Grady..little experiment is done..

[donstevens]

Originally posted by klaucke
Its on my to-do list as well, but I've already ordered all the parts to install a front mount trombone cooler.

Klaucke,

If you are going this far why not spring a few extra bucks for a true heat exchanger to compliment the new oil lines. Most people agree that the trombone is not very effective an you can buy a trombone replacement from Mocal for as little as $300.00 http://www.batinc.net/porsche.htm

Having said that I'll share a little experience I had. I owned a warm running SC several years ago. As I have said in earlier posts, in Tampa rush hour traffic with the A/C blasting, it regularly got to 250F. Plus once it got hot, the ONLY way too get that heat out of the oil was to shut the car off. I bought one of these Mocal trombone replacement kits and I was originally a little disappointed with the results. The car still got hot, about 230, and I really began to worry. Despite more cooling capacity than the trombone, air flow in that fender area is not good. I then added an electric fan which improved airflow somewhat. When I ran the car hard it still got hot BUT the most important thing was that the car would cool right down to 210-215 when I backed out of it. From that perspective, it was a big improvement.

So, you may want to consider this as I think you'll be disappointed with the trombone by itself.

Don

[Brother]

i think this is a little bit of a conduction vs convection argument.

As you increase the airflow, the time the air spends next to a cylinder is less so conductive cooling is lessened.

Convective cooling should increase but it is limited. If you pass this limit, then all you are really doing is adding more combustion events.

[randywebb]

huh??

[island911]

Originally posted by randywebb
huh??

No, Randy; what he says is true.

When pushing cooling air, you definitely want to stay OUT of the supersonic flows. . . they *will* add heat.

[randywebb]

that I believe - tho I have spent some fair amt. of time in libraries to find the 1930's pre-supersonic flow analyses....

it was the 'conduction' comment above that got a 'huh'

[donstevens]

Originally posted by Brother

If you pass this limit, then all you are really doing is adding more combustion events.

I agree with this. I think the same goes for the air going over the oil cooler. The basic cooler only has so much surface area so only x amount of heat transfer can occur. There is undoubdtedly a point where extra airflow is offset by more combustion events. My gut feel and very limited, unscientific testing lead me to believe it around between 2500 and 3000 rpm on my engine.


Don

[Brother]

I think you're right Don. That is what I've found in all my unscientific runs.

Also, according to Bruce Andersen, my fan has a 1.67:1 Ratio.

[island911]

Originally posted by Brother
.. .
As you increase the airflow, the time the air spends next to a cylinder is less so conductive cooling is lessened. . ..

I think this needs to be straightened out. (corrected)

Conduction, to the air (as happens for convective cooling) will have increasingly MORE air to transfer heat to, as the air velocity (volume) is increased.

Sure, each molecule of air is spending less time picking-up heat, but that is a good thing, as heat transfer happens faster, when the difference in temp's is greater.
...that is; 10mol of air(say 1 mol per second) in 'heat-transfer-contact' will transfer more heat than the "slower moving" of leaving one mol of air in contact for ten seconds (assuming the same starting temp's)

--sorry isf that was tough to follow. Point is, heat tranfer rate is driven by temp differences. . . and as one mass (say a mol of air) lingers to take on heat, its temp is then closer to what it's taking heat from . .. .and thus becomes less efficient at taking heat.