more BOOOOST!

[JShadzi at aol.com]

> 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.

Yes

>
> 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 temps.  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 going to be heated in a consistent ratio.  But the oil will likely show a much wider range of temperature as a result of this due its lower specific heat, and remember, if there isn't much of an "overheat" condition to the water, 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 (faster 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 witout 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 the oil.   Also, aside from all the explanations, this has always been my real 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 everyone is making out to be (which I agree with wholeheartedly), then it will increase the temperature of the coolant _before_ the radiator, which is exactly 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 coolant is really cooling things down.

>
> The reason for my focus on the oil sprayers, is that this is the one place 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 can pick up heat, are also bathed in water jackets to keep them from overheating.  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 into the coolant, its temperature will rise, right??

> Remeber the schematic, though.  The oil is probably getting *cooled* as it flows through the nicely water-cooled head, but the heated oil from the sprayers gets to the temp sender prior to any appreciably cooling.
>

Right, but that schematic is on a what, 30 second cylcle maybe?  That theory 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 coolant we've been bickering about ;)

> Of course, knowledge as tot he relative amount of oil taking all these different paths through the engine would be a nice bit of info.
>

Yes

> But as I pointed out earlier, most of this wondering and theory is irrelevant 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.  Which 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 oil 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 real 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.

Javad