Quote:
Originally Posted by merkil
If I remember correctly for a previous post in another thread z1 examined the oil path and the placement if the oil temp sensor and has stated that the oil temp sensor is on the inlet path before the oil goes into the engine. If the gauge is reading 180F then that is the coldest point (after the cooler if you have one) and the oil will be hotter once it hits the engine up top.
Some ppl seem to think there is about a 20 deg difference between the gauge reading and what the temp is of the oil in the engine.
If you think about it, this might be somewhat close as stage 2 limp mode kicks in when the gauge reads 280F but the oil would actually be around 300F in the engine.
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Anything empirical I can find on modern oils basically points to anything below 300* as acceptable for short periods of time. Running over that on an enduro race could present a problem...
I've found less clear info on how cool is too cool, but if memory serves, ol' A.G. Bell (another plug by me for he
) notes in several engine building and tuning texts that anything below about 160* F is insufficient for optimal lubing. Technical papers by SAE and whatnot may yield more specific values...
I usually aim for about 175* - 180* as a good lower bound for high load, with about 200* - 210* as ideal, based in part on evidence that the OEM Nissan tune tends to pull a little ignition timing above as you creep above 200* F.
Any water or fuel that may be in the oil is almost certainly not a significant factor at that point (and ideally those values began close to zero anyway...), as another poster noted.
Nissan's 260* F (is it 280*F?) limp mode threshold is undoubtedly tied as much to minimizing warranty claims as anything.
Otherwise I am unaware of any clear data on the point at which the VQ37HR components will begin to fail based on over-heated oil providing insufficient lubrication.
That's all assuming, of course, that the OEM gauge data and what the ECU responds to is consistent with the values obtained from empirical testing...