[Shotimes] Re: synthetic oil and oil pressure and race fuel

[Zach Leahy]

Not sur eon the original post, but I am running an external air/oil
cooler in addition to a remote filter.  After all the lines are added,
and the cooler and FL1A filter, the capacity is 7.5qts!  That alone is
really nice.

Running with Mobil 1 5W30 at the track I saw oil temps standing right
at 250 F.  Water temps were not quite as high, about 20 degrees
behind.  While the oil/water cooler is more effective than the oil air
as you mentioned it has limitations, and it also only works when the
oil temp is lower than the water.  around town idling (stuck in
traffic jam) the water temp can exceed the oil temp, and then your
oil/water cooler is actually heating up the oil.

The external oil/air cooler makes a difference, albeit not huge, but
it's not a huge cooler either.  It fits nicely (with some rigging and
hole saw work) right behind the Ford oval on the front.  (mine does,
any bigger and it won't.

The drop in oil temp has not been unrealistically huge, but it helps
some.  I am measuring my oil temp in the pan, near the exhaust, so I
may have slightly higher numbers due to exhaust and catalyst heat
bleeding over.  Hard to say exactly.

I don't have pictures right this second, but I may be willing to get
some if anyone is interested.  it was at the convention and a few
people saw it, but not many, it's inconspicuous, so it goes un-noticed
easily.

Z



On 7/26/05, Leigh Smith <leigh1322@comcast.net> wrote:
> You mentioned over 250F. I wonder how much over? If it only hit 260F why
> worry about it?....
> ..
> I know you push your car prety hard, so this is unfortunately a little
> long...
> ..
> I agree you'd like to keep the oil temp under 250F or so, but on the track
> for long periods that just may not be possible without an aggressive cooler
> setup. I used to have a 7500 rpm small block chevy with 411s and an oil temp
> guage. Any extended cruise over 50 mph (3000 rpm) and the oil temp would
> climb past 240F like 10F per 5-10mph. Piston speed friction and valve spring
> pressure generate most of the oil heat. I've seen as high as 300F. My road
> race open track time was oil temp limited before I added oil coolers. Chevys
> racing recommendations are 150 to 270F at all times, with good oil pressure.
>  ..
> Cold oil increases oil pressure, hot oil decreases it... Get it hot enough
> and your idle oil pressure just about goes to zero! BTDT
> ..
> I would not eliminate the stock oil to water cooler. It actually performs 2
> functions. It warms the oil with a cold motor more quickly to above 180F.
> Cold engines are where most bearing damage / wear occurs. Also water cools
> 5-10 times as well as air. If you've ever added a trans cooler, they
> recommend keeping the stock water based one and adding an air based one
> downstream. Do the same for the oil. If you remove the stock one you could
> easily be removing more heat capacity than you are adding.
> ..
> On the other hand, the water based cooler is never going to drop the oil
> temp below 205F if the water temp is 190F. You could run the oil as cold as
> 180F but it should stay below 250-260F for longevity.  If you rig up an
> external oil filter, you'll have a hot oil hose that you could run thru an
> external air to oil cooler. I suspect the factory oil flow is filter first,
> cooler second. That would mean your new air cooler would take the edge off
> of the extra heat, but the factory one would still be there to make sure the
> temp is above 190F. A sound design.
> ..
> If you wanted to add a huge oil cooler, and bypass the factory one, you
> might be able to get temps down near 180F, but then you would need a
> thermostat as well. And the oil would warm up more slowly increasing rod
> bearing wear.....
> ..
> Past 260-280F dino oil breaks down quicker (carbonizes) leaving deposits,
> etc. If you see oil temps like that you would be well advised to change the
> oil after every event. Synthetic has much more temp resistance, and leave
> much less deposits anyway, so that oil changes due to high temp would not be
> necessary. Another thing that happens with very hot dino oil is that some of
> it literally evaporates, (the low molecular weight organics) causing your
> oil level to drop and forcing you to add oil. That doesn't happen with the
> synthetics either. Those (dino oil) deposits cause both engine wear and the
> piston carbon deposits increase the pinging tendency upping the octane
> requirement, which may impact the timing tune-up.... another topic - but
> yes, it's all related.
> Lee
> 
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