity.

Usually everything works fine until a couple of things happen. In the case of modern late model engines, the green movement is to blame for part of the problem. In the last few years, Nissan has worked hard to make their cars green and more recyclable. In an engine traditionally one of the most toxic areas was the bearings. A few years ago, many Nissan bearings were made of trimetal construction using layers of lead, zinc and tin alloys of different percentages. This tri metal construction has been a mainstay of heavy duty bearing construction and composition for decades. The old Nissan bearings were very strong, heat resistant and durable. It’s a little known secret that old L-Series Nissan bearings are so strong and durable that many race engine builders use them, adapting them to other engines. The Infiniti IRL engine used in Indy cars used off the shelf L-Series bearings for this reason.
Sometime in the last few years, in an effort to be greener, Nissan discontinued the use of lead in all engine bearings. We know of this through discussions of sources deep within Nissan which will have to remain unnamed. At this time the engineers at Nissan noticed that warranty claims for bearing failure in the RB26 GT-R engine, another Nissan engine noted for running high oil temps, spiked. Nissan launched an intensive study on the reasons of this bearing failure and discovered that the new environmentally friendly bearings started to loose their load bearing capacity at temperatures as low as 260 degrees. Although there was plenty of reserve strength for normal passenger cars, the turbo high output RB motor pushed many sets of bearings to the failure point. Although you think of lead as a very soft metal with a low melting point, it was still a major contributor to the bearings mechanical properties and resistance to heat.

So as the oil temperatures climb, the bearings soften and loose their load bearing capacity, if the temperature climbs past 300 degrees and the engine is being pushed hard the bearing material can start to flake and spall. This disrupts the hydrodynamic film allowing metal to metal contact, resulting in catastrophic failure of the bearings, the crank, rods and even the entire engine often within seconds. Oil also begins to deteriorate quickly at temperatures above 260 degrees. It starts to oxidize and thicken, loosing its lubricity while forming sludge and varnish. This further compounds the problem, generating more drag and heat in the bearing/crank interface area.

cossie1600

Once again, I don't disagree with what you said for the most part except the 260F figure is not as concrete as you make it. For one, there just aren't that many bearing failures to support your claim. Two, a good full synthetic is good enough to support 260F without breaking down immediately. Will you be able to go 10K miles at 260F, of course not. Yet for a few hundred miles, I don't see any problems. I have hit 270F many times and I had my oil analysis done at 3000 miles, car had no abnormal materials in the oil.

matcop

I can attest to Seb over at Specialty Z doing great work. One of the very few shops that I trust. I use 0W-40 synthetic synthetic oil in my car. I change before and right after the track. Also, I could probably get away changing the diff fluid every other time at the track, may be a little OCD but i Dont want to take any chances. I change the diff fluid too.

If this is your first time at Fontana, I suggest paying the extra 20 dollars a day and getting a garage. You will be very happy sitting in a garage out of the heat and an actual place to make adjustments if need be.

After the heat, turn the car off, leave the parking brake off, pop the hood sit back and relax.

clintfocus

Like i said, if you are comfortable with operating your 370 at such temps, then that is your decision. Ive given my opinion on the topic, and so have you. Th OP and whoever else reads this thread can make up their own mind whether to follow my advice, or yours. I just tried to put some info out there for people who may not know as well about whats happening while spinning their motors on track. Yes you are correct that there are alot of good quality synthetics out there that can handle 260+ temps, im just of the opinion the VQ shouldnt be operating at that temp under track loads. Call me paranoid.

cossie1600

Very comfortable because I have been doing it for three years, motor is still original amazingly. I don't think I have used anything other than 93 octane either, so weird.

clintfocus

what's 93 octane :P

im sure your tone is tongue and cheek, at least im assuming so.

Alot of people dont run more octane then tuned for on track and depend on the Knock sensor and ECU to pull timing in the case of detonation, im just of the belief why even get to that point, hence i run more effective octane then what im tuned for.

Same with the Oil temps, yes ive hit 260 pre oil cooler, and yes 3 years later my motor is still kicking, but id much rather not be operating at over 240 degrees on track.

Another thing, depending on driving ability and chassis setup, the amount of wide open throttle and load on the engine per lap varies from owner to owner, less experience guys may not hit 250 oil temp till 8 laps in, more experience guys may hit the same temps 3-4 laps in. So there are more variables then what can be discussed on a forum. I guess if you're having fun and not getting towed home by AAA, you're ok

Kingbaby

very paranoid....if you prepare for the heat I'm sure your car will hold up OP...

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cossie1600

Have you ever monitor the difference in power output on the first lap of a session vs. the last lap with telemetry? I don't know about your car, but the difference in my car is marginal at best. I can easily match my top speed on lap 1 and the last lap even after accounting for how I come off the previous corner. I am not sure how much timing the ECU is pulling from the engine exactly. I am sure it pulled some due to the higher intake temp, but the actual difference in power is marginal at best. No way I buy into the whole knock sensor is sucking power out of the car BS, especially on a stock vehicle and the 370 especially. Racing gas is $6 or 7 bucks a gallon, I can spend the money on another track day.

I would be more worried about crashing than mechanical failures

clintfocus

i never said i can "feel" the difference in power, nor have a monitored the difference with telemetry. I dont bring it up as a performance advantage, its just a little extra insurance by raising the detonation threshold a bit.

Also, i didnt say fill up your tank on race fuel, i said mix in some so your over all effective octane is higher. I do about a 1/4 tank of 100 mixed with the 3/4 of 91 ill already have in the tank (since all be have out here in socal is primarily 91 octane and that is what my car was tuned on)

a few gallons of race fuel is not alot of money, and its a nice bit of extra safety. Ive done it with all my cars in the past, both my street cars that see track duty, and my past competition time attack car and because of this ie never ran into detonation related problems or failures

Sh0velMan

I can tell you this, definitive proof or not, if my oil gets north of 240 degrees, I'm backing way off until it drops back down, or parking it all together. If there's even a chance that the bearings might last longer by not exposing them to those kinds of temps, I'll err on the side of caution.

I have a massive oil cooler and have never seen temps over 220, but that's probably because I'm a terrible driver.

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