Sat, 10 Aug 2002 02:26:49 -0400
> Well, first, there are two issues raised in this thread.
> The first, and important one, is Marc's apparent high oil temp while
> cruising at part throttle, which will, as you and others have suggested,
> best be approached by a combination of tweaking his fuel delivery,
> directly measuring EGT, and perhaps using a more reliable oil
> temperature gauge.
> Second, and far lower in importance, more like the "after the race"
> chat, than the race itself, is this "issue" of the oil and water temps
> seeming to be "unrelated", or at least related in a complex way.
> > Theoretically, I just don't see how high EGT can _only_ effect oil temp=
s=2E Its not that the oil and water are exchanging heat, its that they are=
both collecting the same heat from the same source, which correlates them.
> Well, first, yes, under any particular condition, the oil and water are g=
oing to be heated in a consistent ratio. But the oil will likely show a mu=
ch wider range of temperature as a result of this due its lower specific he=
at, and remember, if there isn't much of an "overheat" condition to the wat=
er, as it goes up a few degrees the thermostat opens more, balancing it. I=
would hazard a guess that over 120 C the oil
> thermostat is wide open and can't change anything as the oil goes up (fas=
ter than the water).
> IE, under these conditions the oil "cooling" system is already maxed, so
> the oil temp rises steadily to some equilibrium level - where the
> increased temp finally dissipates as fast as it accumulates, via the oil
> cooler, oil pan surface, oil to water transfer, etc. In the meantime
> the water cooling system is not stressed and so maybe only fluctuates by
> 5 degrees, barely noticeable on the gauge.
> > Granted, there is the cooling capacity issue, and that the radiator has=
sooo much extra cooling capacity that it can shed all the extra heat witou=
t the temp gauge budging, but, the temp sensor is located at the top of the=
water neck, before water enters the radiator, thus, you should see a quick=
bump in temps if EGT's are really that high and causing heavy heating of t=
he oil. Also, aside from all the explanations, this has always been my re=
al work observation.
> I agree there, as far as the coolant temp sender location. It is at a
> "hot" location.
Yes, if in fact the coolant is pulling as much heat out of the enging as ev=
eryone is making out to be (which I agree with wholeheartedly), then it wil=
l increase the temperature of the coolant _before_ the radiator, which is e=
xactly where the temp sender is. And, a significant heat increase in load =
or EGT, for example, will reflect more than 5 degrees if in fact the coolan=
t is really cooling things down.
> The reason for my focus on the oil sprayers, is that this is the one plac=
e where oil can gain heat (pushing its temps up fast) that is *not*
> water cooled. The head, the block, the turbo, all places where th eoil c=
an pick up heat, are also bathed in water jackets to keep them from overhea=
ting. The piston isn't. of course this is why those with more experience =
at blowing up engines see nifty holes in their pistons -
> right? They get the hottest when things are out of control (or at least
> out of the "happy" range).
Right, the pistons have the least cooling, but if all that heat is going in=
to the coolant, its temperature will rise, right??
> Remeber the schematic, though. The oil is probably getting *cooled* as i=
t flows through the nicely water-cooled head, but the heated oil from the s=
prayers gets to the temp sender prior to any appreciably cooling.
Right, but that schematic is on a what, 30 second cylcle maybe? That theor=
y holds up for less than a minute in which case, now the heat is everywhere=
oil in the engine is, and now its in contact with that super conductive co=
olant we've been bickering about ;)
> Of course, knowledge as tot he relative amount of oil taking all these di=
fferent paths through the engine would be a nice bit of info.
> But as I pointed out earlier, most of this wondering and theory is irrele=
vant to the "problem." Sure, the oil temp will vary wider and faster than =
the water temp, for the reasons I have been struggling to write about. But=
if Marc has an EGT problem at some running condition, the solution is more=
and better measurement combined with some tweaking of his EFI tables. Whi=
ch might even be fixed by now after he gets to
> play with your numbers - which have more time (and measurement) put into
> them so far than the East Coast contingent has had the opportunity to do.
Yes, tweaking will tell, and I'm not arguing that high EGT's won't raise oi=
l temps, but I've been arguing that they will coolant temps also, which is =
the case IME.
> I'm not debating your vaster experience or expertise in this area...
> just trying to put into words a series of long term layman's
> observations and thoughts on this little sidebar to the main question.
> And of course, as we all know, I might be totally wrong -
> but I'm a -
> dancing fool... yeah!
Sure, understood, if we can keep our Ego's out of it (ya, right, I know) we=
will come to a good conclusion, especially after Marc figures out what is =
up with his car anyway! IME, though, when tuning part throttle and I see r=
eal high EGT's, I am able to measure a heat increase in the cooling system =
too, that's why Marc's clues just didn't add up for me. Anyway, we'll get =
to the bottom of it.