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)

[914werke]

Coming from a background in general aviation...I suggest you're overthinking it.

Our cooling systems are ridiculously simple. It's not "laminar" flow in any sense of the word, that air is coming and going all over the place. Our cooling systems are nothing more than dumping as much air as possible to the top of the engine so that it flows to the lower pressure bottom side, taking heat with it.

You can either increase the pressure on top, or decrease the pressure below. Or both. Either will improve airflow and BTU scavenging.

Overthinking it... quite possibly. (IMG:style_emoticons/default/biggrin.gif) But Im thinking your characterization of the the T4 air cooling flow is probably ... a bit harsh (IMG:style_emoticons/default/laugh.gif)

Musing a little more...
On the early 1.7L's they had a funky oil bath air filter element & a.... pre-heater system.
The heat was derived from a duct attached the rearmost cyl. tin (#1) & ...via flow of air from front to back of motor forced by the Impeller. (IMG:style_emoticons/default/confused24.gif)
Why not use that same design application to, if as you say, dump cooling air to the rear cylinders on both sides ? You could use the Fan that is already in the Eng bay for additional flow? (IMG:style_emoticons/default/rolleyes.gif)

[Superhawk996]

You could use the Fan that is already in the Eng bay for additional flow? (IMG:style_emoticons/default/rolleyes.gif)

Might not be quite that simple.

You need to be conscious that pressure differential dictates direction of airflow.

Example: if the auxiliary fan isn’t running - the engine fan will blow air out of the auxiliary fan - decreasing airflow available to the engine.

Similarly if the auxiliary fan was able to overpower the engine fan you could end up with degraded cooling. Not likely but something that should be considered. Probably would want a one way flapper on the aux fan to prevent that sort of reverse airflow - similar to the little flaps down on the heat exchangers.

What complicates this is that the engine fan is operating at variable speed while the auxiliary electric fan will operate at fixed speed. Might be hard to ensure the balance never results in airflow being pumped in the wrong direction.