T4 Engine tin: thermal design Options

[914werke]

So seeing a product recently got me thinking about the result of its application & my own observations of how well (or not) the T4 handles air flow, Engine block cooling & resulting oil temperatures. (IMG:style_emoticons/default/smile.gif)

Its somewhat well known that ...in the 914.. the T4 suffers from less than optimal cooling from the front mounted impeller/fan particularly to the #3 Cylinder
& that it is vitally important to seal the tins multiple openings to contain as much laminar air flow front to back over the finned cylinders.
In a gross approach, the goal was to seal the engine compartment "intake" air on top from the eng. heated "cooling" air below the tins.
When a motor is new and all its components serviced & refreshed, the design does, or did, a pretty good job.
After years of use (neglect), elements (oil dirt mice ext) conspire to restrict that air flow.
As well as eng. heat causing hardening of rubber pieces that are intended to help contain that cooling air below.
Now almost 50 yrs on I see fewer & fewer "STOCK" engine configurations which you can guess usually means more heat to deal with.
Jake addressed the cooling air via his(?) DTM solution, but IMO its not very practical for stock or near stock motors (& expensive)

The go-to response to eliminate that heat is usually an additional or a remote oil cooler which comes with its own set of challenges. (IMG:style_emoticons/default/confused24.gif)
How about KISS (IMG:style_emoticons/default/biggrin.gif) Has anyone used any of the Fiberglass based stick-on reflective heat shielding products on the engine-sides of the tin?
Idea being rather than allow heat absorption to all the those steel pieces reflect it back to carried away by the cooling air?

BTW Im not a Porsche engineer...but I did stay in a Holiday Inn last night (IMG:style_emoticons/default/happy11.gif)

[Superhawk996]

Still thinking about this. Not sure copper “tin” would net much improvement.

Why not?

The convective cooling of the engine by air is a function of the temperature delta between the air and the cylinder heads.

If the cooling air effectively gets pre-heated by picking up lots of heat from the tin, then the air is less effective at cooling the head.

In this case, I’m not sure how much of a temperature rise would occur if the “tin” was really effective? Would be interesting to do some CFD thermal modeling to understand it better before making parts. Would also be interesting to set up a bunch of thermocouples to measure it if parts were made.

About a year or two ago I did work up some napkin sketch assumptions showing that getting cooler ambient air into the engine compartment didn’t make as much of a cooling improvement as some thought it ought to. This is because the temperature delta is dominated by the head temperature which is 2-3 times hotter than ambient air.

Example delta Temp = head temp - ambient air. So we end up with something like 300F (head) - 100F ambient air = delta T of 200F

So let’s ASSUME that the copper tin allows the cooling air to preheat by 20F more than steel.

Now we have 300F - 120F = 180 delta T for the air available to cool the head. 10% less delta Temp available to cool the head.

See why this might not actually net improved cooling?